Submarine Warfare, Past, Present, and Future

The whole object of modern warfare is to keep the enemy ignorant of your whereabouts and your actions, and to mislead him whenever possible, and for this reason smokeless powder, torpedoes, disappearing guns, &c., have come into use, false attacks are considered admissible, and every advantage is taken of cover and entrenchments. The only “cover” possible in naval warfare is beneath the waves, and it is difficult to see any greater inhumanity in submarine than in military mining, which certainly dates from very early times. If it is lawful to sap and mine before a fortified town, and to blow up an army as it marches unsuspectingly over “mined” ground, it is surely permissible to send ships sky-high by mines and to sink them by torpedoes.

Mr. A. F. Yarrow has remarked that it seemed strange that an artilleryman behind ten or twenty feet of earthwork, hurling explosive shells at an almost unseen foe, should be held as fighting fairly, while in the case of the torpedoist, who has the pluck to accompany his missile to within a short distance of his enemy, it should be considered an unfair mode of attack.

Yet so it is, and we find in a recent number of the Engineer^[1] that submarine warfare is placed on a par with guerilla warfare and train-wrecking. “The torpedoing of a single German ironclad by a submarine would almost certainly be followed by a refusal to recognise submarines as belligerents.”

The question of the laws and usages of civilised warfare has been the subject of many books and articles, and conferences have been called to endeavour to arrive at some understanding on the subject. An International Conference on the “Usages of War,” held at Brussels in 1874 at the instance of Alexander II., considered among other things, “the means of injuring an enemy,” and suggested the prohibition of the use of poison and poisoned weapons, murder by treachery, and murder of a disarmed enemy, projectiles causing unnecessary suffering, and prohibited by the declaration of St. Petersburg in 1818; “ruses de guerre” were, however, declared permissible.

In connection with the Boer War it is interesting to note that differences arose at this Conference between the representatives of the large States possessing great standing armies, and of the minor States with small armies. The former thought that war should be the business of professional trained soldiers, that they, and as a rule they alone, should fight, that war should follow a regular course, and that the worthlessness, from a military point of view, of the sporadic efforts of partisan warfare should be recognised, and that when a battle was won and the seat of Government was in the possession of an invader the inhabitants should respect the conquerors as the de facto and de jure Government. If they interrupted communications and cut off isolated bodies of troops they were to be dealt with not as honourable combatants, but as assassins and marauders.

The “Geneva Convention” met at Geneva on August 8, 1864, and on the 22nd of the same month an International Code was adopted by all civilised powers, except the United States. The code mainly concerned itself with the succour of the wounded in time of war, and certain cruel methods of warfare, such as the use of explosive bullets, were condemned, Great Britain agreeing not to use such weapons in war against civilised nations.

The Peace Conference at the Hague was opened on May 18, 1899. Of the eight proposals submitted for discussion, the second was the prohibition of the use of new arms and explosives, the third the restriction of the use of existing explosives and the prohibition of projectiles and explosives from balloons, and the fourth the prohibition of submarine torpedo boats, and the agreement not to construct boats with rams in the future.

The final act embodying the results of the Conference contained three declarations. 1. Prohibition of the throwing of projectiles and explosives from balloons or any other analogous means. This prohibition to be in force for five years. 2. Prohibition of projectiles intended solely to diffuse asphyxiating or deleterious gases. 3. Prohibition of the use of bullets which expand easily in the human body.

It may be noted that Great Britain did not bind herself to accept any of these three declarations.

“The laws of war,” wrote Montague Bernard, “are nothing at all but the usages according to which warfare by land and sea is carried on, and the collection of the whole body of usages represents what we call the laws of war.... The student of history is apt to be a little puzzled by frequent reference to ‘laws’ with which he is tacitly assumed to be familiar. What are these laws? Where are they written? What authority do they command? They are a body of usages, for the most part conditional, which have arisen principally from motives of convenience and the extension of commerce.”

