The Romance of War Inventions
by Thomas W. Corbin · English · Gutenberg #34459 · 524,555 chars · public domain (US)
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Title: The Romance of War Inventions
Author: Thomas W. Corbin
Release date: November 27, 2010 [eBook #34459]
Most recently updated: October 26, 2021
Language: English
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THE ROMANCE OF WAR INVENTIONS
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THE ROMANCE OF WAR INVENTIONS
[Illustration: A TANK.
These weird-looking engines are literally moving forts, and are the
evolution of a peaceful agricultural machine fitted with "caterpillar"
wheels, that is, a broad band encircles the driving wheels, and so the
whole construction moves as it were on its own revolving platform and is
thus prevented from sinking into the soft ground. The principle itself
is not new, as it was adapted to transport carts during the Crimean
War.]
THE ROMANCE OF WAR INVENTIONS
A Description of Warships, Guns, Tanks,
Rifles, Bombs, and Other Instruments
and Munitions of Warfare, How
They Were Invented & How
They Are Employed
by
T. W. CORBIN
Author of "The Romance of Submarine Engineering,"
"Mechanical Inventions of To-Day,"
&c., &c., &c.
With many Illustrations
London
Seeley, Service & Co. Limited
38 Great Russell Street
1918
* * * * *
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root idea is excellent, and it is excellently carried out, with full
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Telegraph._
By Prof. G. F. SCOTT ELLIOT, M.A., B.Sc.
The Romance of Savage Life
The Romance of Plant Life
The Romance of Early British Life
By EDWARD GILLIAT, M.A.
The Romance of Modern Sieges
By JOHN LEA, M.A.
The Romance of Bird Life
By JOHN LEA. M.A. & H. COUPIN, D.Sc.
The Romance of Animal Arts and Crafts
By SIDNEY WRIGHT
The Romance of the World's Fisheries
By the Rev. J. C. LAMBERT, M.A., D.D.
The Romance of Missionary Heroism
By G. FIRTH SCOTT
The Romance of Polar Exploration
By CHARLES R. GIBSON, F.R.S.E.
The Romance of Modern Photography
The Romance of Modern Electricity
The Romance of Modern Manufacture
The Romance of Scientific Discovery
By CHARLES C. TURNER
The Romance of Aeronautics
By HECTOR MACPHERSON, Junr.
The Romance of Modern Astronomy
By ARCHIBALD WILLIAMS,
B.A. (Oxon.), F.R.G.S.
The Romance of Early Exploration
The Romance of Modern Exploration
The Romance of Modern Mechanism
The Romance of Modern Invention
The Romance of Modern Engineering
The Romance of Modern Locomotion
The Romance of Modern Mining
By EDMUND SELOUS
The Romance of the Animal World
The Romance of Insect Life
By AGNES GIBERNE
The Romance of the Mighty Deep
By E. S. GREW, M.A.
The Romance of Modern Geology
By J. C. PHILIP, D.Sc., Ph.D.
The Romance of Modern Chemistry
By E. KEBLE CHATTERTON, B.A.
The Romance of the Ship
The Romance of Piracy
By T. W. CORBIN
The Romance of Submarine Engineering
The Romance of War Inventions
By NORMAN J. DAVIDSON, B.A. (Oxon.)
The Romance of the Spanish Main
SEELEY, SERVICE & CO., LIMITED.
* * * * *
CONTENTS
CHAPTER PAGE
I. HOW PEACEFUL ARTS HELP IN WAR 17
II. GUNPOWDER AND ITS MODERN EQUIVALENTS 27
III. RADIUM IN WAR 39
IV. A GOOD SERVANT, THOUGH A BAD MASTER 49
V. MINES, SUBMARINE AND SUBTERRANEAN 61
VI. MILITARY BRIDGES 75
VII. WHAT GUNS ARE MADE OF 92
VIII. MORE ABOUT GUNS 108
IX. THE GUNS THEY USE IN THE NAVY 120
X. SHELLS AND HOW THEY ARE MADE 135
XI. WHAT SHELLS ARE MADE OF 146
XII. MEASURING THE VELOCITY OF A SHELL 159
XIII. SOME ADJUNCTS IN THE ENGINE ROOM 164
XIV. ENGINES OF WAR 169
XV. DESTROYERS 184
XVI. BATTLESHIPS 191
XVII. HOW A WARSHIP IS BUILT 202
XVIII. THE TORPEDO 215
XIX. WHAT A SUBMARINE IS LIKE 223
XX. THE STORY OF WIRELESS TELEGRAPHY 240
XXI. WIRELESS TELEGRAPHY IN WAR 252
XXII. MILITARY TELEGRAPHY 264
XXIII. HOW WAR INVENTIONS GROW 276
XXIV. AEROPLANES 284
XXV. THE AERIAL LIFEBOAT 297
INDEX 313
LIST OF ILLUSTRATIONS
A TANK _Frontispiece_
PAGE
MACHINE-GUN VERSUS RIFLE 32
AN ITALIAN MINE-LAYER 64
AN INCIDENT AT LOOS 80
AN 18-POUNDER IN ACTION 96
A GERMAN AUTOMATIC PISTOL 112
BOMB THROWING 136
BOMB-THROWERS AT WORK 160
THE TRIPOD MAST 208
LISTENING FOR THE ENEMY 248
DIAGRAM SHOWING THE PRINCIPLE BY WHICH THE AERIALS
ARE CONNECTED TO THE APPARATUS 251
THE PARENT OF THE TANK 280
THE "GUARDIAN ANGEL" PARACHUTE 304
THE ROMANCE OF WAR INVENTIONS
CHAPTER I
HOW PEACEFUL ARTS HELP IN WAR
In the olden times warfare was supported by a single trade, that of the
armourer. Nowadays the whole resources of the greatest manufacturing
nations scarcely suffice to supply the needs of their armies. So much is
this the case that no nation can possibly hope to become powerful in a
military or naval sense unless they are either a great manufacturing
community or can rely upon the support of some great manufacturing ally
or neutral.
It is most astonishing to find how closely some of the most innocent and
harmless of the commodities of peace are related to the death-dealing
devices of war. Of these no two examples could be more striking than the
common salt with which we season our food and the soap with which we
wash. Yet the manufacture of soap furnishes the material for the most
furious of explosives and the chief agent in its manufacture is the
common salt of the table.
Common salt is a combination of the metal sodium and the gas chlorine.
There are many places, of which Cheshire is a notable example, where
vast quantities of this salt lie buried in the earth.
Fortunately it is very easily dissolved in water so that if wells be
sunk in a salt district the water pumped from them will have much salt
in solution in it. This is how the underground deposits are tapped. It
is not necessary for men to go down as they do after coal, for the water
excavates the salt and brings it to the surface.
To obtain the solid salt from the salt water, or brine as it is called,
it is only necessary to heat the liquid, when the water passes away as
steam leaving the salt behind.
Important though this salt is in connection with our food, it is perhaps
still more important as the source from which is derived chlorine and
caustic soda. How this is done can best be explained by means of a
simple experiment which my readers can try in imagination with me or,
better still, perform for themselves.
Take a tumbler and fill it with water with a little salt dissolved in
it. Next obtain two short pieces of wire and two pieces of pencil lead,
which with a pocket lamp battery will complete the apparatus. Connect
one piece of wire to each terminal of the battery and twist the other
end of it round a piece of pencil lead. Place these so that the ends of
the leads dip into the salt water. It is important to keep the wires
out of the solution, the leads alone dipping into the liquid, and the
two leads should be an inch or so apart.
In a few moments you will observe that tiny bubbles are collecting upon
the leads and these joining together into larger bubbles will soon
detach themselves and float up to the surface. Those which arise from
one of the leads will be formed of the gas chlorine and the others of
hydrogen.
It will be interesting just to enumerate the names of the different
parts of this apparatus. First let me say that the process by which
these gases are thus obtained is called electrolysis: the liquid is the
electrolyte: the two pieces of pencil lead are the electrodes. That
electrode by which the current enters the electrolyte is called the
an-ode, while the other is the cath-ode. In other words, the current
traverses them in alphabetical order.
Now it is familiar to everyone that all matter is supposed to consist of
tiny particles called Molecules. These are far too tiny for anyone to
see even with the finest microscope, so we do not know for certain that
they exist: we assume that they do, however, because the idea seems to
fit in with a large number of facts which we can observe and it enables
us to talk intelligibly about them. We may, accordingly, speak as if we
knew for a certainty that molecules really exist.
Now when we dissolve salt in water it seems as if each molecule splits
up into two things which we then call "ions." Salt is not peculiar in
this respect, for many other substances do the same when dissolved in
water. All such substances, since they can be "ionized," are called
"ionogens."
Now the peculiarity about ions is that they are always strongly
electrified or charged with electricity.
At this stage we must make a little excursion into the realm of
electricity. You probably know that if a rod of glass be rubbed with a
silk handkerchief it becomes able to attract little scraps of paper.
That is because the rubbing causes it to become charged with
electricity. In like manner a piece of resin if rubbed will become
charged and will also attract little pieces of paper. A piece of
electrified resin and an electrified glass rod will, moreover, attract
each other, but two pieces of resin or two pieces of glass, if
electrified, will repel each other. This leads us to believe that there
are two kinds of electrification or two kinds of electrical charge. At
first these two kinds were spoken of as vitreous or glass electricity
and resinous electricity, but after a while the idea arose that there
was really one kind of electricity and that everything possessed a
certain amount of it, the electrified glass having a little too much of
it and the electrified resin a shade too little of it. From this came
the idea of calling the charge on the glass a "positive" charge and that
on the resin a "negative" charge. Recent investigations seem to show
that we have got those two terms the wrong way round, but to avoid
confusion we still use them in the old way.
It will be sufficient for our purpose, therefore, if we assume that
every molecule of matter has a certain normal amount of electricity
associated with it and that under those conditions the presence of the
electricity is not in any way noticeable. When a molecule becomes
ionized, however, one ion always seems to run off with more than its
fair share of the electricity, the result being that one is electrified
positively, like rubbed glass, while the other is negatively charged,
like rubbed resin.
Thus, when the common salt is dissolved in water, two lots of ions are
formed, one lot positively charged and the other lot negatively. Each
molecule of salt consists of two atoms, one of sodium and one of
chlorine: consequently, one ion is a chlorine atom and the other is a
sodium atom, the latter being positive and the former negative.
Now the electrodes are also charged by the action of the battery. That
connected to the positive pole of the battery becomes positively charged
and the other negatively. The anode, therefore, is positive and the
cathode negative.
It has been pointed out that two similarly charged bodies, such as two
pieces of glass or two pieces of resin, repel each other, while either
of these attracts one of the other sort. Hence we arrive at a rule that
similarly charged bodies repel each other, while dissimilarly charged
bodies attract each other.
Acting upon this rule, therefore, the anode starts drawing to itself all
the negative ions, in this case the atoms of chlorine, while the cathode
gathers together the positive ions, the atoms of sodium. Thus the action
of the battery maintains a sorting out process by which the sodium is
gathered together around one of the electrodes and the chlorine round
the other. Those ions, by the way, which travel towards the _an_-ode
are called _an_-ions, while those which go to the cath-ode are termed
cat-ions.
Thus far, I think, you will have followed me: the chlorine is gathered
to one place and the sodium to the other. The former creates bubbles and
floats up to the surface and escapes. But where, you will ask, does the
hydrogen come from, which we found, in the experiment, was bubbling up
round the cathode. Moreover, what becomes of the sodium?
Both those questions can be answered together. The sodium ions, having
been drawn away from their old partners the chlorine ions, are unhappy,
and long for fresh partners. They therefore proceed to join up with
molecules of water. But water contains too much hydrogen for that. Every
molecule of water has two atoms of hydrogen linked up with one of
oxygen, but sodium does not like two atoms of hydrogen: it insists on
having one only. Accordingly the oxygen atom from the water, together
with one of the hydrogen atoms, join forces with the sodium atom into a
molecule of a new substance, a most valuable substance in many
manufactures, called Caustic Soda, while the odd atom of hydrogen,
deprived of its partners, has nothing left to do but to cling for a
while to the cathode and finally float up and away.
The sum-total of the operation therefore is this: when we pass an
electric current through salt water, between graphite electrodes,
chlorine goes to the anode and escapes, while caustic soda is formed
round the cathode and hydrogen escapes. Let us see now how this is
applied commercially.
For the production of Chlorine the apparatus need be little more than
our experimental apparatus made large. The anode can be covered in such
a way as to catch the gas as it bubbles upwards. In times of peace this
gas is chiefly used for making bleaching powder. It is led into chambers
where it comes into contact with lime, with which it combines into
chloride of lime, a powder which is sometimes used as a disinfectant,
but the chief use of which is for bleaching those cotton and woollen
fabrics for the manufacture of which this country is famous throughout
the world.
The Germans, however, have taught the world another use for chlorine.
Those gallant Canadians who were the first victims of the attack by
"poison gas" who suddenly found themselves fighting for breath, and a
few of whom, more fortunate than the rest, have reached their homes
shattered in health with permanent damage to their lungs, those brave
fellows suffered from poisoning by chlorine.
We cannot obtain the other product, the caustic soda, by the same simple
means. In our little experiment we succeeded in manufacturing some of it
in the region around the cathode, and had we drawn off some of the
liquid from there we would have been able to detect its presence. But it
would have been mixed up with much ordinary salt, and for commercial
purposes we need the caustic soda separate from the salt. The principle
is, however, just the same, as you will see.
Imagine a large oblong vat divided by vertical partitions into three
separate chambers. These partitions do not quite reach the bottom of
the vessel, so that there is a means of communication between all three
chambers. This is closed, however, by filling the lower part of the vat
with mercury up to a level a little higher than the lower ends of the
partitions.
Thus we have three separate chambers with communication between them but
that communication is sealed up by the mercury.
The two end chambers are filled with salt water, or brine, while the
centre one is filled with a solution of caustic soda. In each end
compartment is a stick of graphite, both being electrically joined
together and so connected up that they form anodes, while in the centre
compartment is the cathode.
When the current flows from the anodes it carries the sodium ions with
it, just as it did in our little experiment. But its course, this time,
is not straight, since in order to travel from anode to cathode it has
to pass through the openings in the partitions, in other words through
the mercury.
On arrival at or near the cathode the ions of sodium cause the caustic
soda to be formed just as in our experiment, but in this case, you will
notice, the formation takes place in a chamber from which the salt brine
is completely excluded by the mercury.
Brine is continually fed into the outer chambers and the solution of
caustic soda is drawn from the centre one, while the chlorine is
collected over the anodes.
And now we can go a step further on our progress from common salt to
explosive.
In the soap works there are enormous coppers in which are boiled various
kinds of fat. The source of the fat may be either animal or vegetable,
many kinds of beans, nuts and seeds furnishing fats practically
identical with that which can be got from the fat flesh of a sheep, for
instance. To this fat is added some caustic soda solution and the whole
is kept boiling for some considerable time. This protracted boiling is
to enable the soda thoroughly to attack the fat and combine with it,
whereby two entirely new substances are formed.
At first the two new substances are not apparent, for they remain
together in one liquid. The addition, however, of some brine causes the
change to become obvious for something in the liquid turns solid, so
that it can be easily taken away from the rest. That solid is nothing
else than soap. It remained dissolved in the water which forms part of
the liquid until the salt was put in, but as it will not dissolve in
salt water, as you will discover if you attempt to wash in sea water, it
separates out as soon as the salt is added.
But still a liquid remains: what can that be? It is mainly salt water
and glycerine, that sticky stuff which in peace times we put on our
hands if they get sore in winter, or take, in a little water, to soothe
a sore throat. That it has other and very different uses was brought
home to me when, during the war, I tried to buy some at a chemist's,
only to learn that it could not be sold except in cases of extreme need
under the orders of a doctor.
The mixed liquid is distilled with the result that the water is driven
off and the salt deposited, which with other minor purifying processes
gives the pure glycerine.
The next step takes us to the explosives factory, where the glycerine is
mixed with sulphuric and nitric acids. Now glycerine, as you will have
observed, comes from the animal or vegetable sources and therefore is
one of those substances known as "organic," and, like many other of the
organic compounds, it consists of carbon, hydrogen and oxygen. Nature
has a marvellous way of combining these same three things together in
many various ways to form many widely different substances and if, to
such a compound, we can add a little nitrogen, we usually get an
explosive. Thus, the glycerine, with some nitrogen from the nitric acid,
becomes nitro-glycerine, a most ferocious and excitable explosive, the
basis of several of those explosives without which warfare as we know it
to-day would be impossible.
CHAPTER II
GUNPOWDER AND ITS MODERN EQUIVALENTS
The origin of gunpowder appears to be lost in antiquity. At all events
it has been in use for many centuries and is still made in many
countries.
Most boys have tried to make it at some time or other and with varying
degrees of success. Such experiments generally lead to a glorious blaze,
a delightfully horrid smell and no harm to anyone, the experimenter
owing his safety to his invariable lack of complete success, for
although other and better explosives have superseded it for many
purposes it is capable of doing a lot of harm when it is well made.
It consists of a mixture of charcoal, sulphur and saltpetre ground up
very fine and mixed very intimately together. The mixture is wetted and
pressed into cakes and dried, after which it is broken up into small
pieces. The precise proportions of the various materials seem to vary a
great deal in different countries, but generally speaking there is about
75 per cent of saltpetre (or to give it its scientific name, nitrate of
potash), 15 per cent of charcoal and 10 per cent of sulphur.
Now gunpowder, like all explosives, is simply some thing or mixture of
things which is capable of burning very quickly. When we light the fire
we set going the process which we call combustion, or burning, and, as
we know from our own experience, that process causes heat to be
generated.
What takes place in the fire-grate is that the carbon of the coal enters
into combination with oxygen from the air, the two together forming a
new compound called "carbonic acid gas." There is nothing lost or
destroyed in this process, the carbon and oxygen simply changing into
the new substance, and could we weigh the gas produced we should find
that it agreed precisely with the weight of the carbon and oxygen
consumed. For the purpose for which we require the fire, namely, to heat
the room, the chief feature about this process is not what is formed in
the shape of gas, for that simply goes off up the chimney, but the heat
which is liberated. We believe that in some mysterious way the heat is
locked up in the coal. Latent is the term we use, which means hidden: in
other words we believe that the heat is hidden in the coal: we cannot
feel it or perceive it in any way, but it comes out when we let the
carbon combine with the oxygen.
