Buffon's Natural History, Volume 02 (of 10)
by comte de Georges Louis Leclerc Buffon · English · Gutenberg #45602 · 425,730 chars · public domain (US)
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Title: Buffon's Natural History, Volume 02 (of 10)
Author: comte de Georges Louis Leclerc Buffon
Editor: James Smith Barr
Release date: May 7, 2014 [eBook #45602]
Most recently updated: October 17, 2026
Language: English
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*** START OF THE PROJECT GUTENBERG EBOOK BUFFON'S NATURAL HISTORY, VOLUME 02 (OF 10) ***
_Barr's Buffon._
-===-
Buffon's Natural History.
CONTAINING
A THEORY OF THE EARTH,
A GENERAL
_HISTORY OF MAN_,
OF THE BRUTE CREATION, AND OF
VEGETABLES, MINERALS,
_&c._ _&c._
FROM THE FRENCH.
WITH NOTES BY THE TRANSLATOR.
=============
IN TEN VOLUMES.
=============
VOL. II.
-===-
London:
PRINTED FOR THE PROPRIETOR,
SOLD AND BY H. D. SYMONDS, PATERNOSTER-ROW.
----
1797.
CONTENTS
OF
THE SECOND VOLUME.
Proof of the Theory of the Earth.
_Page_
Article XI. _Of Seas and Lakes_ 1
Article XII. _Of the Flux and Reflux_ 58
Article XIII. _Of the Inequalities at the Bottom of the
Sea, and of Currents_ 71
Article XIV. _Of regular Winds_ 86
Article XV. _Of irregular Winds, Hurricanes, and
other Phenomena, caused by the Agitation
of the Sea and Air_ 108
Article XVI. _Of Volcanos and Earthquakes_ 133
Article XVII. _Of New Islands, Caverns, Perpendicular
Clefts, &c._ 171
Article XVIII. _Of the Effects of Rain--of Marshes,
Subterraneous Wood and Water_ 205
Article XIX. _Of the Changes of Land into Sea and Sea
into Land_ 247
_Conclusion of the Theory of the Earth_ 251
History of Animals.
Chapter I. _A comparison between Animals, Vegetables
and other Productions of Nature_ 255
Chapter II. _Of Reproduction in general_ 272
Chapter III. _Of Nutrition and Growth_ 298
Chapter IV. _Of the Generation of Animals_ 311
Chapter V. _Exposition of the Systems in Generation_ 329
BUFFON's
NATURAL HISTORY.
_PROOF OF THE THEORY OF THE EARTH._
ARTICLE XI.
OF SEAS AND LAKES.
The ocean surrounds the earth on all sides, and penetrates into the
interior parts of different countries, often by large openings, and
frequently by small straits; it forms mediterranean seas, some of which
participate of its motions of flux and reflux, and others seem to have
nothing in common with it except the continuity of water. We shall
follow the ocean through all its extent and windings, enumerating at
the same time all the mediterranean seas, and endeavour to distinguish
them from those which should be only called bays, or gulphs, and lakes.
The sea which washes the western coasts of France forms a gulph between
Spain and Britain; this gulph, which mariners call the Bay of Biscay,
is very open, and the point which projects farthest inland is between
Bayonne and St. Sebastian; another great projection is between Rochelle
and Rochefort: this gulph begins at Cape Ortegal, and ends at Brest,
where a strait commences between the south point of Britain and Cape
Lizard. This strait, which at first is very large, forms a small gulph
in Normandy, the most projecting point of which is at Auranche; it
continues pretty broad until it comes to the channel at the foot of
Calais, where it is very narrow; afterwards it grows broader on a
sudden, and ends between the Texel and the coast of England at Norwich;
at the Texel it forms a small mediterranean sea, called _Zuyder-zee_,
and many other great canals, which are not very deep.
After that the ocean forms a great gulph called the German Ocean; it
begins at the northern point of Scotland, runs along the eastern
coast of Scotland and England as far as Norwich, from thence to the
Texel, along the coasts of Holland and Germany, Jutland, Norway, and
above Bergen. This gulph might be taken for a mediterranean sea,
because the Orkney islands partly shut up its opening, and seem
to be directed as if they were a continuation of the mountains of
Norway. It forms a large strait, which begins at the southern point
of Norway, and continues very broad to the Island of Zetland, where
it narrows all at once, and forms between the coasts of Sweden, the
islands of Denmark and Jutland, four small straits; after which it
widens to a small gulph, the most projecting point of which is at
Lubec: from thence it continues pretty broad to the southern extremity
of Sweden, when it grows broader and broader, and forms the Baltic
Sea, which is a mediterranean, extending from south to north near 300
leagues, comprehending the gulph of Bothnia, which is in fact only a
continuation of it. This sea has two more gulphs, that of Livonia,
whose most projecting point is near Mittau and Riga, and that of
Finland, which is an arm of the Baltic, extending between Livonia and
Finland to Petersburgh, and communicating with the lake Ladoga, and
even with the lake Onega, which communicates by the river Onega to the
White Sea. All this extent of water, which forms the Baltic Sea, the
gulphs of Bothnia, Finland, and Livonia, must be looked upon as one
great lake, supported by a great number of rivers which it receives,
as the Oder, the Vistula, the Niemen, the Droine, in Germany and
Poland; other rivers in Livonia and Finland; others still greater,
which come from Lapland, Tornea, the Calis, Lula, Pithea, Uma, and
many others that come from Sweden. These rivers, which are very large,
are more than 40, including the rivers they receive, which cannot fail
of producing a quantity of water sufficient to support the Baltic.
Besides, this sea has no flux nor reflux, although it is very narrow
and very salt. If we consider also the bearing of the country, and
the number of lakes and morasses in Finland and Sweden, we shall be
inclined to look on it not as a sea, but as a great lake formed by the
abundance of waters from the adjacent lands, and which has forced a
passage near Denmark into the ocean, where in fact, according to the
account of mariners, they still continue to flow.
From the beginning of the gulph which forms the German Sea, and which
terminates above Bergen, the ocean follows the coasts of Norway,
Swedish Lapland, North Lapland, and Muscovy Lapland, at the eastern
part of which it forms a large strait, which borders a mediterranean
called the White Sea, which may be likewise regarded as a great lake;
for it receives 12 or 13 rivers, all very considerable, and which
are more than sufficient to support it; its water is but a little
salt. Besides, in many parts it is very near communicating with the
Baltic Sea; it has even a real one with the gulph of Finland, for,
by ascending the river Onega, we come to a lake of the same name;
from this lake Onega there are two rivers of communication with the
lake Ladoga; this last communicates by a large arm with the gulph of
Finland; and there are many parts in Swedish Lapland, the waters of
which run almost indifferently either into the White Sea, or the gulphs
of Bothnia and Finland; and all this country being full of lakes and
morasses, the Baltic and White Seas seem to be the receptacles of its
waters, and which afterwards discharge themselves into the Frozen and
German Sea.
Quitting the White Sea, and coasting the island of Candenos and the
northern coasts of Russia, the ocean forms a small arm in the land at
the mouth of the river Petzora. This arm, which is about 40 leagues
long, by 8 or 10 broad, is rather a mass of water formed by the river
than a gulph of the sea, and also has but little saltness. The land
there forms a projecting cape, terminated by the small islands of
Maurice and of Orange; and between this promontory and the lands which
border the Strait of Waigat to the south, there is a small gulph about
30 leagues depth inland. This gulph belongs to the ocean, and is not
formed by the land waters. We afterwards meet with Waigat's Strait,
which is nearly under the 70th degree of north latitude. This strait is
not more than 8 or 10 leagues long, and communicates with the sea which
waters the northern coasts of Siberia. As this strait is shut up by the
ice the greatest part of the year, it is very difficult to get into
the sea beyond it. The passage has been attempted in vain by a great
number of navigators, and those who fortunately passed it have left
us no exact charts of that sea, which they have termed the Pacific
Ocean. All that appears by the most recent charts, and by Senex's
globe of 1739, is, that this sea might be entirely mediterranean, and
not communicating with the great sea of Tartary, for it appears to
be enclosed and bounded on the south by the country of the Samoides,
which is at present well known, and which extends from the Straits of
Waigat to the river Jenisca; on the east it is bounded by Jelmorland,
on the west by Nova Zembla; and although we are not acquainted with the
extent of this sea to the north and north-east, yet as there does not
appear any interruption of the lands, there is great probability of
its being only a mediterranean, and bounded by land on that side: what
indeed proves this is, that by leaving Waigat's Strait you may coast
Nova-Zembla all along its western and northern coasts as far as Cape
Desire; that after having past this cape, keeping along the coast to
the east of Nova Zembla, you arrive at a small gulph, which is about
the 75th country of Jelmorland was discovered in 1664, which is only a
few leagues distant from Nova Zembla, so that the only land which has
not yet been discovered is a small spot near this little gulph; and
this part is perhaps not thirty leagues long; so that if the Pacific
Sea communicated with the ocean it must be at this little gulph, which
is the only way by which they can join; and as this small gulph is
in the 75th degree, even if the communication should exist, we must
always keep five degrees towards the north to gain the great sea. It
is evident, therefore, that if we would acquire the northern route to
China, it would be much better to pass by the north of Nova Zembla, at
the 77th or 78th degree, where the sea is more open, and has less ice,
than to attempt the road through the icy strait of Waigat, with the
uncertainty of getting out of this sea, which there is so much reason
to believe mediterranean.
By following, therefore, the ocean along the coasts of Nova Zembla
and Jelmorland, these lands are discoverable as far as the mouth of
Chotanga, which is about the 73d degree, beyond which there is an
unknown coast of about 200 leagues: we have only an account of them
from the Muscovites, who have travelled by land into those climates;
they state the country to be uninterrupted, have marked out the rivers
in their charts, and called the people _populi palati_. This interval
of coasts, still unknown, extends from the mouth of Chotanga to that of
Kauvoina, in the 66th degree of latitude; the ocean there forms a bay,
whose most projecting point in land is at the mouth of the Len, which
is a very considerable river. This bay is very open, belongs to the
Tartarian sea, and is called the Linchidolin, where the Muscovites have
a whale fishery.
From the mouth of the Len we may follow the coasts of Tartary more
than 500 leagues towards the east, to a peninsula inhabited by the
Schelates. This is the most northern extremity of Tartary, and is
situate about the 72d degree of latitude. In this 500 leagues the
ocean makes no interruption by bays nor arms, only a considerable
elbow from the peninsula of the Schelates to the mouth of the river
Korvinea. This point of land also forms the eastern extremity of the
old continent, and whose western is at Cape North in Lapland; so that
the old continent has about 1700 leagues northern coasts, comprehending
the sinuosities of the bays, from Cape North in Lapland to the farthest
point of land belonging to the Schelates, and about 1100 leagues in a
straight line.
Let us now take a view of the eastern coasts of the old continent,
beginning at the farthest point of land which the Schelates inhabit,
and descending towards the equator. The ocean at first forms an elbow
between the country of the Schelates, and the land inhabited by the
people called Tschutschi, which projects a considerable way into the
sea. To the south of this island it forms a small bay, called the Bay
of Suctoikret, and afterwards another smaller bay, which projects like
an arm 40 or 50 miles into Kamtschatka; the ocean then enters into
the land by a long strait, filled with many small Islands between the
southern point of Kamtschatka and the northern point of Jesso, and
forms a great mediterranean, which it is proper we should now trace
throughout. The first is the sea of Kamtschatka, in which is a very
considerable island, called Amour, or Love Island. This sea has an arm
to the north-east; but this arm, and the sea of Kamtschatka itself,
might possibly be, at least in part, formed by the rivers, which run
therein, from the lands of Kamtschatka and from Tartary. Be this as it
will, the sea of Kamtschatka communicates with the sea of Corea, which
makes the second part of this mediterranean; and all this sea, which
is more than 600 leagues in length, is bounded upon the west and north
by Corea and Tartary, and on the east and south by Kamtschatka, Jesso,
and Japan, without having any other communication with the ocean than
that of the fore-mentioned strait, for it is not certain whether that
which is set down in some maps between Japan and Jesso really exists;
and even if this strait does exist, the sea of Kamtschatka and Corea
will still be regarded as forming a great mediterranean, divided from
the ocean on every side, and could not be taken for a bay, for it has
no direct communication with the ocean by its southern strait, but with
the sea of China, which is rather a mediterranean than a gulph of the
ocean.
It has been observed in the preceding article, that the sea has a
constant motion from east to west; and that consequently the great
Pacific Sea made continual efforts against the eastern countries;
an attentive inspection of the globe will confirm the consequences
which we have drawn from this observation; for from Kamtschatka to
New Britain, discovered in 1700 by Dampier, and which is the 4th or
5th degree in the south latitude, the ocean appears to have washed
away part of the land on these coasts for upwards of 400 leagues, and
consequently the eastern bounds of the old continent formerly extended
much farther than at present; for it is remarkable, that New Britain
and Kamtschatka, which are the most projecting lands towards the east,
are under the same meridian. All countries have their greatest extent
from north to south. Kamtschatka reaches at least 160 leagues from
north to south, and that point which is washed by the Pacific Sea on
the east, and on the other by the mediterranean sea above mentioned, is
divided in the direction, from north to south by a chain of mountains.
After these the lands of Jesso and Japan form another extent of
land, whose direction is also north and south, extending upwards of
400 leagues, between the Great Sea and that of Corea. The chain of
mountains of Jesso, and of Japan, cannot fail of being directed from
north to south, since these lands, which are 400 leagues in this
direction, are not more than 50 or 60 from east to west. Therefore
the lands of Kamtschatka, Jesso, and the eastern part of Japan, must
be regarded as contiguous, and directed from north to south. Still
pursuing the same direction, after having passed Cape Ava at Japan,
we meet with the island of Barnevelt, and three other islands, which
are placed in the direction of north and south, and extend about 100
leagues. We afterwards meet with three other islands, called the
islands of Callanos, then the Ladrones, which are fourteen or fifteen
in number, all placed in the same direction from north to south,
and all together occupying a space of more than 300 leagues in this
direction, by so trifling a breadth, that its greatest does not exceed
seven or eight leagues from east to west. It therefore appears to me
that Kamtschatka, Jesso, eastern Japan, the islands of Barnevelt, the
Callanos, and the Ladrones, are only the same chain of mountains, and
the remains of an old country, which the ocean has at one time covered
and gradually retired from. All these countries in fact appear to be
only mountains, and the islands to be their points or peaks, while
the low lands are covered with the ocean. What is related in Lettres
Edifiantes, appears, to be true, and that in fact a quantity of islands
have been discovered, called the new Philippine Islands, and that their
position is really such as is given by Father Gobien; and it cannot be
doubted but that the most eastern of these islands are a continuation
of the chain of mountains which forms the Ladrones, for these eleven
eastern islands are all placed in the same direction from north to
south, occupying a space of more than 200 leagues in length, the
broadest of which is not more than 7 or 8 leagues from east to west.
But if these conjectures are thought too presumptuous, on account of
the great intervals between the islands bordering on Cape Ava, Japan,
and the Callanos, and between these islands and the Ladrones, and
between the Ladrones and the new Philippines, the first of which is
in fact about 160 leagues, the second 50 or 60, and the third near
120, I shall answer that the chains of mountains often extend much
farther under the waters of the sea, and that these intervals are
small in comparison of the extent of land which these mountains in
the above direction present, which is 1100 leagues, computing them
from the interior part of Kamtschatka. In short, if we wholly reject
this idea, as to the quantity of land the ocean must have gained on
the eastern coasts of the continent, and on that suit of mountains,
still it must be allowed that Kamtschatka, Jesso, Japan, the islands
Bonga, Tanaxima, those of Great Lequeo, King's Island, Formosa, Vaif,
Basha, Babuyane, Lucca, Mindano, Gilolo, &c. and lastly, Guinea,
which extends to New Britain, and is situate under the same meridian
as Kamtschatka, do not form a continuation of land of more than 2200
leagues, interrupted only by small intervals, the greatest of which
perhaps is not more than 20 leagues, so that the ocean has formed in
the lands of the eastern continent a great bay, which commences at
Kamtschatka and ends at New Britain. This bay is interspersed with many
islands, and has every appearance of having been gained from the land,
consequently we may suppose, with some probability, that the ocean, by
its constant motion from east to west, has by degrees acquired this
extent on the eastern continent, and has formed mediterraneans, such
as Kamtschatka, Corea, China, and perhaps all the Archipelago; for the
earth and sea are there so blended that it evidently appears to be an
inundated country, of which we only see the eminences and high lands,
while the lower are hid under the waters of the ocean. This supposition
appears to be in some measure confirmed by the water being more shallow
than in other seas, and the innumerable islands resembling the tops of
mountains.
If we particularly examine these seas, we shall find the sea of China
forms a very deep bay in its northern part, which commences at the
island of Fungma, and terminates at the frontier of the province of
Pekin, about 50 leagues distance from that capital of the Chinese
empire. This bay, in its most interior and narrowest part, is called
the Gulph of Changi. It is very probable that this gulph, and a part of
the sea of China, have been formed by the ocean, which has submerged
all the ancient country, of which only the islands before-mentioned
are now to be seen. In this southern part are the bays of Tonquin and
Siam, near which is the peninsula of Malacco, formed by a long chain
of mountains, whose direction is from north to south, and the Andaman
islands, another chain of mountains in the same direction, and which
appear to be only a succession of the mountains of Sumatra.
The ocean afterwards forms the great Gulph of Bengal, in which we may
remark, that the peninsula of Indus forms a concave curb towards the
east, nearly like the great bay of the eastern continent, which seems
to have been also produced by the same motion of the ocean from east
to west. In this peninsula are the mountains of Gates, which have a
direction from north to south, as far as Cape Comorin, and the Island
of Ceylon seems to have been separated from this part of the continent.
The Maldiva islands are only another chain of mountains, whose
direction is also the same. After these follows the Arabian Gulph,
which sends out four arms into the country; the two greatest on the
western side, and the two smallest on the east. The first of these arms
on the east side is the Bay of Cambaia, which is not above 50 or 60
leagues in length: this receives two very considerable rivers, viz. the
Tapti and the Baroche, which Pietro de Valle calls the Mehi: the second
arm, towards the east, is famous for the velocity and height of its
tides, which are greater than in any other part of the world, and which
extends for more than 50 leagues. Many rivers fall into this gulph, as
the Indus, the Padar, &c. which have brought so great a quantity of
earth and mud to their mouths as to raise the bottom almost to a level,
the inclination of which is so gentle, that the tide extends to a very
great distance. The first arm on the west side in the Persian Gulph,
which spreads more than 250 leagues on the land; and the second is the
Red Sea, which extends more than 680, computing it from the island
Socotora. These two arms should be regarded as two mediterranean seas,
taking them from beyond the straits of Ormuz and Babelmandel: they
are both subject to the tides, but this is occasioned by their being
so near the equator, where the motion of the tides is much greater
than in any other climate; and besides they are both very long and
narrow. The motion of the tides is more rapid in the Red Sea than in
the Persian Gulph, because the Red Sea is near three times longer and
quite as narrow. The Red Sea does not receive any river whose motion
might oppose the tides, whereas the Persian Gulph receives three very
considerable ones in its most projecting extremity. It appears very
apparently that the Red Sea has been formed by an eruption of the
ocean, for the bearing of the lands are exactly similar, the coasts
on each side of the straits follow the same direction,, and evidently
appear to have been cut by waters.
