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 Oil-tempering the lining of a Big Gun (See page 76) 
 
INVENTIONS OF THE 
 GREAT WAR 
 
INVENTIONS OF THE 
 GREAT WAR 
 
 BY 
 
 A. RUSSELL BOND 
 
 MANAGING EDITOR OF "SCIENTIFIC AMERICAN/' 
 
 AUTHOR OF "ON THE BATTLE-FRONT 
 
 OF ENGINEERING," ETC. 
 
 WITH MANY 
 ILLUSTRATIONS 
 
 NEW YORK 
 THE CENTURY CO. 
 
 1919 
 
Copyright, 1918, 1919, by 
 THE CENTUBY Co. 
 
 Published, June, 1919 
 
is 
 
 PREFACE 
 
 The great World War was more than two- 
 thirds over when America entered the struggle, 
 and yet in a sense this country was in the war 
 from its very beginning. Three great inven- 
 tions controlled the character of the fighting 
 and made it different from any other the world 
 has ever seen. These three inventions were 
 American. The submarine was our invention ; 
 it carried the war into the sea. The airplane 
 was an American invention ; it carried the war 
 into the sky. We invented the machine gun; it 
 drove the war into the ground. 
 
 It is not my purpose to boast of American 
 genius but, rather, to show that we entered the 
 war with heavy responsibilities. The inven- 
 tions we had given to the world had been de- 
 veloped marvelously in other lands. Further- 
 more they were in the hands of a determined 
 and unscrupulous foe, and we found before us 
 the task of overcoming the very machines that 
 we had created. Yankee ingenuity was faced 
 with a real test. 
 
 459572 
 
vi PREFACE 
 
 The only way of overcoming the airplane was 
 to build more and better machines than the en- 
 emy possessed. This we tried to do, but first 
 we had to be taught by our allies the latest re- 
 finements of this machine, and the war was over 
 before we had more than started our aerial pro- 
 gram. The machine gun and its accessory, 
 barbed wire (also an American invention), were 
 overcome by the tank; and we may find what 
 little comfort we can in the fact that its inven- 
 tion was inspired by the sight of an American 
 farm tractor. But the tank was a British cre- 
 ation and was undoubtedly the most important 
 invention of the war. On the sea we were faced 
 with a most baffling problem. The U-boat could 
 not be coped with by the building of swarms of 
 submarines. The essential here was a means 
 of locating the enemy and destroying him even 
 while he lurked under the surface. Two Amer- 
 ican inventions, the hydrophone and the depth 
 bomb, made the lot of the U-boat decidedly un- 
 enviable and they hastened if they did not ac- 
 tually end German frightfulness on the sea. 
 
 But these were by no means the only inven- 
 tions of the war. Great Britain showed won- 
 derful ingenuity and resourcefulness in many 
 
PREFACE vii 
 
 directions; France did marvels with, the air- 
 plane and showed great cleverness in her devel- 
 opment of the tank and there was a host of 
 minor inventions to her credit; while Italy 
 showed marked skill in the creation of large air- 
 planes and small seacraft. 
 
 The Central Powers, on the other hand, were 
 less originative but showed marked resourceful- 
 ness in developing the inventions of others. 
 Forts were made valueless by the large portable 
 Austrian guns. The long range gun that 
 shelled Paris was a sensational achievement, 
 but it cannot be called a great invention because 
 it was of little military value. The great Ger- 
 man Zeppelins were far from a success because 
 they depended for their buoyancy on a highly 
 inflammable gas. It is interesting to note that 
 while the Germans were acknowledging the fail- 
 ure of their dirigibles the British were launch- 
 ing an airship program, and here in America 
 we had found an economical way of producing a 
 non-inflammable balloon gas which promises a 
 great future for aerial navigation. 
 
 The most important German contribution to 
 the war it cannot be classed as an invention 
 was poison gas, and it was not long ere they re- 
 
viil PREFACE 
 
 gretted this infraction of -the rules of civilized 
 warfare adopted at the Hague Conference ; for 
 the Allies soon gave them a big dose of their 
 own medicine and before the war was over, 
 fairly deluged them with lethal gases of every 
 variety. 
 
 Many inventions of our own and of our allies 
 were not fully developed when the war ended, 
 and there were some which, although primarily 
 intended for purposes of war, will be most serv- 
 iceable in time of peace. For this war was not 
 one of mere destruction. It set men to thinking 
 as they had never thought before. It intensi- 
 fied their inventive faculties, and as a result, the 
 world is richer in many ways. Lessons of 
 thrift and economy have been taught us. Man- 
 ufacturers have learned the value of standardi- 
 zation. The business man has gained an appre- 
 ciation of scientific research. 
 
 The whole story is too big to be contained 
 within the covers of a single book, but I have 
 selected the more important and interesting in- 
 ventions and have endeavored to describe them 
 in simple language for the benefit of the reader 
 who is not technically trained. 
 