Why these two things combine at all is one of those mysteries which may
never be solved. We have theories on the subject, but all we really know
is that under certain conditions if they be in contact with one another
they will combine, apparently for the simple reason that it is their
nature so to do.
When we apply the match to the fire all we do is to set up the
conditions under which the carbon and oxygen are able to follow their
natural instincts, so to speak.
A coal fire, as we all know, burns slowly, for the simple reason that it
is only at the surface of the lumps that carbon and oxygen are in
contact. If we grind up the coal into a fine powder and then blow it
into a cloud, so that every tiny particle is surrounded with air, a
spark will cause an explosion. That is how these terrible explosions in
coal-pits are caused.
This is sometimes seen on a small scale when one shakes the empty
fire-shovel after putting coal on the fire to get rid of the fine dust
adhering to it and to save making a mess in the fender. That little
cloud of fine dust will often burst into flame like a mild explosion.
We see from this that to make an explosion we require fuel, just as we
do to make a fire: but we need that it shall be very intimately mixed
with oxygen, so that all of it can burn up in practically a single
instant. Now in gunpowder we get these conditions fulfilled. We have the
carbon in the shape of charcoal, we also have some sulphur which
likewise burns readily, and we have saltpetre which contains oxygen.
Thus, you see, we do not need to go to the air for the oxygen, for the
gunpowder possesses it already, locked up in the saltpetre. Moreover, we
can see now why it is so important for all the materials to be ground up
very fine, for it is only by so doing that we can ensure that every
particle of charcoal or sulphur shall have particles of saltpetre close
by ready to furnish oxygen at a moment's notice.
Another thing to be observed, for it lets us into the great key to the
manufacture of nearly all explosives, is the scientific name of
saltpetre. It is "nitrate of potassium," and all substances whose names
begin with "nitr-" contain nitrogen: while the termination "ate"
signifies the presence of oxygen. We need the oxygen to make the
explosion but we do not need the nitrogen, yet the latter has to be
present for without it the oxygen would be too slow in getting to work.
Nitrogen is one of the strangest substances on earth. Extremely lazy
itself, it has the knack of hustling its companions, particularly
oxygen, and making them work with tremendous fury. Whenever we get the
lazy gas nitrogen to enter into a combination with other things we may
confidently look for extraordinary activity of some sort.
So when we put a light to a quantity of gunpowder we set up those
conditions under which the carbon and oxygen can combine, and at the
same moment our lazy friend the nitrogen turns out his partner oxygen
from the nitrate in which they were till then combined and a sudden
burning is the result. The solid gunpowder is suddenly changed into a
volume of hot gas 2500 times as great. That is to say, one cubic inch of
gunpowder changes suddenly into 2500 cubic inches of gas. That sudden
expansion to 2500 times its volume is what we term an explosion. If it
takes place in an enclosed space so that the gas formed wants to expand
but cannot, the result is a pressure of about forty tons per square
inch.
If that enclosed space were the interior of a gun, that force of forty
tons per square inch would be available for driving out the projectile.
Now, gunpowder is still used for sporting purposes and also for some
special purposes in warfare, but it has the great disadvantage that it
makes a lot of smoke, so that the enemy would be easily able to locate
the guns were it to be used in them. As we know so well, by the messages
from France, guns and rifles drop their shells and bullets apparently
from nowhere and are extremely difficult to locate. That is owing to the
use of improved powders one of the great features of which is their
smokelessness.
The reason why gunpowder makes a dense smoke, is because the burning
which takes place is very incomplete. Therefore, by some such means as a
more intimate mixture of the materials a better and more complete
burning must be brought about.
One of the best known of the new powders (they are all spoken of as
powders, whatever their form, since they have taken the place of the old
gunpowder) is nitro-glycerine, the basis of which is glycerine.
The way in which we obtain this useful material has already been
explained. It consists of carbon, a lot of hydrogen and some oxygen.
These are not merely mixed together but are in combination, just as
oxygen and hydrogen are combined in water. Carbon and hydrogen will both
combine with oxygen and will give off heat in the process, but in
glycerine they are already happily united together and so glycerine
itself is no use as an explosive. If, however, we bring nitric acid and
sulphuric acid into contact with it a pair of new partnerships is set
up, one being water and the other a compound containing carbon and
hydrogen, a lot of oxygen and, most important of all, some of that
disturbing, restless though lazy nitrogen.
This is nitro-glycerine, a particularly furious explosive, for that
curious nitrogen seems to be so uncomfortable in his new surroundings
that at the smallest provocation he will break up the whole combination
and then there will be a mass of free atoms of carbon, hydrogen and
oxygen, all seeking new partners, just right for a glorious explosion.
So furious and untamed is this stuff that it was almost useless until
the famous Nobel hit upon the idea of taming it down by mixing it with
an earth called Kieselguhr, which reduces its sensitiveness sufficiently
to make it a very safe explosive to use. To this mixture Nobel gave the
name of dynamite.
It is interesting at this point to compare the action of this typical
modern explosive with that of the older gunpowder. The latter is only a
mixture: the former is a chemical compound. The smallest particle of
material in the gunpowder is a little lump containing millions of
molecules and still more of atoms: when the nitrogen has broken up the
original nitro-glycerine, just before the explosion actually takes
place, we have a mixture of _single atoms_. Thus the mixture is far more
intimate in the latter case and the burning is therefore quicker and
more thorough.
[Illustration: MACHINE-GUN _versus_ RIFLE.
This illustrates the rapidity and accuracy with which the modern rifle
can be used. Sergeant O'Leary, V.C., tackled a gun crew of five and
killed them all before they had time to slew their gun round--a striking
contrast to the "Brown Bess" of a hundred years ago.]
Another well-known explosive is gun-cotton. Surely this must be a fancy
name, for what can harmless, simple cotton have to do in connection with
guns. It is a perfectly genuine descriptive name, however. It seems very
strange at first, but it is perfectly true that nitrogen, as it turned
glycerine into dynamite, can also turn cotton into gun-cotton. Cotton
consists mainly of cellulose, a compound of carbon, hydrogen and oxygen,
happily combined together and therefore showing, as we well know from
experience, no tendency whatever to change into anything else, least of
all to "go off bang." But that state of things is very much changed when
we have induced nitrogen to take a hand in the game.
In actual practice, cotton waste, pure and clean, is dipped into a
mixture of sulphuric and nitric acids whereby the cellulose becomes
changed into nitro-cellulose, just as a similar process changes
glycerine into nitro-glycerine. The whole process of manufacture is of
course far more than that simple dipping, but that is the fundamental
fact of it all. The rest is concerned with getting rid of the
superfluous acid, tearing the stuff into pulp and pressing it into
blocks. It is probably the safest of explosives, since it can be kept
wet, in which case the danger of an accidental explosion is practically
nil, provided reasonable care be taken. Even when dry, it behaves in a
very kindly way. If hit with a hammer, it only burns for a moment just
at the point struck. If ignited with a red-hot rod, it burns but does
not explode, unless it is enclosed. The burning, that is to say, is not
sufficiently rapid to constitute an explosion.
On the other hand, if it be exploded by a detonator, by which is meant a
small quantity of a very powerful explosive, such as fulminate of
mercury, fired close to it, it then goes off with a violence which
leaves little to be desired.
It would be better still could we persuade a little more oxygen to enter
into its composition, for as it is there is not quite enough to burn up
the other matters completely. That, however, does not cause smoke, since
the combustion is complete enough to change everything into invisible
gases. With more oxygen more heat might be generated and the power of
the explosion be made greater. Still, even as it is, the explosion of
gun-cotton has been estimated by a high authority to produce a pressure
of 160 tons per square inch, four times as much as gunpowder.
Nitro-glycerine has the advantage of a rather larger proportion of
oxygen to carbon, resulting in its being rather more energetic.
Yet another class of explosive is made from Coal Tar. This is a
by-product in the manufacture of gas for lighting and also in the
manufacture of coke for industrial purposes. It comes from the retorts
along with the gas in a gaseous form but condenses into a black liquid
in the pipes and more particularly in an arrangement of cooled pipes
called a condenser specially placed to intercept it.
In the chemist's eyes it is the most interesting of liquids, for it is
full of mysteries and possibilities. The most wonderful achievements of
chemistry have it for their raw material and there is still scope for
much more in the same direction.
If the tar be gently heated in a closed vessel it will evaporate and the
vapour can be led to another vessel, there cooled and converted back
into a liquid. This looks rather like doing work for nothing, but the
various liquids, of which tar is a mixture, evaporate at different
temperatures, so that this furnishes a means of separating them. The
first liquid thus procured is known as coal tar naphtha, and if it be
again distilled it can be subdivided further, the first liquid separated
from it being known as Benzine. This, again, is another of those almost
numberless things which consist of carbon and hydrogen. Also, like the
other similar substances which we have been discussing, it can, if
treated with nitric acid, be made to take into partnership a quantity of
oxygen and nitrogen.
Thus we get nitro-benzene. We can repeat the process, when it will take
more and become di-nitro-benzene. Again we can repeat it, thus producing
tri-nitro-benzene.
The second liquid separated from coal tar naphtha is called Toluene,
which again is composed of carbon and hydrogen in slightly different
proportions. Like its confrère benzene it, too, can be treated with
nitric acid, becoming nitro-toluene and then di-nitro-toluene and
finally tri-nitro-toluene, the deadly explosive of which we read in the
papers as T.N.T.
After the naphtha has been removed from the tar another substance is
obtained called Phenol, which in a prepared form is familiar to us all
as the disinfectant Carbolic Acid. It also can be treated with nitric
acid, to produce tri-nitro-phenol, otherwise known as Picric Acid, which
after a little further treatment becomes the famous "Lyddite."
Most of the actual explosives used in warfare are prepared from one or
more of the above-mentioned compounds. For example, nitro-glycerine and
gun-cotton, having been dissolved in acetone (another compound of
carbon, hydrogen and oxygen) and a little vaseline added, form a soft
gelatinous substance which on being squeezed through a fine hole comes
out looking like a cord or string, and hence is called Cordite.
Other explosives are finished in the form of sheets, the dissolved
gun-cotton or whatever it may be being rolled between hot rollers which
give it the convenient form of sheets and at the same time evaporate the
solvent.
By combining these various substances various characteristics can be
given to the finished explosive. For instance, the one which drives the
shell from the gun, known as the propellant, must not be too sudden in
its action. It must push steadily. Its purpose is to drive the shell not
to burst the gun, wherefore its action must be comparatively slow and
continuous so long as the shell is still in the gun. It must "follow
through" as the golf player would put it.
The charge in the shell, however, needs to go off with the greatest
possible violence so as to blow the shell to pieces and to scatter the
fragments so that they do the maximum of damage.
Those explosives, whose function is thus to burst with a sudden shock,
are called High Explosives, as distinguished from the propellants which
produce a more or less sustained push.
The great fundamental principle which enables large quantities of these
powerfully explosive substances to be handled with comparative safety
involves the use of two different substances in combination. That which
is used in quantity and which actually does the work is made
comparatively insensitive, indeed in some cases it is very insensitive,
so that it can safely travel by train, by ship and by road and also may
be handled by the soldiers and sailors with very little risk. Some of
these compounds can be struck or set on fire with impunity. They are
none the less violent, however, when, by the agency of a suitable
detonator they are caused to explode.
The detonator, of course, has to be very sensitive indeed, but it need
only be used in very small quantities, so that by itself it, too, is
comparatively safe. Fulminate of mercury is often employed for this
purpose--a compound based upon mercury but in which nitrogen of course
figures largely.
Thus, there are two things necessary for the successful explosion, one
of which is powerful but insensitive, while the other is highly
sensitive but relatively harmless since it is never allowed to exist in
large quantities, and as far as possible these are kept apart until the
last moment.
One other thing may be mentioned in regard to this matter which is of
the greatest importance. That is the necessity for the utmost uniformity
in these various compounds, so that when the gunners put a charge into a
gun they can rely upon it to throw the shell exactly as its predecessor
did. Modern artillery seeks to throw shell after shell within a small
area which would clearly be quite impossible if one charge were liable
to be stronger or weaker than another, for we can easily see that the
more powerful the impetus given the farther will the shell go.
To secure this uniformity the greatest care is taken at all stages of
the manufacture, and various batches of the same stuff are tested and
mixed, and any of them turning out a little too strong are placed with
some a little too weak, so that their faults may neutralize each other.
By such methods as these a remarkable degree of uniformity is attained,
the result of which we see when we read in the papers of the wonderfully
accurate gunnery of which our soldiers and sailors are capable.
In conclusion, a word of warning may be appropriate. Reference has been
made above to the safety of modern explosives in the absence of the
detonators, but do not let that lead anyone to take liberties. Should
any reader come into possession of any of these materials, even in the
smallest quantities, let him treat it with the utmost respect, for
although what has been said about safety is quite correct, it only means
comparative safety, there can be no absolute safety where these
substances are concerned.
CHAPTER III
RADIUM IN WAR
When we remember how all forms of scientific knowledge were called upon
to help in the great struggle, it is not surprising to hear that,
although in a comparatively humble way, Radium has had to do its share.
Now radium is one of the most, if not actually the most, remarkable
substance known. About a generation ago scientific men, or some of them
at all events, were getting rather cocksure. Of course they were quite
right when they realized how much was known about things and what great
strides had been made during the years through which they had lived.
They were proud of the achievements of their scientific friends, for I
am not imputing personal vanity to anyone, and they had reason to be
proud. They made the mistake, however, of thinking that in one direction
at least they had learnt all that there was to be known. The present
generation of scientific men seem to be almost too prone to go to the
other extreme and to dwell rather much on how little we know now and the
wonderful things which are going to be discovered in time.
But that is by the way. A generation ago men seem to have pretty well
made up their minds that they knew all about atoms. They said that
everything was made up of atoms, that the atoms could not be subdivided
nor changed into anything else except temporarily by combination with
other atoms, and that when these combinations were broken up the atoms
remained just as before, quite unchanged. They believed that the atoms
were unchangeable and everlasting. Professor Tyndall, in a famous
address, referred to this in somewhat flowery language, telling his
hearers that the atoms would be still the same when they and he had
"melted into the infinite azure of the past," which a wag translated
into the slang expression of the time, "till all is blue."
Now not very long after Professor Tyndall made this historic speech
Professor Henri Becquerel, of Paris, was trying some experiments with
phosphorescent materials, that is, materials which glow in the darkness.
In the course of these experiments he used some photographic plates upon
which, to his surprise, he found marks which he thought ought not to
have been there. Thinking at first that he had accidentally "fogged" his
plates, as every photographer has done at some time or other, he tried
his experiments again with special care but still he got the mysterious
marks.
Those marks were caused by some of those "unchangeable and everlasting"
atoms deliberately and of their own accord blowing themselves to bits.
For the celebrated Frenchman was not content to let the matter of those
mysterious marks rest: he wanted to know what caused them and he did not
desist until he was on the track of the secret. It appeared after
careful investigation that they were made by the action of something in
some of the ore of the metal "uranium" which he had been using.
Moreover, this something evidently had the power of penetrating through
the walls of the dark-slide to the plate within. Finally, it was tracked
down to the uranium itself which was unquestionably proved to be giving
off something in the nature of invisible light, or at all events
invisible rays, of strange penetrative power. A little later it was
observed that certain ores of uranium seemed to give off these rays more
freely than would be accounted for by the amount of uranium present,
from which fact it was inferred that there must be something else
present in the ore capable of giving off the rays much more powerfully
than uranium can. Madame Curie ultimately found out two such substances,
one of which she called, after her native land, Polonium (for she is a
Pole), and the other Radium. It is the latter which is responsible for
by far the greater part of the rays formed.
The rays are invisible, but they affect a photographic plate in the same
way that light does. They also make air into a conductor of electricity
and if allowed to impinge upon a surface coated with a suitable
substance they cause it to glow.
This spontaneous giving off of rays is now spoken of by the general term
of "radio-activity," and it has grown into an important branch of
science. A number of other substances have been found to exhibit the
same peculiar ray-forming powers, notably Thorium, one of the components
of the incandescent gas mantle by the prolonged application of a
fragment of which to a photographic plate an impression can be obtained
due to the rays.
What, then, are these rays? It is found that they are of three kinds,
not that they vary from time to time, but that they can be sorted out
into three different sorts of rays which are given off simultaneously
all the time.
The first sort are stopped by a sheet of paper, the second passing
easily through a thick metal plate, while the third appear to be
identical with X-rays.
For convenience the three sorts are termed Alpha, Beta and Gamma rays,
respectively, after the first three letters of the Greek alphabet.
Further, the Alpha rays prove to be a torrent of tiny particles about
the size of atoms, indeed if they be collected the gas Helium is
obtained, so that evidently they are helium atoms, and since that is one
of those substances whose molecules consist of a single atom each they
are also molecules of helium. No doubt the reason why they are so easily
stopped by a piece of paper is because being complete atoms they are
large, huge indeed, compared with the particles which form the Beta
rays, for they are apparently those same electrons which are found in
the X-ray tube, and which are at least 2000 times smaller than the
smallest atom.
When the electrons in the vacuum tube are suddenly brought to a
standstill X-rays are given off and in like manner X-rays no doubt would
be given off when they start on their journey, providing that they
started suddenly enough. Hence it is the starting or sudden
explosion-like ejection of the Beta particles which is believed to give
rise to the Gamma rays.
The strength or intensity of the rays can be measured very conveniently
by their action in making air conductive to electricity, for which
purpose a very beautiful but simple instrument called an Electroscope is
employed. It consists generally of a glass-sided box or else a bottle
with a large stopper, consisting of sulphur or some other particularly
good insulator. Through this a wire passes down into the inside of the
vessel terminating in a vertical flat strip to the upper end of which is
attached a similar strip of gold leaf or aluminium foil. Normally the
leaf hangs down close to the strip, but if the wire above the stopper be
electrified by touching it with a piece of sealing-wax rubbed lightly
against the coat sleeve the charge of electricity passes down into the
inside and causes both strip and leaf to become so electrified that they
repel each other.
Owing to the non-conductivity of the air in its normal condition the
leaf will, if the insulation of the stopper be good, remain projecting
almost horizontally for some time until, as it loses its charge by a
slow leakage, it gradually settles down close to the strip.
