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Inventions Of The Great War

<h2>CHAPTER XVI Reclaiming the Victims of the Submarine</h2> Nearly fifteen million tons of shipping lie at the bottom of the sea, sunk by German U-boats, and the value of these ships with their cargo is estimated at over seven billion dollars. In one year, 1917, the loss was nearly a million dollars a day. Of course these wrecks would not be worth anything like that now, if they were raised and floated. Much of the cargo would be so damaged by its long immersion in salt water that it would be absolutely valueless, but there are many kinds of merchandise that are not injured in the least by water. Every ship carries a certain amount of gold and silver; and then the ship's hull itself is well worth salving, provided it was not too badly damaged by the torpedo that sank it. Altogether, there is plenty of rich treasure in the sea awaiting the salvor who is bold enough to go after it. 311 To be sure, not all of the U-boat's victims were sunk in deep water. Many torpedoed vessels were beached or succeeded in reaching shallow water before they foundered. Some were sunk in harbors while they lay at anchor, before the precaution was taken of protecting the harbors with nets. The Allies did not wait for the war to end before trying to refloat these vessels. In fact, during the war several hundred ships were raised and put back into service. A special form of patch was invented to close holes torn by torpedoes. Electric pumps were built which would work under water and these were lowered into the holds of ships to pump them out. The salvors were provided with special gas-masks to protect them from poisonous fumes of decayed matter in the wrecks. Our own navy has played an important part in salvage. Shortly after we entered the war, all the wrecking-equipment in this country was commandeered by the government and we sent over to the other side experienced American salvors, provided with complete equipment of apparatus and machinery. The majority of wrecks, however, are found in the open sea, where it would have been foolish312 to attempt any salvage-operations because of the menace of submarine attack. On at least one occasion a salvage vessel, while attempting to raise the victims of a submarine, fell, itself, a prey to a Hun torpedo. Now that this menace has been removed, such vessels as lie in comparatively shallow water, and in positions not subject to sudden tempests, can be raised by the ordinary methods; or if it is impracticable to raise them, much of their cargo can be reclaimed. However, most of the torpedoed ships lie at such depths that their salvage would ordinarily be despaired of. <h3>IN THE DEPTHS OF THE SEA</h3> It will be interesting to look into conditions that exist in deep water. Somehow the notion has gone forth that a ship will not surely sink to the very bottom of the deep sea, but on reaching a certain level will find the water so dense that even solid iron will float, as if in a sea of mercury, and that here the ship will be maintained in suspension, to be carried hither and yon by every chance current. Indeed, it makes a rather fantastic picture to think of these lost ships drifting in endless procession, far down313 beneath the cold green waves, and destined to roam forever like doomed spirits in a circle of Dante's Inferno. But the laws of physics shatter any such illusion and bid us paint a very different picture. Liquids are almost incompressible. The difference in density between the water at the surface of the sea and that at a depth of a mile is almost insignificant. As a matter of fact, at that depth the water would support only about half a pound more per cubic foot than at the surface. The pressure, however, would be enormous. Take the Titanic, for instance, which lies on the bed of the ocean in water two miles deep. It must endure a pressure of about two long tons on every square inch of its surface. Long before the vessel reached the bottom her hull must have been crushed in. Every stick of wood, every compressible part of her structure and of her cargo, must have been staved in or flattened. As a ship sinks it is not the water but the ship that grows progressively denser. The Titanic must have actually gained in weight as she went down, and so she must have gathered speed as she sank. We may be certain, therefore, that every victim314 of Germany's ruthless U-boats that sank in deep water lies prone upon the floor of the sea. It matters not how or where it was sunk, whether it was staggered by the unexpected blow of the torpedo and then plunged headlong into the depths of the sea, or whether it lingered, mortally wounded, on the surface, quietly settling down until the waves closed over it. Theoretically, of course, a perfect balance might be reached which would keep a submerged vessel in suspension, but practically such a condition is next to impossible. Once a ship has started down, she will keep on until she reaches the very bottom, whether it be ten fathoms or ten hundred. <h3>A SUBMARINE GRAVEYARD</h3> Instead of the line of wandering specters, then, we must conjure up a different picture, equally weird—an under-world shrouded in darkness; for little light penetrates the deep sea. Here in the cold blackness, on the bed of the ocean, the wrecks of vessels that once sailed proudly overhead lie still and deathly silent—some keeled over on their sides, some turned315 turtle, and most of them probably on even keel. Here and there may be one with its nose buried deep in the mud; and in the shallower