It is of course recognised that the only force which supports international law is the appeal to the conscience of the nation, for there is no international tribunal to punish countries for deeds committed in time of war. While it is unlikely that the rough game of war ever will be played (it certainly never has been in the past) in exact conformity with the rules of the jurists, there are certain methods of waging war which England would not employ, and certain acts which she would not commit in the event of hostilities breaking out between herself and a civilised country.

She would not use explosive bullets. She would not fire on undefended towns, and would endeavour to avoid the destruction of non-combatants and their property. She would not poison wells, she would not endeavour to accomplish the assassination of a commander-in-chief, she would not abuse a flag of truce, she would not murder prisoners who behaved themselves, and put to death those who surrendered.

On the other hand, she would consider herself at perfect liberty to employ submarine boats, torpedoes, and mines, both military and naval; to discharge shells filled with high explosives, whether lyddite, melinite, or other substance, from aerial machines; to intercept the enemy’s messages and to mislead him by sending false ones; to commence hostilities without issuing a declaration of war;^[2] to fire on, and if necessary sink, the merchant ships of the enemy; to starve a garrisoned town; to erect wire entanglements and similar obstructions; to offer wrecking lights as navigation lights; and to employ any “stratagem” or “ruse de guerre” which might serve some useful end. With regard to stratagems, it appears to be quite proper to disguise ships and men, and to use false signals, false colours, and neutral flags, though a British naval officer would probably not fire into his enemy before hauling down his neutral or false colours.

Vice-Admiral Rodney M. Lloyd pointed out in a recent letter to the Times that while in naval warfare all stratagems were admitted, expected, and provided against, in military operations, on the contrary, some acts of a similar kind appeared to be objected to. The Boers, for instance, frequently disguised themselves in British khaki uniforms, and endeavoured to delude sentries and guards.

Some writers refer to this as “the abuse of the khaki uniform” and “the treacherous use of the khaki uniform,” but if such things are permitted in naval operations it is difficult to see why they should be considered immoral if practised on land.

Apropos it may be mentioned that during some Russian naval manœuvres the admiral’s ship was destroyed by the following trick. A party of volunteers from other squadrons came alongside the cruiser Africa, the flagship, in a Finnish coasting smack, and one of the volunteers, dressed as a peasant, came on board with a telegram. Whilst the attention of the Africa’s crew was diverted the other volunteers fastened a small buoy with the inscription, “Frigate Prince Pojarsky,” under the stern of the flagship.

Of course there is a very thin line which separates what is considered fair and what is considered unfair warfare among civilised communities. Lord Dunsany said that he was not perfectly sure that there could not be something said in favour of poisoning wells. “We have heard something about poisoning the air. The French some time ago had what they called bullets asphyxiants. These would have utterly poisoned a whole ship’s crew. If these missiles may be used, then it comes to this: that it is lawful to poison the air, but not lawful to poison the water.”

Lyddite shells seem rather to resemble these bullets asphyxiants, for their stench is reported to be terribly stupefying to those in the immediate neighbourhood when they burst. But whereas explosive shells fired from guns are considered “legitimate,” shells fired from rifles are regarded as “illegitimate.”

Respecting the question of poisoning wells, Colonel Lonsdale Hale has remarked that so long as this was done openly, and the fact notified in some way to those who would use them, there seemed to be nothing more to be said against this forbidden practice than against the permitted practice of depriving the enemy of good water supply by filling in wells and by cutting off the good water, as the Germans did at Metz and Paris, and reducing their enemy’s water supply to the sewage-receiving Moselle and Seine. If it was permissible to starve one’s enemy by denying him solid food, it seemed to him equally permissible to starve him by denying him liquid food.

Wolff and Bynkerhoeck, two of the originators of international law, thought the use of poison in warfare perfectly legitimate. Vattel considered the practice interdicted by the law of nature which did not allow of the multiplying the evils of war beyond all bounds. To get the better of the enemy he must be struck, and if once disabled, what necessity, he asked, was there that he should eventually die of wounds.

Opinion also differs as to the morality of attacking undefended towns and injuring the property of non-combatants during a war.