At the extremity of the Red Sea is that famous neck of land called the
Isthmus of Suez, which forms a barrier to the Red Sea, and prevents
its communication with the Mediterranean. In a preceding article we
noticed the reasons which inclined us to think that the Red Sea is
higher than the Mediterranean, and that if the Isthmus of Suez was
cut, an inundation and an augmentation of the latter might ensue. To
which we shall subjoin, that if even it should not be agreed that the
Red Sea is higher than the Mediterranean, it cannot be denied that
there is neither flux nor reflux in the Mediterranean, adjoining to
the mouths of the Nile; and that, on the contrary, in the Red Sea the
tides are very considerable, and raise the water several feet, which
circumstance alone would suffice to send a quantity of water into the
Mediterranean if the Isthmus was broken. Besides, we have an example on
this subject quoted by Varenius, who says in page 100 of his Geography:
"Oceanus Germanicus, qui est Atlantici pars, inter Frisiam & Hollandium
se effundens, efficit sinum, qui et si parvis sit respectu celebrium
sinum maris, tamen & ipse dicitur mare, alluitque Hollandiæ emporium
celeberrimum, Amstelodamum. Non procul inde abest lacus Harlemensis,
qui etiam mare Harlemense dicitur. Hujus altitudo non est minor
altitudine sinus illius Belgici, quem diximus & mittit ramum ad urbem
Leidam, ubi in varias fossas divaricatur. Quoniam itaque nec lacus
his, neque sinus ille Hollandici maris inundant adjacentes agros (de
naturali constitutione loquor, non ubi tempestatibus urgentur, propter
quas aggeres facti sunt) pater inde, quod non sint altiores quam agri
Hollandiæ. At vero Oceanum Germanicum esse altiorem quam terras hasce,
experti sunt Leidenses, cum suscepissent fossam seu alveum ex urbe sua
ad Oceani Germanici littora, prope Cattorum vicum perducere (distantia
est duorum milliarum) ut, recepto per alveum hunc mari, possent
navigationem instituere in Oceanum Germanicum, & hinc in varias terræ
regiones. Verumenimvero cum magnam jam alvei port em perfecissent,
desistere coacti sunt, quoniam turn demum per observationem cognitem
est, Oceani Germanici aquam esse altiorem quam agrum inter Leidam et
litus Oceani istius; unde locus ille, ubi fodere desierunt dicitur,
_Het malle Gat_. Oceanus itaque Germanicus est aliquantum altior quam
sinus ille Hollandicus, &c." Therefore, as the German Sea is higher
than that of Holland, there is no reason why we should not believe the
Red Sea may be higher than the Mediterranean. Herodotus and Diodorus
Siculus speak of a canal of communication between the Nile, the
Mediterranean, and the Red Sea, and M. Del'isle published a map in
1704, in which he traces one end of a canal to the most eastern part
of the Nile, and which he judges to be a part of that which formerly
joined the Nile with the Red Sea.[A]
[A] See Mem. de l'Acad. Sciences, 1734.
In the third part of a book entitled, "Connoisance de l'Ancien Monde,
or the Knowledge of the Old World," printed in 1707, we meet with the
like sentiment; and it is there said, from Diodorus Siculus, that it
was Neco, King of Egypt, who began this canal, that Darius, King of
Persia, continued it, and that it was finished by Ptolemy II. who
conducted it as far as the city Arsinoe, and that it could be opened
and shut when they found it needful. Without desiring to deny these
circumstances, I must own, that to me they appear doubtful. I do not
know whether the violence and height of the tide in the Red Sea, would
not be necessarily communicated to this canal; it appears to me, at
least, that it would have required great precautions to confine the
waters, to avoid inundations and to preserve this canal in good repair.
Though historians assert that this canal was undertaken and finished,
yet they do not tell us the length of its duration; and the remains
which are pretended to be even now perceptible, are perhaps all that
was ever done of it. The name of the Red Sea has been given to this arm
of the ocean, because it has the appearance of that colour in every
part where corals, or madrepores, are met with at the bottom. In the
Histoire General des Voyages, vol. i. pages 198 and 199, it is said,
"Before he quitted the Red Sea, D. Jean examined what might have been
the reason why that name was given to it by the ancients, and if, in
fact, this sea differed from others in its colour. He knew that Pliny
had given several opinions on the origin of this name. Some derived it
from a King named Erythros, who reigned in those parts, and which, in
the Greek language, signifies red. Others imagined that the reflection
of the sun produces a reddish colour on the surface of the water, and
others that the water was naturally red. The Portuguese, who had made
several voyages to the entrance of the straits, asserted that all the
coasts of Arabia were very red, and that the sand and dust which the
wind carries into the sea, tinged the water of the same colour.
"D. Jean, who examined the nature of the water, and the qualities of
the coasts as far as Suez, asserts, that far from being naturally red,
the water is of the same colour as in other seas, and that the sand and
the dust having nothing red in themselves could not give this tinge to
the water. The earth of both countries, he says, is generally brown;
it is even black in some places, and in others white. On the coasts
of Suaquem, where the Portuguese had not penetrated, he saw three
mountains streaked with red, but they were of a very hard rock, and the
neighbouring country was of the common colour.
"The truth is, that this sea is throughout of an uniform colour, which
is easy to be demonstrated; but it must also be owned, that in some
parts it appears to be red through chance, and in others green and
white; the explanation of which phenomena is as follows: From Suaquem
to Kossir, that is, for the space of 136 leagues, the sea is filled
with shoals and rocks of coral; this name is given to them, by reason
that their form and colour render them so extremely like coral, that
it requires great circumspection not to be deceived. There are two
sorts of them, the one white and the other red; in many parts they
are covered with a kind of gum, or glue, of a green, and in others
with a deep orange. Now the water of this sea is so transparent that
the bottom may be seen at 20 fathoms deep, especially from Suaquem to
the extremity of the gulph; it appears, therefore, to take the colour
of the matters it covers; as for example, when the rocks are covered
with a green gum, the water above appears of a deeper green than the
rocks themselves; and when the bottom is only sand, the water appears
white: so likewise when the rocks are coral, the water seems to be
tinged with red; and as these last coloured rocks are more frequently
met with there than any other, D. Jean concludes, that the name of the
Red Sea was affixed to the Arabian Gulph in preference to the Green
or White. He applauds himself on this discovery, because the method
by which he ascertained it left him no room for doubt. He caused a
float to be moored against the rocks in the parts which were not deep
enough to permit vessels to approach them, and the sailors could often
execute his orders with facility, without the sea being higher than the
stomach at more than half a league from the rocks. The greatest part
of the stones and pebbles they drew up, in those parts where the water
appeared red, was also of that colour: in the water which appeared
green, the stones were green, and if the water appeared white, the
bottom was white sand, without any other mixture."
The direction of the coast of the Red Sea, from Cape Gordafu to the
Cape of Good Hope, is pretty equal; in the course of which there are
no bays, excepting an arm on the coast of Melinda, that might be
supposed as belonging to a large one provided the island of Madagascar
joined the continent, which most probably was formerly the case,
notwithstanding it is now divided by the straits of Mosambique. The
coast bears the same direction from the Cape of Good Hope to Cape Negro
on the west side of Africa; it has the appearance of being a chain of
high mountains, extends about 500 leagues, but contains scarcely any
rivers of importance. Beyond Cape Negro however the land is much lower,
and is supplied by several considerable rivers beside the Coanza and
the Zaire; and between that and Cape Gonsalvez, which is computed to
be about 420 leagues, there are the mouths of no less than twenty-four
large rivers; from this last Cape to Cape Trois-pointes it is an open
bay, in about the centre of which is a considerable projection called
Cape Formosa. On the southern side are the islands Fernanda, St.
Thomas, and the Prince's Island, and which there is reason to suspect
are part of a chain of mountains from Rio del Rey to the river Jamoer.
The water turns somewhat into the land between Cape Trois-pointes
to Cape Palmas, from the latter of which it is an open sea to Cape
Tangrin; beyond this Cape there is a small bay towards Sierra Leona,
and another in which are the islands of Bisagas. We then come to a
considerable projection into the ocean called Cape Verd; of which the
islands of that name are supposed to be a continuation, although it
is more probable they are so of Cape Blanc, which is both higher and
extends farther into the sea. From Cape Blanc to Cape Bajador is a
mountainous and hard coast to which the Canary Islands seem to belong.
Turning from Africa we find an open bay extending to Portugal, and in
about the centre of which are the straits of Gibraltar, through which
the water runs with great rapidity into the Mediterranean, which
flows almost 900 leagues into the interior part of land, and is the
cause of many curious circumstances; 1st, it has no tides, at least
that are visible, excepting in the Gulph of Venice and what are almost
imperceptible at Marseilles and at Tripoli; 2dly, it surrounds a number
of extensive islands, for instance, Sardinia, Sicily, Corsica, Cyprus,
Majorca, and Italy, which is the largest known. It has also a fertile
Archipelago; indeed it is from the Mediterranean Archipelago, that all
collections of islands have been so denominated; this indeed has the
appearance of belonging more to the Black Sea than the Mediterranean;
nor is it in the least unlikely that Greece was at one time covered
with the waters of the Black Sea, which empties itself into the
Marmora, and from thence finds its way into the Mediterranean.
Some have asserted there was a double current in the Straits of
Gibraltar, the one superior, which carries the water of the ocean into
the Mediterranean, and the other inferior, which carries them in the
contrary direction; but this opinion is evidently false, and contrary
to the laws of hydrostatics: it has likewise been asserted to be the
case in many other places, as in the Bosphorus, the strait of Sund, &c.
and Marsilli relates even experiments made in the Bosphorus, to prove
the truth of these opposite currents; but the experiments must have
been badly made, since the matter is totally repugnant to the nature
and motions of the waters; besides Greaves in his Pyramidography,
page 101 and 102, proves, by able experiments, that there is no such
thing as a current in the Bosphorus, whose direction is opposite to
the superior: what may have deceived Marsilli and others, is possibly
the circumstance, that in the Bosphorus, the Straits of Gibraltar, and
in all rivers which flow with rapidity, there is a considerable eddy
along the shores, the direction of which is generally contrary to the
principal current of the waters.
Let us now shortly trace all the coasts of the new continent. Cape
Hold-with-Hope, lying in the 73d degree north latitude, is the most
northern land we are acquainted with in New Greenland, and is not above
160 or 180 leagues distant from Cape North in Lapland. From this cape
we may follow the coast of Greenland as far as the polar circle, where
the ocean forms a broad strait between Iceland and Greenland. It is
pretended that this country, adjacent to Iceland, is not the ancient
Greenland which the Danes formerly possessed as a province dependant
on their kingdom; for in that there were civilized Christians, who
had bishops, churches, and several towns wherein they carried on
their commerce. The Danes also visited it frequently, and as easily
as the Spaniards can go to the Canaries: there still exists, as it is
asserted, laws and ordinances for the government of this province, and
those not very ancient: nevertheless, without attempting to divine how
this country became absolutely lost, it is certain not the least trace
of what we have related is to be met with in New Greenland. The people
are wild and savage; there is no vestiges of any edifice; nor have
they a word in their language which has an affinity with the Danish;
in short, there is nothing which might give us room to judge that
this is the same country. It is even almost a desert, and surrounded
with ice for the greatest part of the year. But as these lands are of
a vast extent, and as the coasts have been but little frequented by
modern navigators, they may have missed the spot where the descendants
of these polished people inhabit; or the ice having become more
abundant in this sea, may prevent any approach to the shore near them:
nevertheless, if we can rely on maps, this whole country has been
coasted, and according to them it forms nearly a peninsula, and at the
extremity of which are the two straits of Forbishers and of Friesland,
where it is extremely cold, although they are not higher than the
Orkneys, that is, at 60 degrees.
Between the west coast of Greenland and that of Labrador, the ocean
forms a gulph, and afterwards a large mediterranean, which is the
coldest of all seas, and the coasts of which are pot perfectly known.
By following this tract due north, we come to Davis's Strait, which
leads to the Christian Sea, and is terminated by Baffin's Bay, which
has the appearance of forming a kind of road into Hudson's Bay.
Cumberland Strait, which as well as Davis's may lead to the Christian
Sea, is narrower and more liable to be frozen: that of Hudson,
though much more to the south, is also frozen during one part of the
year. A very strong motion of the tide has been remarked in these
straits, which is quite contrary to what is the case in the inland
seas of Europe, as neither the Baltic nor Mediterranean have any;
this difference seems to arise from the sea's motion, which always
moving from east to west, occasions high, tides in the Straits, whose
openings are turned towards the east; whereas in those of Europe, which
open to the west, there is no motion; the ocean by its general motion
enters into the first, and avoids the last; and this is the reason
that there are such violent tides in the seas of China, Corea, and
Kamtschatka.
Proceeding from Hudson's Strait towards Labrador, we come to a narrow
opening, in which Davis, in 1586, sailed as far up as 30 leagues,
and trafficked with the inhabitants, but no one has since attempted
a discovery of this arm of the sea, and we are only acquainted with
the country of the Esquimaux of all the adjacent land. The fort Pon
Chartrin is the only and the most northern habitation of this country,
which is separated from the island of Newfoundland by the little strait
of Belleisle, which is not much frequented. As the eastern coast of
Newfoundland is in the same direction as the coast of Labrador, we must
regard the latter as a part of the continent, the same as Isle-royal
appears to have been a part of Arcadia. There is no very considerable
depth either on the great or other banks, where they fish for the cod;
but as they slant for a distance under water, very violent currents are
produced. Between Cape Breton and Newfoundland is a very broad Strait,
by which we enter a small mediterranean, called the Gulph of St.
Lawrence. This sea has an arm which extends far into the country, and
seems to be only the mouth of the river St. Lawrence. The motion of the
tides is extremely plain in this arm of the sea, and even at Quebec,
which projects more into the country, the waters rise several feet.
On quitting the Gulph of Canada, and following the coast of Arcadia,
we meet with a small gulph called Boston-Bay, which forms a small
square inlet into the land. But before we trace this coast farther,
it is just to remark, that from Newfoundland to the most projecting
Antille island, even to Guiana, the ocean forms a very great bay, which
reaches as far as Florida, at least 500 leagues. This bay of the new
continent is similar to that of the old, of which we have taken notice,
where the ocean, after having made a gulph between Kamtschatka and New
Britain, afterwards forms a vast mediterranean, which comprehends the
seas of Kamtschatka, Corea, China, &c. so that in the new continent
the ocean, after having formed a great gulph between Newfoundland and
Guiana, forms a very large mediterranean, extending from the Antilles
to Mexico, which confirms our observations on the motion of the sea
from east to west, for it appears that the ocean has equally gained on
the eastern coasts of America and Asia. These great gulphs in the two
continents are under the same degrees of latitude, and nearly of the
same extent.
If we examine the position of the Antilles, beginning at Trinidad,
which is the most south, we cannot doubt but that Tobago, Trinidad,
the Grenades, St. Vincent, Martinico, Mary Galante, Antigua, and
Barbadoes, with every other island adjacent, at one time formed a chain
of mountains, whose direction was from south to north, like that of the
island of Newfoundland, and the country of the Esquimaux; afterwards
the direction of the Antilles is from east to west, beginning at
Barbadoes, then passing by St. Bartholomew, Porto Rico, St. Domingo,
and Cuba, and nearly the same as Cape Breton, Acadia, and New England.
All these islands are so adjacent to each other, that they may be
looked upon as an interrupted tract of land, and as the summit of an
overflown country now possessed by the sea. Most of them in fact are
only points of mountains, and the sea which surrounds them is a real
mediterranean where the motion of the flux and reflux is scarcely
more sensible than in our Mediterranean, although the openings they
present to the ocean are directly opposite to the motion of the waters
from east to west, which must contribute to elevate the tides in the
gulph of Mexico; but as this sea is very broad, the flux and reflux
communicated to it by the ocean, dispersing over so large a space,
becomes almost insensible at the coast of Louisiana, and many other
places.
The old and new continent appear, therefore, both to have been
encroached upon by the ocean in the same latitudes. Both have a vast
mediterranean and a great number of islands, which are situated nearly
in the same latitudes; the only difference is, that the old continent
being much broader than the new, there is in the western part of it a
mediterranean, of which nothing similar can be found in the new; but
it appears that all which has happened to the eastern countries of the
old world has also happened to the eastern part of the new, and that
the greatest revolutions are nearly in the middle and towards their
equators, where the most violent motion of the ocean is made.
The coasts of Guiana, comprehended between the mouth of the river
Oroonoko and the Amazones, presents nothing remarkable, but the latter,
which is the broadest in the universe, forms a considerable extent of
water near Coropa, before it arrives at the sea, by the two different
mouths which surround the island of Caviana. From the mouth of the
Amazones to Cape St. Roche, the coast runs almost straight east; from
Cape St. Roche to St. Augustine it runs south, and from Cape St.
Augustine to the Bay of All Saints it turns towards the west, so that
this part of Brazil forms a considerable projection in the sea, which
directly faces a like projection of land in Africa. The Bay of All
Saints is a small arm of the ocean, running about 50 leagues into the
land, and is much frequented by navigators. From this bay to Cape St.
Thomas the coast runs direct south, and afterwards in a south-west
direction as far as the mouth of the Plata, where the sea forms an arm
projecting nearly 100 leagues into land. From thence to the extremity
of America, the ocean forms a great gulph, terminated by the adjacent
lands of Terra del Fuega, as Falkland Island, Cape Assumption, and the
land discovered in 1671. At the bottom of this bay is the Straits of
Magellan, which is the longest in the world, and where the tides flow
extremely high. Beyond Magellan is that of La Maire, which is shorter,
and at last Cape Horn, which is the south point of America.
We must remark on the subject of these points that they all face the
south, and most of them cut by straits which run from east to west;
the first is that of South America, which faces the southern pole,
and is cut by the Strait of Magellan; the second, that of Greenland,
which also directly faces the south, and is also cut from east to west
by Forbisher's Strait; the third that of Africa, which also faces the
south; and beyond the Cape of Good Hope are banks and shoals, that
appear to have been divided from it; the fourth, the peninsula of
India, which is cut by a strait that forms the island of Ceylon, and
facing the south like all the rest. Hitherto we perceive no reason to
be given for this similarity, and can only remark such are the facts.
From Terra del Fuega, all along the western coast of South America,
the ocean very considerably penetrates into the land; and this coast
seems exactly to follow the direction of the lofty mountains which
cross all South America, from south to north, from the equator to the
Arctic Pole. Near the equator the ocean forms a considerable gulph,
beginning at Cape St. Francois, and reaching as far as Panama, the
famous isthmus, which, like that of Suez, prevents the communication
of the two seas, and without which there would be an entire separation
of the old and new continents. From thence to California there is
nothing remarkable. Between the latter and New Mexico an arm branches
off, called Vermilion Sea, at least 200 leagues in length. In short,
the western coasts of California have been followed to the 43d degree,
at which latitude Drake, who was the first that made the discovery of
the land to the north of California, and who called it New Albion,
was obliged, through excessive cold, to change his course, and to
anchor in a small bay which bears his name, so that these countries
have not been discovered beyond the 43d and 44th degree, any more than
the lands pf North America beyond Moozemlaki under the 48th degree,
and the Assiniboils under the 51st. The country of the first savages
extends much more to the west than the east. All beyond, throughout an
extent of more than 1000 leagues in length, and as many in breadth,
is unknown, excepting what the Russians pretend to have discovered in
their excursions from Kamtschatka to the eastern part of North America.
The ocean, therefore, surrounds the whole earth without any
interruption, and the tour of the globe may be made from the south
point of America; but it is not yet known whether the ocean surrounds
the northern part of the globe in the like manner; and all mariners
who have attempted to go from Europe to China by the north-east of
north-west have alike miscarried in their enterprises.
The lakes differ from the mediterraneans; the first do not receive
any water from the ocean; on the contrary, if they have communication
with the seas, they furnish them with water. Thus the Black Sea, which
some geographers have regarded as an arm of the Mediterranean, and
consequently as an appendix of the ocean, is only a lake, because,
in place of receiving water from the Mediterranean, it supplies it
with some, and flows with rapidity through the Bosphorus into the lake
called the Sea of Marmora, and from thence through the Strait of the
Dardanelles into the Grecian Sea. The Black Sea is about 250 leagues
long by 100 broad, and it receives a great number of rivers, as the
Danube, the Nieper, the Don, the Boh, the Donjec, &c. The Don, which
unites with the Donjec, forms, before it arrives at the Black Sea, a
lake, called the Palus Meotis, which is more than 100 leagues in length
by 20 or 25 broad. The sea of Marmora, which is below the Black Sea, is
a smaller lake than the Palus Meotis, being not more than 50 leagues
long and 8 or 9 broad.