 A. EUSSELL BOND 
 
 New York, May, 1919 
 
CONTENTS 
 
 CHAPTER PAGE 
 
 I THE WAR IN AND UNDER THE GROUND . 3 
 
 II HAND-GRENADES AND TRENCH MORTARS . 20 
 
 III GUNS THAT FIRE THEMSELVES .... 41 
 
 IV GUNS AND SUPER-GUNS 62 
 
 V THE BATTLE OF THE CHEMISTS .... 85 
 
 VI TANKS . . . . / . V |S V . 107 
 
 VII THE WAR IN THE AIR . . ., > ? . . 123 
 
 VIII SHIPS THAT SAIL THE SKIES , . ..'-. 148 
 
 IX GETTING THE RANGE . . . ' . . .-> 169 
 
 X TALKING IN THE SKY . . . . . . 184 
 
 XI WARRIORS OP THE PAINT-BRUSH . . . 209 
 
 XII SUBMARINES . . . ... . . . 232 
 
 XIII GETTING THE BEST OP THE U-BOAT . . 253 
 
 XIV ' 'DEVIL'S EGGS " . A . . . -; . . 276 
 XV SURFACE BOATS v . 298 
 
 XVI RECLAIMING THE VICTIMS OF THE SUBMA- 
 RINES . . , . , . . . . . 310 
 
 INDEX - 339 
 
LIST OF ILLUSTRATIONS 
 
 Oil-tempering the lining of a big gun . Frontispiece 
 
 FACING 
 
 PAGE 
 
 Lines of zig-zag trenches as viewed from an aero- 
 
 plane . . ...... * > . . . . 8 
 
 French sappers using stethoscopes to detect the 
 
 mining operations of the enemy .... 9 
 A 3-inch Stokes mortar and two of its shells . . 36 
 Dropping a shell into a 6-inch trench mortar . 36 
 The Maxim machine-gun operated by the energy 
 
 of the recoil .......... 37 
 
 Colt machine-gun partly broken away to show the 
 
 operating mechanism . . . , . . .37 
 The Lewis gun which produces its own cooling 
 
 current ...... ..... 44 
 
 The Benet-Mercie gun operated by gas ... 44 
 Browning machine gun, weighing 34V2 pounds . 45 
 Browning machine rifle, weight only 15 pounds 45 
 Lewis machine-guns in action at the front . . 52 
 An elaborate German machine-gun fort ... 53 
 Comparative diagram of the path of a projectile 
 
 from the German super-gun ..... 60 
 One of our 16-inch coast defence guns on a dis- 
 
 appearing mount ...... 61 
 
 Height of gun as compared with the New York 
 
 City Hall .......... 61 
 
 The 121-mile gun designed by American ordnance 
 
 officer ....... .* ..... 68 
 
 American 16-inch rifle on a railway mount . . 69 
 
 xi 
 
xii ILLUSTRATIONS 
 
 FACING 
 PAGE 
 
 A long-distance sub-calibered French gun on a 
 
 railway mount 76 
 
 Inside of a shrapnel shell and details of the fuse 
 
 cap 77 
 
 Searchlight shell and one of its candles ... 77 
 Patting on the gas masks to meet a gas cloud at- 
 tack 84 
 
 Even the horses had to be masked 85 
 
 Portable flame-throwing apparatus .... 85 
 Liquid fire streaming from fixed flame-throwing 
 
 apparatus 92 
 
 Cleaning up a dugout with the "fire-broom" . 93 
 British tank climbing out of a trench at Cambrai 112 
 Even trees were no barrier to the British tank . 113 
 The German tank was very heavy and cumber- 
 some 113 
 
 The speedy British " Whippet " tank that can 
 
 travel at a speed of twelve miles per hour . 120 
 The French high-speed "baby" tank .... 120 
 Section through our Mark VIII tank showing the 
 
 layout of the interior 121 
 
 A Handley-Page bombing plane with one of its 
 
 wings folded back 128 
 
 How an object dropped from the Woolworth 
 
 Building would increase its speed in falling 129 
 Machine gun mounted to fire over the blades of 
 
 the propeller 136 
 
 Mechanism for firing between the blades of the 
 
 propeller 136 
 
 It would take a hundred horses to supply the 
 
 power for a small airplane 137 
 
 The flying-tank 144 
 
 An. N-C (Navy-Curtiss) seaplane of the type that 
 
 made the first flight across the Atlantic . . 145 
 A big German Zeppelin that was forced to come 
 down on French soil , . 148 
 