If, however, a piece of radium be brought near while it is sticking out,
the leaf will fall almost instantly. X-rays have a similar effect even
from several feet or yards away.
The intensity of the radio-activity of different substances can be
compared by noting the difference in the rate at which the leaf falls
under the influence of each.
What is happening, then, to the atoms of radium, which causes them to
show these curious effects and to give off these strange rays? To give
any intelligent answer to that question we are bound to assume that
which the older generation of scientists thought impossible, namely,
that atoms can be broken up. Then we are forced to believe that the
atoms of this particular substance radium are of a peculiarly flimsy
unstable sort, so that they cannot permanently hold their parts together
but are liable to break up, as far as we can see through their own
inherent weakness and under the influence of disruptive forces at work
within themselves.
We must remember, however, that the tiniest speck of matter which we can
see contains a number of atoms of such a size as to be quite beyond the
grasp of our minds. To give a rough idea of it in figures is useless as
no one can comprehend the real value of a figure or two followed by
probably from a dozen to twenty "noughts." It is best to content
ourselves with the general statement that a speck of matter only just
visible to the eye contains an exceedingly vast number of atoms. Of
course a speck of radium is no exception to this and we must remember,
too, that all of them do not break up at once. Indeed, the number
breaking up at any time are actually countable by means of a very simple
contrivance and a sensitive electrometer. Consequently, in view of the
enormous number present and the comparatively small number breaking up
at any moment, it is not surprising to hear that, so it is estimated,
the process can go on for an almost indefinite number of years,
certainly for hundreds. There are, moreover, certain facts which we need
not go into here from which the above fact can be clearly inferred,
quite apart from what has been said about the vast numbers of the atoms.
It seems as if the uranium atoms break up first, giving off helium atoms
and electrons and leaving an intermediate substance called Ionium which
in its turn breaks up giving off the same things again and leaving
radium. That in its turn goes through a complicated series of changes
still giving off the same alpha particles or atoms of helium and
electrons until, it is suggested, it finally settles down into the
simple commonplace metal lead of which we make bullets and water pipes
and such-like ordinary things.
We see then that all through its history--its radio-active history at
any rate--this stuff is throwing off atoms of helium at a very high
velocity (about 50,000 miles a second), and if it be enclosed in
anything this enclosing vessel or substance will be subjected to a
continual bombardment by the alpha particles. Now just as a piece of
iron gets hot if we hammer it, so the enclosing matter is heated by the
continual blows which it is receiving night and day, year in and year
out, from the alpha particles.
Consequently the immediate surroundings of a speck of radium are always
slightly raised in temperature.
Moreover, if a speck of radium be placed against a screen covered with
suitable materials each particle which strikes it will make a little
splash of light. At least that is what it looks like when seen through a
magnifying glass, but to the naked eye there only appears a beautiful
steady glow.
Suppose, then, that instead of putting the speck of radiant matter in
front of a screen we mix it up intimately with a fluorescent substance
such as sulphide of zinc, we then get the same conditions in a slightly
different form. Each particle of the substance serves as a tiny screen
which glows every time a particle hits it. Thus is produced a luminous
paint which glows by night, suitable for painting the dials of
instruments which have to be used in the dark.
No doubt some of my readers will have experienced the strangely mingled
delight and horror of seeing a Zeppelin in the night sky intent on
dropping murder and death on the sleeping civilians of a peaceful town
or city. Some too may have witnessed the later acts in that wonderful
drama, when, beside the silvery monster illuminated by the beams of the
searchlight there must have been, though quite invisible, a little
aeroplane manned by one man or at most two. That aeroplane was, no
doubt, fitted with instruments at which the pilot glanced now and then
and which he was able to see and read because of the tiny speck of
radium mixed into the paint. The little alpha particles gave him the
light by which to see, but they gave no help to the Germans on the
Zeppelin. Hence, in due time he did his work and the gigantic balloon,
the pride of the Kaiser and his hordes, fell to the ground, a blazing
wreck. How he did it I cannot tell, but of this I am sure, that most
probably radium helped him by making luminous and visible the
instruments which guided him.
But probably it has rendered and will still render us even greater
services in the way of helping to repair the damages to our injured
manhood. How many men came back from the war crippled with rheumatism
because of the hardships through which they went. That disease is
believed to be due to a substance which mingles with the blood and
which, although usually liquid and harmless sometimes changes into a
solid and settles in the joints. Now it is believed that radium properly
administered will act upon that solid and cause it to change back into
its liquid form again, thereby curing the disease. Certainly many of the
mineral springs at such places as Bath and Buxton give forth a water
which shows a certain amount of radio-activity and it may be that which
gives those waters their healing properties. If so, we may look forward
with confidence to the time when radio-activity will be induced to play
a still more successful part in meeting this painful and widespread
illness.
Then, of the other ills which will inevitably arise in our men through
the hardships which they have endured are sure to be some of the
cancerous type, many of which appear to succumb to treatment by radium.
If a very small quantity indeed be carried for a few days in a pocket it
will imprint itself upon the skin beneath as if it burnt the tissues. It
is never advisable, therefore, to carry radium in the pocket without
special precautions. One cannot help feeling, however, that in that
little fact is a hint of usefulness when the best modes of application
have been discovered, for as a means of safely and painlessly burning
away some undesirable growth it would seem to be without a rival. It is
said, too, that it has the strange power of discriminating between the
normal and the abnormal, attacking the latter but leaving the former, so
that when applied, say, to some abnormal growth like cancer it may be
able to remove it without harmful effect upon the surrounding tissues.
Of this, however, it is too soon to write with confidence. It has not
been known long enough for our doctors to find out the best modes of
use, but that will come with time: meanwhile there are indications that
in all probability it will render good service to mankind.
CHAPTER IV
A GOOD SERVANT, THOUGH A BAD MASTER
One morning during the war the whole British nation was startled to
learn that Mr. Lloyd George, then the Minister of Munitions, had taken
over a large number of distilleries. Could it be that he, a teetotaller
and temperance advocate, was going to supply all his workers with
whiskey? Or was he going to close the places so as to stop the supply of
that tempting drink?
Neither of these suggestions was his real reason. What he wanted the
distilleries for was to make alcohol for the war, not for drinking
purposes but for the very many uses which only alcohol can fulfil in
most important manufactures.
Probably alcohol is the next important liquid to water. For example,
certain parts of shells have to be varnished and the only satisfactory
way to make varnish is to dissolve certain gums in alcohol. The spirit
makes the solid gum for the time being into a liquid which we can spread
with a brush, yet, after being spread, it evaporates and passes off into
the air, leaving behind a beautiful coating of gum. That is how all
varnishing is done, the alcohol forming the vehicle in which the solid
gum is for the moment carried and by which it is applied. It is far and
away the most suitable liquid for the purpose, and without it varnishing
would be very difficult and unsatisfactory. Hence one need for alcohol,
to carry on the war.
Then again some of the most important explosives are solid or
semi-solid, and yet they require to be mixed in order to form the
various "powders" in use by our gunners. The best way to bring about
this mixture is to dissolve the two components in alcohol, thereby
forming them both into liquids which can be readily mixed. Afterwards
the alcohol evaporates; indeed, one of its great virtues for this and
similar purposes is that it quietly takes itself off when it has done
its work like a very well-drilled servant.
What then is this precious liquid and how is it produced? In order to
answer that question it is necessary first to state that there are a
whole family of substances called "alcohols," all of which are composed
of carbon, hydrogen and oxygen in certain proportions. There are also a
number of kindred substances also, not exactly brothers but first
cousins, so to speak, which because of their resemblance to this
important family have names terminating in "ol."
They owe their existence to the wonderful behaviour of the atoms of
carbon. In order to obtain some sort of system whereby the various
combinations of carbon can be simply explained chemists picture each
carbon atom as being armed with four little links or hooks with which it
is able to grapple, as it were, and hold on to other atoms. Each
hydrogen atom, likewise, has its hook, but only one instead of four.
Now it is easy to picture to ourselves an atom of carbon in the middle
with its hooks pointing out north, south, east and west with a hydrogen
atom linked on to each. That gives us a picture of the molecule of
Methane, the gas which forms the chief constituent of coal gas such as
we burn in our homes. Methane is also given off by petroleum and it is
the cause of the explosions in coal mines, being known to the miners as
"firedamp." It is the first of a long series of substances which the
chemist called paraffins. The first, as you see, consists of one of
carbon and four of hydrogen. Add another of carbon and two more of
hydrogen and you get the second "Ethane." Add the same again and you get
the third, Propane, and so on until you can reach a substance consisting
of thirty-five parts of carbon and seventy-two parts of hydrogen. All we
need trouble about, however, is the first two, Methane and Ethane.
We have pictured to ourselves the molecule of methane: let us do the
same with ethane. Imagine two carbon atoms side by side linked together
or hand in hand. Each will be using one of its hooks to grasp one hook
of its brother atom. Hence each will have three hooks to spare on to
which we can hook a hydrogen atom. Thus we get two of carbon and six of
hydrogen neatly and prettily linked up together. The atoms form an
interesting little pattern and to build up the various paraffin
molecules with a pencil and paper has all the attractions of a puzzle or
game. All you have to do is to add a fresh atom of carbon alongside the
others and then attach an atom of hydrogen to each available unused
hook. If you care to try this you will get the whole series, each one
having one atom of carbon and two of hydrogen more than its predecessor.
If you mix together a quantity of methane and an equal quantity of
chlorine, which I have shown you in another chapter how to get from
common salt, a change takes place, for in each molecule of methane one
hydrogen atom becomes detached and an atom of chlorine takes its place.
How or why this change occurs we do not know. It is a fact that the
chlorine has this power to oust the hydrogen and there we must leave it,
for the present at any rate. The substance so formed is called methyl
chloride.
In another chapter reference has been made to that substance which is
made from common salt and which is so important in so many manufactures
called caustic soda. If we bring some of it into contact with the methyl
chloride the chlorine is punished for its rudeness in displacing the
hydrogen; it is paid back in its own coin, for it is in turn displaced
not this time by a single atom but by a little partnership called
"hydroxyl" one atom of hydrogen and one of oxygen acting together. We
can again form a neat little picture of what happens. The oxygen atom
has two hooks, one of which it gives to its friend the hydrogen atom and
thus they go about hand-in-hand, the oxygen having one unused hook with
which to hook on to something else. In this case it hooks on to that
particular hook from which it pushes the chlorine.
We have thus seen two changes take place. First, the hydrogen is
displaced by the chlorine: then the chlorine is turned out and its place
taken by the hydroxyl. And during both these changes the central carbon
atom and its three hydrogen partners have remained unaffected. Those
four atoms are called the methyl group, and a methyl group combined with
a hydroxyl group forms _methyl alcohol_.
Similar changes can be brought about with Ethane as with Methane, and in
them the two carbon atoms and the five hydrogen remain unchanged, whence
they too are regarded as a group, the Ethyl group, and an ethyl group
hooked on to a hydroxyl group gives us a molecule of _ethyl alcohol_.
These groups of which we have been speaking never exist separately
except at the moment of change, but in the wonderful changes which the
chemist is able to bring about the atoms forming these groups seem to
have a fondness for keeping together and moving together from one
substance into another. In a word, they behave as if they were each a
single atom and they are called by the name of Radicles; the word simply
means a little root.
The methyl radicle and the ethyl radicle, since they form the basis of
two of the paraffin series, are called paraffin radicles, so that we can
describe this useful alcohol as a paraffin radicle with a hydroxyl
radicle hooked on to it. If we use the methyl radicle we get methyl
alcohol: if we use the ethyl radicle we get ethyl alcohol.
Now ethyl alcohol is the spirit which is contained in all strong drink.
Whiskey has as much as 40 per cent and brandy and rum about the same,
while ale has only about 6 per cent. All of them may be regarded as
impure forms of ethyl alcohol, the various impurities giving to each its
particular taste.
Ethyl alcohol, too, is what is sold at chemists' shops as "spirits of
wine," where also we can purchase that which is familiar as "methylated
spirits," whereby there hangs a tale.
All Governments regard alcohol for drinking as a fit subject for
taxation. When anyone buys a drink with alcohol in it a part of what he
pays goes to the Government in the form of duty. On the other hand, when
alcohol is used for trade purposes, for making varnish or something like
that, there is no reason whatever why it should be charged with duty.
But if the varnish manufacturer is to have alcohol duty-free what is to
prevent him from using some of it for drinking?
To get over the difficulty, that which is supplied to him or to anyone
else for trade purposes is deliberately adulterated so as to make it so
extremely nasty that no one is likely to want to put it in his mouth.
It so happens that methyl alcohol, while as good as the other for many
purposes, is horrible to the taste and so it forms a very convenient
adulterant for this purpose. Therefore, when methylated spirit is sold
to you for drying your photographs, the chemist gives you ethyl alcohol
with enough methyl alcohol in it to make sure that neither you nor
anyone else will ever want to drink it.
That, then, is alcohol: a near relative of paraffin oil and also of coal
gas, yet it is from neither of these that we get it. The changes
described above enable you to realize what it is, but they do not tell
how it is made in large quantities.
Ethyl alcohol is obtained from sugar by the employment of germs or
microbes. Any sort of sugar will do: it need not be sugar such as we
eat. In practice the sugar is usually obtained from starch, that very
common substance which forms the material of potatoes, grain of all
kinds, beans and so on. There is a kindly little germ which will quite
readily turn starch into sugar for us if we give it the chance.
The maltster starts the process. He gets some grain, and spreading it
out in a damp condition upon his floor sets it a-growing. As soon as it
has just started to grow, however, he transfers it to his kiln, where by
heating it he kills the young plants. As is well known, every seed
contains the food to nourish the little growing plant until it is strong
enough to draw its supplies from the soil and the food thus provided for
the young wheat plant is starch, which, when it is ready for it, it
turns into sugar. The little shoot lives on sugar and the maltster and
distiller conspire to steal that sugar intended for the baby plants and
turn it into alcohol.
So the little plant liberates by some wonderful means a material called
diastase, which has the power of changing starch into sugar. It does it,
of course, for the purpose of providing its own necessary food, but the
maltster does not want the process to go too far: he only wants to
produce the diastase, and that is why he kills the plants, after which
he has finished with the matter and hands the "malted" grain or "malt"
over to the distiller for the next process.
The distiller mixes the malt with warm water, whereupon the diastase
commences the conversion of the starch of the grain. At this stage fresh
grain may be added and potatoes, indeed almost anything composed largely
of starch for the diastase to work upon. The process goes on until, in
time, the liquid consists very largely of sugar dissolved in water,
which is strained away from what is left of the grain, etc.
Malt sugar is very similar to, but not quite the same as, cane sugar. It
consists of twelve parts of carbon, twenty-two of hydrogen and eleven of
oxygen. It is an interesting little puzzle to sketch those atoms out on
paper, each with its proper number of hooks, and see how they can be
combined together. Malt sugar, milk sugar and cane sugar all consist of
the same three elements in the same proportions and the difference
between them is no doubt due to the different ways in which the atoms
can be hooked up together.
Yeast is next added to the liquid, upon which the process of
fermentation is set up, the tiny living cells of the yeast plant
producing a substance which is able to change the sugar into alcohol.
The alcohol thus formed is, of course, combined with water, but it can
be separated from it by gentle heating since it passes off into vapour
at a lower temperature than does water. Thus the vapour first arising
from the mixture is caught and cooled whereby the liquid alcohol is
obtained. This operation, called fractional distillation, has to be
repeated if alcohol quite free from water is required, in addition to
which the attraction which quicklime has for water is called into play
to coax the last remnant of water from the other.
And now, how about the methyl alcohol? That is obtained in quite a
different way, by heating wood and collecting the vapours given off by
it. Hence it is often called "wood spirit."
As a matter of fact, at least two very valuable substances are obtained
by this operation, methyl alcohol and acetone.
The vapours given off by the wood are cooled, whereupon tar is formed
while upon it there floats a dark liquid which contains the wood spirit,
acetic acid and acetone.
To capture the acetic acid lime is added to the mixture, and since there
is a natural affinity between them, the acetic acid and lime combine
into a solid which remains behind when the whole mass is suitably
heated. What comes over in the form of vapour is a mixture of water,
acetone and wood spirit. The former is enticed away by the use of
quicklime, while the other two are separated by the process of
fractional distillation already referred to.
Now let me ask you to form another little picture, either in your mind
or with paper and pencil. Imagine two methyl radicles, each, let me
remind you, a carbon atom with three hydrogen atoms hooked on and one
spare hook. Also imagine one atom of oxygen with its two hooks
outstretched like two arms, and just link one radicle on to each. Then
you have the picture of methyl ether. All the ethers are formed by
taking two of the paraffin radicles and linking them together by means
of the two hooks of an oxygen atom. The ether which is so largely used
in hospitals for wounded soldiers is _ethyl_ ether, consisting of two
ethyl radicles joined by oxygen. How it is made we will come to in a
moment, but as you see already it is a close relative of alcohol.
Now from methyl ether take away the central oxygen and in its place put
carbon. This atom will have two hooks to spare which it can employ to
hold on to the two hooks of the oxygen. The result is a molecule of
acetone.
This is used as a solvent in a similar manner to alcohol for many
purposes, and there was a great demand for it no doubt during the war.
One interesting use of acetone is in connection with the gas acetylene.
Of great use both for lighting and also in conjunction with oxygen for
welding and cutting metals, this gas suffers from the disadvantage that
it cannot be compressed into cylinders and carried about as oxygen can.
It can, however, be dissolved in acetone. The cylinders in which it is
carried are therefore filled with coke saturated with acetone and then
when the acetylene is pressed in it dissolves, coming out of solution
again as soon as the pressure is released. In this dissolved condition
it is quite safe to carry about.
For a moment let us turn back to the commencement of the chapter to the
subject of methane. When mixed with chlorine, it will be remembered,
one hydrogen atom gave place to a chlorine atom. If the process be
repeated another hydrogen atom will be displaced in the same way, while
a further repetition will result in the removal of a third, when there
will be a carbon atom in the centre with three chlorine and one hydrogen
hooked on to it. With that picture in your mind's eye you will be
contemplating the molecule of that wonderful and beneficent substance,
chloroform. When we think of the numberless operations which have been
carried out by the surgeons in the course of this last war we realize a
little how great is the total sum of pain and suffering which has been
saved through the agency of this substance, this simple neat little
arrangement of five tiny atoms.