waters we may come across one pinned down by the stern, but with its head buoyed by a pocket of air, straining upward and swaying slightly with every gentle movement of the sea, as if still alive. This submarine graveyard offers wonderful opportunities for the engineer, because the raising of wrecked vessels is really a branch of engineering. It is a very special branch, to be sure, and one that has not begun to receive the highly concentrated study that have such other branches as tunneling, bridge-construction, etc. Nevertheless it is engineering, and it has been said of the engineer that his abilities are limited only by the funds at his disposal. Now he has a chance to show what he can do, for there are hundreds of vessels to be salved where before there was but one. The vast number of wrecks in deep water will make it pay to do the work on a larger and grander scale than has been possible heretofore. Special apparatus that could not be built economically for a single316 wreck may be constructed with profit if a number of vessels demanding similar treatment are to be salved. The principal fields of German activities were the Mediterranean Sea and the waters surrounding the British Isles. Although the submarine zone covered some very deep water, where the sounding-lead runs down two miles without touching bottom, obviously more havoc could be wrought near ports where vessels were obliged to follow a prescribed course, and so most of the U-boat victims were stricken when almost in sight of land. In fact, as was pointed out in a previous chapter, it was not until efficient patrol measures made it uncomfortable for the submarines that they pushed out into the open ocean to pursue their nefarious work. The Lusitania went down only eight miles from Old Head of Kinsale, in fifty fathoms of water. If we draw a line from Fastnet Rock to the Scilly Islands and from there to the westernmost extremity of France, we enclose an area in which the German submarines were particularly active. The soundings here run up to about sixty fathoms in some places, but the prevailing depth is less than fifty fathoms. In317 the North Sea, too, except for a comparatively narrow lane along the Norwegian coast—which, by the way, marked the safety lane of the German blockade zone—the chart shows fifty fathoms or under. If our salvors could reach down as far as that, most of the submarine victims could be reclaimed. But fifty fathoms means 300 feet, which is a formidable depth for salvage work. Only one vessel has ever been brought up from such a depth and that was a small craft, one of our submarines, the F-4, which sank off the coast of Hawaii four years ago. <h3>DIFFERENT WAYS OF SALVING A WRECK</h3> There are four well-known methods of raising a vessel that is completely submerged. Of course, if the ship is not completely submerged, the holes in her hull may be patched up, and then when her hull is pumped out, the sea itself will raise the ship, unless it be deeply embedded in sand or mud. If the vessel is completely submerged, the same process may be resorted to, but first the sides of the hull must be extended to the surface to keep the water from flowing in as fast as it is pumped out. It is318 not usual to build up the entire length of the ship. If the deck is in good condition, it may suffice to construct coffer-dams or walls around several of the hatches. But building up the sides of a ship, or constructing coffer-dams on the ship's deck is a difficult task, at best, because it must be done under water by divers. A record for this type of salvage work was established by the Japanese when they raised the battle-ship Mikasa that lay in some eighty feet of water. Her decks were submerged to a depth of forty feet. It is doubtful that this salvage work could be duplicated by any other people of the world. The wonderful patriotism and loyalty of the Japanese race were called forth. It is no small task to build a large coffer-dam strong enough to withstand the weight of forty feet of water, or a pressure of a ton and a quarter per square foot, even when the work is done on the surface. Perfect discipline and organized effort of the highest sort were required. Labor is cheap in Japan and there was no dearth of men for the work. Over one hundred divers were employed. In addition to the coffer-dam construction much repair work was necessary. Marvelous acts of devotion and heroism319 were performed. It is rumored that in some places it was necessary for divers to close themselves in, cut their air supply-pipes and seal themselves off from the slightest chance of escape; and that there were men who actually volunteered to sacrifice their lives in this way for their beloved country and its young navy. Where, indeed, outside of the Land of the Rising Sun could we find such patriotic devotion! A second salvage method consists in building a coffer-dam not on the ship but around it, and then pumping this out so as to expose the ship as in a dry-dock. Such was the plan followed out in recovering the Maine. Obviously, it is a very expensive method and is used only in exceptional cases, such as this, in which it was necessary to make a post-mortem examination to determine what caused the destruction of the vessel. Neither of these methods of salvage will serve for raising a ship sunk in deep water. <h3>RAISING A SHIP ON AIR</h3> A salvage system that has come into prominence within recent years consists in pumping320 air into the vessel to drive the water out, thus making the boat light enough to float. This scheme can be used only when the deck