ILLUSTRATIONS xiii 
 
 I-ACING 
 PAGE 
 
 Observation car lowered from a Zeppelin sailing 
 
 above the clouds 149 
 
 Giant British dirigible built along the lines of a 
 Zeppelin 156 
 
 One of the engine cars or * ' power eggs " of a Brit- 
 ish dirigible 156 
 
 Crew of the C-5 (American coastal dirigible) 
 starting for Newfoundland to make a trans- 
 atlantic flight |. . . . 157 
 
 The curious tail of a kite balloon 160 
 
 Observers in the basket of an observation balloon 160 
 
 Enormous range-finders mounted on a gun turret 
 
 of an American warship 161 
 
 British anti-aircraft section getting the range of 
 
 an enemy aviator ........ 176 
 
 A British aviator making observations over the 
 
 German lines -.,.* 177 
 
 Radio headgear of an airman 192 
 
 Carrying on conversation by radio with an aviator 
 
 miles away 192 
 
 Long distance radio apparatus at the Arlington 
 
 (Va.) station 193 
 
 A giant gun concealed among trees behind the 
 
 French lines 212 
 
 Observing the enemy from a papier-mache replica 
 
 of a dead horse 213 
 
 Camouflaged headquarters of the American 26th 
 
 Division in France 220 
 
 A camouflaged ship in the Hudson River on Vic- 
 tory Day 221 
 
 Complex mass of wheels and dials inside a German 
 
 submarine 240 
 
 Surrendered German submarines, showing the net 
 
 cutters at the bow 241 
 
 Forward end of a U-boat ,..,.. 
 
TIT ILLUSTRATIONS 
 
 PAGE 
 
 A depth-bomb mortar and a set of * * ash cans ' ' at 
 
 the stern of an American destroyer . . . 257 
 A depth bomb mortar in action and a depth bomb 
 
 snapped as it is being hurled through the 
 
 air . . . . . ....... 260 
 
 Airplane stunning a U-boat with a depth bomb . 261 
 The false hatch of a mystery ship ..... 268 
 
 The same hatch opened to disclose the 3-inch gun 
 
 and crew ........... 268 
 
 A French hydrophone installation with which the 
 
 presence of submarines was detected . . 269 
 Section of a captured mine-laying U-boat . . 272 
 A paravane hauled up with a shark caught in its 
 
 jaws / ........ ,. ... 273 
 
 A Dutch mine-sweeper engaged in clearing the 
 
 North Sea of German mines ..... 288 
 Hooking up enemy anchored mines . . . .289 
 An Italian "sea tank" climbing over a harbor 
 
 boom ............ 300 
 
 Deck of a British aircraft mothership or "hush 
 
 ship" ......... ... 301 
 
 Electrically propelled boat or surface torpedo, at- 
 
 tacking a warship ........ 304 
 
 Hauling a seaplane up on a barge so that it may 
 
 be towed ... ........ 305 
 
 Climbing into an armored diving suit .... 320 
 
 Lowering an armored diver into the water . . 320 
 A diver's sea sled ready to be towed along the 
 
 bed of the sea ......... 321 
 
 The sea sled on land showing the forward horizon- 
 
 tal and after vertical rudders ...... 321 
 
 The diving sphere built for deep sea salvage op- 
 
 erations ........... 324 
 
 The pneumatic breakwater ....... 325 
 
INVENTIONS 
 OF THE GREAT WAR 
 
INVENTIONS 
 OF THE GREAT WAR 
 
 CHAPTER I 
 
 THE WAR IN AND UNDER THE GROUND 
 
 FOR years the Germans had been preparing 
 for war. The whole world knew this, 
 but it had no idea how elaborate were their 
 preparations, and how these were carried out 
 to the very minutest detail. When the call to 
 arms was sounded, it was a matter of only a 
 few hours before a vast army had been assem- 
 bled fully armed, completely equipped, ready 
 to swarm over the frontiers into Belgium and 
 thence into France. It took much longer for 
 the French to raise their armies of defense, 
 and still longer for the British to furnish 
 France with any adequate help. Despite the 
 heroic resistance of Belgium, the Entente Allies 
 were unprepared to stem the tide of German 
 
4 INVENTIONS OF THE GREAT WAR 
 
 soldiers who poured into the northern part of 
 France. 
 
 So easy did the march to Paris seem, that the 
 Germans grew careless in their advance and 
 then suddenly they met with a reverse that sent 
 them back in full retreat. However, the mili- 
 tary authorities of Germany had studied not 
 only how to attack but also how to retreat and 
 how to stand on the defensive. In this, as in 
 every other phase of the conflict, they were far 
 in advance of the rest of the world, and after 
 their defeat in the First Battle of the Marne, 
 they retired to a strong position and hastily 
 prepared to stand on the defensive. When 
 the Allies tried to drive them farther back, they 
 found that the German army had simply sunk 
 into the ground. The war of manoeuver had 
 given way to trench warfare, which lasted 
 through long, tedious months nearly to the end 
 of the great conflict. 
 