The late Admiral Aube, when he was head of the French Admiralty, said the proper way of bringing this country to order was to burn Brighton and Scarborough and a few other places; and Admiral Sir J. C. Dalrymple Hay, Bart., has remarked that he could not say he thought that he was wrong. According to the latter, the object of each side is to do the greatest possible destruction to the enemy, and also to make him cave in; the whole of the country is engaged in war, they pay taxes for the war, they encourage their soldiers and sailors to fight courageously, they suffer for the war in various ways and they urge it on; and they must expect to suffer accordingly.

Humanitarians affirm that in actual war soldiers and sailors of the Dalrymple Hay school would be too human to act up to their expressed opinions; the probability is that England would only resort to such measures if the enemy were determined to employ them. Vice-Admiral Bourgois, in his book “Les Torpilleurs,” made a strong protest against the doctrines of those who advocated the bombardment of undefended towns and the sinking without warning of defenceless merchant ships. He urged that the nationality of the vessel should first be verified, and then provision made for the crew and passengers.

Apart from the “Hague enthusiasts” who are for prohibiting the employment of high explosives, aerial torpedoes, and submarine torpedo boats, there is another class of humanitarians who urge the adoption of all new and deadly engines of warfare, apparently with the idea that if war is made sufficiently terrible no nation would dare fight another. “The more terrible the anticipation of naval war,” says a writer, “as fashion and science continue the contest, the less likely will be its realisation.”

The late M. Bloch, as we know, considered war to be tactically, strategically, economically, and morally impossible, but as he assured us also in his book, “Is War Impossible?” that bayonets were quite out of date, one may be forgiven for not paying much heed to his lucubrations.

Admiral Porter, of the U.S. Navy, considered that if war was made so dangerous that every combatant would to a certainty be killed, then there would be an end of the business and the Peace Society could put up their shutters.

The newspapers, especially the halfpenny ones, are constantly informing us of the discovery of new engines of warfare of terrible potency. Mr. Tesla is going to wipe out the British Fleet by simply touching a button on his waistcoat or elsewhere. Mr. Hudson Maxim has devised a method of throwing aerial torpedoes carrying each of them one ton of high explosive which is so efficacious that one cruiser lying just out of range of our guns would destroy all our battleships with the greatest ease. Dr. Barton is building an airship which will throw explosives on the enemy below, who will be powerless to retaliate, and so on.

The wars of the future, so the halfpenny journalists inform us, will be either waged under the seas or above the clouds, and we seem to be approaching the time imagined by Lord Tennyson, whose swain (in “Locksley Hall”)—

If wars ever die out, it will certainly not be owing to the destructive capabilities of the weapons employed. In the eyes of old Geoffrey de Vinesauf the naval conflicts of his time were as terrible as he could well imagine them to be, but a hundred years hence a Conference will doubtless be held at Tokyo to consider what restrictions should be placed on the use of submarine boats and aerial machines in time of war.

Those who are in favour of utilising the latest resources of science for the purpose of warfare are in reality more humane in the truest sense of the word than those who seek to limit nations in their choice of weapons. Vice-Admiral Sir John Fisher, who was one of those chosen to represent Great Britain at the Hague Conference, expressed himself strongly on the cruelty of making war on “humane” or moderate principles, and it is an undoubted fact that in spite of the deadly nature of modern arms, wars, on land at least, are not so destructive of life nor do they cause so much misery and suffering as they did formerly.

We can speak with more certainty with regard to warfare on land than we can to warfare on sea, but though the next great naval fight between two nations will certainly entail terrible suffering on the combatants (especially on those whose stations are below), it may be said that on the whole they will neither cause such wholesale misery nor be so protracted as the naval battles of old.

“Every war,” said Captain Herbert in a recent lecture at the Royal United Service Institution on “The Ethics of Warfare,” “marks a step. In 1885 the Servians, when they invaded Bulgaria, paid conscientiously in good coin for every fowl or pig seized in farmhouses, for every glass of brandy drunk in village inns; and when the tables were turned, and the Bulgarians invaded Servia, the Bulgarian soldiers and the Servian traders fraternised most cordially in the alehouses of Pirot. To come to the latest European war—that between Turkey and Greece in 1897—we have the testimony of the war correspondents that the behaviour of the Ottoman soldiery was quite exemplary. If things continue in this wise we shall perchance hear in the next century of every rifle discharge being preceded by a conciliatory caution and every bursted shell being followed by a humble apology.”