and bulkheads of the boat are strongly built and able to stand the strain of lifting the wreck, and when the hole that sank the vessel is in or near the bottom, so as to allow enough airspace above it to lift the boat. The work of the diver in this case consists of closing hatches and bulkhead doors, repairing holes in the upper part of the hull, and generally strengthening the deck. It must be remembered that a deck is built to take the strain of heavy weights bearing down upon it. It is not built to be pushed up from beneath, so that frequently this method of salving is rendered impracticable because the deck itself cannot stand the strain. <div class="center"><div class="container"> <div id="ip_320" class="figleft" style="width: 357px;"> <ANTIMG src="images/i_320.jpg" width-obs="357" height-obs="262" alt="" /> <div class="caption">Climbing into an Armored Diving Suit</div> </div> <div id="ip_320b" class="figright" style="width: 359px;"> <ANTIMG src="images/i_320b.jpg" width-obs="359" height-obs="200" class="p4" alt="" /> <div class="caption">Lowering an Armored Diver into the Water</div> </div></div> </div> A more common salvage method consists in passing cables or chains under the wreck and attaching them to large floats or pontoons. The slack in the chains is taken up when the tide is low, so that on the turn of the tide the wreck will be lifted off the bottom. The partially raised wreck is then towed into shallower water, until it grounds. At the next low tide, the321 slack of the chains is again taken in, and at flood-tide the wreck is towed nearer land. The work proceeds step by step, until the vessel is moved inshore far enough to bring its decks awash; when it may be patched up and pumped out. Where the rise of the tide is not sufficient to be of much assistance, hydraulic jacks or other lifting-apparatus are used. <div class="center"><div class="container"> <div id="ip_321" class="figleft" style="width: 360px;"> <ANTIMG src="images/i_321.jpg" width-obs="360" height-obs="233" alt="" /> <div class="caption">A Diver's Sea Sled ready to be towed along the bed of the sea</div> </div> <div id="ip_321b" class="figright" style="width: 364px;"> <ANTIMG src="images/i_321b.jpg" width-obs="364" height-obs="258" alt="" /> <div class="caption">The Sea Sled on Land showing the forward horizontal and after vertical rudders</div> </div></div> </div> <h3>SALVING THE U. S. SUBMARINE F-4</h3> If the salvor could always be assured of clear weather, his troubles would be reduced a hundredfold, but at best it takes a long time to perform any work dependent upon divers, and the chances are very good when they are operating in an unsheltered spot, that a storm may come up at any time and undo the result of weeks and months of labor. This is what happened when the submarine F-4 was salved. After a month of trying effort the submarine was caught in slings hung from barges, lifted two hundred and twenty-five feet, and dragged within a short distance of the channel entrance of the harbor, where the water was but fifty feet deep. But just then a violent storm arose, which made the barges surge back and forth and322 plunge so violently that the forward sling cut into the plating of the submarine and crushed it. The wreck had to be lowered to the bottom and the barges cut free to save them from being smashed. At the next attempt to raise the F-4 pontoons were again used, but instead of being arranged to float on the surface, they were hauled down to the wreck and made fast directly to the hull of the submarine. Then when the water was forced out of the pontoons with compressed air, they came up to the surface, bringing the submarine with them. In this way all danger of damage due to sudden storms was avoided because water under the surface is not disturbed by storms overhead; and when the wreck was floated, the pontoons and submarine formed a compact unit. While this method of salvage seems like a very logical one for work in the open sea, one is apt to forget how large the pontoons must be to lift a vessel of any appreciable size. Not only must they support their own dead weight, together with that of the sunken vessel, but some allowance must usually be made for dragging the wreck out of the clutches of a sandy or muddy bottom. Imagine the work of building323 pontoons large enough to raise the Lusitania. They would have to have a combined displacement greater than that of the vessel itself, and they would have to be so large that they would be very unwieldy things to handle in a seaway. It is for this reason that submarine pontoons are not often used to take the entire weight of the vessel. So far they have been employed mainly to salve small ships and then only to take a portion of the weight, the principal work being done by large wrecking-cranes. Instead of horizontal pontoons it has been suggested that vertical pontoons be employed, so as to provide a greater lifting-power without involving the use of enormous unwieldy units. Ships are not built so that they can be picked up by the ends. Such treatment would be liable to break their backs in the middle. Were they built more like a bridge truss, the salvor's difficulties would be materially lessened. It would be a much simpler matter to raise a vessel with pontoons were it so constructed that the chains of the pontoon could be attached to each end of the hull. But because a ship is built to be supported by the water uniformly throughout its length, the salvor must use a324 large number of chains, properly spaced along the hull, so as to distribute the load uniformly and see