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 quant.i.ties.

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 pa.s.ses 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 ma.s.s 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 c.o.ke 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 repet.i.tion 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 pa.s.sing 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 quant.i.ty of explosives so arranged that they blow up when the enemy pa.s.s 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 circ.u.mstances. Not so, however, with submarine mines on which much ingenuity has been expended, the mines being made in workshops ash.o.r.e 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 ash.o.r.e. Being laid by divers and securely anch.o.r.ed 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 pa.s.s 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.

[Ill.u.s.tration: 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 sh.o.r.e 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 ill.u.s.trate 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 sh.o.r.e 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 pa.s.sage.

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 anch.o.r.ed, the loop being fastened by means of a link. This link, however, contains a small quant.i.ty of explosive which can be fired from the sh.o.r.e. 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.