Dr. J. Macdonell, in a recent lecture, has touched on this subject. “It must be owned,” he says, “that the progress in mitigating the evils of war have been immense—that acts of useless violence which were once habitual are now exceptional, and are punished or condemned by military opinion. Ask those who say, ‘Things are much as they were: the grim realities of war no better than before,’ to note the matter-of-fact way Comines de Hoissard relates cruelties as the necessary accompaniments of warfare; then compare with such passages some of the many handbooks published by European Governments for the use of their troops. It has been truly said that the difference between the methods of the Thirty Years’ War and of the War of the Spanish Succession is the difference between darkness and twilight; the difference between warfare as understood by Tilly and Pappenheim and that described in modern official Manuals is the difference between light and darkness. Everywhere is recognised that only effective injuries are justifiable. The modern soldier strikes hard, he doesn’t mutilate or destroy for the love of destruction.”

The Rev. Edmund Warre has drawn a vivid picture of the wretched plight of the slaves labouring at the oars, who suffered intense discomfort and were in continual danger.

“In a hot climate, with but very little ventilation, it must have been exceedingly trying to take part in a laborious mechanical toil with perhaps some hundred or two of human beings stark naked and packed so closely that there was not room, as Cicero says, for even one man more. The heat, the smells, the toil must have been terrible to any one undergoing it against his will—so terrible as to suggest that even death itself were better than such drudgery. A dull dead feeling of despair must have crept over man and crew in such a case, and though the lash might keep them going under ordinary circumstances, such spirits could not be relied upon in times of emergency, Besides the question of discomfort, the actual danger was very great. The crews were liable at any moment to be drowned or burnt, or, in the case of defeat, butchered by the victors—perhaps, as at Sybota, deliberately in cold blood. Conceive the moment of conflict and its horrors, when the sharp-pointed beak came crashing through the timbers, smashing them right and left along with the helpless mass of human beings, while the water followed swift upon the blow, perhaps just giving time to the Thranites (the rowers on the topmost of the three benches in the Trireme, who had the most work and the longest oars) to swarm up upon the deck, while the helpless Thalamites (the rowers on the lowest bench) were drowned at once.”

Science, although she is continually placing man in possession of weapons more terrible and more destructive than those of the previous generation, really acts for the good of humanity at large, who owe a debt of gratitude to the mechanical geniuses who have evolved modes of warfare which enable war to be waged with as little unpleasantness as possible to the peaceful populations that have no concern with it.

In one respect at least modern warfare is certainly more humane than that of olden times, and this is in the treatment of the wounded and the captured. In ancient warfare the fate of the captive was death or slavery, and in early battles no quarter was given, except to personages of great distinction, and the object of both sides was to slay as many of their opponents as possible, and as surrender only made the prisoner the perquisite of his captor, the fighting was both bloody and fierce. Even as late as 1780 a prisoner was still viewed as the property of the victor, and there was a regular scale or tariff of payments.

One instance culled from an account of a battle between Christians and Turks, written by Geoffrey de Vinesauf, must suffice.

“Drawing the hostile galley with them to the shore the victors exposed it to be destroyed by our people of both sexes who met it on land. Then our women seized and dragged the Turks by the hair, beheading them and treating them with every indignity and savagely stabbing them, and the weaker their hands so much the more protracted were the pains of death to the vanquished, for they cut off their heads not with swords but with knives.”

Dr. Macdonell has pointed out that the only notable survival of barbarism in respect to captives was the rule—abrogated apparently in some countries but retained by us for reasons never satisfactorily explained—that the crews of pirate vessels captured at sea were treated as prisoners of war.