 The Germans found it necessary to make the 
 stand because the Eussians were putting up 
 such a strong fight on Germany's eastern fron- 
 tier. Men had to be withdrawn from the west- 
 ern front to stem the Russian tide, which meant 
 that the western armies of the kaiser had to 
 
WAR IN AND UNDER THE GROUND 5 
 
 cease their offensive activities for the time be- 
 ing. The delay was fatal to the Germans, for 
 they had opposed to them not only brave men 
 but intelligent men who were quick to learn. 
 And when the Germans were ready to resume 
 operations in the West, they found that the 
 Allies also had sunk into the ground and had 
 learned all their tricks of trench warfare, add- 
 ing a number of new ones of their own. 
 
 The whole character of the war was changed. 
 The opposing forces were dead-locked and 
 neither could break through the other's lines. 
 The idea of digging into the ground did not 
 originate with this war, but never before had 
 it been carried out on so extensive a scale. 
 The inventive faculties of both sides were vainly 
 exercised to find some way of breaking the 
 dead-lock. 'Hundreds of new inventions were 
 developed. The history of war from the days 
 of the ancient Eomans up to the present time 
 was searched for some means of breaking down 
 the opposing lines. However, the dead-lock 
 was not broken until a special machine had been 
 invented, a traveling fort. But the story of 
 that machine is told in another chapter. 
 
 At the outset the Allies dug very shallow 
 
6 INVENTIONS OF THE GREAT WAR 
 
 ditches, such as had been used in previous 
 wars. When it was found that these burrows 
 would have to be occupied for weeks and months, 
 the French and British imitated the Germans 
 and dug their trenches so deep that men could 
 walk through them freely, without danger of ex- 
 posing their heads above ground; and as the 
 ditches grew deeper, they had to be provided 
 with a firing-step on which the riflemen could 
 stand to fire over the top of the trenches. The 
 trenches were zig-zagged so that they could not 
 be flanked, otherwise they would have made dan- 
 gerous traps for the defenders; for had the 
 enemy gained one end of the trench, he could 
 have fired down the full length of it, killing or 
 wounding every man it contained. But zig- 
 zagging made it necessary to capture each turn 
 separately. There were lines upon lines of 
 these trenches. Ordinarily there were but 
 three lines, several hundred feet apart, with 
 communicating trenches connecting them, and 
 then several kilometers l farther back were re- 
 serve trenches, also connected by communicat- 
 ing trenches with the front lines. 
 
 i A kilometer is, roughly, six tenths of a mile ; or six miles 
 would equal ten kilometers. 
 
WAR IN AND UNDER THE GROUND 7 
 
 Men did not dare to show themselves out in 
 the open near the battle-front for a mile or more 
 behind the front-line trenches, for the enemy 's 
 sharp-shooters were always on the watch for a 
 target. The men had to stay in the trenches 
 day and night for two or more weeks at a time, 
 and sleeping-accommodations of a very rough 
 sort were provided for them in dugouts which 
 opened into the trenches. The dugouts of the 
 Allies were comparatively crude affairs, but the 
 Germans spent a great deal of time upon their 
 burrows. 
 
 UNDERGROUND VILLAGES 
 
 When the French first swept the Germans 
 back out of their trenches along the Aisne, they 
 were astonished to find how elaborate were these 
 underground dwellings. They found that the 
 ground was literally honeycombed with rooms 
 and passageways. Often the dugouts were 
 two stories in depth and extended as much as 
 sixty feet below the level of the ground. In 
 fact, all along this part of the front, the Ger- 
 mans had a continuous underground village in 
 which thousands of men were maintained. The 
 officers' quarters were particularly well fitted 
 
8 INVENTIONS OF THE GREAT WAR 
 
 up, and every attention was given to the com- 
 fort of their occupants. There were steel 
 door-mats at the entrances of the quarters. 
 The walls were boarded and even papered. 
 The bedrooms were fitted with spring beds, 
 i chiffoniers, and wash-stands, and all the rooms 
 were lighted with electric lamps. There were 
 spacious quarters for the men, with regular 
 underground mess halls and elaborate kitchens. 
 There were power-plants to furnish steam for 
 the operation of pumps and for the lighting- 
 plants and for other purposes. 
 