Some ancients, and among the rest Diodorus Siculus, have asserted that
the Euxine, or Black Sea, was formerly only a large river or lake,
and had no communication with the Grecian sea; but being considerably
increased with time by the rivers which fell into it, the waters
forced a passage at first on the side of the Cyanean islands, and
afterwards on the side of the Hellespont. This opinion appears to be
very probable, and the operation is easily explained; for supposing the
bottom of the Black Sea was formerly lower than it is at present, then
the rivers which come into it would have raised it by the mud and sand
which they brought with them, until the surface of the water became
higher than the land, when consequently it would have forced a passage
for itself, and as the rivers still continue to bring sand and earth,
and at the same time the quantity of water diminishes in the rivers,
in proportion as the mountains from which they drew their sources are
lowered, it may happen in a course of years that the Bosphorus will
be again filled up; but as these effects depend on many causes, it is
scarcely possible to give more than mere conjectures thereon. From this
testimony of the ancients, Mr. Tournefort, in his voyage to the Levant,
says, on ancient authority, that the Black Sea receiving the waters of
a great part of Europe and Asia, after being considerably increased,
opened itself a passage by the Bosphorus, and afterwards formed the
Mediterranean, or so considerably augmented it, that it became a great
sea, and forced itself a road through the strait of Gibraltar, by which
the island of Atlantis, mentioned by Plato, was entirely overflowed.
This opinion has no foundation, since we are certain that it is the
ocean which flows into the Mediterranean, and not the Mediterranean
into the ocean. Besides, M. Tournefort has not combined two essential
facts, both of which he mentions: the first is, that the Black Sea
receives nine or ten rivers, not one of which but supplies it with more
than the Bosphorus throws out: and the second, that the Mediterranean
does not receive more water from rivers than the Black Sea, although it
is seven or eight times larger, and that what the Bosphorus supplies
it with does not make the tenth part of what falls into the Black Sea;
how then could this tenth part of what falls into a small sea have
formed not only a larger sea, but have also so greatly increased the
waters, as to have broken down the lands at the strait of Gibraltar,
and overflow an island larger than the whole of Europe? It is easy to
perceive that this passage of M. Tournefort has not had due reflection.
The Mediterranean receives at least ten times more water from the ocean
than from the Black Sea, because the Bosphorus is only 800 feet broad
in its narrowest part, whereas the strait of Gibraltar is more than
5000, and that, even supposing their velocity to be equal, still the
depth of the straits of Gibraltar is by far the greatest.
M. de Tournefort, who ridicules Polybius on his predicting that the
Bosphorus would be filled up in time, did not pay sufficient attention
to circumstances, when he asserted that event to be impossible. This
sea receives eight or ten great rivers, and as most of them bring sand
and mud, must it not gradually be choaked up? Must not the winds and
the natural current of the waters towards the Bosphorus, convey thither
a part of these matters? It is, therefore, very probable that in a
course of time the Bosphorus will be filled, when the waters of the
rivers which come into the Black Sea shall be gradually diminished;
now all rivers daily diminish, because the vapours collected by the
mountains being the first sources of rivers, their quantity must
decrease as the mountains diminish in height.
The Black Sea in fact receives more water from rivers than the
Mediterranean, and the same author observes, "the greatest rivers in
Europe fall into the Black Sea, by means of the Danube, in which the
rivers of Suabia, Franconia, Bavaria, Austria, Hungary, Moravia,
Corinthia, Croatia, Bothnia, Servia, Transilvania, Wallachia, empty
themselves; those of Black Russia and Podolia, go into the same sea
by the Niester; those of the southern and eastern parts of Poland, of
the northern parts of Muscovy, and the country of the Cossacks, enter
therein by the Neiper or the Boristhenes; the Tanais and Copa also fall
into the Black Sea by the Cimmerian Bosphorus; the rivers of Mingrelia,
of which Phasis is the principal, also voids itself into the Black Sea,
as does the Casalmac, the Sangaris, and other rivers of Asia Minor
which have their course towards the north; nevertheless the Thracian
Bosphorus, which is the only outlet from it, is not comparable to any
of these great rivers."
These facts prove, that evaporation alone carries off a very
considerable quantity of water, and it is from this great evaporation
from the Mediterranean that the ocean continually flows thither through
the straits of Gibraltar. It is difficult to estimate the quantity
of water any sea receives; we should be acquainted with the breadth,
depth, and rapidity of all the rivers which enter therein, how much
they increase and diminish in the different seasons of the year, and
how much it loses by evaporation; the last of which is most difficult;
for even supposing it proportional to the surfaces, it must be more
considerable in a hot than in a cold climate; besides, water mixed with
salt and bitumen, evaporates more slowly than fresh water; a troubled
sea more quickly than one that is tranquil; and the difference of depth
has also some effect: in short, so many circumstances enter into this
theory of evaporation that it is scarcely possible to calculate any
exact estimations on it.
The water of the Black Sea appears to be less clear and less saline
than that of the ocean. There are no islands in it, and its tempests
are more violent and more dangerous than in the ocean, because the
whole body of its waters being contained in a bason, which has but a
small outlet, when they are agitated, they have a kind of whirling
motion which strikes the vessels on every side with an insupportable
violence.
Next to the Black Sea the greatest lake in the universe is the Caspian
Sea, whose extent in length from north to south is about 300 leagues,
and scarcely more than fifty broad. This lake receives the Wolga and
some other considerable rivers, as the Kur, the Faie, and the Gempo;
but what is singular, it does not receive any on its eastern side; the
country on that side being only a desert of sand almost unknown. Czar
Peter I. sent some engineers there to design a chart of the Caspian
Sea, who discovered that its figure was quite different from that given
by former geographers, who had represented it to be round, whereas it
is very long and narrow. The eastern coasts of this sea, as well as the
neighbouring country, were unknown: even the existence of lake Aral,
which is 100 leagues distant from it towards the east, was doubtful,
or at least thought to be a part of the Caspian Sea, so that before
the discoveries of the Czar there was unknown land in this climate
upward of 300 leagues long by 100 or 150 broad. Lake Aral is nearly
an oblong, and may be 90 or 100 leagues long, by 50 or 60 broad; it
receives two very considerable rivers, the Sideroias and the Oxus, but
as well as the Caspian has no outlet for its waters; and it bears the
further resemblance, for as the Caspian receives no river on the east,
so lake Aral receives none on the west, from which we may presume, that
formerly these two lakes were but one, and that the rivers having, by
degrees, diminished, left a great quantity of sand and mud, and which
forms the country that now divides them. There are some small islands
in the Caspian, and its waters are much less saline than those of the
ocean; storms are here very dangerous, and large vessels are not used
in it for navigation, because it has many sand banks, shoals and rocks
scattered under the surface of the water. Pietro della Valle says,
"The largest vessels employed on the Caspian Sea, along the coasts of
Mazanda in Persia, where the town of Ferhabad stands, although they
are called ships, appear smaller than our Tartanes. Their sides are
high, and they draw but little water, having a flat bottom. They give
this form to their vessels, not only because this sea is shallow, but
because it is filled with shoals and sand banks; so that if the vessels
were not fabricated in this manner they could not be used with safety.
Indeed, I was astonished, why at Ferhabad they fish only for salmon,
which are found at the mouth of the river, some poor sturgeons, and
other sort of fresh water fish, of little value: I attributed the cause
of it to their ignorance of the arts of fishing and navigation until
the Cham of Esterabad, whose residence is at a sea port, informed me
that the waters are so shallow 20 and 30 leagues from shore that it
was impossible to cast the nets with the chance of taking any fish, and
that it was for this reason they gave the above-mentioned form to their
vessels, which are not mounted with any cannon, as but few corsairs and
pirates ever visit this sea."
Struys and other travellers have asserted, that in the neighbourhood
of Kilan, there were two gulphs wherein the rivers of the Caspian were
ingulphed, and carried afterwards by subterranean canals into the
Persian Gulph. De Fer and other geographers have even marked out these
gulphs in their maps, nevertheless we are assured by the people sent by
the Czar that they do not exist.[B]
[B] See Mem. Acad. Sciences, 1721.
The circumstance of willow leaves being seen in great quantities on the
Persian Gulph, and which are supposed by the same authors to come from
the Caspian Sea because there are no such trees on the Persian Gulph,
is fully as improbable as their subterraneous gulphs, and which Gemelli
Careri, as well as the Muscovites, asserts are entirely imaginary: in
fact, the Caspian is near one third smaller than the Black Sea, which
last also receives much more water by rivers than the former: the
evaporation therefore is sufficient to carry off all its water, nor is
it necessary to suppose subterraneous gulphs in the Caspian any more
than in the Black Sea.
There are lakes which do not receive any rivers, and from which none go
out. There are others which both receive and discharge and some that
only receive them. The Caspian Sea, lake Aral, and the Dead Sea, are
of the last kind; they receive the waters of many rivers, and contain
them. In Asia Minor there is a small lake of the like kind, and one
much larger in Persia, on which the town of Marago stands; its figure
is oval, and it is about ten or twelve leagues long, by six or seven
broad; it receives the river Tauris, which is not very considerable.
There is also a similar small lake in Greece, about 12 or 15 leagues
from Lepanto, which are the only lakes of that kind known in Asia. In
Europe there is not one which is considerable; in Africa there are many
small ones, as those which receive the rivers Ghir, Zez, Touguedout,
and Tasilet. These four lakes are pretty near each other, and situate
towards the frontiers of Barbary near the deserts of Zara; there is
another situated in the country of Kovar, which receives the river
of Berdoa. In North America, where there are more lakes than in any
other part of the world, not one of this kind is known, at least if we
except two small collections of water formed by rivulets, the one near
Guatimapo, and the other some leagues from Realnuevo, both in Mexico.
But in South America, at Peru, there are two contiguous lakes, one of
which, lake Titicaca, is very large, and receives a river whose source
is not very remote from Cusco, and from which no river issues: there
is one smaller in Tucuman, which receives the river Sala; and another
larger in the same country, which receives the river Santiago, and
three or four others between Tucuman and Chili.
The lakes which receive no rivers, and from which no rivers issue,
are greater in number than those just spoken of; these lakes are
kinds of pools where the rain water collects; or may proceed from
subterraneous waters, which issue in form of springs, in low places,
where they cannot afterwards find any drain. The rivers which overflow
may likewise leave stagnate waters in the country, which may remain
for a long time, and only be replenished by other inundations. The
sea has often inundated lands and formed saline lakes therein, like
that at Haarlem, and many others in Holland, to which, no other origin
can be attributed; or by losing its natural motion, might quit some
land, and leaving water in the lowest places may have formed lakes,
which have continued to be supported by rains. In Europe there are
many small lakes of this kind, as in Ireland, Jutland, Italy, in the
country of the Grisons, Poland, Muscovy, Finland, and in Greece. But
all these lakes are very inconsiderable. In Asia there is one near the
Euphrates, in the desert of Irac, more than 15 leagues long: another
in Persia nearly of the same extent, and on which the towns of Kelat,
Tetuan, Vastan, and Van, are situated; another small one in Chorazan
near Ferrior; another in Independent Tartary, called Lake Levi; two in
Muscovy Tartary, another in Cochinchina, and one in China very large,
and not far distant from Nankin; this last, nevertheless, communicates
with the adjacent sea, by a canal several leagues in length. In Africa
there is a small lake of the same kind in the kingdom of Morocco;
another near Alexandria, which appears to have been left by the sea;
another very considerable one formed by the rain in the desert Azarad,
about the 30th degree latitude; this lake is eight or ten leagues long;
another still larger on which the town of Gaoga is situate, in the 27th
degree; another much smaller, near the town of Kanum, under the 30th
degree; one near the mouth of the river Gambia; many more in Congo,
about the 2d or 3d degree of south latitude; two more in the country
of the Caffrees, one called the Lake Rufumbo, of no great length, and
another in the province of Arbuta, which is perhaps the greatest lake
of this kind, being about 25 leagues in length by seven or eight in
breadth; there is also one of these lakes at Madagascar, near the east
side, about the 29th degree of south latitude.
In America there is one of these lakes in the middle of the peninsula
of Florida, in its centre is an island called Serope; the lake of
Mexico is also of this kind, this is almost round, and about 10 leagues
diameter; there is another still larger in New Spain, 25 leagues
distant from the coast of Campeachy Bay, and another smaller in the
same country near the coast of the South Sea. Some travellers have
asserted that there was in the inland parts of Guiana a very great lake
of that kind; it is called the Golden Lake, or Lake Parima. They have
related surprising things of the riches of the neighbouring country,
and of the quantity of gold dust that is found in this lake. They give
it an extent of more than 400 leagues in length, and 125 in breadth. No
river, they say, goes out nor enters therein; although many geographers
have marked this lake in their maps, it is not probable there is any
such existing.
But the most general and largest lakes are those which receive and give
rise to other great rivers: as their number is very great I shall speak
only of the most considerable, or of the most remarkable. Beginning
at Europe, we have in Switzerland the lake of Geneva, Constance, &c.;
in Hungary, the lake Balaton; in Lavonia, a large lake, and which
separates this province from Russia; in Finland, the lake Lapwert,
which is very long, and is divided into many arms, and lake Oula, which
is of a round figure; in Muscovy, lake Ladoga, more than 25 leagues
long by above 12 broad. Lake Onega is as long, but not so broad. Lakes
Ilmen and Belozo, from whence issue one of the sources of the Wolga;
the Iwan-Osero, from whence issues one of the sources of the Don: two
other lakes from whence the Vitzogda derives its origin; in Lapland,
the lake from which issues the river Kimi; another much larger near the
coast of Wardhus, and many others, from whence issue the rivers Lula,
Pithea, and Uma. These are not very considerable. In Norway two more
of nearly the same size as those of Lapland: in Sweden, lake Vener,
which is as large a lake as Meler, on which Stockholm is situated; and
two others less considerable; one is near Eveldal, and the other near
Lincopin.
In Siberia, in Muscovy, and in Independent Tartary, there are a great
number of these lakes, the principal of which is the great lake Baraba,
which is more than 100 leagues long, and whose waters fall into the
Irtis; the great lake Estraguel, the source of the same river: many
other smaller, the sources of the Jenisca; the great lake Kita, the
source of the Oby; another larger, the source of the Angara; lake
Baical, which is more than 70 leagues long, and is formed by the same
river Angara; lake Pehu, from which issues the river Urack, &c. In
China and Chinese Tartary, lake Dalai, from whence issues the large
river Argus, which falls into the river Amour; the lake of the three
mountains, the source of the river Helum; the lakes Cinhal, Cokmor,
and Sorama, the sources of the river Honaho; two other lakes adjacent
to the river Nankin, &c. In Tonquin, lake Guadag, which is very
considerable. In India, the lake Chiamat, from whence issues the river
Laquia, adjacent to the sources of the rivers Ava, Longenu, &c. This
lake is more than 40 leagues broad by 50 long. There is another at the
origin of the Ganges; and one bordering on Cashmere is the source of
the river Indus, &c.
In Africa is lake Cavar, and two or three others adjacent to the mouth
of Senegal river. Lakes Guarda and Sigismus make but one lake, of a
triangular form, about 100 leagues long by 75 broad, and contain a very
considerable island. In this lake the Niger loses its name, and takes
that of Senegal, in the course of which, towards the source, we meet
with another considerable lake, called Bournou, where the Niger again
loses its name, for the river which comes therein is called Gambaru. In
Ethiopia, at the sources of the Nile, is the great lake Gambia, upwards
of 50 leagues long. There are also many lakes on the coast of Guinea,
which appear to have been formed by the sea, and there are only a few
lesser lakes in the remaining part of Africa.
North America may be styled the country of lakes; the greatest are lake
Superior, upwards of 125 leagues long by 50 broad; lake Huron, upwards
of 100 leagues long by 40 broad; lake Illionois, which, comprehending
the Bay of Puanto, is quite as extensive as lake Huron; lakes Erio, and
Ontario, together upwards of 80 leagues long, from 20 to 25 broad; the
lake Mistasin, to the north of Quebec, is about 50 leagues in length;
and lake Champlain, to the south of it, is nearly of the same extent;
lake Alemipigon, and the lake Christinaux, both to the north of lake
Superior, are also very considerable; the lake Assiniboils contains
many islands, and is upwards of 75 leagues long; there are also,
independent of that of Mexico, two large lakes in that country, the one
called Nicaragua, in the province of that name, which is upwards of 70
leagues long.
In South America there is a small lake, the source of the Maragnon, and
another larger which is the source of the river Paraguay; also the lake
Titicares, which falls into the river Plata; two smaller lakes which
flow into the same river; and some others, not very considerable, in
the inland part of Chili.
All lakes from which rivers derive their origin, those which fall into
the course of rivers, and which carry their water thereto, are not
salt. Almost all those, on the contrary, which receive rivers without
others issuing thereout, are salt; this seems to favour the opinion
that the saltness of the sea arises from the salts which rivers wash
from the earth, and continually convey into it; for evaporation cannot
carry off fixed salts, and consequently those which rivers carry into
the sea remain therein. Although river water appears to taste fresh, we
well know that it contains a small quantity of salt, and in course of
time might have acquired such a considerable degree, as to occasion the
present saltness of the sea, and which must still continue increasing.
It is thus, therefore, as I imagine, that the Black Sea, the Caspian,
lake Aral, &c. have become salt. With respect to lakes, which do not
receive any river, nor from which does any issue, are either fresh or
salt, according to their different origins; those near the sea are
generally salt, and those remote from it are fresh, because the one has
been formed by the inundations of the sea, and the others proceed from
springs of fresh water.
The lakes any ways remarkable are the Dead Sea, the waters of which
contain much more bitumen than salt: it is called the Bitumen of Judea,
but is no other than the Asphaltes, which has caused some authors to
call it the Asphaltic Lake. The lands which border this lake contain a
great quantity of this bitumen; and many have supposed, as the poets
feign of lake Avernus, that no fish could live therein, and birds which
attempted to fly over it were suffocated; but neither of these lakes
produce such mortal events; fish live in both, birds pass over them,
and men bathe therein without the least danger.
At Boleslaw, in Bohemia, there is said to be a lake, wherein are holes,
whose depth is unfathomable, from which impetuous winds issue, which
are carried over all Bohemia, and in winter raise pieces of ice of an
100 weight in the air.
A petrified lake in Iceland is also mentioned; and lake Neagh, in
Ireland, has also the same property; but these petrifactions are no
other than incrustations, like those made by the water of Arcueil.
ARTICLE XII,
OF THE FLUX AND REFLUX.
Water has but one natural motion; like other fluids it always descends
from the higher into the lower places, unless obstructed by some
intervening obstacle. When it reaches the lowest place it remains
there calm and motionless, at least without some foreign causes which
agitates and disturbs it. All the waters of the ocean are collected in
the lowest parts of the surface of the earth, of course the motions
of the sea must proceed from external causes, the principal of which
is the flux and reflux, which is alternatively made in a contrary
direction, and from which results a general and continual motion in the
sea from east to west. These two motions have a constant and regular
relation with the motions of the moon. When the moon is new, or at
the full, this motion from east to west is more sensible, as well as
that of the tides, which upon most shores ebb and flow every six hours
and a half: that it is always high tide whenever the moon is at the
meridian, whether above or below the horizon of the place; and low tide
when the moon rises or sets. The motion of the sea from east to west
is constant and invariable, because the ocean in its flux moves from
east to west, and impels towards the west a great quantity of water,
and the reflux seems to be made in a contrary direction, by reason of
the small quantity of water then driven towards the west; the flux,
therefore, must rather be regarded as a swelling, and the reflux as a
subsiding of the water, which instead of its disturbing the motion from
east to west, produces and continually restores it, although in fact it
is stronger during the rise, and weaker during the fall, from the above
reason.