that too much weight does not fall on this or that pontoon. The main problem, however, is to get hold of the wreck and this requires the services of divers, so that if there were no other limiting factor, the depth to which a diver may penetrate and perform his duties sets the mark beyond which salvage as now conducted is impossible. <div id="ip_324" class="figcenter" style="width: 351px;"> <ANTIMG src="images/i_324.jpg" width-obs="351" height-obs="473" alt="" /> <div class="captionl">(C) International Film Service</div> <div class="caption0">The Diving Sphere built for Deep Sea Salvage Operations</div> </div> A common diver's suit does not protect the diver from hydraulic pressure. Only a flexible suit and a thin layer of air separates him from the surrounding water. This air must necessarily be of the same pressure as the surrounding water. The air that is pumped down to the diver not only serves to supply his lungs, but by entering his blood transmits its pressure to every part of his anatomy. As long as the external pressure is equalized by a corresponding pressure within him, the diver experiences no serious discomfort. In fact, when the pressure is not excessively high he finds it rather exhilarating to work under such conditions; for, with every breath, he takes in an abnormal amount of oxygen. When325 he returns to the surface he realizes that he has been working under forced draft. He is very much exhausted and he is very hungry. It takes a comparatively short time to build up the high internal pressure, which the diver must have in order to withstand the pressure of the water outside, but it is the decompression when he returns to the surface that is attended with great discomfort and positive danger. If the decompression is not properly effected, the diver will suffer agonies and even death from the so-called "Caisson Disease." <div id="ip_325" class="figcenter" style="width: 549px;"> <ANTIMG src="images/i_325.jpg" width-obs="549" height-obs="346" alt="" /> <div class="caption">The Pneumatic Breakwater—Submerged Air Tubes protecting a California Pier from Ocean Storms</div> </div> <h3>A HUMAN SODA-WATER BOTTLE</h3> We know now a great deal more than we used to know about the effect of compressed air on the human system, and because of this knowledge divers have recently descended to depths undreamed of a few years ago. When a diver breathes compressed air, the oxygen is largely consumed and exhaled from the lungs in the form of carbon-dioxide, but much of the nitrogen is dissolved in the blood and does not escape. However, like a bottle of soda-water, the blood shows no sign of the presence of the gas as long as the pressure is maintained. But326 on a sudden removal of the pressure, the blood turns into a froth of nitrogen bubbles, just as the soda-water froths when the stopper of the bottle is removed. This froth interrupts the circulation. The release of pressure is felt first in the arteries and large veins. It takes some time to reach all the tiny veins, and serious differences of pressure are apt to occur that often result in the rupture of blood-vessels. The griping pains that accompany the "Caisson Disease" are excruciating. The only cure is to restore the blood to its original pressure by placing the patient in a hospital lock, or boiler-like affair, where compressed air may be admitted; and then to decompress the air very slowly. It is possible to relieve the pressure in a bottle of soda-water so gradually that the gas will pass off without the formation of visible bubbles, and that is what is sought in decompressing a diver. After careful research it has been found that the pressure may be cut down very quickly to half or even less of the original amount, but then the diver must wait for the decompression to extend to the innermost recesses327 of his being and to all the tiny capillaries of his venous system. In the salvage of the F-4 a diver went down 306 feet, and remained on the bottom half an hour. The pressure upon him was 135 pounds per square inch, or about 145 tons on the surface of his entire body. Some idea of what this means may be gained if we consider that the tallest office building in the world does not bear on its foundations with a greater weight than 215 pounds to the square inch or only about 50 per cent more than the crushing pressure this diver had to endure. It took the diver a very short time to go down. On coming up he proceeded comparatively rapidly until he reached a depth of 100 feet. There he found the bottom rung of a rope ladder. On it he was obliged to rest for several minutes before proceeding to the next rung. The rungs of this ladder were 10 feet apart, and on each rung the diver had to rest a certain length of time, according to a schedule that had been carefully worked out. At the top rung, for instance, only 10 feet from the surface, he was obliged to wait forty minutes. In all, it328 took him an hour and forty-five minutes to come up to the surface. The decompression was complete and he suffered no symptoms of the "Caisson Disease." But he was so exhausted from his efforts that he was unfit for work for several days. Yet the operations that he performed at the depth of 300 feet would not have taken more than a few minutes on the surface. <h3>A SUBMARINE REST-CHAMBER</h3> The Germans have paid a great deal of attention to deep-diving operations, and no doubt while their U-boats were sinking merchant ships German salvors were anticipating rich harvests after hostilities ended. One scheme they developed was a submarine rest-chamber which could be permanently