 There was a chalk formation here in which 
 were many large natural caves. One enormous 
 cave was said to have held thirty thousand 
 soldiers, and in this section the Germans kept 
 large reserve forces. By digging far into the 
 ground, the German troops secured protection 
 from shell-fire; in fact, the horrible noise of 
 battle was heard only as a murmur, down in 
 these depths. With characteristic thorough- 
 ness, the Germans built their trench system for 
 a long stay; while the Allies, on the other hand, 
 looked upon their trenches as merely temporary 
 quarters, which would hold the enemy at bay 
 until they could build up armies large enough 
 
(C) Underwood & Underwood 
 
 Lines of Zig-Zag Trenches as viewed from an Airplane 
 
Courtesy of "Scientific American " 
 
 French Sappers using Stethoscopes to detect the 
 Mining Operations of the Enemy 
 
WAR IN AND UNDER THE GROUND 9 
 
 to drive the invaders out of the country. The 
 construction of the trenches along some parts 
 of the battle-line was particularly difficult, be- 
 cause of the problem of drainage. This was 
 especially true in Flanders, where the trenches 
 in many cases were below water-level, and 
 elaborate pumping-systems had to be installed 
 to keep them dry. Some of them were concrete- 
 lined to make them waterproof. In the early 
 stages of the war, before the trenches were 
 drained, the men had to stand in water for a 
 good part of the time, and the only way they 
 could get -about at all in the miry trenches was 
 by having "duck-boards" in them. Duck- 
 boards are sections of wooden sidewalk such as 
 we find in small villages in this country, con- 
 sisting of a couple of rails on which crosspieces 
 of wood are nailed. These duck-boards fairly 
 floated in the mud. 
 
 Some of the trenches were provided with 
 barbed-wire barriers or gates calculated to halt 
 a raiding-party if it succeeded in getting into 
 the trench. These gates were swung up out 
 of the way, but when lowered they were kept 
 closed with a rather complicated system of bolts 
 which the enemy would be unable to unfasten 
 
10 INVENTIONS OF THE GREAT WAR 
 
 without some delay; and while he was strug- 
 gling to get through the gate, he would be a 
 target for the bullets of -the defenders. 
 
 HIDING RAILROADS IN DITCHES 
 
 Because of the elaborate system of trenches, 
 and the distance from the front line to that part 
 of the country where it was safe to operate in 
 the open, it was necessary to build railways 
 which would travel through tunnels and com- 
 municating trenches to the front lines. These 
 were narrow-gage railroads and a special stan- 
 dard form of track section was designed, which 
 was entirely of metal, something like the track 
 sections of toy railroads. The tracks were 
 very quickly laid and taken up at need. The 
 locomotives had to be silent and smokeless and 
 so a special form of gasolene locomotive was 
 invented to haul the little cars along these minia- 
 ture railroads to the front lines. Usually the 
 trench railroads did not come to the very front 
 of the battle-line, but their principal use was 
 to carry shell to the guns which were located 
 in concealed positions. Eailroad or tramway 
 trenches could not be sharply zig-zagged but had 
 to have easy curves, which were apt to be recog- 
 
WAR IN AND UNDER THE GROUND 11 
 
 nized by enemy airplanes, and so they were 
 often concealed under a covering of wire strewn 
 with leaves. 
 
 PERISCOPES AND * ' SNIPERSCOPES " 
 
 But while the armies were buried under- 
 ground, it was necessary for them to keep their 
 eyes upon each other so that each might be 
 ready for any sudden onslaught of the other. 
 Snipers were always ready to fire at any head 
 that showed itself above the parapet of the 
 trench and so the soldiers had to steal an idea 
 from the submarines and build them periscopes 
 with which they could look over the top of their 
 trenches without exposing themselves. A 
 trench periscope was a very simple affair, con- 
 sisting of a tube with two mirrors, one at the 
 top and one at the bottom, set at such an angle 
 that a person looking into the side of the tube 
 at the bottom could see out of the opposite side 
 of the tube at the top. 
 
 Observation posts were established wherever 
 there was a slight rise in the ground. Some- 
 times these posts were placed far in advance of 
 the trenches and sometimes even behind the 
 trenches where it was possible to obtain a good 
 
12 INVENTIONS OP THE GREAT WAR 
 
 view of the opposing lines. Sometimes a tunnel 
 would be dug forward, leading to an outlet 
 close to the enemy's lines, and here an observer 
 would take his position at night to spy with his 
 ears upon the activities of the enemy. Ob- 
 servers who watched the enemy by day would 
 often not dare to use periscopes, which might 
 be seen by the enemy and draw a concentrated 
 fire of rifles and even shell. So that every 
 manner of concealment was employed to make 
 the observation posts invisible and to have 
 them blend with their surroundings. Observ- 
 ers even wore veils so that the white of their 
 skin would not betray them. 
 