The principal circumstances of this motion are, 1. That it is more
sensible when the moon is new, or at the full, than in the quadratures:
in spring and in autumn it is also more violent than at any other time
of the year; and it is weaker in the solstices, which, is occasioned
by the combination of the attraction of the moon and sun. 2. The wind
often alters the direction and quantity of this motion, particularly
that which constantly blows from the same quarter. It is the same
with respect to large rivers which convey their waters into the sea
and produce a current there, often extending several leagues, which
is strongest when the direction of the wind agrees with the general
motion. Of this we have an example in the Pacific Ocean, where the
motion from east to west is constant and very perceptible. 3. We must
remark that when one part of a fluid moves, the whole mass receives the
motion; now in the motion of the tides a great part of the ocean moves
in a very sensible manner, and consequently the ocean is agitated by
this motion throughout its whole extent.
Perfectly to comprehend this we must attend to the nature of the power
which produces the tides. We have observed that the moon acts upon the
earth by a power called attraction by some, and by others gravity:
this force penetrates through the globe, is exactly proportioned to
the quantity of matter, and decreases as the square of the distance
increases. Let us next examine what must happen to the waters when the
moon is at the meridian of any one place.--The surface of the waters
being immediately under the moon is then nearer that planet than any
other part of the globe; hence this part of the sea must be elevated
towards the moon, by forming an eminence, the summit of which must
be opposite to the moon's centre; for the formation of this eminence
the waters at the bottom, as well as at the surface, contribute their
share, in proportion to the proximity they are in of the moon, which
acts upon them in the inverse ratio of the squares of their distances:
thus the surface of that part of the sea is first raised; the surface
of the neighbouring parts will be likewise elevated, but to a less
height, and the water at the bottom of all these parts will be raised
by the same cause; so that all this part of the sea growing higher
and forming an eminence, it is necessary that the water of the remote
parts, and on which this force of attraction does not act, proceeds
with precipitation to replace the waters which are thus elevated and
drawn towards the moon. This is what produces the flux, or high tide,
which is more or less sensible on different coasts, and which agitates
the sea not only at its surface but even to the greatest depths. The
reflux, or ebb, happens afterwards by the natural inclination of the
water, for when the moon no longer uses its power, the water which was
raised by this foreign power retakes its level, and returns to the
shores and places it had been forced to quit. When the moon passes to
the antipode, or opposite meridian, the same effect ensues, though
from a different cause, In the first case the waters rise because they
are nearer the planet than any other parts of the globe; and in the
second it is from the contrary reason, they rise because she is the
most remote from them; and this it is easily perceived must produce
the same effect, for the waters of this part being less attracted
than those of the opposite hemisphere, they will naturally recede
and form an eminence, the summit of which will answer to the point
of the least action that is directly opposite to the moon's station,
or where she was thirteen hours before. When the moon arrives at the
horizon the tide is ebb, the sea is then in its natural state, and
the water in a direct equilibrium; but when she is at the opposite
meridian this equilibrium can no longer exist, since the waters of
the part opposite to the moon being at the greatest distance possible
from her, they are less attracted than the remaining part of the
globe, and hence their relative weight, which always retains them in
an equilibrium, impels them towards the opposite point to the moon.
Thus in the two cases, when the moon is at the meridian of a place, or
at the opposite meridian, the water must be raised nearly to the same
height, and consequently fall and rise, when the moon is at the horizon
either at her rising or setting. Thus a motion, such as we have just
mentioned, necessarily disturbs the whole mass of the sea, and agitates
it throughout its whole extent and depth; and if this motion appears
insensible in the open seas, it is nevertheless no less real; but as
the winds cannot ruffle the bottom in an equal degree with the surface,
the motion of the tides is necessarily more regular there, although
directed alternately in the same manner as at the top.
From this alternative motion of flux and reflux there results, as
already observed, a continual motion of the sea from east to west,
because the moon, which produces the tides, proceeds from east to
west, and successively acting in the same direction, the water follows
her course. This motion is most considerable in all sraits; for
example, at the straits of Magellan the water rises nearly 20 feet, and
continues so for six hours, whereas the reflux lasts only two[C], and
the water runs towards the west. This evidently proves that the reflux
is not equal to the flux, and that from both there results a motion
towards the west, much stronger in the time of the flux than in that of
the reflux. This is the reason that in open seas, remote from land, the
tides are only felt by the general motion of the waters from east to
west.
[C] See Narborough's Voyage.
The tides are stronger in the torrid zone between the tropics than in
the rest of the ocean: they are also more sensible in places which
extend from east to west, in long and narrow gulphs, and on the coasts
where there and isles and promontories. The greatest known flux is at
one of the mouths of the river Indus, where the water rises thirty
feet. It rises also very remarkably near Malays, in the straits of
Sund, in the Red Sea, in Nelson's Bay, at the mouth of the river St.
Lawrence, on the coasts of China, Japan, Banama, in the Gulph of
Bengal, &c.
The motion of the sea from east to west is more sensible in particular
places. Mariners have observed it in sailing from India to Madagascar
and Africa; it is also very perceptible in the Pacific Sea, and
between the Malaccas and Brazil: but this motion is most violent in
the Straits; for example, the waters are carried with such great force
in that direction through the Straits of Magellan that it is felt to
a great distance in the Atlantic; and it is supposed that this caused
Magellan to conjecture there was a strait by which the two seas had a
communication. In the Manilla straits, and in all the channels which
divide the Maldivian islands, the sea flows from east to west, as well
as in the Gulph of Mexico, between Cuba and Jucatan. In the gulph of
Paria this motion is so violent that the strait is called the Dragon's
Mouth. In the Canadian and Tartarian Seas it flows also with violence,
as well as in the Strait of Waigat, through which it conveys enormous
masses of ice into the northern seas of Europe. The Pacific Ocean flows
from east to west, through the Straits of Java; the sea of Japan flows
towards China, the Indian Ocean flows towards the west, through the
Straits of Java and other Indian islands; we cannot, therefore, doubt
that the sea has a constant and general motion from east to west, and
it is certain the Atlantic flows towards America, and that the Pacific
Sea goes from it, as is evident at Cape Current between Lima and Panama.
In short, the alternatives of the flux and reflux are regularly made
in six hours and a half on most coasts, though at different hours,
according to the climate and position of the lands: thus the sea coasts
are continually beaten by the waves which at each time wash away some
small parts of their matters, which they transport to a distance, and
deposit at the bottom of the sea; so likewise the waves convey, and
leave on the lower shores, shells, sands, &c. these by degrees form
horizontal strata, which accumulating, become downs and hills, exactly
similar to others, both as to form and internal composition. From this
constant action, the sea naturally shuts itself out from the lowest
coasts, and gains upon the highest.
To give an idea of the efforts of a troubled sea against coasts, I
shall relate a fact which has been affirmed to me by a creditable
person, and which I the readier gave credit to, having seen something
nearly similar. In the principal islands of the Orkneys there are
coasts composed of rocks perpendicularly divided to the surface of the
sea, to the height of near 200 feet. The tides in this place rise very
considerable, as is common in all parts where there are projecting
lands and islands; but when the wind is very strong, and the sea swells
at the same time, the motion is so great, and the agitation so violent,
that the water rises to the summit of these rocks, and falls again in
the form of rain: it throws to this great height gravel and stones from
the foot of the rocks, and some of them even broader than the hand.
In the port of Livourne, where the sea is much more calm, I saw a
tempest in December, 1731, wherein they were obliged to cut down
the masts of some vessels that had been forced from their anchors
by the wind, and driven into the road. The sea swelled above the
fortifications, which were of a considerable height, and as I was on
one of the most projecting works, I could not regain the town before I
was wetted by the sea-water much more than I could have been by the
most plentiful rain.
These examples are sufficient to shew with what violence the sea acts
against some coasts. This continual agitation destroys and diminishes
by degrees the land. The water carries away all these matters, and
deposits them as soon as it arrives at a part where the troubled sea
subsides into a calm. In tempestuous weather the water is foul, from
the mixture of matters detached from the shore and bottom of the sea,
which then casts on the coasts a number of things that it brings from a
distance, and which are never met with but after storms; as ambergris
on the west of Ireland, and yellow amber on those of Pomerania,
cocoa-nuts on the coasts of India, &c. and sometimes pumice and other
singular stones. We can quote on this occasion a circumstance related
in the new travels to the American Islands. "Being at St. Domingo,
says the author, among other things they gave me some light stones,
which the sea brought to the coast when there had been strong southerly
winds; there was one two feet and a half long by eighteen broad, and
one thick, which did not quite weigh five pounds: they are as white
as snow, much harder than pumice, of a fine consistency, having no
appearance of being porous, but when thrown into water, rebounded
like a ball thrown on the ground, and it was with great difficulty
they could be forced under the water with the hand." The stone must
have been a very fine and close-grained pumice, which had issued
from some volcano, and which the sea had conveyed, as it transports
ambergris, cocoa-nuts, common pumice-stone, seeds of plants, rushes,
&c. Observations of this kind have been generally made on the coasts
of Ireland and Scotland. The sea by its general motion from east to
west must convey the productions of our coast to those of America; and
it is by some irregular motions that the productions of the East and
West Indies, as well as the northern climates, are brought upon our
shores. There is a great appearance that the winds cause those effects;
large spots have often been observed in the high seas, far from shore,
covered with pumice-stones; they could only come from the volcanoes
in islands or on the continent, and which the current had transported
to the middle of the seas. Before the southern part of America was
known, and in the time when the India Sea was thought to have no
communication with our ocean, appearances of this kind afforded the
first supposition of it.
The alternative motion of the flux and reflux, and the constant motion
of the sea from cast to west, presents different phenomena in different
climates, according to the bearing of the land and the height of the
coasts. There are parts where the general motion from east to west is
not perceptible; there are others where the sea has even a contrary
motion, as on the coast of Guinea. But these contrary motions are
occasioned by the winds, by the position of the lands, by the waters
of large rivers, and by the disposition of the bottom of the sea; all
these causes produce currents which alter, and often change the general
motion in many parts of the sea; but as the motion from east to west
is the greatest, most general and constant, it must also produce the
greatest effects, and all taken together, the sea must gain ground
towards the west, and lose it towards the east; although it may happen
that on those coasts where the west winds blow during the greatest
part of the year, as in France and England, the sea may gain on the
east, yet these particular exceptions do not destroy the effect of the
general cause.
ARTICLE XIII.
OF THE INEQUALITIES AT THE BOTTOM OF THE SEA, AND OF CURRENTS.
The coasts of the sea may be distinguished into three kinds, 1st, the
elevated coasts, which are rocks and hard stones, generally divided
perpendicularly, and which rise sometimes to the height of 7 or 800
feet. 2d, The low coasts, some of which are almost level with the
surface of the water, and others rising with a moderate elevation,
often bounded by rocks at the water's edge, forming shelves and
breakers, which render the approach to shore very difficult and
dangerous. 3dly, Downs, which are coasts formed by sand which the sea
accumulates, or brought or deposited by rivers; these downs form hills
more or less elevated, according to the accumulated sand.
The coasts of Italy are bordered by several sorts of marble and
stone; these rocks appear at a distance as so many pillars of marble
perpendicularly divided. The coasts of France from Brest to Bourdeaux
are almost surrounded with rocks just at the water's edge, which
occasion dangerous breakers. The coasts of England, Spain, and many
others, are also bordered with rocks and hard stone; excepting some
parts which are made use of for bays, ports, and havens.
The depth of water along the coasts is in proportion to their
elevation. The inequalities at the bottom of the sea near the coasts,
correspond also with the inequalities of the surface of the ground
along the shore. A celebrated navigator has made the following
observations on this subject.
"I have constantly remarked, that where the coasts are defended
by steep rocks, the sea is there very deep, and seldom affords a
probability of anchoring; and, on the contrary, where the ground
inclines from the coast to the sea, however elevated it may be further
inland, the bottom is good there, and consequently admits of anchorage.
"According to the declivity of land, as it approaches the water's
edge, so we generally find our anchor ground, and either approach or
keep at a distance from shore agreeable to the steepness of the land;
for I never saw or heard of a coast where the land is of a continual
height, without some vallies lying intermixed with the high-lands;
they are the subsiding of low lands, and afford good anchoring, the
earth being lodged deep under water; for this reason it is we find good
harbours upon coasts which abound with steep cliffs, because the land
has subsided between them. But Where the declensions from the hills is
not within land but towards the main sea, as at Chili and Peru, and
the coasts are nearly perpendicular, as in the countries running from
the Andes, it is very deep, and has scarcely any creeks or harbours.
The coasts of Gallicia, Portugal, Newfoundland, the islands of Juan
Fernando and St. Helena, &c. are somewhat similar to those of Peru,
yet good harbours are not so scarce, as there is always good anchorage
where there are short ridges of land. In general the land under water
seems to be exactly proportioned to the rising of the contiguous part
above, and therefore, where the lands upon the shores are steep, there
is but little security for ships, they being very easily driven from
their moorings; yet although steep cliffs denote this disadvantage,
they assure us of this benefit also, that we can sail close to them
with safety, besides being able to see them at a considerable distance;
whereas low lands are frequently not discovered until we are near, and
always experience the hazard of running aground. This fact of good
anchorage where the lands on the coast are low, might be illustrated by
many instances in the bays of Campeachy, Honduras, Panama; the coasts
of Portobella, Carthagena, Guinea, Callifornia, China, Coromandel, &c.
but going into particulars would be almost endless, as I very seldom
found it otherwise than that deep waters and high shores went together,
as well as low lands and shallow seas."
The fact therefore of there being considerable mountains, and other
inequalities, at the bottom of the sea is fully confirmed by the
observations of navigators. Divers also assure us, there are smaller
inequalities formed by rocks, and that it is much the coldest in the
vallies of the sea. In general the depths in great seas, as we have
already observed, increase proportionably to their distance from shore.
By Mr. Buache's chart of that part of the ocean between the coasts of
Africa and America, and by the divisions he has given of the sea from
Cape Tagrin to Rio-Grande, there appears to be similar inequalities in
the ocean to those on land. That the Albrolhos, where there are some
rocks at the surface of the water, are only the tops of very large
and lofty mountains, of which Dolphin island is one of the highest
peaks. That the islands of Cape de Verd are also the tops of mountains
that there are a great number of shoals in the sea, which round the
Albrolhos descends even to unknown depths.
With respect to the quality of the different soils which form the
bottom of the sea, as we must rely on divers and the plumb, we can say
nothing exact or precise concerning it; we only know that there are
parts covered with mud to a considerable thickness, on which anchors
have no hold; in these parts probably the mud of rivers are deposited.
In other parts are sands similar to those on land. In others are
shells, heaped up together, madrepores, corals, and other productions
of insects, which begin to unite and appear like stones; in others are
fragments of stones, gravel, and often entire stones and marble. For
example, in the Maldivian islands the buildings are made of a hard
stone weighed up from several fathoms under water. At Marseilles very
good marble is obtained from the bottom of the sea, which, so far from
wasting and spoiling stone and marble, in our discourse on minerals,
we shall prove they are formed and preserved therein; whereas the sun,
earth, air, and rain water, corrupts and destroys them.
The bottom of the sea must be composed of the same matters as our
habitable land, because the very same substances are contained in the
one as the other; places are found at the bottom of the sea, covered
with shells, madrepores, and other productions of sea matters, as we
meet with on earth an infinity of quarries and banks of chalk and other
matters replete with the same sort of shells, madrepores, &c. so that
in all respects the dry parts of the globe resemble those covered by
the water, both in composition of matters, and inequalities of the
superfices.
It is to these inequalities at the bottom of the sea, we must attribute
the origin of currents, for if the bottom was equal and level, there
would be no other current than the general motion from east to west,
and a few others which might be caused by the action of the winds; but
a certain proof that most currents are produced by the flux and reflux,
and directed by the inequalities at the bottom of the sea, is, that
they regularly follow the tides, and change their direction at each ebb
and flow. See Pietra della Valle on the subject of the currents of the
gulph of Cambay, and the accounts of all navigators, who unanimously
assert that in those parts where the flux and reflux of the sea is the
most violent, the currents are also most rapid.
Therefore it cannot be doubted but that the tides produce currents
whose direction always answers that of the opposite hills and all
mountains between which they flow. Currents produced by winds, also
follow the direction of those hills which are under the water, seldom
running opposite to the wind which produces them, any more than those
which are occasioned by the tides follow the direction of their
original cause.
To give a clear idea of the productions of currents, we shall first
observe they are to be met with in every sea; that some are rapid,
and others slow; that some are of great extent, both in length and
breadth, and others short and narrow; that the same cause, whether the
wind or tides, which produces these currents, frequently gives to each
of them a velocity and direction very different; that a north wind,
for example, which should give the water one general motion towards
the south, on the contrary, produces a number of currents, separated
from each other, and very different both in extent and direction; some
flowing towards the south, others south-east, and others south-west;
some are very rapid, others slow; some long and broad, others short
and narrow; in fact, their motions are so various that we have no idea
left of their original cause. When a contrary wind succeeds, all these
currents take an opposite course, and follow in a contrary direction,
precisely in the same manner as would be the case upon land between two
opposite and adjacent hills, provided it was covered with water, as
is seen at the Maldiva and all the islands of the Indian seas, where
the currents run, and the winds blow, for six months in a contrary
direction. The same remark has been made on currents between shoals
and sandbanks. In general all currents, whether caused by the motion
of flux or reflux, or the action by the wind; have the same extent and
direction throughout their whole course, yet differ from each other
in most respects, which can proceed only from the inequalities of the
hills, mountains, and vallies, at the bottom of the sea, it being
certain that the current between two islands follows the direction of
the coasts; and the same is observable between banks of sand, shoals,
&c. we must, therefore, look on the hills and mountains of the bottom
of the sea as banks which direct the current; and hence a current is a
river, the breadth of which is determined by that of the valley through
which it flows: its rapidity depends on the force which produces it,
combined with the breadth, of the interval through which it must
pass: and its direction is traced by the position of the hills and
inequalities between which it must take its course.
We shall now give a reason for the singular correspondence between the
angles of mountains and hills, which are to be met with in every part
of the world. We have already remarked that when a river, &c. forms an
elbow, one of the borders forms on one side a projection inland, and
the other forms a point from land, and that through all the sinuosities
of their course this correspondence is always found. This fact is
founded on the laws of hydrostatics. It would be easy to demonstrate
the cause of this effect; but it is sufficient that it is general and
universally known, and that all the world may be convinced of it by
their own eyes, that when the banks of a river form a projection inland
to the left hand, the other shore forms a projection from land to the
right.
Hence the currents of the sea must be looked upon as great rivers,
subject to the some laws as those on land, and will, like them, form
in the extent of their course many sinuosities, whose projections or
angles will correspond; and as the banks of currents are hills and
mountains, above or below the surface of the water, they will have
given these eminences the same form as is remarked on the shores
of rivers; therefore we must not be astonished that our hills and
mountains, which have been formerly covered by the sea, and formed by
the sediments which the waters have left, should, by the motion of
its currents, have taken this regular figure, and all the angles are
alternately opposite; they have been the shores of the currents or
rivers of the sea, and have therefore necessarily taken a figure and
direction similar to those of the shores of the rivers of the earth.
This alone, independent of the other proofs we have given, would be
sufficient to evince that the earth of our continent and islands have
been covered with waters of the ocean, and doubtless throws great light
upon the Theory which I have endeavoured to prove well founded; for it
was not sufficient to have proved that the strata of the earth were
formed by the sediments of the sea; that the mountains were elevated
by the successive accumulation of such sediments; and that they were
composed of shells and other marine productions; but it required also
a reason why the angles of mountains so exactly correspond; this could
only be done by an investigation into the real cause, which had not
hitherto been attempted, and which, being united with the rest, forms a
body of proofs as complete as may be had in physics, and establishes my
Theory to be founded on facts, independent of all hypothesis.
The principal currents of the ocean are those observed in the Atlantic
Sea, near Guinea. They extend from Cape Verd to the Bay of Fernandes.