Now that again is obtained in manufacture from alcohol. Alcohol,
bleaching powder and water are mixed and then distilled, by which of
course is meant that the mixture is evaporated by heat and the vapour
collected and cooled back into liquid again. The liquid so obtained is
chloroform.
Hardly less important than this, in our military hospitals, is ether, to
which reference has already been made. It, too, is manufactured from
alcohol. The alcohol, together with sulphuric acid, is placed in a still
and heated, the vapour given off being led to another vessel and there
condensed. The liquid thus obtained is ether and so long as the supply
of fresh alcohol is kept up the production of ether goes on
continuously.
The sulphuric acid does not disappear and so does not need to be
replaced, from which it would appear as if it might just as well not be
there, but that is not the case. It plays the part of what is called a
"catalyst," one of the curiosities of chemistry. There are many
instances in which two things will combine only in the presence of a
third which appears to be itself unaffected. This third substance is a
catalyst. It reminds one of the clergyman at a wedding who unites others
but remains unchanged himself.
In conclusion, one may mention that many of the medicines with which our
injured men were coaxed back to health and strength owe their existence
to alcohol, for many drugs are obtained from vegetable substances by
dissolving out a part of the herb with alcohol.
Thus, as a drink, it is unquestionably very harmful. Indeed, in that way
it probably kills more people per year than its use in the manufacture
of explosives caused in the worst year of the war. Yet it also furnishes
chloroform, ether and medicinal drugs and performs a whole host of
useful services to mankind. Finally, if oil and coal should ever run
short it is quite prepared to run our engines for us. Truly it is a
wonderful substance.
CHAPTER V
MINES, SUBMARINE AND SUBTERRANEAN
The word mine in its military sense originally meant just the same as it
does in the ordinary way, but like many other words it has got twisted
into new uses the connection of which with the original meaning is very
obscure. One of the most striking of these verbal puzzles is the
submarine _mine_. There seems at first sight not the remotest connection
between the floating barrel of explosives concealed beneath the water
and what we ordinarily call a mine. The explanation of this is that the
term has acquired this meaning after passing through a series of stages.
When soldiers "mine" for the purpose of blowing up their enemies they
dig a hole in the ground, and conceal therein a quantity of explosives
so arranged that they blow up when the enemy pass over or near. The
operation of digging the hole in the earth is clearly akin to the work
of the miner and so such is quite appropriately called a "mine."
The hole may be dug from the surface downwards, the marks of excavation
being afterwards covered up and obliterated as much as possible. In
other cases the hole may be a tunnel starting from a trench and driving
towards the enemy's position. The idea, of course, is to burrow until
the end of the tunnel is just under some important part of the enemy's
works or fortifications. When the end of the tunnel has reached the
right spot explosives can be placed there, the tunnel partly stopped to
prevent the explosion from driving back upon those who make it and the
whole fired at the desired moment.
This tunnelling is also called "sapping" and the tunnel itself a sap.
Military engineers are often spoken of as "sappers and miners" as if the
two things were clearly different, but as a matter of fact both are
often used to describe the same thing. Roughly, we may say that a mine
which stays still in the hope that the enemy will walk upon it is a mine
proper, while a mine which itself progresses towards the enemy until it
ultimately goes off beneath him, is a "sap" and the making of such a
thing is "sapping." Or we might say that sapping is under-mining, in
which sense we use it in general conversation when we speak of something
sapping a man's strength. Soldiers speak of their engineering comrades
as "sappers" just as they term artillerymen "gunners," but the only
reason why they call them by that name instead of miners is because the
latter is a well-known term applied to those who work in coal mines.
A subterranean mine, then, is nothing more or less than a hole in the
ground, made in any way that may be convenient, filled with explosives
and fired at a suitable time to do damage to the enemy.
In other words, it is simply some explosive _concealed in the ground_
with means for firing it, and when the sailor _conceals explosives in
the sea_ so that they may blow up the enemy's ships, he borrows his
military comrades' term and calls it a "mine" too.
Counter-mining is the enemy's reply to mining. Suppose I was foolish
enough to wish to blow up my neighbour who lives in the house opposite
to mine. I might start from my cellar and dig a tunnel under the road
until I knew that I had arrived under his dwelling. But suppose that he
got to know of my little scheme: he could then try counter-mining. In
this case it would mean starting a tunnel of his own from his cellar
towards my tunnel: then, as soon as the two tunnels had come
sufficiently near to each other, he could let off his explosives thereby
wrecking my tunnel and putting an end to my operations while yet I was
only half-way across the road. Thus he would stop me before I had had
time to harm him, and since he need only tunnel just far enough to
render the necessary explosion harmless to his house, while I to succeed
would have to tunnel right across the road, the man who is
counter-mining always has a slight natural advantage over the man who is
doing the mining. If only he gets to know what is going on in time he
can always retaliate.
All forms of land mine are improvised on the spot according to
circumstances. Not so, however, with submarine mines on which much
ingenuity has been expended, the mines being made in workshops ashore
ready for laying and then laid by ships and sometimes by divers.
Of these there are two main kinds, those which are put in place in times
of peace for the protection of particular harbours and channels, and
those which are simply dropped overboard from a mine-laying ship during
the actual war.
They all consist essentially of a case of iron or steel plates riveted
together just as a steam boiler is made, in fact the cases are made in a
boiler shop. The charge is gun-cotton fired by a detonator, the latter
being excited by a stroke from a hammer, as in a rifle, or else by
electricity. In the latter case, a tiny filament of platinum wire is in
contact with the detonator, and the wire being heated by the current,
just as the filament of a lamp is, the detonator is fired by the heat.
Of the permanent mines whereby the entrances to important channels are
protected arrangements are often made for firing by observation, that is
to say, by the action of an observer ashore. Being laid by divers and
securely anchored to heavy weights laying on the bottom, wires are
carried from the mines to the observation station. The observer watches
and fires the mines at the right moment by simply pressing a key thereby
making the electrical circuit.
More often, however, mines are fired by contact. Observation mines have
the advantage that while they may be exploded under an enemy they will
allow a friendly ship to pass in perfect safety. Contact mines, on the
other hand, will afford protection against attacks by night when enemy
craft may attempt to creep in under cover of darkness.
[Illustration: AN ITALIAN MINE-LAYER.
This photograph was taken looking down upon the deck of the ship. The
mines run upon rails, and are pushed by the men towards the stern,
whence they are dropped one at a time into the water. The splash
indicates that one has just fallen.]
Contact mines are often fired electrically, sometimes by batteries of
their own inside their own cases, or else by current from the shore
through wires, the circuit being completed by an automatic device of
some sort actuated unwittingly by the unfortunate victim.
One of these contact devices will illustrate the general character of
them all. Imagine a little vessel with mercury in it: it is, generally
speaking, of some insulating material, but right at the bottom is a
metal stud with which the mercury makes contact. The rim may likewise be
of metal or a metal rod may project downwards into it: it matters not
which, for we can see at once that it is quite easy so to arrange things
that whereas, while upright, the mercury shall be well clear of the
upper contact, it shall when the vessel is tilted flow on to it, thereby
bridging from lower contact to upper contact and completing the circuit.
Of course, a mine must only go off when actually struck by a ship and
not when it is gently swung to and fro by the action of tide or current
in the water. That is easily arranged, for the vessel and contacts can
be so shaped that contact is not made until an angle of tilt is reached
which no tide or ordinary commotion of the water could bring about.
It is clearly possible, too, to combine the contact and observation
arrangements in such a way that contact mines can be made safe for
friendly ships during the daytime. It is only necessary to adopt the
shore battery arrangement already mentioned and disconnect the batteries
during the day or when no enemy is in sight, restoring the connection
during the darkness or in the event of hostile ships trying to rush the
passage.
Another interesting scheme for keeping mines safe until required is to
anchor them in what is termed a "dormant" condition. This means that a
loop is taken in the wire rope by which they are anchored, the loop
being fastened by means of a link. This link, however, contains a small
quantity of explosive which can be fired from the shore. This has the
effect of breaking the link, releasing the loop and allowing the mine to
float upwards to the full length of the rope. Thus the mine is down
deep, well below the bottom of the biggest ship until released for
action.
It is doubtful whether much use is made nowadays of permanent mines of
the types just described, for they have, no doubt, been largely
displaced by the temporary mine which can be laid in a moment by simply
being dropping overboard from a ship, but it is quite possible that some
of the defences of, say, the Dardanelles, were of the permanent nature.
So let us pass on to the temporary mines. These were used by the Germans
from the first few hours of the war. One of the first naval incidents
was when our ships discovered a small German excursion steamer which had
been converted into a mine-layer strewing these deadly things
surreptitiously in the North Sea in the hope that some of our vessels
would run upon them. Needless to say, that ship went on no more excursions.
Laid thus, it is evident that there can be no wires running ashore, so
that all mines of this class must be contact mines. What makes them of
extreme interest is the way they are laid. Just think for a moment what
is involved. From the very nature of things their laying must often be
done in secret. It is not the British practice to place them in the open
seas, except avowedly, after due notice, in certain specified areas,
where they are laid quite openly under the protection of adequate forces
to ensure against interruption. There is little doubt, however, that
they have laid many a mine field secretly in purely German waters, while
everyone knows that the Germans have not hesitated to sow the shipping
routes broadcast with these things, such work of course being done
secretly and largely at night.
The mine can therefore only be laid by dropping it into the water and
leaving it. Yet it must not float on the surface or it will be easily
seen and picked up; it must float below, so that the unsuspecting ship
may run upon it. And it is quite impossible to make a thing float in
water anywhere except upon the surface. If it does not float upon the
surface it sinks to the bottom: there is no "half-way house" between.
Many people are surprised to hear this, judging, no doubt, by the fact
that a balloon floats _in_, and not on, the air and expecting an object
floating in water to be able to do the same thing. The difference is due
to the fact that air is easily compressible, so that the air close to
the earth is denser, more compressed, and therefore heavier, than the
air higher up owing to its having the whole weight of the upper air
pressing downwards upon it. The density of the air diminishes, for this
reason, as one ascends, and a balloon which displaces more than its own
weight of air at the surface of the earth rises until it has reached
just that height when the air displaced exactly equals in weight the
balloon itself: then it goes no higher.
Precisely the same conditions exist in the sea except that water being
incompressible is no denser at the bottom of the sea than on the
surface. Therefore, if a thing sinks at all it sinks right to the
bottom.
There is one very ingenious device for overcoming this difficulty by
means of a motor and propeller. The mine has enclosed in its case a
motor driven by a store of compressed air which operates a propeller. In
this it is somewhat like a torpedo, but in this case the propeller is
set vertically so that its action lifts the mine up in the water. Now
the mine is so weighted that it just and only just sinks when dropped
in, but on reaching a certain depth the motor starts and by means of the
propeller raises it nearly to the surface again. On nearing the surface
the motor stops and the mine sinks once more, only to be raised again in
due course, so that the thing keeps on rising and falling; it never
rises above a certain depth nor falls below a certain depth, but
oscillates continually between its two limits.
The question then arises, what starts and stops the motor at precisely
the right moments to produce this result? It is done by means of a
hydrostatic valve. As just pointed out, the water at the bottom of the
sea is supporting the weight of all that water which is above it. The
water is not compressed by this, but the pressure is there all the same.
Obviously the degree of pressure at any point depends upon the weight of
the layer of water above, and since the weight of that layer will
obviously increase and diminish with its thickness it follows that,
starting from the surface, where the pressure is nil, we get a perfectly
steady and regular increase as we descend, until we reach the maximum at
the bottom. Now within the mine is a small watertight diaphragm, the
outer surface of which is in contact with the water and upon which,
therefore, the water presses. As the mine descends, therefore, this
diaphragm is bent inwards more and more by the pressure of water and
that is made to start the motor. Adjustments can easily be made so that
a certain degree of bending shall result in starting the motor, which is
the same as saying that the motor shall start automatically at a certain
depth. Likewise as the mine rises under the influence of the propeller
the pressure decreases, the diaphragm straightens out and at a certain
predetermined depth the motor is stopped.
When, finally, the store of motive power is exhausted the mine sinks to
the bottom and is lost, a very valuable feature from a humanitarian
point of view, since it means that the active life of the mine is short
and it cannot go straying about the oceans for weeks or even months,
finally blowing up some quite innocent passenger ship.
More often, however, this difficulty of depth is overcome by anchoring
the mine at the depth most suitable for striking the bottom of a passing
ship. But here again there seem to be insuperable difficulties, for the
depth of the sea varies and so the length of the anchor rope must be
varied with almost every mine that is laid. It has been found possible,
however, to make the mines automatically adjust the length of their own
anchor ropes so that the desired result is attained without difficulty
no matter how deep the sea may be. Let me describe how it is done in the
Elia mines used by Great Britain. The inventor, Captain Elia, was an
officer in the Italian Navy.
The mine consists of three parts: (1) the mine proper, a case containing
the explosive, gun-cotton and the firing mechanism; (2) the anchor; and
(3) the weight, all of which are connected together by suitable wire
ropes.
The mine is lighter than water and so floats: the anchor, which bears no
resemblance to the ordinary anchor but which is an iron case containing
mechanism, only able to act as an anchor by virtue of its weight, is
heavier than water and so sinks, while the weight of solid cast iron
sinks more readily still.
The anchor is often fitted with wheels so that it forms a truck upon
which the mine and the weight are placed, the whole running upon rails
laid on the deck of the mine-layer. As this ship steams ahead the men
push the mines along the rails, dropping them over the stern at regular
intervals.
When the thing reaches the water, the weight sinks the most rapidly,
thereby tugging at the chain whereby it is connected to the anchor. The
latter, being less compact, sinks more slowly so that the pull upon the
rope is maintained until at last the weight rests upon the bottom. _Then
and only then is the pull relaxed._ Now inside the anchor is a winch,
upon which is wound a length of flexible wire rope, the other end of
which is attached to the mine. The latter, it will be remembered, is
light enough to float and so, since it lies upon the surface while the
anchor sinks, the rope is drawn off the winch. But there is a spring
catch which is able to hold the winch and to prevent it from paying out
rope, and that catch is only held off by the pull of the weight.
Consequently, as soon as the weight touches the bottom and its pull upon
the anchor ceases, the winch is gripped by the catch, no more rope is
paid out, and from that moment, as the anchor descends, it drags the
mine down with it.
The result, then, is that the mine becomes anchored at a depth below the
surface roughly equal to the length of the rope connecting weight to
anchor.
Mines of this kind can, of course, be fired electrically by the tilting
of a cup of mercury or similar device as already described. Another
arrangement is to fit projecting horns upon the surface of the mine made
of soft metal so that they will be bent or crushed by a strong blow such
as a passing ship would give. This breaks a glass vessel inside,
liberating chemicals which cause detonation.
The method adopted in the Elia mines is to have a projecting arm pivoted
upon the top of the mine. The mine is spherical (they are nearly all
either spherical or cylindrical), with the rope attached to the South
Pole, so to speak, and the arm pivoted to the North Pole. As the mine
floats in the water the arm projects out horizontally. The effect of
this arrangement is that when a ship strikes the mine the latter rolls
along its side, but the arm being too long, simply trails along. Thus
the spherical case of the mine turns while the arm remains still and
that is made to unscrew and eventually release a hammer which, striking
the detonator, fires the mine.
In other words, this type of mine is exploded not by the ship giving it
a blow, but by its rubbing itself along in contact with the mine. The
great advantage of this is that it is only a ship that can do this. No
chance commotion in the water can do it: no chance blow from floating
wreckage can do it: only the rubbing action of a ship can accomplish it.
Such a mine, too, is less likely to be affected by counter-mining, of
which more presently.
Apparently the laying of these mines must be very dangerous work, for
since a blow will explode most of them, what is to prevent their
receiving that blow while on the deck of the mine-layer, or at all
events as they are dropped into the water.
In all cases, precautions are taken against such an event. Sometimes a
hydrostatic valve is employed, the arrangement being that the firing
mechanism is locked until released by the valve, until, that is, the
mine is immersed to a predetermined depth in the water.
Another device for the same purpose is a lump of sugar. The mine is so
made that it cannot be fired until this lump has been melted by the
action of the water: sal ammoniac is another substance employed for the
same purpose. The technical term for this is a "soluble seal." The
firing arrangement, whatever it may be, is sealed up so that it cannot
come into operation until the seal has been dissolved away by the water,
or until the mine has been in the water long enough for the mine-layer
to get out of harm's way.
Another interesting feature of the Elia mine is connected with the
source of the power which drives the hammer which causes the explosion.
The anchor, it will be remembered, pulls the mine down under water, the
latter being of itself buoyant. There is a continual pull, therefore,
upon the rope by which the mine is held under. It is that pull which
works the hammer.
And now observe the beautiful result of that simple arrangement. Suppose
the mine breaks its rope and gets loose, so that it can drift about and
carry danger far and wide. It can break loose and it can drift about,
but at the very moment of getting loose the danger vanishes, for the
rope ceases to pull and the firing mechanism loses its motive power.
In other mines the same result has been sought by means of clockwork,
which throws the firing arrangements out of action after the lapse of a
given time. This scheme of Captain Elia's, however, whereby the very act
of breaking adrift produces its own safeguard, is one of the most
delightful instances of a happy invention.
In conclusion, just a word about the measures taken against mines.
Counter-mining is one. It consists in letting off other mines in the
midst of a mine-field with the purpose of giving them such a shaking up
that some of them will be exploded by the shock.
The simplest and indeed the only effective way, however, seems to be the
simple primitive method of dragging a rope along between two light
draught vessels and thus tearing the mines up by their roots, so to
speak. The very act of thus dragging it along by its anchor rope often
causes a mine to explode, well astern of the mine-sweeping vessels, but
sometimes they are pulled up and fired or sunk by a shot from a gun
which the sweeper carries for the purpose.
The sweeping up of the mine-fields is a duty often allotted to the steam
fishing boats or trawlers, whose crews seem particularly well fitted for
the work. It is a hazardous duty, and many lives have been lost through
it. Let us hope that in time to come all submarine mines and the dangers
connected with them will be a thing of the past, for they are mean,
cowardly and contemptible weapons.