located on the bottom of the sea close to the point where the salvage operations were to take place. This chamber consists of a large steel box which is supplied with air from the surface and in which divers may make themselves comfortable when they need a rest after arduous work. Entrance to the chamber is effected through a door in the floor. The pressure of the air inside prevents the water from rising into the chamber and329 flooding it. From this submarine base the divers may go out to the wreck, either equipped with the ordinary air-tube helmets or with self-regenerating apparatus which makes them independent of an air-supply for a considerable period of time. When the diver has worked for an hour or two, or when he is tired, he may return to this chamber, remove his helmet, eat a hearty meal, take a nap if he needs it, and then return to the salvage work without going through the exhausting operation of decompressing. <h3>CUTTING METAL UNDER WATER WITH A TORCH</h3> The work of the diver usually consists of far more than merely passing lines under a sunken hull. It is constantly necessary for him to cut away obstructing parts. He must sometimes use blasting-power. Pneumatic cutting-tools frequently come into play, but the Germans have lately devised an oxy-hydrogen torch for underwater use, with which the diver can cut metal by burning through it. This is accomplished by using a cup-shaped nozzle through which a blast of air is projected under such pressure330 that it blows away the water over the part to be cut. The oxygen and hydrogen jets are then ignited electrically, and the work of cutting the metal proceeds in the hole in the water made by the air-blast. A similar submarine torch has recently been developed by an American salvage company. It was employed successfully in cutting drainage-holes in the bulkheads of the St. Paul, which was raised in New York Harbor in the summer of 1918. <h3>EXPLORING THE SEA BOTTOM IN A DIVER'S SLED</h3> The diver's sled is still another interesting German invention. It is a sled provided with vertical and horizontal rudders, which is towed by means of a motor-boat at the surface. The diver, seated on the sled, and provided with a self-contained diving-suit, can direct the motor-boat by telephone and steer his sled up and down and wherever he chooses. And so without any physical exertion, he can explore the bottom of the sea and hunt for wrecks. <h3>ARMORED DIVING-SUITS</h3> From time to time attempts have been made to construct a diver's suit that will not yield331 to the pressure of the sea, so that the diver will not be subjected to the weight of the water about him, but can breathe air at ordinary atmospheric pressure. Curious armor of steel has been devised, with articulated arms and legs, in which the diver is completely encased. With the ordinary rubber suit, the diver usually has his hands bare, because he is almost as dependent upon the sense of touch as a blind man. But where the pressure mounts up to such a high degree that a metal suit must be used, no part of the body may be exposed. If a bare hand were extended out of the protecting armor it would immediately be mashed into a pulp and forced back through the opening in the arms of the suit. The best that can be done, then, is to furnish the arms of the suit with hooks or tongs or other mechanical substitutes for hands which will enable the diver to make fast to the wreck or various parts of it. But if a diver feels helpless in the bag of a suit now commonly worn, what would he do when encased in a steel boiler; for that is virtually what the armored suit is! A common mistake that inventors of armor units have made is to fail to consider the effects of the332 enormous hydraulic pressure on the joints of the suit. In order to make them perfectly tight, packings must be employed, and these are liable to be so jammed by the hydraulic pressure that it is well nigh impossible to articulate the limbs. Again, the construction of the suit should be such that when a limb is flexed it would not displace any more water than when in an extended position, and vice versa. A diver may find that he cannot bend his arm, because in doing so he would expand the cubical content of his armor by a few cubic inches, and to make room for this increment of volume it would be necessary for him to lift several hundred pounds of water. The hydraulic pressure will reduce the steel suit to its smallest possible dimensions, which may result either in doubling up the members or extending them rigidly. But these difficulties are not insuperable. There is no reason why a steel manikin cannot be constructed with a man inside to direct its movements. <h3>THE SALVOR'S SUBMARINE</h3> Other schemes have been devised to relieve the diver of abnormally high air-pressure.333 One plan is to construct a large spherical working-chamber strong enough to withstand any hydraulic pressure that might be encountered. This working-chamber is equipped with heavy glass ports through which the workers can observe their surroundings in the light of an electric search-light controlled from within the chamber. The sphere is to be lowered to the wreck from a barge, with which it will be in telephonic communication and from which it will be supplied with electric current to operate various electrically driven mechanisms. By means of electromagnets this sphere may be made fast to the steel hull of the vessel and thereupon an electric drill is operated to bore a hole in the ship and insert the hook of a hoisting-chain. This done, the sphere would be moved to