Their motion is from west to east; that is contrary to the general
motion of the sea. These currents are so rapid that vessels sail in
two days from Moura to Rio de Benin, a course of 150 leagues; but they
require six or seven weeks to return; nor would it be possible to get
out of these climates if advantage was not taken of the tempestuous
winds which suddenly rise in them; but there are entire seasons during
which vessels cannot stir, the sea being continually calm, excepting
what arises from the currents, which is always directed towards the
coasts, and never extend more than 20 leagues from shore. Near Sumatra
there are rapid currents, which flow from south to north, and which
probably formed the gulph at Malacca. There are also considerable
currents between Java and Magellan, the Cape of Good Hope, and the
island of Madagascar, especially on the coast of Africa, between
Natal and the Cape. In the Pacific Sea, on the coast of Peru, and the
rest of America, the sea moves from south to north, and a south wind
continually blowing there seems to be the cause. The like motion
is observed on the coasts of Brazil; from Cape St. Augustine to the
Antilles; from the mouth of the Manilla strait to the Philippine
islands; and in the port of Kubuxiu at Japan[D].
[D] See Varen. Geography, page 140.
There are violent currents in the sea adjacent to the Maldivian
islands; and between those islands these currents flow, as already
observed, constantly for six months from east to west, and during the
other six months they follow the direction of the monsoons, and it is
probable they are produced by those winds.
We speak here only of currents, whose extent and rapidity are very
considerable, for in every sea there are an infinity of currents,
though of no great importance. The flux and reflux, the winds, and all
other causes which agitate the waters, produce currents, more or less
perceptible, in different parts. We have observed that the bottom of
the sea, like the surface of the earth, is overspread with mountains
intersected with inequalities and divided by banks of sand. In all
mountainous places currents will be violent; in all places where the
bottom of the sea is level they will be almost imperceptible; the
rapidity of the current will increase in proportion to the obstacles
the water meets with, or rather to the contraction of the spaces
through which they incline to pass. Between two chains of mountains the
current will be so much the stronger as the mountains are near. It will
be the same between two banks of sand, or two neighbouring islands. It
is also remarked in the Indian ocean, which is divided with an infinity
of islands and banks, there are rapid currents throughout, which render
the navigation of that sea dangerous.
It is not inequalities at the bottom of the sea alone which form
currents, but the coasts themselves have a similar effect, as the water
is repelled at greater or lesser distances: this repulsion of the
waters is a kind of current which circumstances can render continual
and violent; the oblique position of a coast, the vicinity of a bay,
or of some great river, a promontory; in one word, every particular
obstacle which opposes the general motion, will always produce a
current. Now, as nothing is more irregular than the bottom and borders
of the sea, we must cease from being surprised at the great number of
currents which every where appear.
All currents have a determinate breadth, which depends on that of
the interval between the two eminences which serves it for a bed.
The currents flow into the sea as rivers flow on land, and they
produce similar effects. They form their bed, and give to eminences
corresponding angles. In one word, it is these currents which hollowed
our vallies, formed our mountains, and gave to the surface of the
earth, when it was under water, the form it now retains.
If any doubt of the correspondence of the angles of mountains remains,
I appeal to the sight of every man who makes the observation. Every
traveller, with the smallest attention, will perceive that the opposite
sides of a hill exactly correspond. Whenever the hills to the right of
the valley form a projection, those opposite recede to the left. These
hills have also nearly the same elevation, and it is very rare to see
any great inequality of height in the two hills separated by a valley.
I can assert, that the more I have looked on the circumference and
heights of hills, the more I have been convinced of the correspondence
of the angles, and of the resemblance they have with the beds and
borders of rivers; and it is by reiterated observations on this
surprising regularity and resemblance that my first ideas of this
Theory of the Earth arose. Let us add to these observations that of the
parallel and horizontal situation of the strata, that of the shells
being dispersed throughout the earth, and incorporated in every matter;
and it must be admitted, that on a subject like this we cannot have a
greater degree of probability.
ARTICLE XIV.
OF REGULAR WINDS.
Nothing can appear more irregular and variable than the force and
direction of winds in our climates; but there are countries where this
irregularity is not so great, and others where the winds constantly
blow in one direction, and with almost the same degree of strength.
Although the motion of the air depends on a great number of causes,
there are nevertheless principal ones, of which it is difficult to
estimate the effects, because of the modifications from secondary
causes. The most powerful cause is the heat of the sun, which produces
successively a considerable rarefaction in different parts of the
atmosphere, and gives rise to an east wind that constantly blows
between the tropics, where rarefaction is the greatest.
The force of the sun's attraction, and even that of the moon on the
atmosphere, are inconsiderable in comparison with that just mentioned;
it is true, this force produces in the air a motion similar to that
of the flux and reflux in the sea, yet it must not be supposed that
the air, because it has a spring, and is 800 times lighter than water,
receives, by the action of the moon, a more considerable motion than
that of the waters of the sea; for the distance of the moon being the
same, a sea of any fluid matter will have nearly the same motion,
because the force which produces it penetrates the matter, and is
proportional to its quantity; thus a sea of water, air, or quicksilver,
would elevate itself nearly to the same height, by the action of the
sun and moon; hence we see that the the influence of the planets
in the atmosphere is not considerable, and although it must cause a
slight motion of the air from east to west, this motion is insensible
in comparison with that produced by the heat of the sun; but as the
rarefaction will be always greatest when the sun is at the zenith, the
current of air must follow the sun, and form a constant wind from east
to west. This wind blows continually over the sea in the torrid zone,
and in most parts of the land between the tropics; it is this wind
we feel at the sun's rising; and in general the east winds are more
frequent and impetuous than the west; this general wind from east to
west extends even beyond the tropics, and blows so constantly in the
Pacific Sea, that vessels which sail from Acapulco to the Philippines,
perform their voyage, which is more than 2700 leagues, without any
risque, and almost without any need of directing their course. In the
Atlantic, between Africa and Brazil, this wind is also constant: it is
felt also between the Philippines and Africa, but not in so constant a
manner, by reason of the islands, and different obstacles that are met
with in that sea; for during the months of January, February, March,
and April, it blows between the Mozambique coast and India, but during
the other months, it gives place to different winds: and although this
east wind is less felt on the coasts than in the open sea, and still
less in the middle of continents than on the coasts; nevertheless there
are places where it blows almost continually, as on the east coasts of
Brazil, on the coasts of Loango, in Africa, &c.
This east wind continually blowing under the line, is the cause, that
sailing from Europe to America, the course of the vessel is directed
from the north to the south, along the coasts of Spain and Africa, to
within 20 degrees of the equator, where this east wind is met with,
which carries them directly to the coasts of America. The voyage from
Acapulco to the Philippine islands, is made in two months by the favour
of this east wind: but the return from them to Acapulco is longer and
more difficult. At 28 or 30 degrees on this coast from the line, the
western wind is nearly as constant, which is the reason that vessels
returning from the East Indies to Europe, do not follow the same track
as in going; those from New Spain sail north along the coasts till they
arrive at the Havannah, and from thence they continue northward, until
they meet with the westerly winds which carry them to the Azores and
afterwards to Spain. So likewise in the South Sea, those which return
from the Philippines, or China, to Peru, or Mexico, sail north as far
as Japan, and navigate under that parallel to a certain distance from
California, from whence, coasting along New Spain, they arrive at
Acapulco. These winds do not always blow from one point, but in general
from the south-east from April to November, and from the north-east
from November to April.
The east wind, by its action, increases the general motion of the
sea from east to west; it also produces currents which are constant,
some flowing from east to west, others from west to east; and from
the east to the south-west or north-west, following the direction of
the eminencies and chains of mountains at the bottom of the sea, the
vallies that divide them serving as channels to these currents. The
alternative winds which blow sometimes from the east, and sometimes
from the south, produce also currents which change their direction at
the same time with these winds.
The winds which blow continually for some months, are generally
followed by contrary winds, and therefore mariners are obliged to wait
for that which is favourable to their voyage. When these winds change,
a calm or dangerous tempest generally ensues, and which continues for
several days, sometimes a month, and has been known for more than two.
These general winds caused by the rarefaction of the atmosphere, are
differently combined and modified by different causes in different
climates. In that part of the Atlantic, under the temperate zone,
the north wind blows almost constantly during the months of October,
November, December, and January, which makes those months the most
favourable to embark from Europe to India, in order to pass the line
by the aid of these winds; and it is known by experience, that ships
which quit Europe in the month of March frequently do not arrive
sooner at Brazil than those which sail in the October following. The
north wind almost continually reigns during winter in Nova Zembla, and
other northern coasts. The south wind blows during the month of July
at Cape de Verd, when the rainy season, or winter of these climates
sets in. At the Cape of Good Hope the north-west wind blows during
the month of September. At Patna, in the East Indies, the north-west
wind blows during the months of November, December, and January, and
produces heavy rains; but the east wind blows during the other nine
months. In the Indian ocean, between Africa and India, as far as the
Malacca islands, the monsoons reign from east to west from January to
the beginning of June, the west winds begin in the months of August or
September; during the interval of June and July, there are dreadful
tempests generally from the north winds; but on the coasts these winds
vary much more than in the open sea.
In the kingdom of Guzarat, and on the coasts of the neighbouring sea,
the north winds blow from March till September, and during the other
months south winds almost always reign. The Dutch, to return from Java,
generally set sail in the month of January or February, when they have
the assistance of an easterly wind which is felt as far as the 18th
degree of South latitude; afterwards they meet with the south winds
which carry them to St. Helena[E].
[E] See Varen. Geography, gener. cap. 20.
There are regular winds produced by the melting of snows, which the
ancient Greeks have noticed. During summer a north-east wind, and
in winter one from the south-east, were noticed in Greece, Thrace,
Macedonia, the Egean sea, and as far as Egypt and Africa; the same kind
of winds have been remarked at Congo, at Guzarat, and at the extremity
of Africa, which are all produced by the melting of the snows. The flux
and reflux of the sea also produce regular winds which remain only a
few hours, and in many places winds are observed to blow from the land
during night, and from the sea during the day, as on the coasts of New
Spain, Congo, the Havannah, &c.
The north winds are pretty regular in the polar circles; but the nearer
we approach the equator, the weaker they become: a circumstance equally
common to the two poles.
In the Atlantic and Ethiopian ocean within the tropics there is an
east wind which blows all the year without any considerable variation,
excepting some few small places, where it changes according to
circumstances and the position of the coasts. First, near the coasts
of Africa, having passed the Canary islands, about the 28th degree
of north latitude, a fresh wind blowing from the north-east or
north-north-east, is sure to be met with; this wind accompanies the
vessels to the 10th degree of the same latitude; about 100 leagues
from the coast of Guinea; where at the 4th degree north latitude they
meet with calms and tornadoes. Secondly, in going to America by the
Caribbee islands, this wind is found to veer more and more to the east,
in proportion as they approach the coast. Thirdly, the limits of these
variable winds in the Atlantic, are greater on the American coasts than
on those of Africa. A south or south-west wind blows continually all
along the coast of Guinea for a space of 500 leagues from Sierra Leona
to the island of St. Thomas; the narrowest part of that sea is from
Guinea to Brazil, being not more than 500 leagues across. Nevertheless,
ships which sail from Guinea do not direct their course straight to
Brazil, especially when they sail in the months of July and August, for
the purpose of taking advantage of the south-east winds which reign at
that time[F].
[F] See Abridg. Phil. Tran. vol. II, page 129.
In the Mediterranean the east wind blows from the land in the evening
at the sun's setting, and the west wind from the sea at its rising in
the morning. The south wind, which is commonly attended with rains,
and which generally blows at Paris, Burgundy and Champagne about the
beginning of November, gives place to mild and temperate breezes that
produce that fair weather vulgarly called the summer of St. Martin's.
Doctor Lister pretends that the east wind that blows between the
tropics all the year, is produced by the vapour of the plant called sea
lentil, which is extremely plentiful in those climates, and that the
difference of the winds on the land proceeds only from the different
disposition of the trees and forests; and he very seriously gives this
ridiculous imagination for a cause of the wind, by saying, that at noon
the wind is strongest because the plants are hotter and respire the
most, and that it blows from east to west, because all plants, somewhat
like sun-flowers, turn and respire with the sun.
Other authors have mentioned the motion of the earth on its axis as the
cause of this wind: this opinion is specious; and every person, even
but little initiated in mechanics, must comprehend, that no fluid which
surrounds the earth can have a particular motion from the rotation
of the globe; that the air can have no other motion than that of the
earth, and that all turning together at one time, this rotative motion
must be as insensible in the atmosphere, as it is on the surface of the
earth.
The principal cause of the winds, as we have observed, is the heat of
the sun; on this subject we refer to Halley's Treatise in Phil. Trans.
All causes which occasion rarefaction or condensation in the air will
produce winds, whose directions will be opposite to the places where is
the greatest rarefaction or condensation.
The pressure of the clouds, the exhalations of the earth, the
inflammation of meteors, &c. are causes which also produce considerable
agitations in the atmosphere. Each of these causes combining in
different manners, produces different effects. It appears to me,
therefore, a vain attempt to assign a theory of the winds, for which
reason I shall limit myself to the study of their history.
If we could have a course of observations on the direction, power,
and variation of the wind in different climates; if this course of
observations was exact and extensive enough for us to perceive the
result of these vicissitudes of the air in every country, we should
arrive at that degree of knowledge, from which at present we are very
remote; but a short time has passed since meteorological observations
have been made, and possibly much more will pass before we know how to
employ the results of them, although they are the only means that we
have to arrive at some positive knowledge on this subject.
On the sea the winds are more regular than on land, because the sea
is an open space, in which nothing opposes their direction, while on
land mountains, forests, and towns, form obstacles which change their
course. Winds reflected by the mountains are often as impetuous as in
their first direction: these winds are very irregular, because their
course depends on the size, height, and situation of the mountains
which reflect them. The sea winds blow with greater power than the
land winds, are not so variable, and last longer. Land winds, however
violent, have moments of remission, and sometimes of quiet, but at sea
their currents are constant and continual, without any interruption.
In general on the sea the east wind, and those which come from the
poles, are stronger than the west and those which proceed from the
equator. On the land the west and south winds are more or less violent,
according to the situation of the climates. In spring and autumn all
winds are more violent than in summer or winter, and for these reasons;
first, in spring and autumn are the highest tides, and consequently
the winds that these tides produce are most violent at those seasons;
secondly, the motion which the action of the sun and moon produce in
the air is also greater in the season of the equinoxes; thirdly, the
melting of the snows in spring, and the condensation of the vapours
that the sun raises during summer, which refall in plentiful rains
during autumn, produce, or at least increase the wind; fourthly, the
change from heat to cold, or from cold to heat, cannot be made without
increasing and diminishing consequently the volume of air, which alone
must produce very high winds.
Contrary currents are often observed in the air; some clouds move in
one direction, while others, which are higher or lower, move in a
directly opposite one; but this contrariety of motion does not remain,
being commonly produced by the resistance of some large clouds that
force the wind into another course, but which returns again as soon as
the obstacle is dissipated.
The winds are more violent in mountainous places than in plains, and
increase until we reach the common height of the clouds, that is to
say, to about one quarter, or one third of a league perpendicular
height; beyond that height the sky is generally serene, at least during
the summer, and the wind gradually diminishing. It is even asserted to
be quite insensible at the summit of the highest mountains; but these
summits being covered with snow and ice, it is natural to suppose that
this region of air is agitated by the wind when the snow falls, and
only during summer that the winds are not to be perceived. In summer
the light vapours which are raised above the summit of these mountains
fall in the form of dew, whereas in winter they condense and fall in
snow or ice, which in winter may raise considerable winds, even at that
height.
A current of air increases in velocity where the space of its passage
is straitened: the same wind which was moderate in an open plain
becomes violent in passing through a narrow passage in a mountain, or
between two lofty buildings; and its most violent action is at the top
of these structures or mountains, for air being compressed by these
obstacles, its density and mass becomes increased, and as the velocity
remains, the force or momentum of the wind naturally becomes much
stronger. This is the cause that near a church or castle the winds seem
to be stronger than at a distance from them. I have often remarked,
that the wind reflected from a lone building is more violent than the
direct wind which produced it. This can only be occasioned by the
impelled air being compressed against the building, and by that means
adds to its force.
The density of the air being greatest at the surface of the earth, we
might be led to imagine that the greatest action of the wind should be
there also; and I indeed think this is really the case when the sky is
serene; but when it is covered with clouds, the most violent action
of the wind is at the height of these clouds, which generally fall in
rain or snow. The strength of the wind, therefore, must be estimated,
not only by the velocity, but also by the density of the air; for it
will often happen that one wind, which shall have no more velocity than
another, will, nevertheless, root up trees and overturn buildings,
only from the air impelled by this wind being denser; and this evinces
the imperfection of the machines invented to measure the velocity of
the wind.
Particular winds, whether direct or reflected, are more violent than
general ones. The interrupted action of land-winds depends on the
compression of the air, which renders each blast much more violent than
if the wind blowed uniformly. A strong continued wind never occasions
such disasters as the rage of those produce which blow, as it were, by
fits; but we shall give examples thereof in the following article.
We may consider the winds, and their directions, under general points
of view, from which possibly we may derive useful instructions; for
example, we might divide the winds into zones. The east wind, which
extends to about 25 or 30 degrees on each side the equator, exerts its
action round the globe in the torrid zone; the north wind almost always
as constantly in the frigid zones. Therefore it may be said that the
east wind occupies the torrid zone, the north wind the frigid zones,
and with respect to the temperate zone, the winds which reign there are
merely currents of air produced by these two winds, whose direction
tends to the eastern points. With respect to the westerly winds, which
often reign in the temperate zones, both in the Pacific and Atlantic
Oceans, they may be regarded as winds reflected by the lands of Asia
and America, deriving their origin from the east and north winds.
Although we have said that, generally speaking, the east winds reign
around the globe to about 25 or 30 degrees on each side the equator,
it is nevertheless certain, that in some parts they do not extend so
far, and their direction is not always from east to west, for on this
side the equator it is east-north-east, and beyond the equator it is
east-south-east, and the further we remove from the equator the more
the direction is oblique. The equator is the line under which the
direction of the wind from east to west is the most exact; for example,
in the Indian ocean, the general wind from east to west scarcely
extends beyond 15 degrees. Sailing from Goa to the Cape of Good Hope
this wind is not felt till we have past the equator; but after arriving
at the 12th degree south latitude, it continues to the 28th degree. In
the sea which divides Africa from America there is an interval from
the 4th degree north latitude to the 10th or 11th degree south, where
this general wind is not perceivable; but beyond the 10th or 11th
degree it reigns as far as the 30th.
There is also much exception with regard to the trade winds, whose
motion is alternative. Some remain a longer or a shorter time, others
extend to greater or less distances; others are more or less regular,
and more or less violent. Varenius speaks thus of a principal phenomena
of these winds. "In the ocean between Africa and India, as far as
the Malaccas, the east winds begin to reign in January and last to
the beginning of June; in August or September the west winds begin
and continue during three or four months. In the interval of these
monsoons, that is from the end of June to the beginning of August,
there is no wind on that sea, but they have violent storms which come
from the north.
"These winds are subject to the greatest variations near the land, for
ships cannot depart from the Malabar coast, nor other western ports on
the coasts of the peninsula of India, to sail to Africa, Arabia, or
Persia, but from January to April or May; for from the end of May, and
during the months of June, July, and August, there are such violent
tempests from the north or north-east that ships are not able to keep
the sea. On the other side of this peninsula, in the sea which bathes
the Coromandel coast, these tempests are not known.
"To sail from Java, Ceylon, and many other places, to the Malacca
islands, the month of September is the most proper time, because the
west wind begins to blow in these parts; nevertheless, at 15 degrees
south of the equator, we lose this west wind and meet with the general
winds, which blow south-east. To sail from Cochin to Malacca they
depart in March, because the west winds begin to blow at that time;
therefore these westerly winds blow at different times in different
parts of the Indian sea; and it is necessary to sail at different
periods in going from Java to the Malaccas, from Cochin to Malacca,
from Malacca to China, and from China to Japan.
"At Banda, the west winds finish at the end of March, calms reign
during April, in May the east winds begin again with great violence.