 Snipers were equally ingenious in concealing 
 themselves. They frequently used rifles which 
 were connected with a dummy butt and had 
 a periscope sighting-attachment. This attach- 
 ment was called a "sniperscope." The rifle- 
 barrel could be pushed through a loophole in 
 the parapet and the sniper standing safely be- 
 low the parapet could hold the dummy butt to 
 his shoulder and aim his rifle with perfect ac- 
 curacy by means of the periscope. It was next 
 to impossible to locate a sniper hidden in this 
 way. One method of doing it was to examine 
 
WAR IN AND UNDER THE GROUND 13 
 
 rubbish, tin cans, or any object that had been 
 penetrated by a bullet and note the direction 
 taken by the bullet. This would give a line 
 leading toward the source of the shot, and 
 when a number of such lines were traced, they 
 
 Redrawn from Military Map Reading by permission of E. 0. McKay 
 FIG. 1. A "sniperscope" with which a sharpshooter could take 
 aim without showing his head above the parapet 
 
 would cross at a spot where the sniper or 
 his gun w r as stationed, and a few shell would 
 put the man out of business. Dummy heads 
 of papier mache were sometimes stuck above 
 the parapet to draw the fire of enemy snip- 
 ers and the ^bullet-holes which quickly ap- 
 
14 INVENTIONS OF THE GREAT WAR 
 
 peared in them were studied to discover the lo- 
 cation of the snipers. 
 
 Sometimes fixed rifles were used. These 
 were set on stands so that 'they could be very 
 accurately trained upon some important enemy 
 
 Redrawn from Military Map Reading by permission of E. C. McKay 
 FIG. 2. A fixed rifle stand arranged to be fired after dark 
 
 post. Then they could be fired in the dark, 
 without aiming, to disturb night operations of 
 the enemy. Often a brace of rifles, as many as 
 six, would be coupled up to be fired simultane- 
 ously, and by operating a single lever each gun 
 would throw out the empty cartridge shell and 
 bring a fresh one into position. 
 
WAR IN AND UNDER THE GROUND 15 
 
 STEEL BRIER PATCHES 
 
 The most important defense of a trench sys- 
 tem consisted in the barbed-wire entanglements 
 placed before it. Barbed wire, by the way, is 
 an American invention, but it was originally 
 intended for the very peaceful purpose for keep- 
 ing cattle within bounds. Long ago it was used 
 in war, but never to the extent to which it was 
 employed in this world struggle. The entangle- 
 ments were usually set up at night and were 
 merely fences consisting of stout posts driven 
 into the ground and strung with barbed wire 
 running in all directions, so as to make an im- 
 penetrable tangle. Where it w r as possible to 
 prepare the entanglements without disturbance 
 and the position was an important one, the mass 
 of barbed wire often extended for a hundred 
 yards or more in depth. Just beyond the en- 
 tanglements trip-wires were sometimes used. 
 A trip-wire was a slack wire which was laid on 
 the ground. Before being laid, the wire was 
 tightly coiled so that it would not lie flat, but 
 would catch the feet of raiders and trip them up. 
 Each side had "gates" in the line through 
 which this wire could quickly be removed to 
 
16 INVENTIONS OF THE GREAT WAR 
 
 let its own raiding-parties through. Some- 
 times raiders used tunnels, with outlets be- 
 yond the barbed wire, but they had to cut their 
 way through the metal brier patches of their 
 opponents. 
 
 Early in the war, various schemes were de- 
 vised for destroying the entanglements. There 
 were bombs in the form of a rod about twelve 
 feet long, which could be pushed under the wire 
 and upon exploding would tear it apart. An- 
 other scheme was to fire a projectile formed 
 like a grapnel. The projectile was attached 
 to the end of a cable and was fired from a 
 small gun in the same way that life-lines are 
 thrown out to wrecks near shore. Then the 
 cable would be wound up on a winch and the 
 grapnel hooks would tear the wire from its fast- 
 enings. Such schemes, however, did not prove 
 very practicable, and it was eventually found 
 that a much better way of destroying barbed 
 wire was to bombard it with high-explosive 
 shell, which would literally blow the wire apart. 
 But it required a great deal of shelling to de- 
 stroy these entanglements, and it was really 
 not until the tank was invented that such ob- 
 structions could be flattened out so that they 
 
WAR IN AND UNDER THE GROUND 17 
 
 formed no bar to the passage of the soldiers. 
 The Germans not only used fixed entangle- 
 ments, but they had large standard sections 
 of barbed wire arranged in the form of big 
 cylindrical frames which would be carried 
 easily by a couple of men and could be placed 
 in position at a moment's notice to close a gap 
 in the line or even to build up new lines of wire 
 obstruction. 
 
 MINES AND COUNTEB-MINES 
 
 In the earlier stages of the war it proved so 
 impossible to capture a trench when it was well 
 defended by machine-guns that efforts were 
 made to blow up the enemy by means of mines. 
 Tunnels were dug reaching out under the 
 enemy's lines, and large quantities of explo- 
 sives were stored in them. At the moment when 
 it was intended to make an assault, there would 
 be a heavy cannonading to disconcert the enemy, 
 and then the mine would be touched off. In 
 the demoralizing confusion that resulted, the 
 storming-party would sweep over the enemy. 
 Such mines were tried on both sides, and the 
 only protection against them was to out-guess 
 the other side and build counter-mines. 
 