CHAPTER VI
MILITARY BRIDGES
Bridging has always been an important part of actual warfare. In my
school days I studied "Cæsar" from a textbook which is not much in use
nowadays and which had very copious notes, prominent among which was a
description, with drawings, of a bridge made by the Roman Legions in
Gaul. And a fine bridge it was, too. How its details came to be known
was partly through the description given by Cæsar himself and partly by
a study of certain old timbers found in the bed of the Rhone, which
timbers were believed to be relics of the very bridge which the great
Julius himself had had built.
This bridge of nearly two thousand years ago appeared to be built of
baulks of timber fastened together in very much the same manner as that
adopted by the engineering units of the great armies of to-day.
Every observant person has noticed how tall poles and short sticks tied
together with ropes can be fashioned into the firm, strong scaffolding
from which workmen can in safety raise great tall buildings. That mode
of construction can always be used to form a bridge.
Equally well known, no doubt, are the gantries built over the footway
while a large building is in course of construction. Generally of huge
square baulks of timber, they are intended to carry very heavy loads of
materials and to save the public passing beneath from any possibility of
damage through heavy objects falling from above. Those gantries furnish
us with an example of another sort of construction in wood which can be
and is often used in bridging.
When the Germans retired in Northern France they blew up all bridges
behind them, and before the Allies could use those bridges they had to
repair them. If only for foot-traffic, a contrivance of poles, lashed
together after the manner of the builder's scaffold, is ample in most of
such cases and by its means a strong and safe bridge can be made upon
what is left of the old bridge in the course of a few hours. For light
vehicles a similar structure but made stronger by more lashings and of
poles closer together will suffice, but for heavy traffic, with guns and
possibly railway trains, recourse has to be had to the heavy timberwork
exemplified by the builder's gantry. This takes longer to make, since
the timbers are big, heavy and not easy to move about: they are,
moreover, not simply laid beside or across each other and tied, but are
cut the right lengths, and one is notched where the end of another fits
into or against it. The baulks are connected by bolts and nuts for which
holes have to be drilled or by rods of iron with a sharply pointed prong
on each end stretching across from one baulk to another, one prong being
driven into each.
With the long-thought-out military operations of modern warfare it is
just possible that steelwork for repairing certain particular bridges
might be prepared in advance and simply launched across when the time
arrives, but that is manifestly impossible except in certain cases and
under particularly favourable conditions, such as railway facilities for
bringing up the new bridge close to the site where it is to go.
Nearly every military bridge therefore has to be more or less improvised
on the spot. In a highly developed country scaffold poles or baulks may
be found or brought up by road or rail, in less civilised lands their
equivalents may be cut and prepared from neighbouring forests, but all
armies have, as a recognised part of their organisation, certain
engineering "field companies," and "bridging trains," which carry with
them large quantities of material carefully schemed out long in advance,
so shaped and so prepared that it can be fashioned into almost anything,
much as the strips of a boy's "meccano" can be adapted to form a great
variety of objects.
First, there are pontoons, large though light boats or punts, about 20
feet long, constructed of thin wood with canvas cemented all over to
give additional strength and water-tightness. Each pontoon rides upon
its own carriage upon which there are also stowed away quantities of
timbers of various sorts, anchors for holding the pontoons in place,
oars for rowing them, ropes of different kinds, and so on.
Each pontoon, moreover, is divided about the middle into two pieces
called respectively the bow piece and the stern piece. The two are
normally coupled together by cunningly devised fastenings but they can
be quickly separated, in which state they form two shorter boats.
Other carriages carry more timber and material intended for the purpose
of forming "trestle bridges" but which is also usable in connection with
the pontoons.
Of this material the chief sorts are "legs," long straight pieces which
form the uprights; transomes, heavier beams which can be fitted across
horizontally between two legs so that the three form a huge letter H or
a very robust Rugby goal; "baulks" which are light timbers tapered off
towards each end for the sake of lightness and of such size that they
fit snugly into notches which are cut in the upper surface of the
transomes; and planks called "chesses" for forming the floors of a
bridge.
Probably the most dramatic incident of the war was when the British,
having been apparently beaten by the Turks in Mesopotamia, driven far
back and their General and many troops captured, suddenly turned the
tables upon their enemies, driving them from Kut and sending them
fleeing helter-skelter to Bagdad and then beyond. Now the capture of Kut
and then of Bagdad were both made possible by the rapid bridging of the
Tigris, and without doubt this is the sort of material which was used.
Let us see how it is done.
An army arrives at a river across which it is decided to throw a pontoon
bridge. The pontoons are unloaded off their wagons and launched into
the water. One is rowed out and anchored a little way from the shore,
while upon the bank parallel with the river is laid a "transome." On the
centre of the pontoon is a centre beam with notches in it like those in
the transomes and from the one to the other "baulks" are passed.
Meanwhile a second pontoon has been rowed into place and more baulks are
passed from the first pontoon to the second, while chesses are laid upon
the baulks to form a platform or floor.
Thus, pontoon by pontoon, the bridge grows until it has reached the
further bank.
If pontoons are scarce and the loads to be carried by the bridge are
light they are divided in two, and instead of a row of pontoons joined
by "baulks" there is a row of "pieces" joined by baulks. Pieces arranged
thus form a light bridge, pontoons a medium bridge, while pontoons
placed closer together form a heavy bridge. Which shall be built depends
upon the number of pontoons available in relation to the width of the
river and the nature of the traffic which will have to pass over.
An alternative arrangement is to make the pontoons up first into groups
or rafts and then bridge from raft to raft instead of bridging between
pontoons.
There is still another way of making the bridge, and that is to put it
together alongside the bank, afterwards swinging it across the river
like the opening or shutting of a door. Anyone can see that there must
be many advantages in this latter method when it is practicable, since
more men can work at once and with greater safety, for all will be near
the bank.
It is evident that such a structure depends for its security entirely
upon the anchors. Those which are carried for the purpose are like those
of a ship but there may not be enough or they may not suit every kind of
river-bed. They are often improvised therefore. Two wagon wheels lashed
together, with heavy stones clipped between them, are said to be a very
effective anchor. Under certain conditions a net filled with stones is
surprisingly effective. Two pickaxes tied together form a good imitation
of the conventional anchor, as also does a harrow sunk and held down by
stones thrown upon it.
Trestle bridges are made in quite a different way. The trestles are
formed of two legs or uprights with a transome between, a shape which
resembles, as has been already remarked, a very robust Rugby goal. The
transome is connected to the legs by a special form of band which
permits it to be fixed at any height without having to drill any special
holes for the connections. The legs are so shaped at their ends that
they can be shod with steel shoes provided for the purpose, enabling
them to get a good foothold even on shifty soil. The trestles are put
together ashore, and each is taken out in a boat or on a pontoon to the
place where it is to stand. Then it is launched feet foremost into the
water, the boat being on the side away from the shore, so that a rope
from the trestle to the shore will enable men on land to pull the
trestle into an upright position.
[Illustration: AN INCIDENT AT LOOS.
This picture gives us some little idea of the devastation caused by
modern weapons. It also shows the inventiveness of the soldier who makes
his rifle into a battering-ram. Incidentally we see a kind-hearted
soldier rescuing a little girl from danger. This incident really
happened.]
Thus trestle after trestle is added until the bridge has grown right
across the water to the further bank. The trestles cannot fall over
sideways because of their own width, they cannot fall forwards or
backwards because of the "baulks" which pass between them and carry the
floor, but as a precaution diagonal ties of rope are always added here
and there along the bridge, that is to say, two trestles are tied
together with two ropes, each rope passing from the bottom of one
trestle to the top of the other, a form of tying which is very effective
and very easy and simple to carry out.
One interesting thing to notice is the form of the "baulks," in which
connection I would like to remark that when I use the word without
inverted commas I mean it in the ordinary sense as implying a big heavy
timber, but when I use the commas I mean it in its technical sense as it
is used in military engineering. In this latter sense it describes the
timbers specially provided for the purposes just described. Large
supplies of the ordinary heavy baulks could not be carried with an army:
but strength is required nevertheless. Hence the military engineers have
invented a form which combines strength with lightness.
If you stand a plank upon its edge, supported at each end so as to form
a beam, its strength will vary as its width and as the _square of its
height_. If then you double its width you only double its strength, but
if you double its height you multiply its strength _four_ times. If you
halve the width of a given beam you halve its strength, but if you then
double its height you quadruple that half, in other words, without
making the beam any heavier by these two operations you double its
strength. Moreover, if you support a beam at each end and pass a load
over it or spread a load permanently upon it, its greatest strength is
required in the middle. You can shave away the ends without making the
beam as a whole any less strong. So these "baulks" are made like planks,
very oblong if looked at endwise, also thinner at the ends than in the
middle. But if by chance they tipped over on to their sides they would
for that very reason be very weak, and that is why the notches are
provided in the transomes and the centre beams of the pontoons, in order
that the "baulks," having been laid edgewise in them, cannot tip over.
Thus a considerable saving is made in the weight of the bridging
material to be carried.
It sometimes happens that when a trestle is dropped into the water one
leg will fall into a depression in the river-bed or will sink more
deeply if the bed be soft, leaving the whole structure lop-sided and
useless. That, however, is easily overcome, since it is provided
against. A little iron bracket, which is carried for the purpose, is
clipped on to the leg which has sunk near its top and on to it is hung a
pair of pulley blocks--one of those little contrivances which everyone
has seen at some time or another by which one man pulling a chain
quickly can raise, although slowly, a heavy load. By this means the end
of the transome is raised until it is horizontal and the legs have
assumed an upright posture, when the transome is refastened to the leg
in its new position. Thus we see the advantage of clamping the transome
to the leg rather than fixing it with any arrangement of holes. The iron
band, which is fastened on to the transome and which grasps the leg, is
so arranged that the greater the load the more tightly does it hold, so
that it is perfectly safe under all conditions.
The trestle bridge has a great advantage over the floating bridge if the
height of the water varies at all, as for instance, with the tide. The
former remains still, while the latter goes up and down, requiring a
special arrangement to be contrived for connecting it to the shore.
Under some conditions a suspension bridge is the most convenient form of
all, particularly if the banks are high and strong, or if the current be
very rapid or the river-bed very soft. In such cases steel wire ropes
are stretched across the water between two trestles. The latter may be
made in the way just described, but more often they have to be stronger
and are built specially out of big strong timbers securely fastened
together. Their form does not matter much so long as they are strong and
stiff, high enough to carry the ends of the suspension ropes and of such
a shape as not to block the entrance to the bridge itself. The higher
they are the better, because, according to the natural laws which govern
such things, the more sag or dip there is in the ropes across the river
the less severely will they be strained. They need to be very strong, as
the whole weight of the bridge and its load falls upon their shoulders.
The pull of the suspension ropes, moreover, tends to pull them forward
into the water, so they must be held back by other strong ropes called
guys, and the action of these two sets of ropes entails the unfortunate
trestles bearing really _more_ weight than the actual weight of the
bridge and load. The guys, too, require very strong anchorage or at the
critical moment they may give way, when the whole contrivance, with
possibly valuable guns or ammunition on board, will be precipitated into
the water. The men may be able to swim but the guns will sink.
Having, then, constructed a trestle upon each bank, securely guyed it
back and connected the suspension ropes to it, the next operation is to
attach smaller vertical ropes to the suspension ropes at intervals, to
support the ends of the transomes. Then upon the latter are laid
"baulks" and upon them the flooring as usual. Or if ropes be not
sufficiently plentiful, timbers may be lashed on to the suspension ropes
instead, the transomes being fastened to them.
That is all that is absolutely essential to a suspension bridge, but one
so formed would be rather flimsy and unstable. It needs to be stiffened
by diagonal timbers at suitable places and often it has props placed
upon the bank reaching out as far as their length will permit over the
water to steady and consolidate what to commence with is rather too much
like a spider's web. Those little strengthening dodges can be laid down
in no books. They need to be left to the judgment of the men in charge
to do what is necessary in the best way they can with the materials
which happen to be at hand.
But very often warfare has to be carried on in the most outlandish
places where armies can only travel light, and where, hampered by
bridging material of the conventional sort, they would have no chance
in catching up with a fleet and agile native enemy. Yet bridges are
needed even more under those conditions perhaps than under any other.
There are many examples of this in the wars just beyond the frontier in
Northern India. Then ingenuity has to make good the luck of prepared
material and the bridges are made of those materials which happen to be
procurable.
An army in India once wanted to cross a river, where no materials of the
ordinary kind were available. The river, however, was lined with tall
reeds. A reed has for centuries been a favourite example of weakness and
untrustworthiness, so how can reeds be made to form a safe bridge? This
is how it was done.
Great quantities of reeds were cut and were made up into neat round
bundles about a foot in diameter. Ropes were scarce too, but these
likewise were improvised by twisting long grasses into ropes. It is
surprising what good ones can be made in this way, and they served their
purpose well. Many bundles having thus been made numbers of them were
tied together so as to form rafts. Each bundle in fact was a small
pontoon, and the rafts which were thus constituted differed only in size
from the regulation rafts made of pontoons.
While this work was being done two ropes were got across the river and
secured on both banks: then rafts were floated down in succession, each
one on arrival being tied up under the two ropes. Finally a track of
boards was laid over the centre and the bridge was strong enough for
men in fours to walk over it.
Had it been necessary, the floor could have been made of brushwood,
interlaced so as to form a kind of continuous matting or of a layer of
branches covered with canvas. Floors for bridges can be made in many
ways.
A dodge which soldiers in the British Army are taught is how to make
boats for bridging purposes out of a tarpaulin or piece of canvas,
supported on a framework of light wood poles or twigs. The outline of
the boat is first drawn roughly on the ground. Then three posts are
driven in on the centre line of the boat and to the top of these three a
horizontal pole is tied, thin, flexible branches stripped of their bark,
being fixed by having their ends stuck in the ground on either side. The
ends are driven in on the outline already marked out so that when done
the branches form a framework like the ribs of a boat upside down. Other
branches are intertwined among these so as to bind them together and
finally a tarpaulin or canvas sheet is laid over all. A number of boats
formed after this fashion can be used as pontoons to support a bridge,
or several can be made into a raft and towed to and fro--a sort of
floating bridge.
Another scheme is to make a number of crates like those in which
crockery and other things are often packed. These are of very simple and
easy construction, consisting of sticks slightly pointed at the ends
driven into other pieces which are perforated with suitable holes to
receive the ends. The only tools necessary are an axe (or even a
pocket-knife will do) to sharpen the ends and an auger to make the
holes. Almost any sort of wood can be made to serve. The cover for this,
and indeed for most of these improvised rafts, is tarpaulin or canvas,
the latter of which, being the material used for so many purposes, is
almost sure to be available in some form or other.
For instance, every one of those familiar "General Service Wagons" has
its large canvas cover. In fact, a general service wagon, taken off its
wheels and wrapped up in its own canvas cover, makes quite a serviceable
boat, pontoon, punt, barge or whatever you like to call it.
Then there is an ingenious type of little bridge which can be quickly
and easily made where bamboos or similar light canes or sticks are
available. The only tool required in making this is a couple of poles
ten feet or so in length. To commence with, these poles are laid side by
side upon the bank with one end of each pointed out over the water,
overhanging it by about four feet. Two men then climb along these, while
others sit upon the inshore ends to keep them from tipping into the
water.
Seated, then, on the outer ends of the poles the men drive some bamboos
or whatever they are using into the water, after which they tie a
crosspiece to the uprights, so forming a light trestle. Then the poles
are pushed forward until they overhang another four feet beyond the
trestle just made, the other men, of course, continuing to sit upon the
rear ends. And so the bridge grows until it entirely crosses the
stream.
Between the trestles other light poles are laid and tied, forming the
floor upon which men can cross in single file.
Another type, known as the "hop pole" bridge is made of slightly heavier
poles which are tied together in threes so as to form isosceles
triangles. Each triangle forms one trestle.
The two poles which form the sides project a little above the apex so
that in fact we have an isosceles triangle with a V at the apex. To the
root of the V another pole is tied loosely and the whole trestle is
pushed feet first into the water. Then, by pushing the pole, it is
forced into an upright position in which it is secured by the pole being
firmly fixed to the shore and strongly lashed to the root of the V
where, before, it was only loosely tied. A second trestle is then in
like manner fixed in front of the first one, connected to it by a pole
just as the first is connected to the bank. And so the thing grows. To
all the upper ends of the V's a light pole is tied to form a handrail.
In this case, of course, the floor of the bridge is nothing more than a
pole, but with the assistance of a handrail it is quite easy to walk
along a single pole.
And that reminds me of a simple type of suspension bridge which, an
engineer officer once assured me, is actually copied from one habitually
made by some of the Indian natives. It consists of three ropes upon one
of which you walk, while the other two form a handrail upon either side.
The three ropes are held at intervals in their correct relative
positions by little wooden frames formed of three sticks tied together,
one rope being tied to each corner of each triangle.
On the banks stakes are driven in and tied back with cords to give
additional strength, and to them the ends of the ropes are secured. One
drawback to this form of bridge is that the ropes are naturally far from
level and one has to walk down a steep hill to commence with and up
again at the other end. I once saw a specimen of this kind of bridge
across a wide ditch, a part of the old defences of Chatham, and an
elderly gentleman who was with me, a man of considerable proportions,
insisted upon trying it for himself. He took but a step or two when his
foot began to slide downhill along the foot rope faster than he dare
move his hands along the hand ropes, with the result that he was very
soon in a very uncomfortable position. Thus he remained, to the
amusement of all his friends, until two stalwart Royal Engineers came to
his aid and "uprighted" him.
In crossing a swamp something in the nature of a bridge is sometimes
required. Canvas laid upon branches often makes a good road over what
would otherwise be impassable.
Rapidly moving detachments of cavalry are provided with what is called
"air-raft equipment," which enables them to get their light "Horse
Artillery" guns across rivers which would be impassable otherwise. It
consists of sixty bags like huge cylindrical footballs except that the
outer covering is canvas instead of leather. These are blown up partly
by the mouth and partly by pumps provided for the purpose until they
are just about as tight as a football should be. Then they are laid out
in rows of twelve, each row being fastened together by the bags being
tied to a pole running lengthwise of the row. Cords are attached to the
bags for the purpose. The five rows are then placed parallel and
connected together by two light planks called wheelways placed across
the rows and tied thereto.
This arrangement is capable of carrying light guns or ammunition wagons.