In the next great fight on the seas, if a submarine boat should be hit by the quick-firing guns of a battleship she is endeavouring to destroy, her crew, provided they are not sunk like rats in a trap, will be picked up by the ironclad’s boats and kept as prisoners of war till hostilities are at an end.

We are reminded of some lines in Mr. Kipling’s poem, “Kitchener’s School”—

Those who argue in favour of the suppression of under-water warfare have pointed out that whereas the battleship can save the crew of the torpedo vessel, the latter owing to her small size can only steam away, sending the big ship to the bottom, and leave the unfortunate crew to drown or save themselves as best they can, which, with shell and shot flying about, would not be easy. A way out of the difficulty has not been found yet.

What then is the conclusion of the whole matter? It is this. Since the object of war is peace, make war as deadly as possible; since your goal is complete conquest, use all efforts to get it over as quickly as possible. We cannot do better than quote the following remarks made by a speaker during the discussion on Lord Dunsany’s lecture, above referred to.

“In conclusion I would say, save us from the cruel mercies of the weak. War—that splendid mistress for whose favours we have all longed since we reached man’s estate—must be given her full attributes and painted in her most deadly colours in order that the misery, which undoubtedly she brings to the majority of the population, may extend over as short a period as possible. Let us make her as deadly as we can, in the name of humanity and of every good feeling.”

Mr. H. G. Wells, in his “Anticipations,” confesses that his imagination, in spite even of spurring, refuses to see any sort of submarine doing anything but suffocate its crew and founder at sea. “It must involve physical inconvenience of the most demoralising sort simply to be in one for any length of time.... You may of course throw out a torpedo or so with as much chance of hitting vitally as you would have if you were blindfolded, turned round three times and told to fire revolver-shots at a charging elephant.... Given a derelict ironclad on a still night within sight of land, a carefully handled submarine might succeed in groping its way to it and destroying it; but then it would be much better to attack such a vessel and capture it boldly with a few desperate men on a tug. At the utmost, the submarine will be used in narrow waters, in rivers, or to fluster or destroy ships in harbour, or with poor-spirited crews—that is to say, it will simply be an added power in the hands of the nation that is predominant at sea. And even then, it can be merely destructive, while a sane and high-spirited fighter will always be dissatisfied if, with an undisputable superiority of force, he fails to take.”

We are afraid that Mr. Wells has not taken the trouble to keep himself in touch with the latest developments of submarine navigation. As we write, news comes from America of a party who spent fifteen hours under water in the Fulton without suffering any inconvenience. This does not look much like the “suffocation” Mr. Wells anticipates. As to torpedo-firing, French and American boats whilst under way have made excellent practice, both at stationary and at moving targets; while in making the assertion that the submarine will be used in narrow waters, in rivers or in harbours, it is evident that Mr. Wells is unaware of the lengthy voyages made by some of the newest boats.

The David represented the best type of under-water vessel in the sixties; that she is infinitely inferior to the newest Holland type or some of the French vessels of to-day goes without saying, and it will not be surprising if the submarine of thirty years hence bears the same resemblance to the Holland, as the Holland does to the David.

The ideal submarine boat has a speed as great as that of the fastest torpedo-boat, a very wide radius of action, excellent sea-keeping powers, unlimited quantities of air for power and for respiration by the crew; a means of directing its course by vision upon a moving object whilst itself remaining invisible beneath the surface, and is very habitable and comfortable for long periods of time.

The submarine of to-day lacks most of these attributes. It has a slow rate of speed, whether on the surface or submerged, a narrow radius of action, poor sea-keeping powers, a strictly limited quantity of compressed air, and is absolutely blind when beneath the waves. Thus it differs greatly from the ideal boat as sketched above, but its gradual improvement may be safely predicted.

We propose in this chapter to describe, in simple language, the working of a vessel intended for under-water navigation, and to consider what improvements are likely to take place.

Every submarine boat worked by a crew must of necessity be capable of floating on the surface of the water. This is a self-evident proposition, for the crew must have means of ingress and egress, and the only practical way of entering and leaving the boat is by an opening in the hull when she is on the surface.