At Ceylon, the west winds begin about the middle of March, and remain
till the beginning of October, when the east or rather north-east wind
returns. At Madagascar, from the middle of April to the end of May, the
north and north-west winds are constant; but in February and March,
the east and south winds reign. From Madagascar to the Cape of Good
Hope, the north and collateral winds blow during March and April. In
the Gulph of Bengal, the south wind prevails after the 20th of April,
before which time the south-west or north-west winds are predominant.
The west winds are also violent in the sea of China, in June and July,
which is likewise the most suitable season to go from China to Japan;
but to return from Japan to China, February and March are preferred,
because the east or north-east winds prevail.
"There are winds which may be regarded as peculiar to certain coasts;
for example, the south wind is almost continually on the coasts of
Chili and Peru; it begins at the 46th degree south latitude, and
extends beyond Panama, which renders the voyage from Lima to Panama
much easier performed than the return. The west wind blows continually
on the Magellanic coasts, and in the straits of Le Maire. The north and
north-west winds almost continually reign on the Malabar coast. The
north-west wind is very frequent on the coast of Guinea. The westerly
winds reign on the coasts of Japan, in the months of November and
December."
The alternative, or periodical winds, which we have just been speaking
of, are sea winds; but there are also land winds which are periodical,
and return either at a certain season, or in certain days, or even at
certain hours; for example, on the Malabar coast, from September to
April a land wind blows from the eastern side; it generally commences
at midnight, and finishes at noon, and is not felt beyond 12 or 15
leagues from the coast; and from noon till midnight a gentle wind blows
from the west. On the coast of New Spain, in America, and on that of
Congo, in Africa, land winds reign during the night, and sea winds
during the day. At Jamaica the winds blow from all parts of the coast
at once during the night, and therefore vessels cannot go in, nor
depart from it with safety, but in the day time.
In winter the port of Cochin is not to be entered, nor can any vessel
quit it, because the winds blow with such impetuosity, that ships
cannot remain at sea; and besides the west winds, which blow with such
fury, bring to the mouth of the river so great a quantity of sand as
prevents the possibility of ships of any size from entering it during
six months of the year; but the east winds which blow during the other
six months repel these sands, and render the entrance of the river
free. At the strait of Babelmandel there are south-east winds which
reign throughout the season, and are always succeeded by north-east. At
St. Domingo there are two different winds which regularly rise almost
every day, the one a sea wind proceeding from the east, and commences
at 10 o'clock in the morning; the other a land wind comes from the
west, rises at six or seven o'clock in the evening, and remains all
night. There are many other facts of this nature to be extracted from
travellers, the knowledge of which might perhaps lead to a history
of the winds, which would be a useful work equally to navigation and
physics.
ARTICLE XV.
OF IRREGULAR WINDS, HURRICANES, AND OTHER PHENOMENA, CAUSED BY THE
AGITATION OF THE SEA AND AIR.
The winds are more irregular on the land than on the sea, and in high
places than in low. The mountains not only alter the direction of
winds, but even produce some which are either constant or variable
according to different causes. The melting of snow upon the summits of
mountains, generally produces constant winds, which sometimes remain a
considerable time; the vapours that are stopt by mountains accumulate
there, and produce variable winds, very frequent in all climates:
and there are as many variations in the motions of air, as there
are inequalities on the surface of the earth. We can therefore give
only examples, and relate circumstances which are attested; and as we
are deficient in a course of observations on the variation of winds,
and even of the seasons in different countries, we do not pretend to
explain all the causes of these differences, but confine ourselves to
those which appear the most probable.
In straits, on all projecting coasts, at the extremity of all
promontories, peninsulas and capes, and in all narrow bays, storms are
frequent; but without these there are some seas much more tempestuous
than others. The Indian ocean, the Japan and the Magellan seas, that of
the African coast beyond the Canaries, and on the other side towards
the coast of Natal and the Red Sea, are very liable to storms. The
Atlantic is more stormy than the ocean, which from its tranquillity is
called the Pacific Sea; this sea, however, is not absolutely tranquil,
except between the tropics, for the nearer we approach the poles,
the more we are subject to variable winds, whose sudden changes are
frequently the cause of tempests.
All continents are subject to variable winds, which often produce
singular effects; in the kingdom of Cassimir, which is surrounded by
the mountain of Caucasus, at the mountain Pirepinjale, extraordinary
and sudden changes are experienced; we pass, in less than an hour's
travelling, from summer to winter; at this place are two winds, a
north and south, and which, according to Bernier, we successively feel
in less than 200 feet distance from each other; the position of this
mountain must be singular, and merit observation. In the peninsula of
India, which is crossed from north to south by the mountains of Gate,
it is winter on one side, and summer on the other at the same time.
The like difference is met with on the two sides of Rozalgate Cape in
Arabia; the sea to the north of the cape is perfectly tranquil, while
in the south violent tempests are experienced. It is the same in the
island of Ceylon; winter and high winds are experienced in the northern
parts of the island, while in the southern there is fine summer
weather. This contrariety of seasons at the same time not only happens
in many parts of the Indian continent, but also in many islands; for
example, at Cerem, a long island in the vicinage of Amboyna, they
have winter in the northern part, and summer at the same time in the
southern, and the interval that divides the two seasons is not above
three or four leagues.
In Egypt they have a south wind in summer, so hot as to prevent
respiration, and raises such great quantities of sand, that the sky
seems covered with thick clouds; this sand is so fine, and driven with
such force, that it penetrates even into the closest chests. When these
winds last many days they cause epidemical diseases, which are often
followed by a great mortality. It seldom rains in Egypt, nevertheless
every year there are some days of rain in the months of December,
January, and February. Thick mists are more frequent there than rain,
especially in the environs of Cairo; these mists begin in November,
and continue all the winter; and during the whole year there falls so
plentiful a dew, even when the sky is serene, that it might be taken
for a slight rain.
In Persia winter begins in November and lasts till March: the cold
is intense enough to form ice: much snow falls on the mountains, and
often a little in the plains. From March to May the winds blows with
great violence, and bring heat with them. From May to September, the
sky is serene, and the heat moderated by fresh breezes, which rise
every evening and remain till morning. In autumn they have violent
winds, like those of the spring; nevertheless, although these winds
are very violent they scarcely ever produce tempests or hurricanes;
but in summer there often arises along the Persian Gulph a very
dangerous wind, called by the natives Samuel; it is still hotter and
more terrible than that of Egypt. This wind is mortal, and acting
like an inflamed vapour, it suffocates every person unfortunately
enveloped within its vortex. In summer there also rises a wind of the
same kind along the Red Sea, which suffocates men and cattle, and
which conveys so great a quantity of sand that many persons conceive
this sea will in time be choaked up with what falls therein. There
are often clouds of sand in Arabia which darken the air and form
dangerous whirlwinds. At Veru Cruz, when the hot north winds blow, the
houses of the town are almost buried under the sand. In summer hot
winds rise also at Negapatam, in the peninsula of India, likewise at
Petapouli and Masulapatan. These burning winds, which destroy people,
are fortunately of short duration, but they are very violent, and the
greater swiftness they come with the more dreadful are their heats,
whereas all other winds refresh so much the more as their velocity is
greater. This difference proceeds from the degree of heat in the air,
for while the heat of the air is not so great as that of the body of
animals, the motion of the air is refreshing; but if the heat of the
air exceeds that of the body, then its motion heats and burns. At
Goa the winter, or rather the rainy and tempestuous season, is May,
June, and July, and without which rains the heat would be perfectly
unsupportable in that country.
The Cape of Good Hope is famous for its tempests, and the singular
cloud which produces them. This cloud appears at first like a small
round spot in the sky, called by the sailors the Ox's Eye. Probably its
appearing so minute is owing to its exceeding great height.
Of all travellers who have spoken of this cloud, Kolbe appears to have
the most examined it with attention; his words are, "The cloud seen
on the mountains of the Table, or of the Devil, or of the Wind, is
composed, if I am not deceived, of an infinity of small particles,
impelled first against the mountains of the Cape towards the east,
by the easterly wind which blows during almost the whole year in the
torrid zone; these particles are stopt in their course by these high
mountains, and collect on their eastern side; they then become visible
and form these assemblages of clouds, which being incessantly driven
by the east wind, rise to the summit of these mountains; they do not
long remain there at rest, but being obliged to advance, they ingulph
themselves between the hills before them, where they are bound and
confined as in a canal; the wind presses them from above, and the
opposite sides of the two mountains retain them in a direct line: in
advancing they arrive at the foot of a mountain, where the country is
a little more open, they then expand, and become again invisible; but
they are shortly driven against other mountains, by clouds which are
behind them, and thus proceed with much impetuosity, until they arrive
at the highest mountains of the Cape, which are those of the Wind, or
Table, where they have to encounter a wind blowing in an exact contrary
direction; this occasions a dreadful conflict, for the vapours being
impelled behind and repelled before, produce horrible whirlwinds
either on the high mountains of the Table, or adjacent vallies. When
the north-west wind yields, the south-east increases and continues to
blow with more or less violence for six months, it reinforces itself
while the cloud of the Ox's Eye is thick, because the vapours collected
behind press forward, and it diminishes as soon as its thickness is
lessened, because there are fewer particles and less pressure, and it
is entirely lowered when the Ox's Eye is no longer apparent, because no
new or not sufficient vapours any longer come from the east.
"All the circumstances attending this phenomenon lead to an hypothesis,
which well explains every part of them: First, behind the mountain of
the Table we remark a train of light white mists, which commencing on
the eastern descent of this mountain, incline to the sea, and occupy
the mountains of Stone throughout all their extent; I have often
contemplated this train, which according to my opinion was caused by
the rapid passage of the vapour above-mentioned, from the mountains of
Stone to that of the Table.
"Secondly, These vapours must be extremely embarrassed in their road,
by the frequent shocks and counter shocks caused, not only by the
mountains, but also by the south and east winds which reign at places
circumjacent to the Cape: I have already spoken of the two mountains
called Hanging Lip and Norvege, situate on the points of False Bay;
when the particles which I conceive are impelled on these mountains by
the easterly winds, they are repelled from them by the south, which
carry them on the neighbouring mountains; they are stopt there and
appear like clouds, which is often the case upon the mountains of
False Bay. These clouds are frequently very thick above the land which
the Dutch are in possession of, on the mountains of Stenltenborch, of
Drakenstein, and Stone, but particularly on the mountains of the Table,
and of the Devil.
"In short, what confirms me in my opinion is, that constantly two or
three days before the south-east wind blows on the Lion's Head, small
black clouds are perceived above it; these clouds, according to my
opinion, are composed of the particles or vapours which I have spoken
of. If the north-west wind prevails when they arrive there, they are
stopped in their course, but are never driven to a great distance till
the south-east winds commence."
The first mariners who approached the Cape of Good Hope were ignorant
of the effects of these clouds, which appear to form in the air so
slowly, and without any motion, but which in a moment excite the most
dreadful storms that precipitate the largest vessels to the bottom of
the sea. In the country of Natal, a small cloud similar to the Ox's
Eye at the Cape, produces the like effects. In the sea between Africa
and America, especially near the equator, these kind of tempests very
often arise. Near the coast of Guinea, three or four of these storms
sometimes happen in a day; they are also caused and announced by small
black clouds; the rest of the sky being generally serene, and the sea
perfectly calm. The first blast which issues from these clouds is
furious, and would sink ships in open sea, if they did not take the
precaution to furl the sails. It is principally in April, May, and
June these tempests are experienced on the coast of Guinea, because no
regular wind blows there. The stormy season on the coasts of Loango is
in January, February, March, and April. On the other side of Africa,
at Cape of Gardafu, these kinds of tempests rise in May, and the clouds
which produce them are generally in the north like those of the Cape of
Good Hope.
All these tempests are produced by winds which issue from a cloud,
and which have directions either from north to south, or north-east
to south-west, &c. but there are other kinds which are still more
violent, and in which the winds seem to proceed from every quarter at
once; they have a whirling motion, which nothing can resist. A calm
generally precedes these horrible tempests; but in an instant the fury
of the winds raises the waves as high as the clouds. There are parts
of the sea which cannot be approached, from there being constantly
calms and hurricanes in them. The Spaniards have called these places
Calms and Tornados; the most considerable are near Guinea, at two or
three degrees north latitude; they are 300 or 350 leagues in length by
as many in breadth, which forms a space of more than 100,000 leagues
square.
When contrary winds come all at once in the same place, as to a centre,
they produce whirlwinds by the contrariety of their motions; but when
these winds meet with others in opposition, which counterbalance their
action, they then revolve in a considerable circle, and occasion a dead
calm, through which it is impossible for vessels to make their way.
These places of the sea are marked in Senex's globes. I am inclined
to think that the contrariety of the winds alone could not produce
this effect if the direction of the coasts, and the particular form of
the bottom of the sea, did not contribute thereto. I imagine that the
currents caused by the winds, but directed by the form of the coasts
and the inequalities of the bottom of the sea, end at these places, and
that their opposite and contrary direction, in a plain surrounded on
all sides by a chain of mountains, is the real cause of these tornados.
Whirlpools appear to be no other than the eddies of the water formed
by the action of two or more opposite currents. The Euripus, so famous
for the death of Aristotle, alternately absorbs and rejects the water
seven times in twenty-four hours. This whirlpool is near the Grecian
coast. The Charybdis, which is near the straits of Sicily, rejects and
absorbs the water thrice in twenty-four hours. We are not quite certain
as to the number of alternative motions in these whirlpools. Doctor
Placentia, in his treatise, says, that the Euripus has irregular
motions for eighteen or nineteen days every month, and regular ones
for the other eleven; that in general it swells about one foot, and
seldom two: he says likewise that authors do not agree as to the tides
of the Euripus; that some assert it is twice, some seven, others
fourteen times in twenty-four hours, but that Loirius having examined
it attentively, observed it rose regularly every six hours, and with so
violent a motion, that it was sufficient to turn the wheel of a mill.
The greatest known whirlpool is that in the Norway sea, which is
affirmed to be upwards of twenty leagues in circumference. It absorbs
for six hours water, whales, ships, and every thing that comes near it,
and afterwards returns them in the same quantity of time as it drew
them in.
It is not necessary to suppose there are holes and abysses in the
bottom of the sea which swallow up the waters continually; to assign
a reason for whirlpools, it is well known that when water has two
contrary directions, the combination of these motions produce a
whirling, and seem to form a void place in the centre. It is the same
with respect to whirlpools in the sea, they are produced by two or
three contrary currents; and as the flux and reflux, which run every
six hours in contrary directions, are the principal cause of currents,
it is not astonishing that whirlpools, which result from them, attract
and swallow up all that surrounds them, and afterwards reject all they
have absorbed in the same portion of time.
Whirlpools, therefore, are produced by opposite currents, and likewise
by the meeting of contrary winds. These whirlwinds are common in the
sea of China and Japan, near the Antilles, and in many other parts of
the sea, particularly near projecting lands and high coasts; but they
are still more frequent upon land, and their effects are sometimes
prodigious. "I have seen," says Bellarmin, "an enormous ditch dug up
by the wind, and the earth thereof carried to a distance; so that the
place from whence it had been taken appeared a frightful hole, and the
village upon which it was dropped was entirely buried with it."
In the history of the French Academy, and in the Philosophical
Transactions, are the detail of the effects of many hurricanes, which
appear inconceivable and scarcely credible, if the facts were not
attested by a great number of intelligent testimonies.
It is the same with respect to water-spouts, which mariners never see
without fear and amazement; these are very frequent near certain coasts
of the Mediterranean, especially when the sky is cloudy and the wind
blows at the same time from various coasts. They are more common near
the coasts of Laodicea, Grecgo and Carmel, than in other parts of the
Mediterranean. Most of them are large cylinders of water which fall
from the clouds, although it appears, when we are at some distance,
that the water of the sea rises up to the clouds.[G]
[G] See Shaw's Travels, vol. 2. p. 56.
But there are two kinds of water-spouts, the first of which, alluded to
above, is no other than a thick compressed cloud, reduced to a small
space by contrary winds, which, blowing at the same time from many
corners, give it a cylindric form, and causes the water to fall by its
own weight. The quantity of water is so great, and the fall so sudden
and precipitate, that if unfortunately one of these spouts breaks
on a vessel, it shatters it to pieces and sinks it in an instant.
It is asserted, and possibly with foundation, that these spouts
may be broken and destroyed by the commotion which the firing of
cannons excites in the air; which answers to the effect of dispersing
thunder-clouds by the ringing of bells.
The other kind of water-spout is called a typhon, which many authors
have confounded with the hurricane, in speaking of the storms of the
Chinese sea, which is in fact subject to both. The typhon does not
descend from the clouds, but rises up from the sea with great violence.
By whirlwinds, sands, earth, houses, trees, and animals, are raised
in the air, and transported to different parts; but typhons, on the
contrary, remain in the same place, and can only have subterraneous
fires for their origin; for the sea is then in the greatest agitation,
and the air so strongly filled with sulphurous exhalations, that the
sky appears covered with a copper-coloured crust, although there are no
clouds, and the sun or stars may be seen through the vapour. It is to
these subterraneous fires the warmth of the sea of China in winter must
be attributed, as these typhons are there very frequent.[H]
[H] See Acta Eud. Lips. Supplementum, vol. 1. p. 405.
Thevenot, in his voyage to the Levant, says, "we saw water-spouts in
the Persian gulph, between the islands Quesomo, Lareca, and Ormutz. I
think few people have considered water-spouts with so much attention as
I have done. I shall mention my remarks with all possible simplicity,
in order to render them plain and easy to be comprehended.
"The first that we saw appeared on the northern coast, between us
and the island Quesomo, about a gun-shot from the ship: we directly
perceived the water boiled on the surface of the sea, and was raised
about a foot: it was whitish, and the top appeared like a thick black
smoke, so that it properly resembled some burning straw, which only
smoked. It made a noise like a torrent that runs with rapidity into a
deep valley. This noise was mixed with another, similar to the hissing
of serpents: a little afterwards we perceived something like a dark
pipe, which resembled smoke ascending towards the clouds, turning
round with great velocity: this appeared about the thickness of my
finger, and the same noise still continued. After this it disappeared,
having remained somewhat less than a quarter of an hour. This over, we
perceived another on the south side, which began in the same manner
as the preceding: directly after a third made its appearance on the
west, and then a fourth by its side. The farthest of them was not
more than a musket-shot from us. They all appeared like burning heaps
of straw, a foot and a half or two feet high, and were attended with
the same noise as the first. We afterwards saw three pipes or canals
descending from the clouds to the water. They were broad at the top
and lessened downwards, something in the shape of a trumpet, or as
the paps of an animal, drawn perpendicularly down by a heavy weight.
These canals appeared of a darkish white, occasioned, as I think, by
the waters which were in them; for apparently they were formed before
the water entered, as when they were empty they were no longer to be
seen, like as a clear glass tube placed at some distance before our
eyes, is not perceptible if it is not filled with some coloured liquor.
These pipes were not strait but crooked in some places; they were not
even perpendicular, but from the clouds, where they were joined, to
the parts which drew in the water, they were very much bent; and what
is more particular, the cloud, to which the second of the three was
fastened, having been driven by the wind, this pipe followed it without
breaking or quitting the place where it drew in the water, and passing
behind the first, they had for some time the form of St. Andrew's
cross. At the beginning neither of them was more than an inch in
thickness, excepting just at the top, but afterwards the first of the
three increased considerably. The two others scarcely remained longer
than that which we saw on the north side. The second, on the south
side, remained about a quarter of an hour, but the first on that side
remained longer, and gave us some apprehensions. At first it was not
bigger than my finger, afterwards it swelled as thick as my arm, then
as my leg, and at last as the trunk of a large tree, which a man might
encompass with both his arms. We distinctly perceived water through
this transparent body, which ascended in a serpentine manner. Sometimes
it diminished in size at the top, and sometimes at the bottom, then
it exactly resembled a tube with some fluid matter pressed with the
fingers, either above to make this liquor descend, or at bottom to
cause it to ascend; and I am persuaded that it was the violence of
the wind which caused these changes, pressing the pipe in a similar
manner. After this it diminished less than my arm, then returned as
large as my thigh, and then again became very small; at last I saw the
water that was raised from the surface began to lower, and the end of
the pipe divided from it, when, by the change of light from a cloud,
it was lost to our sight; I continued, however, to observe whether
it returned, because I had remarked that the pipe of the second had
appeared to be broken in the middle, and directly after we saw it
whole. This we found was occasioned by the light which hid the half
from us, but the last we saw no more.