The men are expected to ride through the water, but if necessary
something can be laid upon the raft, between the wheelways, to form a
floor upon which men and even horses can ride.
As part of the equipment there is a small collapsible boat with oars and
by its means men first cross, carrying with them a line by which,
afterwards, the raft can be hauled to and fro.
Rafts can be made, too, of hay tightly tied up in waterproof
ground-sheets or tarpaulins or canvas. Indeed, given a little ingenuity
and the need to use it (for it is very true that necessity is the mother
of invention), it is surprising what a large variety of things can be
pressed into this service.
Of course, barrels can be made to form excellent pontoons, but there is
one clever little way of using them which is more than usually
interesting, and with that I must conclude this chapter which has
already exceeded its appointed limits.
Imagine two poles perhaps ten feet long, placed parallel. Between them,
at one end, a barrel is lashed: at the other end is a plank forming with
the poles a T. A man can then sit upon the barrel and paddle about, for
the poles and planks will steady the barrel just as the outriggers and
floats steady the narrow canoes or catamarans of which we read in books
of travel. For that reason a bridge formed of such is called a
"catamaran" bridge. Of course, if there are only a few barrels to be had
they can be fitted out like this and then combined into a raft. Or if
there are enough of them they can be anchored at intervals and poles or
planks laid from one to another so as to form a continuous bridge. Or a
single one may be used as a boat. I can almost fancy I see some of my
readers who have access to a pond rigging up an old barrel in this way,
just to see how it goes.
CHAPTER VII
WHAT GUNS ARE MADE OF
No longer ago than the days of the Crimea, the largest guns were made of
the cheapest and commonest kind of iron, that known as cast iron.
This material has the advantage of being cheap and easily worked, but is
comparatively weak and liable to crack, so that the guns of that time
were comparatively small compared with those of to-day; they could only
withstand a feeble explosion and their range was therefore limited. Had
the energetic explosives of the present time been employed in them they
would inevitably have burst, killing their gunners instead of the enemy.
Attempts were made to strengthen them with bands made of wrought iron, a
form of the metal which is tough and elastic and therefore better able
to withstand sudden shocks than the more brittle cast iron, but it was
not a real success.
At first sight one naturally wonders why the whole gun was not made of
the stronger wrought iron. The reason was that while cast iron can be
melted and poured in a liquid form into a mould, so as to produce the
shape of the gun, wrought iron will not melt. It will soften with heat,
in which condition it can be hammered into shape and, moreover, when in
a very soft state two pieces can be joined by simply forcing them
closely together, which operation is called welding.
With the machinery available now it would be possible to make a gun of
wrought iron, but even a few years ago it would have been quite
impossible. There was an obvious need therefore of a metal which could
be melted and cast in moulds like cast iron, yet tough and strong to
resist shock like wrought iron. Fortunately this problem excited the
interest of a certain Mr. Henry Bessemer, a gentleman who, having made a
considerable fortune through an ingenious method of manufacturing bronze
powder, had sufficient leisure and money to devote himself to its
solution.
The vast steel industries of Great Britain and the United States are the
direct results of this gentleman's labours, and in the latter country
there are quite a number of towns which, being the home of steelworks,
are called by his name.
Iron is one of the most plentiful things in the world. Deposits running
into millions of tons are to be found in many parts, but it is
practically always in the form of ore, that is to say, in combination
with something else generally oxygen and sometimes oxygen and carbon.
The former sort of ore is called oxide of iron and the latter carbonate
of iron, and both of them bear not the slightest resemblance to the
metal. They are just rocks which form part of the earth's crust, and it
is only the metallurgist who can tell what they consist of.
In order that the iron may be obtained from the ore it is necessary for
the oxygen to be separated from it, an operation which requires the
intervention of heat, and the heat must be obtained from a fuel which
consists mainly of carbon. Wood fulfils these requirements, but there is
not enough wood in the whole world to smelt all the iron which we need.
It was not until "pit-cole" displaced "char-cole" (to use the spelling
of the period) that the iron industry began to assume its present
importance.
To produce iron cheaply, therefore, ore and coal should for preference
lie side by side, and in some few favoured localities that state of
things exists. Generally speaking, however, the ore and the coal are not
found together, with the result that one has to be taken to the other,
and in practice it is usually the ore which is taken to the coal. Hence,
the iron and steelworks are generally to be found on the coalfields,
while the ore comes by rail or ship from, it may be, remote parts of the
world.
The method by which the metal is obtained from the ore is in principle
very simple. Coal and ore are mixed together in a furnace, the fire
being fanned by a powerful blast of air. The result is that the bonds
uniting iron and oxygen are relaxed by the heat, when the oxygen, having
a preference for union with carbon rather than with iron, leaves the
latter to join up with some of the carbon of the coal.
The furnace in which this operation is carried out is a tall, vertical
cylinder of iron, lined with firebrick. The fire is at the bottom and
the fresh fuel and ore are thrown in at the top. As the ore is
"reduced" (the chemist's term for removing oxygen from anything) the
liquid iron accumulates in the lowest part of the furnace, whence it is
drawn off at intervals, being allowed to run into grooves or gutters in
a bed of sand, where it solidifies into what is called "pig iron."
Along with the coal and ore, there is thrown into the furnace from time
to time quantities of limestone which combines with the earthy
impurities with which the ore is contaminated. Together these form what
is called "slag," which also exists, while in the furnace, as a liquid,
but is so much lighter than the molten iron that it keeps quite separate
and can periodically be drawn off through a hole higher up than that
through which the iron is obtained. The slag solidifies into a hard
stone which is broken up and used for making concrete and tar-paving,
also for road metal.
The kind of furnace just described is, owing to the strong blast of air
needed for its operation, called a "blast-furnace." One would be
inclined to think that a fire so well supplied with oxygen, both from
the blast and from the ore itself, would cause the fuel to be completely
burnt up, yet such is not the case. The gases which ascend from the fire
consist largely of "carbon-monoxide," a burnable gas with lots of heat
still left in it. Years ago, and one may still see instances of it, this
gas was allowed to escape at the top of the furnace, where it burnt in
the form of a huge flame. In most modern furnaces, however, there is a
kind of plug in the orifice at the top which, while it can be lowered in
order to admit the ore and fuel, normally prevents the escape of the
gases, which are led away through pipes. In some cases the gases are
burnt under boilers to provide the works with steam, in other cases they
heat other furnaces for metallurgical purposes, while in yet others they
are employed to drive large gas-engines to generate electricity. It is
sometimes a difficulty to find useful employment for the vast quantities
of this "blast-furnace gas" which are produced at a large works.
We see, then, how is obtained the pig iron from which the other kinds of
iron and steel are made. It is not pure iron by any means; indeed, it is
not sought to make iron pure, as is the case with most other metals,
since, in its pure state, it is too soft to be of much use. All the
familiar forms of iron and steel are really alloys of iron and carbon, a
fact which tends to give iron its unique position among the metals,
since by exceedingly slight variations in the percentage of carbon we
can vary the properties of the iron to an amazing extent, thereby
producing in effect a wide range of different substances each
particularly suitable for a particular purpose.
To make cast iron, such as the guns of the Crimea were made of, it is
only necessary to melt up some pig iron and to pour it into a mould.
There is scarcely a town in which there is not an iron foundry, either
large or small, and that is the work carried on there. A smaller form of
the blast-furnace, known as a "cupola," melts the pig iron, and the
moulds are generally made of sand. The process of pouring the melted
metal into the moulds is called "casting" and the things so produced are
"castings," and are said to be made of "cast" iron.
[Illustration: AN 18-POUNDER IN ACTION.
The crew consists of six men. No. 1 (the sergeant) gives instructions.
No. 2 stands at the right of the breech. No. 3 fires the gun. No. 4
holds the shell ready for placing in the bore. No. 5 adjusts the fuse
and hands the shell to No. 4. No. 6 prepares the ammunition and hands it
to No. 5. In this picture only three of the crew are left.]
Wrought iron is made by working the molten pig iron instead of casting
it. The work is done in a different type of furnace altogether from the
blast furnace and the cupola. It is more like an oven, in the floor of
which is a depression wherein the molten metal lies. The fire-place is
so arranged that the flames pass over the metal, being deflected
downwards upon it by the roof as they pass.
It should be understood that in casting pig iron one does little more
than form it into some desired shape, the nature of the metal undergoing
little or no change. In working it, however, into wrought iron, we
change its nature.
The pig iron contains from 2 to 5 per cent of carbon, which it obtains
from the coal in the blast-furnace, and it is this particular proportion
of carbon which gives it its own peculiar properties. To convert it into
wrought iron a workman puts a long iron rod into the furnace and stirs
the metal about, thereby exposing it to the air and permitting the
carbon to be burnt out. As it loses carbon the iron becomes less and
less fluid until it reaches a sticky stage. Thus the workman, who is
known by the name of puddler, as the process is called puddling, works
up a ball of decarbonized and therefore sticky iron upon the end of his
rod. Having thus produced a rough ball or lump he draws it out of the
furnace and leaves it to cool.
Thus the result of the puddling process is to produce a number of rough
lumps or balls of iron with only about one-tenth per cent of carbon.
They are next reheated, in another furnace, and a number of them are
hammered together under a mechanical hammer into larger lumps called
blooms or billets. The hammering process has the effect of driving out
impurities and also of improving the texture of the metal.
Iron sheets, bars, rods and so on are formed by heating the billets and
rolling them out in powerful rolling mills, machines which in principle
are precisely similar to the domestic mangle, wherein two iron rollers
with properly shaped grooves in them squeeze out the billet into the
desired form.
Wrought iron, owing to the method by which it is produced, is not
homogeneous, that is to say, it is nor quite the same all through, with
the result that when it is rolled it develops a grain somewhat similar
to the grain in wood, so that if bent across the grain it is somewhat
liable to crack. On the other hand, it has the advantage over steel that
it rusts much less readily. Hence, for outdoor purposes it is still
sometimes preferred to the otherwise more popular steel.
Now the problem which Bessemer set before himself was to find out how to
make a metal which could be cast like cast iron yet should be as strong
and tough as wrought iron. After a little experimenting, by a happy
inspiration, he hit upon the idea of blowing air through a mass of
molten pig iron, thereby burning out the carbon, just as is done in the
puddling process, only much quicker and with less labour. By this means
he produced a metal with less carbon than cast iron and more than
wrought iron, a sort of intermediate state between the two, and to his
joy he found that this "Bessemer steel" could be cast like cast iron yet
had strength and toughness equal to if not superior to that of wrought
iron. Moreover, it was homogeneous and when rolled did not possess the
troublesome grain characteristic of wrought iron.
Having thus found the way to make this new and desirable metal, Bessemer
encountered a great disappointment, so great that it would have entirely
beaten many men. He made samples of steel and submitted them to experts
in iron manufacture. Everyone thought them admirable and many large iron
works were induced by them to make arrangements with Bessemer for the
right to use his process. His name was already famous and it seemed as
if a new fortune was made, when, to his alarm, he learned that wherever
it was tried except in his own works, the process was a miserable
failure. Instead of being at the end of his labours he was just at the
beginning.
It turned out that the particular iron which he happened to buy and use
at his own works was particularly free from an impurity which is,
generally speaking, a great nuisance in iron, namely, phosphorus. It was
pure accident which had led him to use this iron: it happened to be the
kind he could purchase most easily in the small quantities needed for
his experiments but it led him into a great difficulty, for other
people, after paying him for the right to use his process and after
spending large sums on the requisite plant, found themselves unable to
make the steel because of the phosphorus in their iron and finding
themselves unable to make a success were inclined to write him down a
fraud. As it turned out, after much labour on Bessemer's part, it was
due to the presence of tiny percentages of phosphorus in most of the
iron that is produced.
After much trouble he was able to induce certain owners of
blast-furnaces to make, by special methods, a kind of pig iron
practically free from phosphorus and therefore suitable for his process.
This special pig iron was known as Bessemer Pig Iron.
A little later a new inventor, a Welshman, Thomas by name, overcame the
difficulty in another way, but to explain that I must first describe the
Bessemer Converter, the special apparatus designed by Bessemer for
making his steel.
It can best be likened to a huge iron kettle with a big spout at the top
and with two projecting pins, one on each side. These pins rest in
supports, so that it is easy to tilt the whole thing over on to its
side. This is lined with fire-clay or some suitable heat-resisting
material.
Through one of the "pins" (trunnions is their proper name) there runs a
hole, communicating to what we might call a grating in the bottom of the
converter. To this hollow trunnion there is connected the pipe from a
powerful blowing engine, so that air can be driven in at will.
To load or charge the converter it is tilted over somewhat to one side
so that molten pig iron can be poured into it. The blast is then turned
on after which it is raised to an upright position with the air
bubbling up from below through the iron. Thus by being brought into
close contact with air, the carbon is burnt out of the metal until none
is left. That, however, is not desired, so, as soon as the carbon is
known to have all gone, a fresh quantity of molten iron is added of a
special kind, the amount of carbon in which is known very exactly. Thus
all the carbon is first removed and then exactly the right amount is
added, and so the desired result is attained with certainty.
Now Thomas's improvement was this. He discovered that the converter
could be lined with certain substances which have a great attraction for
phosphorus and under those conditions any phosphorus which may be in the
ore goes readily from the iron into the lining, or forms, with material
from the lining, a slag which floats upon the surface of the metal.
When the process is completed the converter is tipped over once more and
the metal, now steel, is poured into rectangular moulds from which the
steel can be lifted after cooling in the form of ingots.
Steel produced by Bessemer's process as improved by Thomas is called
Basic Bessemer Steel.
Incidentally Thomas, by this invention, laid the foundation of much of
the steel industry of Germany and Belgium, for there are enormous
deposits of ore in the neighbourhood of Luxemburg which because of the
presence of phosphorus were useless until Thomas showed how it could be
dealt with.
And there is another interesting feature of this "basic" process.
Phosphorus is a valuable fertilizer, so that the "slag" makes a very
fine chemical manure. It is ground up into a fine powder and is sold to
farmers under the name of Thomas's Phosphate Powder. It owes its
fertilizing virtues to the presence of the phosphorus which it has
stolen from the molten iron.
Bessemer derived a huge fortune from his process after he had fought and
overcome his difficulties, in addition to which he received the honour
of knighthood and became Sir Henry Bessemer.
It will be noticed that one of the virtues of the process is its economy
in fuel. During the whole time that the metal is in the converter, from
twenty to thirty minutes, no fuel is used to keep it hot. The reason for
that is that the carbon which is being got rid of is acting as fuel. It
is burning with the air which is driven through, thereby generating
heat.
In Bessemer's early days, it was arranged that he should attend a
meeting of ironmasters at Birmingham to explain his new process. On the
morning of his lecture two eminent ironmasters were breakfasting
together in a Birmingham hotel when one exclaimed to the other, "What do
you think, there is a fellow coming here to-day to tell us how to make
steel without fuel." To this eminent South Wales ironmaster the proposal
seemed preposterous but it was true all the same.
Although vast quantities of steel are made by the Bessemer process there
is another one of equal importance known as the Siemens-Martin
Open-hearth process. In this the molten metal is kept in a huge bath
practically boiling until the carbon has been reduced to the required
amount. Perhaps the most interesting feature about it is the way in
which fuel is saved by what is called the "regenerative" method due to
that versatile genius Sir William Siemens.
The open-hearth, as it is termed, is a huge rectangular chamber of
firebrick with a firebrick roof, and doors along one side just under the
roof through which the process can be watched and new materials be added
from time to time.
The fire is some way away and not underneath as one might perhaps
expect. Now if a deep coke fire is fed with insufficient air it does not
give off carbonic acid such as usually arises from a fire, and which as
everyone knows will not burn, but a gas called carbon monoxide which
will burn very well. So the fire-place for these furnaces is constructed
in such a manner as to produce carbon monoxide, which then passes
through a huge flue to one end of the open-hearth. Here it meets air
coming through another flue and the two combining burst into flame over
the metal.
The hot gases resulting from this burning pass out through a flue at the
other end of the hearth to a tall chimney which causes the necessary
draught, but on their way they pass through a chamber loosely filled
with bricks. Consequently the hot gases only reach the open air after
having given up much of their heat to these bricks.
After that operation has been going on for a time certain valves are
operated and the gas and air then come in at the other end of the
hearth, travelling through it in the opposite direction. And the air
comes through the chamber which has the hot bricks in it, bringing back
into the furnace a large quantity of that heat which otherwise would
have gone up the chimney but which the bricks intercepted. Thus all day
long does this reversal take place at intervals, the fresh air all the
time picking up and bringing back some of the heat which just previously
had escaped towards but not into the chimney. This arrangement enables
the process to compete, so far as economy is concerned, with the
Bessemer process.
At intervals the steel is tapped off from the furnace and run into
ingot-moulds, the same as with the other process. On the whole it is
regarded as producing a slightly better steel, the operation being under
slightly better control.
However the steel is made the ingots are reheated and either hammered
under a powerful steam hammer or pressed in an enormous hydraulic press.
This greatly improves the quality.
The steel can then be rolled into plates, bars or whatever form may be
required.
The finer qualities of steel such as are used for making sharp tools are
made in quite another way. Instead of being made from crude iron by
taking out the carbon, the materials are the finest qualities of wrought
iron and charcoal which are mixed together in the correct quantities and
melted in a crucible. This cast steel is very hard, so that it will
carry a very fine, sharp edge. It is also capable of being tempered by
heating and cooling, so that the exact degrees of hardness and
toughness can be attained.
Of recent years a special quality of steel for tools called "high-speed"
steel has been produced, mainly by the addition to ordinary cast steel
of a small percentage of tungsten. The advantage of this is that, within
certain limits, this does not soften with heat, and it is, I can assure
you, a great invention in war-time, when a nation is straining every
nerve to turn out guns and shells as fast as possible.
For all these things need to be turned in lathes and if you have ever
watched a metal-turning lathe at work you will have noticed that the
tool which actually takes a shaving off the article being turned tends
to get hot. For this reason lathes are usually fitted with pumps which
pump cold soap-suds on to the tool as it works. What you see there is
the energy employed in shaving the metal being turned into heat in the
tool. If left uncooled by the water it would soon be red-hot. And the
faster the machine works the hotter will the tool get.