We have no doubt that the files of the Patent Office would show that many inventors had designed boats which would sink to a certain depth directly they were placed in the water. While in such a system no time is lost in submersion, there would undeniably be difficulties in the way of coming to the surface, &c.

The first problem, then, which confronts the designer of a submarine boat is to find the most suitable method of sinking it to the depth at which it is intended to navigate.

The most fundamental law of hydrostatics, which applies to all floating bodies, and is equally true of wholly submerged vessels floating at any depth, as of ships of ordinary form, floating on the surface, having only a portion of their volume immersed, is that a ship floating freely and at rest in still water must displace a volume of water having a weight equal to her own weight.

The “displacement” of a vessel is defined as the weight of water displaced, which is equal to the weight of the vessel and that of her lading. A ship floating on the surface “displaces” a certain weight of water; in order to force her beneath the surface two methods are open.

In the first place, her weight is increased by the introduction of water ballast; thus her “displacement” is altered and she sinks until her weight is again equal to the volume of water displaced.

In the second, the weight of the boat remains constant, but the displacement is altered by the drawing in of “cylinders” or “drums;” thus she sinks until her displacement again equals her weight.

The first inventor to employ the latter method was André Constantin, who built a vessel during the siege of Paris, which was furnished with pistons working in two cylinders; on these being drawn in from the interior the boat sank to the required depth. The actual trials were, however, not satisfactory. The Nautilus, of Messrs. Campbell & Ash, which underwent some trials in Tilbury Docks in 1888, depended also on the pulling in of cylinders (ten were employed, five on each side of the vessel), for her submersion; the results were equally discouraging, and some eminent men nearly lost their lives owing to the erratic behaviour of this craft.

No serious ship-constructor would nowadays think of adopting this method of submersion, and we may therefore pass on to consider those which are brought to the submerged condition by the admission of water into special reservoirs or tanks.

Submarine boats so far as their immersion is concerned may be divided into two classes.

1. Those which when submerged possess no floatability.

2. Those which in the same condition possess a small reserve buoyancy or floatability.

Modern submarines almost without exception belong to the second division, as this class has been found to possess great advantages over the first.

Submarines which possess floatability when submerged have a weight which is less than their displacement and some mechanical action must be resorted to to force them below the surface. The first operation consists in introducing a certain amount of water into the tanks so that the boat is brought to the “awash” condition, with the greater part of the hull below water and only the conning tower, &c., appearing above the waves. The complete submersion of the vessel may be attained in two ways: either screws on vertical shafts are employed to “screw” the vessel below the surface, whether at rest or whilst moving; or horizontal rudders, or planes, are used to steer the boat below the surface; this latter method is only applicable to moving vessels.^[3]

Immersion by Screws Mounted on a vertical Shaft.

Just as a ship is driven backwards and forwards in the horizontal plane by means of a screw or screws mounted on a horizontal shaft, so it is possible to drive a ship up and down the vertical plane by means of one or more screws immersed in the water and mounted on a vertical shaft; the boat is by this method literally “screwed down” into the liquid.

The principle of the vertical screw was adopted by Bushnell who, in the description of his submarine vessel, writes: “At the top there was likewise an oar for ascending and descending or continuing at any particular depth.... When the skilful operator had obtained an equilibrium (by means of the forcing pumps) he could row upwards and downwards or continue at any particular depth with an oar placed near the top of the vessel, formed upon the principle of the screw, the axis of the oar entering the vessel. By turning the oar one way he raised the vessel, by turning it in the other he depressed it.”

M. Gaget remarks that “it is very strange that Bushnell should have discovered and concealed with so much care the instrument of propulsion which Sauvage studied and introduced fifty years later.” The fact is, of course, that the principle of the screw-propeller was known in the seventeenth century and that in May, 1785, Joseph Bramah patented a screw-propeller, identical in general arrangement with those in use to-day. The first practical use of the screw was made by John Stevens, who in 1804 launched a steamboat eighteen feet long by fourteen feet beam with a direct acting high-pressure engine having a tubular boiler—and driving a screw with four blades. Although the principle of the screw for ship propulsion was thus recognised at this early period it was not till the thirties (of the nineteenth century) that the screw-propeller succeeded in attracting the attention of the engineering world.