"These water-spouts are very dangerous, for if they fall on a vessel
they entangle in the sails so much that sometimes they raise it up,
and afterwards let it fall with such violence as to sink it; at least
if they do not lift the vessel up, they tear all the sails, or let the
water they contain fall on it, and which often sinks it to the bottom.
There cannot be the least doubt but it is by similar accidents that
many ships, of which we have heard no accounts, have been lost, since
there are but few examples of those that we have known, from certainty,
to have perished in this manner."
I suspect there are many optical illusions in the above account, but
I have recounted them as related, in order that we might compare
them with those of other travellers. The following description is by
M. Gentil, in his voyage round the world. "At eleven o'clock in the
morning, the air being filled with clouds, we perceived about our
vessel, at a quarter of a mile distant, six water-spouts, which made
a noise similar to that of water flowing in subterraneous canals, and
increased until it resembled the whistling which an impetuous wind
makes among the cordage of a ship. We at first observed the water to
boil up about a foot and a half above the surface. Above this boiling
there appeared a mixed or rather a thick smoke, which formed a kind of
canal, that ascended to the clouds. These canals inclined according as
the wind moved the clouds to which they were attached, and in spite of
the wind's impulsion they not only adhered to them, but even lengthened
and shortened themselves in proportion as the clouds rose higher or
lower in the atmosphere.
"These phenomena terrified us greatly, and our sailors, instead of
being bolder, fomented their fears by the dismal tales they told each
other. If these spouts, said they, fall on our vessel, they will lift
her up, and then she will sink by the violence of her fall. Others
contended in a decisive tone, that they would not raise the vessel
up, but if they met it in their course, being full of water, the ship
would break the communication they had with the sea, and the whole body
of the water would fall perpendicularly on the deck of the vessel and
split her to pieces.
"To prevent this misfortune the cannon was loaded, the sailors
pretending the report of a cannon, by agitating the air, dissipated
these phenomena; but we had no need of having recourse to this remedy,
for when they had run about ten minutes about the ship, some at a
quarter of a league, others at a less distance, we perceived the canals
to grow narrower by degrees, till they got loose from the surface of
the sea and then dissipated."
It appears from the description given by these two travellers, that
water-spouts are produced, at least in part, by the action of a fire or
smoke which rises from the bottom of the sea with great force, and that
they are quite different from those produced by contrary winds.
"The water-spouts, says Mr. Shaw, which I had an opportunity of seeing,
appeared as so many cylinders of water, which fell from the clouds,
although by the reflection of the columns which descend, or by the
drops which detach themselves from the water they contain, it sometimes
seems, especially when we are at some distance, that the water is drawn
up from the sea. To render a reason for this phenomena we may suppose
that the clouds being collected in one part by opposite winds, they
force them by pressing them with violence to condense and descend in
this manner."
There still remain many facts to be acquired before we can give a
complete explanation of these phenomena; it appears to me, that if
there are under the waters of the sea, at particular places, soils
mixed with sulphur, bitumen, and minerals, these matters may be
inflamed and produce a great quantity of air, which being newly
generated and prodigiously rarefied, ascends with rapidity, and may
raise these water-spouts from the sea to the sky; so likewise if, by
inflammation, the sulphurous matters which a cloud contains, a current
of air is formed, which descends perpendicularly from the clouds
towards the sea, all its water may follow the current of air, and form
a water-spout which will fall from the sky upon the sea; but it must
be allowed that the explanation of this kind of water-spout, no more
than that we have given of those produced by contrary winds, is not
satisfactory; and it might be asked why these kinds of water-spouts,
which fall perpendicularly from the clouds, are not as often seen on
the land as on the sea?
The History of the Academy, anno 1727, mentions a land water-spout
which appeared at Capestan, near Beziers; it descended from a cloud
like a black pillar, which diminished by degrees, and at length
terminated in a point upon the surface of the earth. It obeyed the wind
which blew from west to south-west. It was accompanied with a very
thick smoke, and made a similar noise to that of a troubled sea. It
tore up and carried away trees to the distance of forty or fifty feet,
marking its way by a large track, on which three carriages might have
passed each other. There appeared another pillar of the same kind, but
which soon joined the first; and after the whole had disappeared, a
great quantity of hail fell on the earth.
This kind of water-spout appears to be still different from the other
two: it is not mentioned to have contained water; and it seems, by what
I have related, and by the explanation given thereof by M. Andoque,
to the academy, that this water-spout was only a whirlwind, rendered
visible by the dust and condensed vapours which it contained.
In the same history, anno 1741, a water-spout is spoken of, seen on the
lake of Geneva; the upper part was inclined to a very black cloud, and
the lower, which was narrower, terminated a little above the water.
This phenomenon remained only a few minutes, and, at the moment it was
dissipated, a thick vapour was perceived at the part where it first
appeared; the waters of the lake boiled and seemed to make an effort
to rise up. The air was very calm during the whole time; and when it
disappeared neither wind nor rain ensued. "After all we are acquainted
with," says the historian of the academy, "concerning water-spouts, is
not this another proof that they are not formed by the conflict of the
winds, but almost always produced by volcanos or subterraneous vapours,
from which we know the bottom of the sea is not exempt? Whirlwinds
and hurricanes, which we commonly thought to be the cause of these
appearances, may possibly be only the effect, or an accidental event
thereof."
ARTICLE XVI.
OF VOLCANOS AND EARTHQUAKES.
The burning mountains, called volcanos, contain in their bowels,
sulphur, bitumen, and other matters of an inflammable nature, the
effects of which are more violent than that of gunpowder, or even
thunder, and have from the earliest ages terrified mankind, and
desolated the country. A volcano is an immense cannon, whose orifice is
often more than half a league: from this wide mouth are vomited forth
torrents of smoke and flames, rivers of bitumen, sulphur, and melted
metals, clouds of cinders and stones, and sometimes it ejects enormous
rocks to many leagues distance, which human powers united could not
move; the conflagration is so terrible, and the quantity of burnt,
melted, calcined, and vitrified matters which the mountain throws
out, is so great, that they destroy cities and forests, cover fields
an hundred and two hundred feet in thickness, and sometimes form hills
and mountains, which are only heaps of these matters piled up together.
The action of this fire, and the force of its explosion, is so violent,
that it produces by its re-action, succussions which shake the earth,
agitate the sea, overthrow mountains, and destroy the most solid towers
and edifices, even to very considerable distances.
These effects, although natural, have been looked upon as prodigies;
and although we see in miniature, by fire, effects nearly similar to
those of volcanos, yet there is something in grandeur, of whatever
nature it may be, that invariably strikes the imagination and
influences the mind, and therefore I am not surprised that some authors
have taken them for the vents of a central fire, and ignorant people
for the mouths of Hell. Astonishment produces fear, and fear is the
mother of superstition. The natives of Iceland imagine the roarings of
the volcano are the cries of the damned, and its eruptions the effects
of the rage of devils, and the despair of the wretched.
All its effects, however, arise from fire and smoke: veins of sulphur,
bitumen, and other inflammable matters, are found in the bowels of
mountains, as well as minerals and pyrites, which ferment when exposed
to air or humidity, and cause explosions proportionate to the quantity
of inflamed matters. This is the just idea of a volcano, and it is easy
for a philosopher to imitate the action of these subterranean fires;
for by mixing together a quantity of brimstone and iron filings, and
burying them in the earth to a certain depth, a small volcano may be
produced, whose effects will be exactly similar; for this mixture
inflames by fermentation, throws off the earth and stones with which it
is covered, and smokes, flames, and explodes like a real volcano.
In Europe are three famous volcanos, Mount Ætna, in Sicily, Mount
Hecla, in Iceland, and Mount Vesuvius, near Naples, in Italy. Mount
Ætna has burnt from time immemorial, its eruptions are very violent,
and the quantity of matter it throws out is so great that after digging
68 feet deep, marble pavements, and the vestiges of an ancient town
have been found buried under this thickness of matter, in the same
manner as the city of Herculaneum has been covered by the matter
thrown out from Vesuvius. New mouths in Ætna were opened in 1650,
1669, and at other times. We see the flame and smoke of this volcano
from Malta, about 60 leagues distance; it smokes continually, and
there are times when it vomits flames, stones, and matters of every
kind with impetuosity. In 1537, there was an eruption of this volcano,
which caused an earthquake in Sicily that continued for 12 days, and
which overthrew a number of houses and public structures; it ceased
by the opening of a new mouth, the lava from which burnt every thing
within five leagues of the mountain. The cinders thrown out by the
volcano were so abundant, and ejected with so much force, that they
were driven as far as Italy; and vessels at some distance from Sicily
were incommoded by them. Farelli says the foot of this mountain is 100
leagues in circumference.
This volcano has now two principal mouths, one narrower than the other;
smoke comes continually from them, but flames never issue but during
the time of eruptions; it is pretended that large stones have been
thrown out by them to the distance of 60,000 feet.
In 1683 a violent eruption caused a terrible earthquake in Sicily; it
entirely destroyed the town of Catanea, and killed more than 60,000
persons in that town, besides those which were destroyed in the
neighbouring towns and villages.
Hecla throws out its fires through the ice and snow of a frozen land;
its eruptions are nevertheless as violent as those of Ætna, and other
volcanos of southern countries. It throws out cinders, lava, pumice
stones, and sometimes boiling water: it is not inhabitable within
six leagues of this volcano, and the whole island of Iceland is very
abundant in sulphur. The history of the violent eruptions of Hecla are
recorded by Dithmar Bleffken.
Mount Vesuvius, according to the historians, did not begin burning till
the seventh Consulate of Titus Vespasian and Falvius Domitian; the top
being opened, it at first threw out stones and rocks, afterwards fire
and lava, which burnt two neighbouring towns, and emitted such thick
smoke that it obscured the light of the sun. Pliny the elder, desirous
of examining this conflagration nearer, was suffocated by the smoke.[I]
[I] See the Epistle of Pliny, jun. to Tacitus.
Dion Cassius relates, that this eruption was so violent, that cinders
and sulphurous smoke were driven as far as Rome, and even beyond the
Mediterranean into Africa. Heraclea was one of the two towns burned
by this first conflagration of Vesuvius, which, in these latter times
has been discovered at more than 60 feet deep, the surface above which
was become, by length of time, arable land and fit for culture. The
relation of the discovery of Heraclea is in the hands of the public,
and we can only wish that some person, versed in Natural History, would
examine the different matters which compose this soil of 60 feet,
attending to their disposition and situation, the alterations they have
produced or suffered, the direction they have taken, and the hardness
they have acquired.
There is an appearance that Naples is situate on a hollow ground,
filled with burning materials, for Vesuvius and Solfatera seem to have
interior communications. When Vesuvius casts out lava Solfatera emits
flames, and when the one ceases the other is extinguished. The city of
Naples is situate nearly between them.
One of the last and most violent eruptions of Mount Vesuvius was in the
year 1737.[J] The mountain vomited, by several mouths, large torrents
of burning metallic matters, which dispersed themselves over the
country, and flowed into the sea. Mons. Montealegre, who communicated
this relation to the Academy of Sciences, observed, with horror, one of
these rivers of fire, whose length, from the mountain to the sea, was
about seven miles, its breadth about 60 feet, its depth 25 or 30 palms,
and in bottoms or vallies 120: the matter which flowed was like the
scum which issues from the furnace of a forge, &c.[K]
[J] It should be remembered, as noticed by Mr. Smellie, that the
original of this work was published by our author in 1749, since when
Vesuvius has undergone several eruptions.
[K] See the Hist. Acad. an. 1737.
In Asia, particularly in the islands of the Indian ocean, there are
many volcanos; one of the most famous is Mount Albours, near Mount
Taurus, eight leagues from Herat; its summit continually smokes, and
it frequently throws out flames and burning matter in such quantities
that the surrounding country is covered with cinders. In the island of
Ternate there is a volcano which throws out matter like pumice-stones.
Some travellers assert that this volcano is most furious at the time of
the equinoxes, because certain winds then reign there, which inflame
the matter that feeds, and has fed this fire for a number of years.[L]
[L] See Argensola's Travels, vol. 1, page 21.
The island of Ternate is but seven leagues round, and is only the
summit of a mountain; it gradually ascends from the shore to the middle
of the island, where the volcano rises to a considerable height, to
the top of which it is very difficult to attain. Many rills of sweet
water descend along the ridge of this mountain, and when the air is
calm, and the season mild, this burning gulph is in less agitation
than during storms and high winds.[M] This confirms what I have said
in a former article, and seems to prove that the fire of volcanos does
not proceed from any considerable depth, but from the top, or at least
not far distant from the summit of the mountain; for if it was not so,
the high winds could not increase their combustion. There are other
volcanos in the Malaccas. In one of the Mauritius islands, 70 leagues
from the Malaccas, there is a volcano, whose effects are as violent as
those of Mount Ternate. Sorca island, one of the Malaccas, was formerly
inhabited. In the middle of this island there is a lofty mountain, with
a volcano at the top. In 1693 this volcano vomited bitumen and inflamed
matters in such a great quantity as to form a burning lake, and which
covered the whole island.[N]
[M] See the Travels of Schuten.
[N] See Phil. Trans. ab. vol. 11 page 391.
At Japan, and in the adjacent islands, there are several volcanos,
which emit flames during the night and smoke in the day. At the
Philippine islands there are also burning mountains. One of the most
famous volcanos of the islands in the Indian ocean, and the most
recent, is that near the town of Panarucan, in the island of Java; it
opened in 1586, and at the first eruption, it threw out an enormous
quantity of sulphur, bitumen, and stones. The same year Mount Gounapi,
in the island of Banda, which continued only seventeen years, opened
and ejected, with a frightful noise, rocks and matters of every kind.
There are also some other volcanos in India, as at Sumatra, and in the
north of Asia, but those are not considerable.
In Africa, there is a mountain, or rather a cavern, called
Beniguazeval, near Fez, which always emits smoke, and sometimes flames.
One of the islands of Cape de Verd, called the Fuogo, is only a large
mountain which burns continually; this volcano throws out cinders
and stones; and the Portuguese, who have attempted several times to
erect habitations in this island, have been constrained to abandon the
project through dread of the volcano. The Peak of Teneriffe, considered
as one of the highest mountains of the earth, throws out fire, cinders,
and large stones; from its top rivulets of melted sulphur flow across
the snow, where it forms veins that are distinguishable at a great
distance.
In America there are a great number of volcanos, particularly in the
mountains of Peru and Mexico; that of Arequipa is one of the most
famous; it often causes earthquakes, which are more common in Peru
than in any other country in the world. The volcano of Carrappa and
that of Malahallo are, according to the report of travellers, the most
considerable, next to that of Arequipa; but there are many others in
these parts of which we have no exact knowledge. M. Bouguer, in his
voyage to Peru, published in the Memoirs of the Academy of the year
1744, mentions two volcanos, called Cotopaxi and Pichincha; the first
at some distance from, the other near the town of Quito; he was witness
of a conflagration of Botopaxi in 1742, and of the orifice which was
made in that mountain; this eruption did no other damage than melting
the snow and producing such torrents of water, that in less than three
hours inundated a tract of country 18 leagues in extent, and overthrew
all they met with in their way.
At Mexico the most considerable volcanos are Popochampeche, and the
Popoatepec; it was near this last that Cortes passed in his voyage
to Mexico; some of the Spaniards ascended to the top, where they saw
the mouth, which was about half a league in circumference. Sulphurous
mountains are also met with at Guadaloupe, Tercera, and other islands
of the Azores; and, if we were to consider as volcanos all those
mountains which smoke, or emit flames, we might reckon more than sixty;
we have only spoken of those formidable volcanos, near which no person
dares to inhabit.
These volcanos which are in such great numbers in the Cordeliers, as I
have formerly said, cause almost continual earthquakes, which prevent
the natives from building with stone above one story high, and to
construct the upper stories of their houses with reeds and light wood.
In these mountains are also many precipices and large vents, the sides
of which are black and burnt, as in the precipice of Mount Ararat, in
Armenia, which is called the Abyss; these abysses are the mouths of
extinguished volcanos.
There was lately an earthquake at Lima, the effects of which were
dreadful. The town of Lima and Port Callao were almost entirely
swallowed up; but the evil was still greater at Callao. The sea rose
and covered every building in that town, drowned all the inhabitants,
and left only one single tower remaining. Of twenty-five ships that
were in this port, four were carried a league upon land, and the rest
were swallowed up by the sea. At Lima, which was a large town, there
remains only twenty-seven houses standing; a great number of persons
were buried in the ruins, particularly monks and religious persons, as
their buildings were higher and constructed of more solid materials
than the other houses. This misfortune happened at night, in October
1746; the shock remained fifteen minutes.
There was formerly near the port of Pisca, in Peru, a famous city,
situate on the sea shore, which was almost entirely destroyed by an
earthquake that happened the 19th of October 1682, for the sea having
extended beyond its common bounds, swallowed up this unfortunate place
with every person that was in it.
If we consult historians and travellers, we shall find relations of
many earthquakes and eruptions of volcanos, whose effects have been
as terrible as those we have just mentioned. Pesidonius, whom Strabo
quotes in his first book, relates, that a city in Phoenicia, near
Sidon, was swallowed up by an earthquake, with the neighbouring
territory, and even two thirds of Sidon; this effect was not so sudden
but that many of the inhabitants had time to avoid it by flight.
This shock extended throughout all Syria, and as far as the Cyclade
islands, and into Euboea, where the fountains of Arethusa suddenly
stopped, and did not reappear for many days after, and then by many
new springs remote from the old ones; that this earthquake did not
cease from shaking the island, sometimes in one part and sometimes
in another, until the earth opened in the valley of Lepanta, and
ejected a great quantity of lava and other inflamed matters. Pliny,
in his first book, chap. 84, relates, that in the reign of Tiberius an
earthquake happened which overthrew twelve towns in Asia: and in his
second book he mentions a prodigy caused by an earthquake. St. Augustin
records, that by a great earthquake there were towns overthrown in
Lybia. In the time of Trajan, the town of Antioch, and a great part of
the adjacent country were swallowed up by an earthquake; and in the
time of Justinian, in 528, it was a second time destroyed by the same
cause, with upwards of 40,000 of its inhabitants. Sixty years after,
in the time of St. Gregory, it felt the effects of a third earthquake,
when 60,000 of its inhabitants perished. In the time of Saladin, in
1182, most of the towns of Syria and Judea were destroyed by the same
calamity. In Calabria and Apulia, there have been more earthquakes
than in any other part of Europe. In the time of Pope Pius II. all the
churches and palaces of Naples were overthrown, and above 30,000 of
its inhabitants killed; the remainder were obliged to live in tents
till houses were built. In 1629, there were earthquakes in Apulia,
which destroyed 7000 persons, and in 1638, the town of St. Euphemia
was swallowed up, and there remains only a stinking lake in its place.
Ragusa and Smyrna, at the same time, were also almost destroyed. There
was an earthquake in 1692, which extended into England, Holland,
Flanders, Germany, and France; it was chiefly felt on the sea coasts
and near large rivers; it shook at least 2600 square leagues; it lasted
only two minutes, and the motion was more considerable on mountains
than in vallies.[O] On the 10th of July, 1688, there was an earthquake
at Smyrna, which began by a motion from west to east; the castle was
at first overthrown, its four walls being divided and sunk six feet in
the sea; this castle stood upon an isthmus, but is at present a real
island, about 100 paces distant from the land. The walls from east to
west are fallen down, those from north to south are yet standing; the
city, which is ten miles from the castle, was destroyed shortly after;
in many places the earth opened, and subterraneous noises were heard;
five or six shocks were felt as night came on, the last continued
only half a minute; the ships in the roads were shaken; the ground of
the town was lowered about two feet; not above a quarter of the town
withstood the shock, and those principally the houses which stood on
rocks; from 15 to 20,000 persons are computed to have been buried under
the ruins.[P] In 1695, an earthquake was felt at Bologna, in Italy, and
it was remarked as a particular circumstance, that the water was much
troubled a day before.[Q][R]
[O] See Ray's Discourses, page 272.