18 INVENTIONS OF THE GREAT WAR 
 
 If it were suspected, from the importance of 
 a certain position and the nature of the ground, 
 that the enemy would probably try to under- 
 mine it, the defenders would dig tunnels of their 
 own toward the enemy at a safe distance be- 
 yond their own lines and establish listeners 
 there to see if they could hear the mining- 
 operations of their opponents. Very delicate 
 microphones were used, which the listeners 
 would place on the ground or against the walls 
 of their tunnel. Then they would listen for the 
 faintest sound of digging, just as a doctor 
 listens through a stethoscope to the beating 
 of a patient's heart or the rush of air through 
 his lungs. When these listening-instruments 
 picked up the noise of digging, the general di- 
 rection of the digging could be followed out by 
 placing the instrument at different positions 
 and noting where the noise was loudest. Then 
 a counter-mine would be extended in that direc- 
 tion, far enough down to pass under the enemy's 
 tunnel, and at the right moment, a charge of 
 TNT (trinitrotoluol) would be exploded, which 
 would destroy the enemy's sappers and put an 
 end to their ambitious plans. 
 
 A very interesting case of mining was fur- 
 
WAR IN AND UNDER THE GROUND 19 
 
 nished by the British when they blew up the im- 
 portant post of Messines Eidge. This was 
 strongly held by the Germans and the only way 
 of dislodging the enemy was to blow off the top 
 of the ridge. Before work was started, geolo- 
 gists were called upon to determine whether 
 or not the ground were suitable for mining- 
 operations. They picked out a spot where the 
 digging was good from the British side, but 
 where, if counter-mines were attempted from 
 the German side, quicksands would be encount- 
 ered and tunneling of any sort would be diffi- 
 cult. The British sappers could, therefore, pro- 
 ceed with comparative safety. The Germans 
 suspected that something of the sort was being 
 undertaken, but they found it very difficult to 
 dig counter-mines. However, one day their 
 suspicions were confirmed, when the whole top 
 of the hill was blown off, with a big loss of 
 German lives. In the assault that followed the 
 British captured the position and it was an- 
 nexed to the British lines. 
 
CHAPTER II 
 
 HAND-GRENADES AND TRENCH MORTARS 
 
 IN primitive times battles were fought hand- 
 to-hand. The first implements of war were 
 clubs and spears and battle-axes, all intended 
 for fighting at close quarters. The bow and ar- 
 row enabled men to fight at a distance, but 
 shields and armor were so effective a defense 
 that it was only by hand-to-hand fighting that a 
 brave enemy could be defeated. Even the in- 
 vention of gunpowder did not separate the com- 
 batants permanently, for although it was possi- 
 ble to hurl missiles at a great distance, cannon 
 were so slow in their action that the enemy could 
 rush them between shots. Shoulder firearms 
 also were comparatively slow in the early days, 
 and liable to miss fire, and it was not until the 
 automatic rifle of recent years was fully de- 
 veloped that soldiers learned to keep their dis- 
 tance. 
 
 When the great European war started, mili- 
 tary authorities had come to look upon war at 
 
 20 
 
HAND-GRENADES 21 
 
 close quarters as something relegated to by- 
 gone days. Even the bayonet was beginning 
 to be thought of little, use. Rifles could be 
 charged and fired so rapidly and machine-guns 
 could play such a rapid tattoo of bullets, that 
 it seemed impossible for men to come near 
 enough for hand-to-hand fighting, except at a 
 fearful cost of life. In developing the rifle, 
 every effort was made to increase its range so 
 that it could be used with accuracy at a distance 
 of a thousand yards and more. But when the 
 Germans, after their retreat in the First Battle 
 of the Marne, dug themselves in behind the 
 Aisne, and the French and British too found it 
 necessary to seek shelter from machine-gun and 
 rifle fire by burrowing into the ground, it be- 
 came apparent that while rifles and machine- 
 guns could drive the fighting into the ground, 
 they were of little value in continuing the fight 
 after the opposing sides had buried themselves. 
 The trenches were carried close to one another, 
 in some instances being so close that the 
 soldiers could actually hear the conversation of 
 their opponents across the intervening gap. Un- 
 der such conditions long-distance firearms were 
 of very little practical value. What was needed 
 
22 INVENTIONS OF THE GREAT WAR 
 
 was a short-distance gun which would get down 
 into the enemy trenches. To be sure, the 
 trenches could be shelled, but the shelling had to 
 be conducted from a considerable distance, 
 where the artillery would be immune to attack, 
 and it was impossible to give a trench the par- 
 ticular and individual attention which it would 
 receive at the hands of men attacking it at 
 close quarters. 
 