Professor Tuck in his boat (1884) placed the propeller directly beneath the centre of the hull, so that it should submerge on an even keel.

Mr. Nordenfelt used vertical screws, which at first he fitted in side sponsons, but afterwards in the fore and aft line, and considered it absolutely essential that a diving boat should be kept horizontal when being submerged, as any inclination downwards with the impetus of a heavy boat would, he considered, almost to a certainty carry the boat below its safe depth, before it could be effectually counteracted by shifting weights. Such a theory was soon shown to be founded on a misapprehension.

Some inventors (Waddington, Baker, &c.) have used four screws operating in pits equidistant from the centre of the boat, two on the upper part and two on the under part, but all such methods have been discarded in the newest designs.

Immersion by Horizontal Rudders.

The ordinary vertical rudder steers the ship either to port or starboard in the horizontal plane, and the horizontal rudder can be used similarly to control its position in the vertical plane.

This method of steering a boat beneath the surface by the inclination of horizontal rudders is, of course, only applicable when the boat is moving.

The position that the horizontal rudder or rudders should occupy is a question about which much has been written, and opinion appears to be still divided on the subject. Some hold that they should be placed at the stern, others that they should be placed on either side of the vessel, and these latter again differ as to whether they should be forward, amidship, or aft. In spite of all the arguments in favour of placing the rudders forward, Captain Hovgaard considers that this disposition can hardly be recommended except in very long boats where it may prove a necessity. The Gustave Zédé has six diving rudders, two forward, two in the centre, and two aft; whilst in the Narval class there are four rudders, two forward and two aft; the Holland submarines have aft rudders only.

Control in the Vertical Plane.

That beautiful machine, the Whitehead torpedo, is maintained at a set depth below the surface by means of a pendulum and a hydrostatic valve which regulate the horizontal rudders, and also in its true course by the gyroscope. In the case of the submarine it is necessary that it should not pass a certain limit when on its downward course, and that it keep so far as is possible the same level throughout its run under water.

The control of the submarine in the vertical plane may be accomplished by the manipulation of the rudders, either automatically, by means of some such arrangement as the hydrostatic valve or pendulum, or by hand, and she can be kept on an even keel and prevented from rising to the surface or sinking to the bottom, when running beneath the waves, by the pumping of water from a reservoir situated aft to one situated forward, or vice versâ, by the admission of water into trimming tanks, by shifting weights, &c. These operations can be carried out either automatically or by hand-operated mechanism.

It will be readily understood that while it is a comparatively simple matter to force a vessel beneath the surface to a depth previously determined, it is not so easy to ensure its keeping at this depth during the whole time it is submerged and maintaining throughout the run a perfectly even keel.

One of the greatest difficulties the inventor of submarine boats has to overcome is their lack of longitudinal stability. Submerged vessels are of two classes, those which are equal in weight to the water they displace, and those which are lighter. Both classes are subject to various disturbances which tend to upset their longitudinal stability and send them up to the surface and down towards the bottom. In Chapter XV. mention is made of the difficulties experienced by those who had to navigate the Nordenfelt.

The principal causes of disturbance have been summed up by Captain Hovgaard in a paper entitled, “The Motion of Submarine Boats in the Vertical Plane,” read before the Institution of Naval Architects at the Annual Meeting in 1901.

1. Faulty use of horizontal rudder. 2. Admission of water through leakages. 3. Expulsion of foul air and products of combustion. 3a. Firing of torpedoes and projectiles. 4. Movements of crew. 5. Existence of free surfaces of liquid. 6. Movements of loose weights, such as fuel. 7. Variations of buoyancy caused by varying density of sea water. 8. Grounding and collision. 9. Variations in speed.

Some of the most important of these disturbances may be briefly discussed.

1. Most modern submarines are provided with more than one pair of horizontal rudders, but if all the rudders should refuse to act and the boat is running down an inclined plane, the only thing to be done is to pump the water out of the tanks and thus bring the boat to the surface.