[P] See the Hist. of the Acad. des Sciences, anno 1688.
[Q] Ibid. anno 1696.
[R] See the Voyages of Mandelso.
At Tercera there happened an earthquake on the 4th of May, 1614, which
overthrew in the town of Angra eleven churches and nine chapels,
besides private houses; and in the town of Praya it was so terrible,
that scarcely an house was left standing. On the 16th of June 1628,
there was an earthquake in the island of St. Michael, the effects of
which was so great, that in a place where the sea was more than 150
fathoms deep an island was thrown up more than a league and a half
long, and upwards of 60 fathoms high. Another happened in 1691, in the
island of St. Michael, which began the 6th of July, and lasted till the
12th of the following month: Tercera and Fayal were agitated the next
morning with so much violence, that they appeared to move; but these
frightful shocks returned there only four times, whereas at St. Michael
they did not cease a moment for several days. The islanders quitted
their houses, which they saw fall before their eyes, and remained all
the time in the fields exposed to the injuries of the weather. The
whole town of Villa Franca was overthrown to its very foundation, and
most of the inhabitants buried under its ruins. In many parts the
plains rose into hills, and in others, mountains were flattened into
vallies. A spring of water issued from the earth, which flowed for four
days, and then ceased all on a sudden. The air and sea, still more
agitated, resounded with a noise which might have been taken for the
roaring of a number of wild animals. Many persons died with the fright;
the ships in the harbour suffered dangerous shocks, and those which
were at anchor, or under sail at 20 leagues distant from the islands,
received great damage. Earthquakes are frequent in the Azores, and
about twenty years before a mountain in St. Michael was overturned by
one of them.[S]
[S] Hist. of Voyages.
In Manilla, in the month of September, 1627, an earthquake levelled one
of the two mountains called Carvallos, in the province of Cagayon; in
1645, one third of the town was destroyed by a like accident, and 300
persons perished. The succeeding year it experienced another; and the
ancient Indians say they were more terrible formerly, which was the
reason they build their houses only of wood; a custom still continued,
and which the Spaniards follow.[T]
[T] See le Voyage de Gemelli Careri, page 120.
"The quantity of volcanos in this island confirms that assertion;
because at certain times they vomit forth flames, shake the earth, and
perform all the effects Pliny attributes to those of Vesuvius; that
is, they change the beds of rivers, drive back the adjacent sea, fill
with cinders the neighbouring plains, and throw out stones to great
distances, with reports louder than those of cannons.
"In 1646, a mountain in the island of Machian split by an earthquake,
with a dreadful noise; from this opening issued a number of flames,
which destroyed several plantations with the inhabitants and all that
was therein. In the year 1685, this prodigious crack was to be seen,
and probably is still apparent; it is called the path of Machian,
because it descends from the top to the bottom, like a road hollowed
out, but which at a distance appears like a path."[U]
[U] See the Hist. of the Conquest of the Malaccas, vol. ii. p. 318.
The history of the French Academy mentions in the following terms, the
earthquakes that took place in 1702 and 1703. "The earthquakes began in
Italy in October 1702, and continued, till July 1703; the country which
suffered the most by them, and where they began, is the town of Norcia,
with its dependencies under the ecclesiastical government, and the
province of Abruzzo, which are situated at the foot of the Apennines on
the south side.
"They were often accompanied with terrible noises in the air, which
also were heard without any dreadful effects, when the sky was serene.
The earthquake which happened on the 2d of February 1703, was the most
violent; it was accompanied, at least at Rome, with a great serenity
of sky and calmness in the air. It lasted at Rome half a minute, and
at Aquila the capital of Abruzzo three hours. It destroyed the whole
town of Aquila, buried 5000 persons under the ruins, and made great
havock in the environs. The vibration of the earth, according to the
observations made by the lamps in the churches, was from south to north.
"It opened two places from whence issued a great quantity of stones,
which entirely covered it and rendered it barren; after the stones they
threw out water above the height of the trees; this lasted half an
hour, and inundated the adjacent fields. The water was whitish, like
soap suds, and had not any remarkable taste.
"A mountain near Sigillo, a city twenty-two miles distant from Aquila,
had on its summit a very large plain surrounded with rocks like a wall.
The earthquake of the 2d of February, changed this plain into a gulph
of unequal breadth, whose greatest diameter is twenty-five fathoms and
the least twenty; the depth of it has not been discovered, although a
line 300 fathoms has been let down in it. At the time this opening was
made, flames were seen to issue out, and afterwards a great smoke which
lasted three days with some interruptions.
"At Genoa on the 1st and 2d of July 1703, there were two slight
earthquakes, the last was felt only by the people on the pier: at the
same time the sea in the port sunk six feet, and remained so a quarter
of an hour.
"The sulphurous water in the road from Rome to Tivoli it diminished two
feet and a half, both in the bason and in the canal. In many places
of the plain, called Testine, the springs and rivulets, which formed
morasses, are all dried up. The waters of the lake called l'Enfer is
also lowered three feet. In place of the ancient springs new ones have
appeared at above a league distance, so that possibly they are the same
waters which have changed direction[V].
[V] Anno 1704, page 10.
"The same earthquake which, in 1538, formed Monti di Cinere, near
Pozzoli, filled lake Lucrin with stones, earth and cinders, so that
this lake is now a marshy ground.[W]
[W] See Ray's Discourses, page 12.
"There are earthquakes also felt at some distance at sea, says Mr.
Shaw; in 1774, being on board the Gazella, an Algerine vessel, mounting
50 guns, three violent shocks were felt one after the other, as if
every time a weight of 20 or 30 tons had been thrown on the ballast.
This happened on a part of the Mediterranean that was more than 200
fathom deep. He relates also, that others had felt earthquakes much
more considerable in other parts, and one among the rest at 40 leagues
west from Lisbon."[X]
[X] See Shaw's Travels.
Schouten, speaking of an earthquake in the Malacca islands, says,
that the mountains were shaken, and the vessels at anchor in 30 or 40
fathoms water were shook, as if they had struck against rocks or banks.
"Experience, continues he, teaches us every day that the same happens
in the open sea, where no bottom is to be met with, and that ships are
tossed to and fro by earthquakes, even where the sea is tranquil."
Gentil, in his voyage round the world, speaks of earthquakes in
the following terms: "I have, says he, made some remarks on these
earthquakes; first, that half an hour before the earth is agitated
every animal is struck with fear; horses snort, break their fastenings,
and fly from the stable; dogs bark; birds, as if stupified, fly into
houses for safety; and rats and mice quit their holes. Secondly, that
vessels at anchor are so violently agitated, that every part of them
seems as if going to pieces, the cannons force themselves loose, and
the masts break in several places. These facts I should scarcely have
given credit to if many unanimous testimonies had not convinced me.
I know the bottom of the sea is a continuation of the land, and that
if one is agitated it will communicate to the other; but I could not
conceive how every part of a vessel, floating in a fluid, should be
affected in the same manner as if she was on the earth: it appeared to
me that her motion should have been such as she experiences in a storm;
besides, in the circumstance which I speak of, the surface of the sea
was smooth, and there was no wind. Thirdly, that if the cavern of the
earth, where this subterraneous fire is contained, has a direction
from north to south, and if the buildings of an adjacent town are in a
parallel line with it, all the houses are overthrown, whereas if this
vein or cavern executes its effects by the breadth of the town, the
devastation of the earthquake, is much less considerable."[Y]
[Y] See Gentil's Voyages, vol. I. page 172, &c.
In countries subject to earthquakes, when a new volcano breaks out
earthquakes cease, and are only felt in the violent eruptions of the
volcano, as is observed in the island of St. Christopher.[Z]
[Z] See Abridgement of Phil. Trans. vol. XI. page 302.
The enormous ravages produced by earthquakes have made some naturalists
think that mountains and other inequalities of the surface of the
globe were only the effects of subterraneous fires, and that all the
irregularities must be attributed to the violent shocks which they have
produced. This, for example, is the opinion of Mr. Ray; he imagines
that all mountains have been formed by earthquakes, or the explosion
of volcanos, as Monti di Cinere, the new island near Santorini, &c.
but he has not considered that the slight elevations formed by the
eruption of a volcano, or by the action of an earthquake, are not
internally composed of horizontal strata, as all other mountains are;
for by digging in the Monti di Cinere we meet with calcined stones,
cinders, burnt earths, metallic dross, pumice-stones, &c. all mixed
and confounded like a heap. Besides, if earthquakes and subterraneous
fires had produced the great mountains of the earth, as the Cordeliers,
Mount Taurus, the Alps, &c. the prodigious force necessary to raise
these enormous masses might, at the same time, have destroyed a great
part of the surface of the globe; and earthquakes, requisite to produce
such effects, must have been of inconceivable violence, since the most
famous of which history makes mention have not had sufficient power to
form a single mountain; for example, in the time of Valentian I. an
earthquake happened, which was felt throughout all the known world;[AA]
and yet not a mountain was thrown up by it.
[AA] As Ammianus Marcellinus relates, lib. 26. cap. 14.
It is nevertheless certain, that although we might be able to find an
earthquake sufficiently powerful to throw up the highest mountains, it
would not be sufficient to disorder the rest of the globe.
For supposing that the chain of the highest mountains which cross
South America from the Magellanic lands to New Grenada, and the Gulph
of Darien, had been produced by an earthquake, and then let us see by
calculations the effect of this explosion. This chain of mountains is
near 1700 leagues in length, and commonly 40 in breadth, comprehending
the Sieras, which are not so lofty as the Andes. The surface therefore
is 68,000 square leagues; I suppose the thickness of the matter
displaced by the earthquake to be about one league, that is, the
height of these mountains taken from the top to the caverns, which
according to this hypothesis must support them, is one league, then I
say, the power of an explosion must have raised a quantity of earth
equal to 68,000 cubical leagues to a league in height. Now the action
being equal to the re-action, this explosion must have communicated
the same motion to the rest of the globe. The whole globe consists of
12,310,523,801 cubical leagues, from which subtracting 68,000, there
remains 12,310,455,801 cubical leagues, the quantity of which motion
will be equal to that of 68,000 cubical leagues raised one league; from
whence we perceive that the force which will have been great enough to
elevate 68,000 cubical leagues would not have displaced the whole globe
a single inch.
There would therefore be no absolute impossibility in the supposition
that mountains have been raised by earthquakes, if their internal
composition as well as their external form were not evident proofs of
their being the work of the sea. Their internal parts are composed
of regular and parallel strata, intermingled with shells, and
their external consists of a figure whose angles are every where
correspondent: is it credible then that this uniform composition and
regular form should have been produced by irregular shocks and sudden
explosions?
But as this opinion has prevailed among some philosophers, and as the
nature and effects of earthquakes are not well understood, it may
possibly be pertinent to hazard a few ideas with a view of explaining
those intricate subjects.
The earth has undergone great changes on its surface; we find at
considerable depths, holes, caverns, subterraneous rivulets, and
void places, which sometimes communicate by chinks, &c. There are
two kinds of caverns; the first are those produced by the action of
subterraneous fires and volcanos; the action of this fire uplifts,
burns, and throws out to a distance the matters that are above, and
at the same time divides and deranges those which are on the sides,
and thus produces caverns, grottos, and irregular holes, but which
however is only effected in the environs of volcanos; and these kinds
of caverns are more rare than those produced by water. We have already
observed that the different strata which compose the terrestrial globe
are all interrupted by perpendicular fissures: the waters which fall
on the surface descend through them; collect when stopped by clay,
and form springs and rivulets; by their natural propensities they seek
out cavities or small vacancies, and always incline to open a passage
till they find a vent, carrying along with them sand, gravel, and other
matters they can divide and dissolve; by degrees, in the internal part
of the earth they form small trenches; and at last issue forth in the
form of springs, either at the surface of the earth, or bottom of the
sea; the matters which they carry along with them, leave caverns whose
extent may be very considerable, the origin of which is quite different
from those produced by volcanos or earthquakes.
There are two kinds of earthquakes, the one caused by the action of
subterraneous fires, and the explosion of volcanos which are only
felt at small distances at the time of eruptions: when the matters
which form subterraneous fires ferment, heat, and inflame, the fire
makes an effort on every side to get out, and if it does not find a
natural vent, it raises the earth above and forces itself a passage by
throwing it out; such is the beginning of a volcano whose effects and
continuation are in proportion to the quantity of inflammable matters
they contain. If the quantity of matters is not considerable, an
earthquake may ensue, without a volcano being formed. The air rarefied
by the subterraneous fire may also escape through small vents, and in
this case there will be only a shock without any eruption or volcano.
But when the inflamed matter is in great quantities and confined by
solid and compressed bodies, then a commotion and volcano is certain
to ensue; but all these commotions form only the first kind of
earthquakes, and can only shake a small space of ground. A violent
eruption of Ætna will cause, for example, an earthquake throughout
the whole island of Sicily; but it will never extend to the distance
of three or four hundred leagues. When any new mouth bursts out in
Vesuvius, there are earthquakes at Naples, and in the neighbourhood of
the volcano; but these earthquakes never shake the Alps, nor extend
into France, or other countries remote from Vesuvius. Therefore
earthquakes produced by volcanos, are limited to a small space, are
properly but the effects of the re-action of the fire; and they shake
the earth, as the explosion of a powder magazine produces a shock
perceptible at many leagues distance.
But there is another kind of earthquake very different in its effects,
and perhaps equally so in its cause; such are felt at great distances,
and shake a long course of ground, without any new volcano, or eruption
in the old ones appearing. We have instances of earthquakes being felt
at the same time in England, France, Germany, and even in Hungary;
these earthquakes always extend more in length than breadth; they shake
a zone of ground with greater or less violence in different places,
and are almost always accompanied with a rumbling noise like that of a
coach rolling over the stones with rapidity.
With respect to the causes of this kind of earthquake, it must be
remembered that the explosion of all inflammable matters produces, like
gunpowder, a great quantity of air; that this air by the heat is in a
state of very great rarefaction, and that by its state of compression
in the bowels of the earth, it must produce very violent effects. Let
us suppose, that at a depth of one or two hundred fathoms, pyrites
and other sulphurous matters are collected in great quantities, and
that by the fermentation produced by the filtration of the water, or
other causes, they inflame; what must happen? First these matters
are not placed in horizontal layers, as are the ancient strata, which
have been formed by the sediment of the waters; on the contrary, they
are formed in perpendicular fissures, in caverns, and in other places
where the water can penetrate. Inflaming, they produce a quantity of
air, the spring of which being compressed in a small space, like that
of a cavern, will not only shake the ground directly above, but will
seek out for passages by which it may escape. The roads which offer
themselves are caverns and trenches, formed by subterraneous rivulets:
into these the rarefied air will precipitate with violence, form in
them a strong wind, the noise of which will be heard at the surface,
accompanied with shocks of the earth, &c. this subterraneous wind,
produced by the fire, will extend as far as the subterraneous cavities,
and cause an agitation more or less violent as it is distant from
the vent, and finds the passages of a larger or lesser extent: this
motion being made longitudinal, the shock will be the same, and the
earthquake be felt through a long zone of ground. This air will not
produce any eruption, or volcano, because it will find sufficient space
to expand, or rather because it will have found vents, and issue forth
in form of wind and vapour. Even should it not be allowed that there
exist internal passages, by which the air and vapours can pass, it
may be conceived that in the place where the first explosion is made,
the ground being lifted up to a considerable height, that the most
adjoining to this spot must divide and split in an horizontal manner by
the force of its motion; and by this means passages communicating one
with the other may be opened to great distances; and this explanation
agrees with every phenomena. It is not at the same moment or hour that
an earthquake is felt in two distant places. Neither fire nor eruption
attend those earthquakes which are heard at a distance, and the noise
always marks the progressive motion of this subterraneous wind. This
theory is confirmed by two other facts; it is well known that mines
exhale unhealthy air and suffocating vapours, independent of the wind
produced by the current of water: it is also known that there are
holes, abysses and deep lakes in the earth, which produce winds, as the
lake Boleslaw, in Bohemia, which we have already spoken of.
All this being considered, I do not see how it can be imagined that
earthquakes produce mountains, since the cause itself of these
earthquakes are mineral and sulphurous matters, which are generally
found only in perpendicular clefts of mountains and other cavities
of the earth; the greatest number of which have been produced by the
operation of water; since this matter by inflaming produces only a
momentary explosion and a violent wind which follows the subterraneous
roads of the water: since the duration of the earthquakes at the
surface of the earth is so short that their cause can only be explosion
and not a durable fire: and in short, since these earthquakes, which
extend to a considerable distance, very far from raising chains of
mountains, do not produce the smallest hills throughout their whole
extent.
Earthquakes are, in fact, most frequent in places near volcanos, as
in Sicily and Naples, but it is known, by observations, that the most
violent earthquakes happen in the time of the greatest eruptions of
volcanos; that they are very limited, and cannot produce a chain of
mountains.
It has been sometimes observed, that the matters thrown out of Mount
Ætna, after laying for many years and afterwards moistened with
the rain, have rekindled and thrown out flames with such violent
explosions as even to produce a slight shock.
In a furious eruption of Ætna in 1669, which began the 11th of March,
the summit of the mountains sunk considerably;[AB] which proves the
fire of this volcano comes rather from the top than from the bottom of
the mountain. Borelli is of the same opinion, and says, "That the fire
of volcanos does not proceed from the centre, nor from the foot of the
mountain, but that it issues from the summit, and flames kindle but at
a small depth."[AC]
[AB] See Trans. Phil. Abridged, Vol. II. page 387.
[AC] Borelli, De incendiis Montis Etnae.
Mount Vesuvius in its eruptions, has thrown out great quantities of
boiling water. Mr. Ray, who thinks that the volcanean fire proceeds
from a great depth, says, that it is the water of the sea which
communicates by subterraneous passages with the foot of the mountain;
he gives, as a proof of it, the dryness of the summit of Vesuvius,
and the agitation of the sea at the time of these eruptions, which
sometimes retreats from the coasts, and leaves the Bay of Naples almost
dry. But, if these facts are true, they do not prove, in a solid
manner, that the volcanean fire proceeds from a great depth; for the
water which is thrown out is certainly rain water, which penetrates
through the fissure, and collects in the cavities of the mountains.
Rills and rivulets flow from those containing volcanos as well as other
lofty mountains, and as they are hollow, and have been more shaken,
it is not astonishing that the water collects in their caverns in
their internal part, and that these waters are thrown out in the time
of eruptions with other matters. With respect to the motion of the
sea, it proceeds solely from the shock communicated to the waters by
the explosion, which causes them to advance or retreat according to
different circumstances.
The matters which volcanos generally throw out, come forth in the form
of a torrent of melted minerals, which inundates all the environs
of those mountains; these rivers of liquified matters extend to
considerable distances, and in cooling form horizontal or inclined
strata, which for position are like the strata formed by the sediment
left by the waters: but it is very easy to distinguish the one from the
other. First, because strata of lava are not throughout of an equal
thickness: secondly, because they contain only matters which have
evidently been calcined, vitrified, or melted; and thirdly, because
they do not extend to any great distance. As there are a great number
of volcanos at Peru, and as the foot of most of the mountains of the
Cordeliers is covered with matters thrown out by eruptions, it is not
astonishing that marine shells are not met with there, as they must
have been calcined and destroyed by the fire; but I am persuaded, if
we dig in argilaceous earth, which, according to M. Bourguet, is the
common earth of the valley of Quito, shells would be found there, as
they are in other places, at least where the ground is not covered,
like that at the foot of the mountains, with matters thrown out of a
volcano.
It has often been asked, why volcanos are all met with at the top of
mountains? I think I have partly given a satisfactory answer to this
question in the preceding article, but I have thought it necessary not
to finish this without farther expla
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