another position, as directed by telephone and another chain made fast. The hoisting-chains are secured to sunken pontoons and after enough of the chains have been attached to the wreck the pontoons are pumped out and the wreck is raised. It is a pity that ship-builders have not had the forethought to provide substantial shackles at frequent intervals firmly secured to the framing.334 A sunken vessel is really a very difficult object to make fast to and the Patent Office has recorded many very fantastic schemes for getting hold of a ship's hull without the use of divers. One man proposes the use of a gigantic pair of ice-tongs; and there have been no end of suggestions that lifting-magnets be employed, but no one who has any idea of how large and how heavy such magnets must be would give these suggestions any serious consideration. But, after all, the chief obstacle to salvage in the open sea is the danger of storms; months of preparation and thousands of dollars' worth of equipment may be wiped out in a moment. <h3>FIGHTING THE WAVES WITH AIR</h3> However, there has been another recent development which may have a very important bearing on this problem of deep-sea salvage work. It has often been observed that a submerged reef, twenty or thirty feet below the surface, may act as a breakwater to stop the storming waves. An inventor who studied this phenomenon arrived at the theory that the reefs set up eddies in the water which break335 up the rhythm of the waves and convert them into a smother of foam just above the reef. Thereupon he conceived the idea of performing the same work by means of compressed air. He laid a pipe on the sea bottom, forty or fifty feet below the surface, and pumped air through it. Just as he had expected, the line of air bubbles produced exactly the same effect as the submerged reef. They set up a vertical current of water which broke up the waves as soon as they struck this barrier of air. The "pneumatic breakwater," as it is called, has been tried out on an exposed part of the California coast, to protect a long pier used by an oil company. It has proved so satisfactory that the same company has now constructed a second breakwater about another pier near by. There is no reason why a breakwater of this sort should not be made about a wreck to protect the workers from storms. Where the water is very deep, it would not be necessary to lay the compressed-air pipe on the bottom, but it could be carried by buoys at a convenient depth. Summing up the situation, then, there are two serious bars to the successful salvage of ships sunk in the open sea—the wild fury of the336 waves on the surface; and the silent, remorseless pressure of the deep. The former is the more to be feared; and if the waves really can be calmed, considerably more than half the problem is solved. As for the pressure of the sea, it can be overcome, as we have seen, either by the use of special submarine mechanisms, or of man-operated manikins or even of unarmored divers. We have reached a very interesting stage in the science of salvage, with the promise of important developments. Fifty fathoms no longer seems a hopeless depth. Even in times of peace the sea exacts a dreadful toll of lives and property. Before the war the annual loss by shipwreck around the British Isles alone was estimated at forty-five million dollars. But the war, although it was frightfully destructive to shipping, may in the long run save more vessels than it sank; for it has given us sound-detectors which should remove the danger of collisions in foggy weather, and the wireless compass, which should keep ships from running off the course and on the rocks. And now, if salvage engineering develops as it should, the sea will be made to give up not only337 much of the wealth it swallowed during the war, but also many of the rich cargoes of gold and silver it has been hoarding since the days of the Spanish galleon. <hr /> 339 <div class="p4e newpage index"> <h2 class="p0 nopage">INDEX</h2> <ul> <li>Air, fighting waves, 334 <ul> <li>raising ship, on, 319</li> <li>war in, 123</li> </ul></li> <li>Airplane, ambulance, 146 <ul> <li>armored, 139</li> <li>artillery-spotting, 131</li> <li>camera, 173</li> <li>cartridges, 131</li> <li>classes of work, 127</li> <li>fighting among clouds, 137</li> <li>flying boats, 144</li> <li>gasolene tank, 130</li> <li>giant, 132</li> <li>hospital, 146</li> <li>launching from ship, 303</li> <li>Liberty motor, 142</li> <li>scouting, 125</li> <li>scouts, 128</li> <li>speed of, 134</li> <li>spotting, 177</li> <li>training spotters, 180</li> <li>wireless telephone, 194</li> <li>See also Seaplane</li> </ul></li> <li>Ambulance airplane, 146 </li> <li>Armored diving-suit, 330 </li> <li>Arms and armor, 111 </li> <li>Artillery, hand, 23 </li> <li>Atmosphere, shooting beyond, 64 </li> <li>Audion, 185 </li> <li class="p1" id="Balloon">Balloon, Blimp, 260 <ul> <li>helium, 164</li> <li>historical, 148</li> <li>hydrogen, 150</li> </ul></li> <li>Balloon, kite, 174 <ul> <li>principles, 150</li> <li>record flight, 65</li> </ul></li> <li>Barbed wire, 15 <ul> <li>cylinders, 17</li> <li>gate, trench, 9</li> <li>gates through, 15</li> <li>shelling, 16</li> </ul></li> <li>Barge for towing seaplanes, 302 </li> <li>Barrage, grenade, 27 <ul> <li>mine, 292</li> </ul></li> <li>Battle-fields, miniature, 180 </li> <li>Blimp, 260 </li> <li>Blisters on ships, 307 </li> <li>Boats, electric, 308 <ul> <li>Eagle, 301</li> <li>flying, 144</li> <li>surface, 298</li> </ul></li> <li>Bombs to destroy barbed wire, 16 </li> <li>Breakwater, pneumatic, 335 </li> <li>Browning, John M., 56 </li> <li>Buildings, shadowless, 227 </li> <li class="p1">Caisson disease, 325 </li> <li>Caliber, 68 </li> <li>Camera, airplane, 173 </li> <li>Camouflage and camoufleurs, 211 <ul> <li>buildings, 227</li> <li>grass, 229</li> <li>horse, 223</li> <li>land, 222</li> <li>roads, 225</li> </ul></li> <li>Camouflage, ships, 211340 </li> <li>Cartridges, aircraft guns, 131 </li> <li>Catapults, 36 </li> <li>Caterpillar tractor, 109 </li> <li>Caves, 8 </li> <li>Coffer-dam, salvage, 318 </li> <li>Color, analyzing, 229 <ul> <li>screens, 229</li> </ul></li> <li>Compass, wireless, 201 </li> <li>Convoy, 267 </li> <li>Countermines, 17 </li> <li class="p1">Deep sea, conditions in, 312 </li> <li>Deep water diving, 327 </li> <li>Depth bombs, 265 </li> <li>Devil's eggs, 276 </li> <li>Diesel engine, 240 </li> <li>Direction-finder, 205 </li> <li>Dirigible, see Balloon </li> <li>Disease, caisson, 325 </li> <li>Diver, armored suit, 330 <ul> <li>caisson disease, 325</li> <li>rest chamber, 328</li> <li>sled, 330</li> <li>submarine torch, 329</li> <li>suit, 324</li> </ul></li> <li>Diving, deep, 324 <ul> <li>record depth, 327</li> </ul></li> <li>Duck-boards, 9 </li> <li>Dugouts, 7 </li> <li>Dummy heads of papier mâché, 13 </li> <li class="p1">Eagle boats, 301 </li> <li>Egg-laying submarines, 287 </li> <li>Eggs, Devil's, 276 </li> <li>Electric motor-boat, 308 </li> <li>Engine, Diesel, 240 </li> <li class="p1">Field-guns, 81 </li> <li>Fire broom, 105 <ul> <li>liquid, 103</li> </ul></li> <li>Forts, machine-gun, 58 </li> <li>Fuse, grenade, 28 </li> <li class="p1">Gas, 85 <ul> <li>American, 102</li> </ul></li> <li>Gas attack, boomerang, 92 <ul> <li>first, 89</li> </ul></li> <li>Gas, chlorine, 87 <ul> <li>diphosgene, 96</li> <li>exterminating rats, 94</li> <li>grenades, 26</li> <li>helium, 164</li> <li>hydrogen, 150</li> <li>lock, 97</li> <li>masks, 99</li> <li>mustard, 98</li> <li>phosgene, 93</li> <li>pouring like water, 86</li> <li>shell, 95</li> <li>sneezing, 98</li> <li>tear, 95</li> <li>vomiting, 98</li> </ul></li> <li>Gasolene-tank, airplane, 130 </li> <li>Gate, barbed wire, trench, 9 </li> <li>Gates through barbed wire, 15 </li> <li>Gatling gun, 43 </li> <li>Geologists, Messines Ridge, 19 </li> <li>Glass, non-shattering, 100 </li> <li>Grapnel shell, 16 </li> <li>Graveyard, submarine, 314 </li> <li id="Grenade">Grenade, disk-shaped, 33 <ul> <li>fuse, 28</li> <li>gas, 26</li> <li>hair brush, 34</li> <li>history of, 23</li> <li>Mills, 29</li> <li>parachute, 31</li> <li>range of, 25</li> <li>rifle, 28</li> <li>throwing implement, 27</li> </ul></li> <li>Grenade, wind-vane safety device, 32 </li> <li>Gun, aircraft, 131 <ul> <li>American, 50-mile, 63</li> <li>big, hiding, 226</li> <li>caliber, 68</li> <li>disappearing, 77</li> <li>double-end, 145</li> <li>18-inch, monitors, 306</li> <li>elastic, 73</li> <li>field, 81</li> <li>42-centimeter, 79</li> <li>how made, 76</li> <li>120-mile, 70</li> <li>long range, German, 62</li> <li>non-recoil, 145</li> <li>on submarine, 249</li> <li>16-inch, coast defense, 78</li> <li>Skoda, 81</li> <li>spotting by sound, 181</li> <li>three-second life, 73</li> <li>12-inch, submarine, 251</li> <li>ways of increasing range, 67</li> <li>wire-wound, 76</li> </ul></li> <li class="p1">Hand-grenade, see Grenade </li> <li>Helium, 164 </li> <li>Hospital, airplane, 147 </li> <li>Horizon, seeing beyond, 219 </li> <li>Howitzer, 79 </li> <li>Hush ships, 304 </li> <li>Hydroaëroplanes, see Seaplanes </li> <li>Hydrogen, weight of, 150 </li> <li>Hydrophone, 270 </li> <li class="p1">Illusions, optical, 215 </li> <li class="p1">Kilometer, length in miles, 6 </li> <li>Kite balloons, 174 </li> <li>Kite, water, 283 </li> <li class="p1">Liberty motor, 142341 </li> <li>Liquid-fire, 103 </li> <li>Locomotives, gasolene, 10 </li> <li>Lusitania, 316 </li> <li class="p1">Machine-gun, 112 <ul> <li>airplane, 127</li> <li>Benèt-Mercié, 52</li> <li>Browning, 53</li> <li>Colt, 44</li> <li>forts, 58</li> <li>Gatling, 43</li> <li>history, 41</li> <li>Hotchkiss, 49</li> <li>Lewis, 50</li> <li>Maxim, 42</li> <li>water-jacket, 47</li> <li>worth in rifles, 58</li> </ul></li> <li>Machine-rifle, 55 </li> <li>Magnets, lifting, salvage, 334 </li> <li>Maps, making with camera, 175 </li> <li>Marne, first battle of, 4 </li> <li>Messines Ridge, mine, 19 </li> <li>Metal-cutting under water, 329 </li> <li>Microphone detectors, mines, 18 </li> <li>Mine-field, North Sea, 290 </li> <li>Mine laying, North Sea, 292 </li> <li>Mine-laying submarine, 287 </li> <li>Mine railroad, 294 </li> <li>Mine-sweeping, 281 </li> <li>Mines, 276 <ul> <li>anchored, 278</li> <li>and counter-mines, 17</li> <li>automatic sounding, 278</li> <li>drift of, 285</li> <li>electric, 277</li> <li>floating, 284</li> <li>Messines Ridge, 19</li> </ul></li> <li>Mines, paravanes, 288342 </li> <li>Monitors, 306 </li> <li>Mortars, 79 <ul> <li>depth bomb, 266</li> <li>flying, 23</li> </ul></li> <li>Mortars, See also Trench mortars </li> <li>Mother-ships for airplanes, 305 </li> <li>Motor-boat, electric, 308 <ul> <li>sea Tank, 299</li> </ul></li> <li>Motor torpedo-boats, 298 </li> <li>Mystery ships, 220 </li> <li class="p1">Net, North Sea, 290 </li> <li class="p1">Ocean currents, 285 </li> <li>Optical illusions, 215 </li> <li>Oxy-hydrogen torch, submarine, 329 </li> <li class="p1">Paint in war, 209 </li> <li>Papier mâché heads, 13 </li> <li>Papier mâché horse, 223 </li> <li>Parachute, 175 <ul> <li>grenade, 31</li> <li>search-light shell, 84</li> </ul></li> <li>Paravanes, 288 </li> <li>Periscope, submarine, 244 <ul> <li>trench, 11</li> </ul></li> <li>Pill-boxes, 59 </li> <li>Pneumatic