Now with the old steel a very little heat will suffice to make it soft,
when its cutting power is lost. So with the old steel, no matter how
much cooling water you might use, there was a distinct limit to the
speed of the lathe and the speed at which the work was finished, for if
that speed were once exceeded a stop became necessary to regrind the
tool or to put in a fresh one.
But with high-speed steel that limit is much higher, for it can get
almost red-hot before it loses its hardness and consequently machines
can be run and jobs finished at a speed which would have been out of
the question only a few years ago. If one belligerent knew how to make
high-speed steel while the other did not the former would have an
enormous advantage in war-time.
Speaking generally, steel such as is used for tools is called hard
steel, while that made by the Bessemer and Siemens-Martin processes is
called mild steel. Leaving out of account for the moment fancy steels
such as that just described, where other metals are added to the
mixture, the essential difference between all the varieties of steel is
simply a slight difference in the percentage of carbon. This is so
remarkable that it is worth while to tabulate these percentages again.
Cast iron has from 2 to 5 per cent.
Steel from one-fifth to one per cent.
Wrought iron less than one-fifth per cent.
Mild steel, which has least carbon of all the varieties of steel and in
this respect is therefore nearest to wrought iron, is used for the same
purposes as wrought iron, such as shipbuilding, bridges and roofs,
tanks, gas-holders, etc. When the Admiralty want a specially fast ship
such as a torpedo-boat destroyer with a hull as light as possible
consistent with strength they have it made of steel with a slightly
larger percentage of carbon so that the steel is stronger and the
vessel's frame can be made lighter. The steel for shells, too, needs to
be of a certain strength to give the best results, so the percentage of
carbon is adjusted accordingly.
For guns themselves, again, special properties are needed, and so not
only is the carbon regulated to a nicety but other things such as nickel
and chromium are added. Altogether, steel is one of the most marvellous
substances known, certainly the most marvellous metal. Copper is just
copper and no more, zinc is just zinc, and the same with lead, but iron
(which really includes steel) can be adapted to so many purposes, can be
endowed at will with so many different properties, that without doubt
iron, common, plentiful iron, is the king of all the metals.
CHAPTER VIII
MORE ABOUT GUNS
As has been remarked elsewhere, some of the guns used by the soldiers in
land warfare are very different from those used in the navy. The latter,
being carried on the ships to which they belong, can be of those
proportions which best suit their purpose. Consequently they are usually
very long compared with their diameter.
The field guns used by the Royal Field Artillery are shorter in
proportion to their calibre than are the big naval guns. Otherwise they
would be far too long to handle in the field. They are mounted on
carriages drawn by horses, and are so handy that they can go anywhere
where infantry can go and can travel just as fast. It takes a very short
time to get them ready for action, too, so that they can accompany
infantry quite freely, neither arm impeding the movements of the other.
The Horse Artillery, again, whose guns are even lighter still, can
accompany cavalry, travelling as fast and coming into action almost as
quickly as the troopers themselves.
The famous French "seventy-fives" (meaning 75 millimetres calibre) which
played such a great part in the war, are field guns intended to move
rapidly and to operate with infantry.
Both these types of gun were used by the British in South Africa, as
also were some field howitzers, a type of gun to which further reference
will be made later. But the Boers taught the world something new as to
the possibilities of moving heavy guns quickly. Perhaps the reason for
this was that they, being something of the nature of amateurs in the art
of warfare, were less under the influence of tradition. Anyway, they
surprised the British by the quick way in which they moved heavy guns,
sometimes into quite difficult positions, over rough ground and up steep
hills. These heavy guns of theirs were called by the British soldiers
"Long Toms."
But the British were quick to respond, particularly the ever-resourceful
navy. When the war broke out there were, in the neighbourhood of Durban,
a number of warships which had as part of their own armament some of
those guns which afterwards became famous as "4·7's," that being the
diameter of the bore in inches. They were of the long shape usual in
naval guns, and it is easy to see that they were much heavier than the
field guns of 3 inches or so in diameter.
Captain Scott (now Admiral Sir Percy Scott) saw that these would be
useful, so he quickly designed some carriages for them, got these made
in the railway workshops at Durban, and in a few hours was rushing them
up to Ladysmith. It was these guns very largely which enabled that town
to hold out for so long, until, in fact, it was triumphantly relieved.
Thus the effect of the Boer war was to show that much heavier weapons
could be manipulated in the field than had been considered possible
before. The Great War which followed but a few years later carried on
this same lesson, for one of the great surprises with which the Allies
were confronted in the early days of the conflict was the inexplicable
fall of fortresses which till then had been deemed almost impregnable.
Liége, Namur, Maubeuge and, finally, Antwerp, all fell to a wonderful
gun of enormous dimensions which the Austrians had produced from up
their sleeve, so to speak. Like conjurers they had kept them secret
until the last moment.
These weapons which made history so fast were of the kind called
howitzers, a name mentioned just now. It should be explained here that
gunners talk of guns and howitzers as if the latter were not guns; but
that is only a convenient habit which has grown up, for the latter are
unquestionably guns. The distinction is, however, so convenient that we
may well adopt it ourselves for the rest of this chapter.
Repeated references have been made already to the question of the length
of guns, and it has been pointed out that to get high velocity, great
range and vigorous hitting power a gun needs to be as long as possible.
On ships this is only limited by the strength of the steel of which the
gun is made, for beyond a certain length the gun bends of its own
weight. Ashore, however, the difficulties of transport impose a further
limitation in most cases, although the famous 4·7, like many other naval
guns, has a length of 50 calibres, and the guns of small calibre do
approximate somewhat to the proportions of the naval guns, since even
then their length comes within manageable limits.
Modern warfare, however, requires the use of larger shells containing
larger charges of explosives, and to fire these requires guns of greater
calibre. We hear of shells of as great a diameter as 16 inches being
thrown into the Belgian fortresses and of course nothing smaller than a
16-inch gun could do that. Now a 16-inch gun, if made to the naval
proportions of 50 calibres or even 45 calibres, would mean a length of
at least 60 to 70 feet. It would also mean a weight exceeding 100 tons,
for the 12-inch naval gun of 50 calibres weighs about 70 tons. And it is
easy to see that such a gun would be very difficult to move on the field
of battle. Indeed, it would be almost useless because of the time it
would take to get it into position and to construct the foundations
which it would need. If the Austrians had only had such as those the
Belgians would have had plenty of time to prepare for them at Antwerp,
whereas it was the quickness with which they brought up their heavy guns
that astonished everyone and took their opponents by surprise.
The secret of this astonishing performance lies in the fact that they
were not guns at all but howitzers, which instead of being long, slender
tubes are short, fat ones, and that involves a different idea in gunnery
altogether. The "gun" fires _at_ an object. The howitzer fires its shell
upwards with the purpose of dropping it _upon_ the object.
The difference between the two is well illustrated by the methods of
practising with them. In learning to work a gun the gunners fire at a
vertical target just as those of you who practise shooting at a
miniature range fire at a target of paper placed vertically against a
wall. The target for howitzer practice, on the other hand, is a square
marked out on the level ground, and the object of the gunners is to see
how great a proportion of a given number of shots they can drop inside
that square.
Of course, being so much shorter the howitzers cannot throw a shell so
far or at such a high velocity as the naval guns, but that can to a
certain extent be compensated for by using a higher explosive for the
propellant. That, however, involves greater stresses in the tube when
firing takes place and also calls for stronger foundations in order that
the aim may be steady.
A great part, too, of the velocity of a naval shell is required for the
penetration of the armour, whereas against forts or earthworks it is
sufficient if the shell "gets there."
Moreover, generally speaking, it is possible to get much nearer to a
fortress or entrenched position for the purpose of attacking it than it
is to an enemy ship on the sea. Except for the occasional help of a mist
there is no "cover" to be obtained at sea, while on land the ground must
be very flat indeed if there is no low hill or undulation behind which a
gun can be set up unnoticed.
The Austrians cherish a piece of steelwork from one of the forts of
Antwerp which they smashed with a shell from one of their big howitzers
at a range of seven miles. They evidently were able to get their big
howitzers within that comparatively short distance of the Antwerp
fortifications without being molested.
[Illustration: A GERMAN AUTOMATIC PISTOL.
The action is fully described on the illustration.]
In this connection one often hears the word mortar used, and just a
reference to that will be appropriate here. Many years ago short guns
which threw their balls very high were in use, and because of their
resemblance to the mortar which is used for pounding up things with the
aid of a pestle these were termed mortars. Later a man named Howitzer
introduced a type of gun which was something of a compromise between the
long thin gun and the short stubby mortar. As time has gone on, however,
the mortars have grown in length while the howitzers have shortened,
until to-day the two names are used almost indiscriminately to denote
the same thing. Hence the giant howitzers of the Austrians are often
spoken of as the "Skoda" mortars, Skoda being the name of the factory
where they were made.
At one time many people wondered why the Germans did not put some of
these huge mortars on their battleships: many thought that they would do
so, and that by that means they would demolish our navy as they had
already smashed the Belgian forts. The reason they did not is, no doubt,
the very simple one, that our naval guns would have probably sunk their
ships before the howitzers could have reached ours, because if they had
attempted to make up for the shortness of the weapons by using higher
explosives, these mortars would, there is little doubt, have knocked to
pieces the ships on which they were mounted.
The old-fashioned fortress, suddenly made "out-of-date" by the Skoda
mortars, was usually armed with guns of the naval type. Sea-coast forts
are always so armed. Nowadays, however, the inland fortress takes the
form of a labyrinth of trenches and underground passages, combined with
deeply excavated chambers known as dug-outs, and these do not fitly
accommodate large guns at all. The guns are placed well back behind the
trenches sheltered behind hills or woods, over which they hurl their
shells. The chief defenders of the actual trench are the machine gun,
which is little more than an automatic rifle on a stand, and the trench
mortar.
We are now in a position to sum up broadly the features of modern
artillery. There is first the naval gun, the ideal gun, long and of
great range, able to send forth its shells with great velocity. This gun
appears again in the sea-coast forts, where the conditions are very much
those which obtain on a ship and where the attacking party is of
necessity a ship.
In the field we have the field and horse artillery, which we may regard
as the naval gun modified somewhat in order to make it easy to move
about, so that it can accompany troops and support the operations of
both infantry and cavalry. These light guns are supported by the field
howitzers, which are also light and easily handled, and the guns of the
4·7 type, originally naval guns but now mounted on wheels and possessing
a certain amount of mobility, not equalling the field guns it is true,
but still very serviceable in a campaign.
Then we have the howitzers of various sizes which have rendered the
old-fashioned steel and concrete forts useless, and which are the chief
weapons used in the modern trench warfare. It is these which blow in the
walls of the trenches and dug-outs, shatter the barbed-wire
entanglements and render it possible for the infantry to attack an
entrenched position.
Finally, we have the machine guns, each of which is equivalent to a
considerable number of riflemen and which, with the trench mortars, form
the chief defences of the actual trench itself. Of course these are only
useful against attacks by infantry: they cannot in any way cope with the
heavy artillery. That has to be dealt with by the opposing artillery
posted away back behind the trenches.
And now let us take a rather more close look at some of these weapons.
Essentially each one is a steel tube. It may be a single tube or it may
be several one outside another. It may even have a layer of wire between
two tubes as many naval guns have. It is invariably (one small exception
will be mentioned later) loaded at the breech or rear end and not
through the muzzle as used to be the custom. For this purpose it needs a
breech-block or door, which can be opened to put in the shell and
explosive, and which can then be closed tightly so that it will not be
driven out or burst open when the explosion takes place and also shall
be gas tight so as not to let any of the force of the explosion escape.
Then the gun must be mounted upon a carriage so that it can be quickly
moved about. The lighter forms of artillery are fired when upon the same
carriage upon which they travel. In years gone by the whole thing,
carriage as well as gun, used to run back when the gun was fired, which
was a great nuisance since it had to be got back into position again
after each shot. To obviate this the gun is now mounted upon a slide,
and it is the slide which is fitted to the carriage. Thus the gun can
slide back without the carriage moving at all. The latter is made very
strong, and shoes are provided at the end of chains which go under the
wheels just like the "drag" which coaches and heavy carts have for use
going down hills. There is also a part like a spade which can be driven
down into the ground so that, what with the shoes and the spade, the
carriage is fixed very firmly.
The gun is kept at the front part of the slide by means of a powerful
spring, which is compressed when the gun is fired but which, as the
force of the recoil is spent, pushes the gun back to its original
position once more. The spring is often reinforced by a cylinder and a
piston with compressed air or water behind it, acting after the manner
of those door checks with which we are all familiar, its function being
to steady the motion of the gun and to let it go gently back to its
place without slamming, just as the door check prevents a door from
slamming.
By this means the gun is returned automatically after each shot to
practically the same position which it occupied before, so that it does
not need re-aiming each time, but only a slight readjustment if even
that. The result of this is that such a gun can be fired very rapidly.
In fact, it can be fired just as fast as the gunners can keep on
reloading it.
The big Skoda mortars owed their mobility to the clever way in which
they were constructed. The gun tube itself, the support for it or
mounting, and the steel foundation were each fitted to a special
motor-driven trolley. The steel foundation was dumped down on the
ground, which of course was prepared for it in advance, then the
mounting was run right on to it so that it simply needed bolting down
and finally the tube was hoisted by specially prepared appliances into
its place. It is said that the whole operation occupied less than an
hour.
For firing, these mortars of course are pointed at a very high angle,
almost like an astronomical telescope. No doubt the gunners have many
jokes about "shooting the moon" and so on, for that is just what they
seem to be attempting. For loading, however, they are lowered into a
horizontal position: the shell comes up on a small hand-truck, is raised
by a specially designed jack until it is level with the breech, and is
then pushed into its place. The breech is then closed, the tube
re-elevated, and all is ready for firing.
Between these two forms of gun, the field gun on its light carriage,
which not only bears it from place to place but forms its support while
in action, and the great mortar carried in parts on specially made
trolleys, there are now an enormous variety of guns and mortars adapted
for the various purposes which experience in the Great War revealed.
Artillery suffered many changes in the light of the South African
campaign and of the Russo-Japanese war, but of far more importance have
been the lessons learnt in Northern France and on the plains of Poland.
To some extent these lessons have been learnt and profited by during the
actual war, but there is no doubt that as men have time to think over
them in the years of peace which are ahead many more developments will
take place. Unless, that is, we are on the threshold of that happy time
when guns and fighting material of all sorts will be looked upon as the
relics of a bad and ruinous time now happily past.
In conclusion, a passing reference must be made to the trench mortars
and similar contrivances which have arisen as the result of the
prolonged spell of trench warfare which no one had ever contemplated.
These are in effect very short range mortars or howitzers, specially
intended for throwing bombs from trench to trench. Some are simply the
larger mortars on a small scale, but one has decidedly original
features.
This consists of a short light mortar into which the bombs are slipped
through the muzzle, thus reverting to the old method of loading. The
propellant is combined with the bomb and there is a percussion cap which
fires it as soon as it strikes the bottom of the tube. Thus the
operation is just about as simple as it can be: the man merely places
the bomb in the upturned muzzle and lets it slide down. An instant
later, up it comes again, to go sailing through the air into the trench
of the enemy a hundred yards away.
One must not conclude this chapter, however, without a reference to
those useful weapons which are known among the soldiers as "Archibalds"
and officially as anti-aircraft guns. These are perhaps the most
familiar guns of all to the general public, since they were installed in
many places in Britain for the purpose of dealing with the Zeppelins. No
doubt not a few of my readers have had the experience of being awakened
from their beauty sleep by the cracking of the anti-aircraft guns and
have seen their shells bursting like squibs in the air.
They are fairly long guns, not unlike field guns, but they are mounted
upon special supports which enable them to be pointed at any angle so
that they can fire right up into the sky. The sights, also, are somewhat
different, being fitted with prisms, or reflectors, so that the gunners
can look along the sights and align the gun upon an object overhead
without lying on their backs.
Much more could be said on this subject, but national interests forbid,
so with this general review of modern artillery we must pass to another
subject.
CHAPTER IX
THE GUNS THEY USE IN THE NAVY
Both the great English-speaking nations are immensely proud of their
navies. They can, on occasion, produce soldiers by the million of the
very highest and most efficient type, but they never feel quite that
pride and patriotic fervour over their soldiers that they do over their
ships of war and their sailors.
The guns, therefore, with which the ships are armed, always form a
subject of great interest, especially those large ones which constitute
the armament of the Dreadnought battleships and battle-cruisers.
Let us first consider what is required in a naval gun, for it must be
remembered that the naval and military weapons are different in some
respects. Experience at the Dardanelles showed that even the guns of the
_Queen Elizabeth_, the largest and most powerful then known, fresh from
the finest factories, were not particularly successful against the
Turkish forts. The Germans, too, set up what was probably a naval gun
and occasionally dropped shells into Dunkirk with it at a range of
twenty miles or so, but without causing much harm, and the fact that
they only did it occasionally and then abandoned it altogether seems to
indicate that in their opinion they were not doing much good with it.
It must not be assumed from this that naval guns are bad guns or poor
guns, however, but simply that they are made for a special purpose for
which they are highly efficient, from which it follows almost as a
natural consequence that they are somewhat less efficient when used for
some other purpose. Their purpose is to pierce the hard steel armour
with which warships are protected and then to explode in the enemy's
interior, whereas in modern warfare the greatest military guns are
chiefly required to blow a big hole in the ground or to shatter a block
of concrete. In both cases the ultimate object is to carry a quantity of
explosive into the enemy's territory and there explode it, but whereas
the land gun has simply to do that and no more, the naval gun has to
pierce thick armour-plate as well.
And just think what that means. Many large ships have their vital parts
protected by armour-plates twelve inches thick. Moreover, the
armour-plates are made of very special steel, the finest that can be
invented for the purpose. Vast sums of money have been expended in
experimenting to find out just the best sort of steel for resisting
penetration by shells. Some time ago I saw several pieces of
armour-plate which had been used in one of these tests. They had been
set up under conditions as nearly as possible the same as those
obtaining on the side of a ship and then they had been fired at from
varying distances, the effects of the various shots being carefully
recorded. And that is only one experiment out of tens of thousands
which have been tried again and again, while the steel manufacturers are
always trying to improve and again improve the shell-resisting
properties of their steel. Thus, we see, the presence of the steel
armour which has to be perforated before the shell can do its work makes
the task set before the naval gun somewhat different from that which
confronts its military brother.