2. By the careful construction of the hull, and by strict control of all sea-valves, the admission of water may be prevented. If the boat is stove in and water enters in any quantity, she will inevitably sink. As an escape some inventors have provided their submarines with detachable boats.

3. Usually the length of the run under water will not be so great that the foul air will need to be got rid of. If necessary it can be expelled by drawing on the store of compressed air, and as the substances withdrawn will always be small, no change in longitudinal balance need be feared if precautions are taken. As all modern submarines are driven by electricity beneath the surface, the expulsion of products of combustion need not be considered.

3a. In the earliest submarine boats the torpedoes consisted of charges of explosive in cases, which were attached to the outside of the vessel to be attacked, or were towed against her sides.

Those who had little faith in the future of under-water warfare declared that a torpedo could never be fired from a tube in a submerged vessel without disastrous effects. The Nordenfelt boats were certainly not successful in discharging torpedoes, for as a general rule they as nearly as possible stood up vertically on their tails and proceeded to plunge to the bottom stern first on these occasions.

However, since then, submarines have fired torpedoes quite satisfactorily under water.

The expulsion of a torpedo from a vessel totally submerged in the water, whether equal to or less than the weight to the water displaced, naturally reduces her weight and tends to send her up towards the surface. This tendency can best be counteracted by the admission of a certain quantity of water ballast into the boat.

The method now usually followed is to allow the surrounding water to enter the tube immediately after the launch of the torpedo, and as the weight of the volume of water admitted will be about equal to that of the missile ejected, the longitudinal stability of the submarine should not be disturbed. When the second torpedo comes to be placed in the tube, the volume of water already in it must of necessity be ejected, and a compensating reservoir may be used to receive it. As each torpedo is fired a certain amount of water, corresponding to the weight of the projectile, must be allowed to enter the compensating reservoir. This may be done automatically.

The Engineer in a leader on January 18, 1901, said: “The discharge of a bow torpedo (by a submarine) would be instantly followed by the rise of the bow; relieved of the weight the boat would tend to stand on end. If going ahead at the time she would immediately come to the surface to be destroyed. If going astern she would plunge downwards and the consequences might be equally serious.... Torpedoes must be fired when the submarine is at rest.”

In spite of this dogma submarines have fired torpedoes whilst in motion with success, and in modern submarines ample provision is made for the loss of weight occasioned by the discharge of the torpedo.

4. Reference has been made to the fact that when the Nordenfelt boat was moving along on an even keel, and a greaser walked forward a couple of feet in his engine room, her head would go down a little, the water would surge forward in the tanks, and she would plunge to the bottom, unless checked in time. It has been said that one man going forward in a submarine boat would cause her to dive to a depth of thirty-six feet in one minute. The movements of the crew may be compensated for by automatic arrangements, but the ideal method would be one in which every one remained immovable at his post during the submerged run.

Steering Below Water.

Quite early in the history of submarine navigation it was found that the compass was not so reliable when the boat was navigating under water as it was when she was on the surface. This is not to be wondered at, for the compass of a submarine is placed in the interior of a tightly-closed metallic shell and in close proximity to an electro-motor and powerful currents capable of influencing it considerably, if not of rendering it altogether useless.

The principal causes of the unreliability of the compass on a submerged boat are:—

1. The currents normally produced by the electric motor.

2. The abnormal currents flowing in certain unknown parts of the hull owing to lack of proper insulation.

3. The permanent or transitory magnetisation of the hull if made of a magnetic metal.

The best position for the compass on a submarine has been a much debated point, but it is now generally agreed to be in the centre of the hull. The conning tower of the first British submarine was made of steel, but it was afterwards replaced by one of brass.

M. M. Gaget in his book^[4] states that so entirely untrustworthy and impracticable has steering by compass in French submarines been found, that the gyroscope has been requisitioned. He inclines to the belief that this instrument is the best indicator of route that has yet been devised, yet he points out the want of some reliable method by which the distance made by a submerged boat could be gauged with accuracy.