breakwater, 335 </li> <li>Pontoons, salvage, 320 </li> <li>Propeller, shooting through, 136 </li> <li class="p1">Radio, see Wireless </li> <li>Railroad, mine, 294 </li> <li>Railways, trench, 10 </li> <li>Range-finder, 170 </li> <li>Range, getting the, 169 </li> <li>Range of guns, increasing, 67 </li> <li>Range, torpedo, 213 </li> <li>Rats, freeing trenches of, 94 </li> <li>Rifle grenade, 28 <ul> <li>safety device, 32</li> </ul></li> <li>Rifle, machine, 55 </li> <li>Rifle stand, fixed, 14 </li> <li>Roads, camouflage, 225 </li> <li class="p1" id="Salvage">Salvage, 310 <ul> <li>diving, 324</li> <li>ice-tongs, 334</li> <li>lifting-magnets, 334</li> <li>methods, 317</li> <li>pneumatic, 319</li> <li>pontoons, 320</li> <li>shackles on ships, 333</li> <li>submarine F-4, 321</li> <li>submarine sphere, 332</li> </ul></li> <li>Scouts, airplane, 128 </li> <li>Sea, deep, conditions, 312 </li> <li>Sea gulls finding submarines, 258 </li> <li>Sea lions locating submarines, 259 </li> <li>Sea tank, 299 </li> <li id="Seaplane">Seaplane, 143 <ul> <li>automatic, 145</li> <li>submarine patrol, 259</li> <li>torpedo, 145</li> <li>towing-barges, 302</li> </ul></li> <li>Search-light shell, 84 </li> <li>Shackles, salvage, 333 </li> <li>Shadowless buildings, 227 </li> <li>Shell, gas, 95 <ul> <li>grapnel, 16</li> <li>search-light, 84</li> <li>shrapnel, 83</li> <li>Stokes mortar, 39</li> </ul></li> <li>Shield on wheels, 114 </li> <li>Ships, airplane, 304 </li> <li>Ships, blisters, 307 <ul> <li>camouflage, 211</li> <li>"clothes-line," 220</li> <li>convoy, 267</li> <li>hush, 304</li> <li>making visible, 230</li> <li>monitors, 306</li> <li>mystery, 220</li> <li>railroads on, 294</li> <li>sunk by submarines, 310</li> </ul></li> <li>Ships, see also Salvage </li> <li>Shrapnel shell, 83 </li> <li>Sled, submarine, 330 </li> <li>Smoke screen, 262 </li> <li>Sniper, locating, 13 </li> <li>Sniperscopes, 12 </li> <li>Sound, detecting submarines, 269 </li> <li>Sound detectors, mines, 18 </li> <li>Sound, spotting by, 181 </li> <li>Sphere, salvor's submarine, 332 </li> <li>Spotting by sound, 181 </li> <li>Spotting gun-fire, 177 </li> <li id="Submarine">Submarine, blindness, 244 <ul> <li>chasers, 255</li> <li>construction, 234</li> <li>depth bombs, 265</li> <li>egg-laying, 287</li> <li>engines, 246</li> <li>F-4, salving, 321</li> <li>getting best of, 253</li> <li>graveyard, 314</li> <li>guns on, 249</li> <li>history, 232</li> <li>hydrophone, 270</li> <li>mine-field, 290</li> <li>mine-laying, 287</li> <li>net, 290</li> <li>oil-tank, 236</li> <li>periscope, 244</li> <li>reclaiming victims of, 310343</li> <li>rest chamber, 328</li> <li>salvage vessel, 332</li> <li>sea-gulls, 258</li> <li>sea-lions, 259</li> <li>seaplanes, 259</li> <li>ships sunk, 310</li> <li>sled, 330</li> <li>steam-driven, 250</li> <li>torch, 329</li> <li>torpedo, 246</li> <li>12-inch gun, 251</li> <li>vs. submarine, 269</li> </ul></li> <li>Super-guns, 62 </li> <li class="p1">Tank, 107 <ul> <li>American, 122</li> <li>flying, 139</li> <li>French, 119</li> <li>German, 120</li> <li>one-man, 114</li> <li>sea, 299</li> <li>small, 121</li> </ul></li> <li>Telegraphy, rapid, 199 </li> <li>Telephone, New York to San Francisco, 186 <ul> <li>wireless, 178</li> </ul></li> <li>Titanic, 314 </li> <li>TNT (trinitrotoluol), 18 </li> <li>Torch, submarine, 329 </li> <li>Torpedo, 299 <ul> <li>boats, motor, 298</li> <li>electrically steered, 308</li> <li>construction, 246</li> <li>getting range, 213</li> <li>proof ships, 306</li> <li>seaplane, 145</li> </ul></li> <li>Towing-barge, seaplane, 302 </li> <li>Trajectory, 22 </li> <li>Trench, gas-lock, 97344 </li> <li id="Trench_mortar">Trench mortar, 36 <ul> <li>pneumatic, 37</li> <li>Stokes, 38</li> </ul></li> <li>Trench railways, 10 </li> <li>Trench warfare, 4 </li> <li>Trenches, 21 <ul> <li>barbed wire gates, 9</li> <li>duck-boards, 9</li> </ul></li> <li>Tunnels, mines, 17 <ul> <li>to observation posts, 12</li> </ul></li> <li class="p1">U-boats, see Submarines </li> <li class="p1">Villages, underground, 7 </li> <li class="p1">Walking-machine, 108 </li> <li>War, paint, 209 </li> <li>Water kites, 283 </li> <li>Waves, fighting with air, 334 </li> <li id="Wireless">Wireless compass, 201 <ul> <li>spy detector, 200</li> </ul></li> <li>Wireless telegraph, rapid, 199 </li> <li>Wireless telegraphy explained, 188 </li> <li>Wireless telephone, 178 <ul> <li>airplane, 184</li> </ul></li> <li>Wireless telephony across Atlantic, 192 </li> <li>Woolworth Building, falling from, 135 </li> <li>Wrecks, see Salvage </li> <li class="p1">Zeppelin and Lowe's balloon, 149 </li> <li>Zeppelin balloon, construction, 156 </li> <li>Zeppelin, suspended observer, 162 </li> <li>Zeppelin's failures and successes, 154 </li> </ul></div> <div class="p4e newpage transnote"> <h2 class="p0 nopage">Transcribers' Note</h2> Punctuation and spelling were made consistent when a predominant preference was found in this book; otherwise they were not changed. Simple typographical errors were corrected; occasional unbalanced quotation marks retained. Ambiguous hyphens at the ends of lines were retained. Some illustrations have been slightly repositioned to improve their appearance in eBooks. Page 76: "eight tenths of an inch" may be a misprint for "eight ten-thousandths of an inch". Page 100: "inhaled air" was misprinted as "inhaled aid". Page 104: "would send the stream" was misprinted as "sent". Page 113: "Secretely" was printed that way. Page 209: "psycologists" was printed that way. </div>     <hr class="full" /> <div style="break-after:column;"></div>

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