These considerations result in the naval gun needing to have as flat a
trajectory as possible and its projectiles the highest possible speed.
Now trajectory, it may be useful to explain, is the technical term
employed to denote the course of a projectile, which is always more or
less curved.
Let us imagine that we see a gun, pointed in a perfectly horizontal
direction, and let us also imagine that by some miracle we have got rid
of the force of gravity and also that there is no air. Under those
conditions the shot from the gun would go perfectly straight and with
undiminished velocity for ever and ever. Then let us imagine that the
air comes into being. The effect of that is to act as a brake which
gradually slows the shell down until finally it stops it. Theoretically,
perhaps, it would never quite stop it, but for all practical purposes it
would.
Again, let us suppose that while the air is absent the force of gravity
comes into play, what effect will that have? It will gradually pull the
shell downwards out of its horizontal course, making it describe a
beautiful curve.
But, someone may think, does not a rapidly-moving body remain to some
extent unaffected by gravity? Not at all: it falls just the same and
just as quickly as if it were falling straight down.
If our imaginary horizontal gun were set at a height of sixteen feet and
a shell were just pushed out of it so that it fell straight down the
shell would touch the ground in one second. If the ground were perfectly
flat and the shell were fired so that it reached a point half a mile
away _in one second_ it would strike the ground exactly half a mile
away. You see, the horizontal motion due to the explosion in the gun and
the downward motion due to gravity go on simultaneously and the two
combined produce the curve.
To make this quite clear, let us imagine two guns precisely alike side
by side and both pointed perfectly horizontally. From one the shell is
just pushed out: from the other it is fired at the highest velocity
attainable: both those shells will fall sixteen feet or a shade more in
one second, and if the ground were perfectly level both would strike the
ground at the same moment although a great distance apart.
Clearly, then, the faster the shell is travelling the more nearly
horizontally will it move, for it will have less time in which to fall,
and the slower the more curved will be its path, from which we see that
the air by reducing the velocity causes the curve to become steeper and
steeper as the shell proceeds.
If, then, our gun is placed low down, as it must be on a ship, to get
the longest range we must point it more or less upwards because
otherwise the shell will fall into the water before it has reached its
target. When we do that we complicate matters somewhat, for gravity
tends to reduce the velocity while the shell is rising and to add to it
again while it is falling. We need not go too deeply into that, however,
so long as we realize that, whatever the conditions may be, the shell in
actual use has to follow a curved course, first rising and then falling.
The really important part about a shell's journey is the end. So long as
it hits it really does not matter what it does on the way, and if it
misses it is equally immaterial. The reason why we need to bother about
the first part of the trip is because upon it depends the final result.
Whatever the trajectory may be we see that the shell must necessarily
arrive in a slanting direction. And the more steeply slanting that
direction is _the less likely is the target to be hit_.
If the shell went straight it would only be necessary to point the gun
in the right direction and the object would be hit no matter how far
away it might be. The more curved the course is, the more likely the
shell is to fall either too near or too far, in the one case dropping
into the water, in the other passing clear over the opposing ship.
Let us look at it another way. Suppose the vital parts of a ship rise 20
feet out of the water and the shell arrives at such an angle that it
falls 20 feet in 100 yards: then, if the ship be within a certain zone
100 yards wide it will be hit in a vital spot. If it be nearer the shell
will pass over, if it be further the shell will fall into the water.
That 100 yards is what is called the "danger zone." If the shell is
falling less steeply, say, 20 feet in 200 yards, then the danger zone
is increased to 200 yards and so on, which gives us the rule that the
flatter the trajectory, or the more nearly straight the course of the
shell the greater is the danger zone and the more likely is the enemy
ship to be hit.
We have established two facts, therefore, first, that the trajectory
must be as flat as possible and, second, that to make it flat the
velocity must be high. We can also see another reason for high velocity,
namely, to give penetrating power.
To obtain a high velocity the gun must be long, and consequently naval
guns are always long, a fact which is very noticeable in the photographs
of warships. The reason for this is quite obvious after a little
thought. You could not throw a cricket ball very far if you could only
move your hand through a distance of one foot. To get the best result
you instinctively reach as far back as ever you can and then reach
forward as far as you are able, so that the ball shall have as long a
journey as possible in your hand. Perhaps you do not know it but all the
time you are moving your hand with the ball in it you are putting energy
into that ball, which energy carries it along after you have let go of
it. And it is just the same with the shell in the gun. So long as it is
in the gun energy is being added to it but as soon as it leaves the
muzzle that ceases. After that it has to pursue its own way under the
influence of the energy which has been imparted to it.
The powder which is employed as the propellant or driving power is of
such a nature and so adjusted as to quantity that as far as possible it
shall give a comparatively slow steady push rather than a sudden shock,
so as to make full use of the gun's length, the expanding gases
following up the shell as it goes forward and keeping a constant push
upon it.
On the other hand, a gun can be too long, for no steel is infinitely
strong and stiff, so that beyond a certain limit the muzzle of the gun
would be likely to droop slightly of its own weight and so make the
shooting inaccurate. The limit seems to be about 50 calibres or, in
other words, fifty times the diameter of the bore.
For a considerable time the standard big gun of the British Navy was the
12-inch, that being the calibre or diameter of the bore. The famous
_Dreadnought_ had guns of that calibre and so had her immediate
successors.
The 12-inch gun of fifty calibres weighs 69 tons and fires a projectile
weighing 850 lbs. which it hurls from its muzzle at a velocity of about
3000 feet per second.
More recently the size has grown to 13½, 14 and even as great as 15
inches calibre, but we may for the moment take the 12-inch gun as
typical of all these large guns and have a look at its construction.
It is made of a special kind of steel known as nickel-chrome gun steel,
formed by adding certain proportions of the two rare metals nickel and
chromium to the mixture of iron and carbon which we ordinarily call
steel. The metal is made after the manner described in another chapter
and is cast into the form of suitably-sized ingots which are afterwards
squeezed in enormous hydraulic presses into the rough shape required.
Besides giving the metal the desired form this action has the effect of
improving its quality. Since a gun is necessarily a tube it may be
wondered why the steel is not cast straight away into that shape instead
of into a solid block and the reason why that is not done is very
interesting. It is found that any impurities in the metal--and it is
impossible to make it without some impurities--collect in that part
which cools last and obviously that part of a block which cools last is
the centre. Thus the impurities gather together in the centre of the
mass whence they are removed when that centre is cut away, whereas if
the first casting were a tube they would collect in a part which would
remain in the finished gun.
The ingot, then, is cast and pressed roughly to shape. Then it is put
into a lathe where it is turned on the outside and a hole bored right
through the centre.
But that is by no means all of the troubles through which this piece of
steel has to pass. It undergoes a very stringent heat treatment, being
alternately heated in a furnace to some precise temperature and then
plunged into oil, whereby the exact degree of hardness required is
attained.
Moreover, this is only one of the tubes which go to make up the gun,
which is a composite structure of four tubes placed one over another
with a layer of tightly wound wire as well.
First, there is the innermost tube, the whole length of the gun, then a
second one outside that, usually made in two halves. Both are carefully
made to fit, and then the outer is expanded by heat to enable it to be
slidden over the inner one, after which on cooling it contracts and fits
tightly. Outside this second tube is wound the wire, or more strictly
speaking tape, for it is a quarter of an inch wide and a sixteenth
thick. It is so strong that a single strand of it could sustain a ton
and a half. It is carefully wound on; first several layers running the
whole length of the gun and then extra layers where the greatest
stresses come, that is to say, near the breech, for that has to
withstand the initial shock of the explosion. Altogether about 130 miles
of wire go on a single gun.
The advantages of this form of construction are many. For one thing, a
wire or strip can be examined throughout its whole length and any defect
is sure to be found, whereas in a solid piece of steel, no matter how
carefully it may be made, there may lurk hidden defects. Moreover, if a
solid tube develops a crack anywhere it is liable to spread, whereas a
few strands of wire may be broken without in any way affecting the rest.
It has been found that even if a shell burst while inside one of these
guns no harm is done to the men in the turret where it stands, a thing
which cannot be said for guns composed entirely of tubes, so that the
merit rests with the wire. A third advantage is that the wire can be
wound on to the tube beneath it at precisely that tension which is
calculated to give the best result, whereas in shrinking one tube on to
another this cannot always be attained.
Over the wire there come two more tubes not running the whole length
but meeting and overlapping somewhat near the middle, so that at one
point there are actually four concentric tubes besides the wire.
At the rear end a kind of cap called the breech-piece covers over the
ends of all the tubes, itself having a central hole into which fits the
breech-block, one of the triumphs of modern engineering, of which more
in a moment.
While we have in mind the wire-wound form of construction it is
interesting to note that something similar but in a crude form was
practised sixty years or more ago. The guns of that era were some of
them even of cast iron while the more refined consisted of a steel tube
strengthened with coils of wrought iron. This iron was first rolled into
flat bars, then it was made hot, and wound on spirally round an iron bar
the same size as the tube. A little hammering converted this spiral into
a tube which was then fitted round the steel tube. Thus, although very
different there is still a distinct resemblance between this old method
and the up-to-date wire-wound weapon.
The manufacture of guns, it may be remarked, owes more to one man than
to any other, namely, Mons. Gustave Canet, a French engineer who, having
fought in the Franco-German War, decided to devote his engineering
talents to developing the artillery of his native land. He spent many
years in England but later established works at Havre for the
manufacture of guns upon improved methods, finally merging his interests
into those of the great French armament firm of Schneider of Creusot.
By French and English artillerists at all events the name of Canet is
regarded with reverence.
But to get back to our naval gun. It will be clear that operations such
as have been described, involving the handling of great tubes fifty feet
or more in length, heating them as required, dipping them in oil while
hot and so on, can only be carried out at works specially designed for
the purpose.
The furnaces where the tubes are heated are well-like formations in the
ground, deep enough to take the tube vertically. To lift them in and out
there have to be tall travelling cranes capable of catching the tube by
its upper end and lifting it right out of the furnace so that its lower
end clears the ground. To accomplish this with a little to spare the
cranes need to be seventy feet or so high.
Then there are deep pits full of oil so that a tube can be heated in a
furnace, drawn out by a crane and quickly dropped into the adjacent oil
bath. Likewise there have to be pits of a third kind wherein a cold tube
can be set up while a hot one is dropped over it for the purpose of
shrinking the latter on.
Then, of course, there have to be lathes of gigantic dimensions capable
of taking a length of nearly sixty feet and of swinging an object
weighing anything up to fifty tons. But of those machines we can only
pause to make mention, for we must pass on to the breech-block, in some
ways the most interesting part of the gun.
When it was first suggested to leave the back end of the gun open so
that the powder and projectiles could be put in that way instead of
through the muzzle, people at once foresaw how much would depend upon
the arrangements for stopping up the hole while the gun was fired. For,
of course, the force of the explosion is exerted equally in all
directions, backward just as much as forward, so that unless very
securely fixed the stopper closing the breech would be liable to become
a projectile travelling in the wrong direction. To fix such a thing
securely enough to avoid accidents would surely take up too much time
and so largely neutralize any advantage arising from its use. These
fears were, indeed, to some extent justified by accidents which actually
occurred with the early examples of breech-loading guns, and for that
reason our own authorities for a time looked askance at breech-loaders.
Now let us take a look at the breech-block of the 12-inch naval gun of
to-day, which never blows out, not even when 350 lbs. of cordite go off
just the other side of it. The explosion hurls an 850-pound shell at the
rate of 3000 feet per second but it never stirs the breech-block. Yet it
can be opened and closed so quickly, including the necessary
fastening-up after closing, that shots can be fired from the gun at the
rate of one every fifteen seconds.
The breech-block partakes of the nature of a plug and also of a door. It
swings upon hinges like the latter but its shape more resembles the
former. If we want to make such a thing very secure we usually make it
in the form of a screw with many threads, but that entails turning it
round many times and that takes time. Given plenty of time to screw the
breech-block into its place and there would never have been any anxiety
as to the possibility of its blowing out, but there is not time. The
problem, therefore, was to get the strength of a screw combined with
quickness of action.
This dilemma is avoided in the following simple manner. The breech-block
is given a screw thread on its exterior surface, and the hole in the
breech-piece is given a similar screw-thread on its inner surface, just
as if the one were to be laboriously screwed into the other after the
manner of an ordinary screw in machinery. Then four grooves are cut
right across the threads on the block and similarly on the breech-piece,
so that at four different places there is no thread left. In other
words, instead of the thread running round and round continuously, each
turn is divided up into four sections with sections of plain unthreaded
metal in between. Thus in a certain position the block can be pushed
into the hole without any threads engaging at all, for each strip of
threaded block passes over an unthreaded strip in the hole and vice
versa, in other words, the threads on the one part miss those on the
other part. Yet an eighth of a turn serves to make all the threads
engage and the thing is held almost as securely as if it were just an
ordinary screw with threads its whole length.
The block is carried upon a hinged arm so that although it can be turned
in this manner it can also be swung back freely when necessary.
Combined with the breech-block is a pneumatic contrivance which blows a
powerful jet of air through the gun every time the breech is opened,
thereby cleaning away the effects of the last explosion.
Each of these great guns is mounted upon a slide so that when it is
fired it can slide back, thereby exhausting the effect of the recoil,
yet can be returned instantly to its original position. Indeed, this
return is brought about quite automatically by the agency of springs,
compressed air and hydraulic power. Thus the gun fires, slides back,
returns and is at once ready for the next shot.
It is trained, or pointed in a horizontal plane, by turning the turret
in which it stands but the correct elevation is gained by the use of
telescopic sights.
The principle of these sights is very simple. Imagine a graduated circle
fixed to the side of the gun. Pivoted at the centre of the circle is a
small telescope. The telescope can be turned round to any angle upon the
circle and it can then be clamped at that particular angle.
The range having been given to the officer in command of the gun from
the range-finding station on another part of the ship, the telescope is
set to the correct angle. Then the gun is elevated or depressed until
the ship being aimed at is precisely in the centre of the field of view
of the telescope, in other words, until the telescope is pointing
exactly at the ship. Then the gun is fired.
The effect, therefore, is this. The telescope always points (while the
gun is being fired) at the object aimed at, but the gun is pointed
upwards at a certain angle, which angle depends upon how the telescope
is set upon the divided circle. Thus the setting of the telescope for a
given range produces the correct upward tilt of the gun for that range.
The breech-block carries a trigger and hammer arrangement whereby the
firing can be done and also an electrical arrangement so that an
electric spark can be employed. Both these firing contrivances are so
made that they cannot be operated until the breech-block has been
inserted and _made secure_. Thus a premature explosion is guarded
against.
CHAPTER X
SHELLS AND HOW THEY ARE MADE
Modern warfare seems to resolve itself very largely into a question of
which side can procure the most shells. During the great war there was a
time when the British and their allies were hard pressed because they
had not sufficient shells. The enemy had in that matter stolen a march
upon them and had during the winter, when military activity is at its
minimum, rapidly produced large supplies of high-explosive shells.
Discovering their lack the British set about remedying it in true
British fashion. It is quite characteristic of this strange people to
let the enemy get ahead at the commencement, after which they pull
themselves together and put on a spurt, so to speak, and after that the
enemy had better prepare for the worst, for defeat is only a question of
time. So, finding themselves short of shells, they set to and dotted the
whole country in an incredibly short time with huge factories entirely
devoted to making shells. Older factories also were adapted to the same
purpose. Places intended and normally used for the manufacture of the
most peaceable things--ploughs, gramophones and piano parts for
example--were soon turning out shells or parts thereof by the thousand.
Electric-light works, waterworks, cotton mills, technical schools, all
sorts of places where, for doing their own repairs or for some similar
reason, there happened to be a lathe or two, all these were organized
and in a few weeks they too were working night and day "something to do
with shells."
Meanwhile other factories were springing up for the purpose of making
explosives while others again were erected for producing the acids and
other chemicals necessary for the explosive works; and yet another kind
of works, the filling factories, came into being as if by magic and
thousands of girls flocked from far and near to these places, there to
fill the shells with the explosives.
Even the soldiers did not realize a few years ago how important the
supply of shells was going to be. The rifle has fallen from its old
place of importance while the gun and the shell have risen to the first
place.
What, then, is a shell? It is what its name implies, a case covering
something else, just as the shell of a fish covers its owner. It is a
hollow cylinder of steel with certain things inside it. Its chief
function is to hold these other things and to be shot out of a gun
carrying them with it to their destination. You want to cause an
explosion in an enemy's ship. You cannot get near enough to put the
explosives there by hand, for he will not let you, so you put them into
a steel shell and then hurl the whole thing at him out of a gun.
[Illustration: BOMB THROWING.
One of the most striking things about the war was the re-invention of
the bomb thrown by hand. This officer hurled bombs at the enemy for
twenty-four hours continuously.]
In the attempt to prevent your doing him any harm by thus throwing boxes
of explosives at him, the enemy clothes the sides of his most valuable
and important ships with thick steel plates, wherefore you have to make
your shell strong and tough so that it shall not splinter against the
armour but shall on the contrary bore its way through, finally exploding
in the interior of the ship.
If it is not a ship that you are attacking but, say, an earthwork or an
arrangement of trenches, then you do not need to penetrate steel armour
and your shell can be thinner and of lighter construction. It still
needs to be strong, however, for it has another function besides simply
carrying the explosive. It must hold the force of the explosion in for a
moment while it gathers force so that when the hour comes the pent-up
energy may strike all round with the utmost violence. Even the most
powerful explosives are comparatively feeble if they go off in the open.
By holding them in check for a moment and then letting their force loose
suddenly you get a much more forceful blow.
Shells which contain only an explosive are called common shells or
high-explosive shells. Shrapnel shells constitute another type in which
the force of the explosion is simply employed to release a number of
round bullets, which strike mainly because of the velocity which they
derive from the original motion of the shell. These are above all things
man-killing shells, for their result is akin to a volley of bullets at
close range.
We can thus sum up the chief types of shell as follows: the naval shell
which has to be capable of penetrating armour: the high-explosive shell
which must be able to break up earthworks and blow down the walls of
trenches: and the shrapnel shell which scatters a shower of bullets and
is most useful in attacks upon bodies of men rather than upon material
structures.
Some shells have their propellent expl
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