 Before we go any farther we must learn the 
 meaning of the word "trajectory." No bullet 
 or shell travels in a straight line. As soon as 
 it leaves the muzzle of the gun, it begins to fall, 
 and its course through the air is a vertical 
 curve that brings it eventually down to the 
 ground. This curve is called the "trajectory." 
 No gun is pointed directly at a target, but above 
 it, so as to allow for the pull of gravity. The 
 faster the bullet travels, the flatter is this curve 
 or trajectory, because there is less time for it 
 to fall before it reaches its target. Modern 
 rifles fire their missiles at so high a speed that 
 the bullets have a very flat trajectory. But in 
 trench warfare a flat trajectory was not de- 
 sired. What was the use of a missile that trav- 
 eled in a nearly straight line, when the object to 
 
HAND-GRENADES 23 
 
 be hit was hiding in the ground? Trench fight- 
 ing called for a missile that had a very high tra- 
 jectory, so that it would drop right into the 
 enemy trench. 
 
 HAND-ABTILLERY 
 
 Trench warfare is really a close-quarters 
 fight of fort against fort, and the soldiers who 
 manned the forts had to revert to the ancient 
 methods of fighting an enemy intrenched be- 
 hind fortifications. Centuries ago, not long 
 after the first use of gunpowder in war, small 
 explosive missiles were invented which could be 
 thrown by hand. These were originally known 
 as "flying mortars/' The missile was about 
 the size of an orange or a pomegranate, and it 
 was filled with powder and slugs. A small fuse, 
 which was ignited just before the device was 
 thrown, was timed to explode the missile when 
 it reached the enemy. Because of its size and 
 shape, and because the slugs it contained corre- 
 sponded, in a manner, to the pulp-covered seeds 
 with which a pomegranate is filled, the missile 
 was called a " grenade.' 7 
 
 Grenades had fallen out of use in modern war- 
 fare, although they had been revived to a small 
 
24 INVENTIONS OF THE GREAT WAR 
 
 extent in the Eusso-Japanese war, and had been 
 used with some success by the Bulgarians and 
 the Turks in the Balkan wars. And yet they 
 had not been taken very seriously by the mili- 
 tary powers of Europe, except Germany. Ger- 
 many was always on the lookout for any device 
 that might prove useful in war, and when the 
 Germans dug themselves in after the First Bat- 
 tle of the Marne, they had large quantities of 
 hand-grenades for their men to toss over into 
 the trenches of the Allies. These missiles 
 proved very destructive indeed. They took the 
 place of artillery, and were virtually hand- 
 thrown shrapnel. 
 
 The French and British were entirely unpre- 
 pared for this kind of fighting, and they had 
 hastily to improvise offensive and defensive 
 weapons for trench warfare. Their hand- 
 grenades were at first merely tin cans filled 
 with bits of iron and a high explosive in which 
 a fuse-cord was inserted. The cord was lighted 
 by means of a cigarette and then the can with 
 its spluttering fuse was thrown into the enemy 
 lines. As time went on and the art of grenade 
 fighting was learned, the first crude missiles 
 were greatly improved upon and grenades were 
 
HAND-GRENADES 25 
 
 made in many forms for special service. 
 
 There was a difference between grenades 
 hurled from sheltered positions and those used 
 in open fighting. When the throwers were 
 sheltered behind their own breastworks, it mat- 
 tered not how powerful was the explosion of the 
 grenade. We must remember that in " hand- 
 artillery " the shell is far more powerful in pro- 
 portion to the distance it is thrown than the 
 shell fired from a gun, and many grenades were 
 so heavily charged with explosives that they 
 would scatter death and destruction farther 
 than they could be thrown by hand. The grena- 
 dier who cast one of these grenades had to 
 duck under cover or hide under the walls of 
 his trench, else the fragments scattered by the 
 exploding missile might fly back and injure him. 
 Some grenades would spread destruction to a 
 distance of over three hundred feet from the 
 point of explosion. For close work, grenades 
 of smaller radius were used. These were em- 
 ployed to fight off a raiding-party after it had 
 invaded a trench, and the destructive range of 
 these grenades was usually about twenty-five 
 feet. 
 
 Hand-grenades came to be used in all the 
 
26 INVENTIONS OF THE GREAT WAR 
 
 different ways that artillery was used. There 
 were grenades which were filled with gas, not 
 only of the suffocating and tear-producing 
 types, but also of the deadly poisonous variety. 
 There were incendiary grenades which would 
 set fire to enemy stores, and smoke grenades 
 which would produce a dense black screen be- 
 hind which operations could be concealed from 
 the enemy. Grenades were used in the same 
 way that shrapnel was used to produce a bar- 
 rage or curtain of fire, through which the enemy 
 could not pass without facing almost certain 
 death. Curtains of fire were used not only for 
 defensive purposes when the enemy was attack- 
 ing, but also to cut off a part of the enemy so 
 that it could not receive assistance and would 
 be obliged to surrender. In attacks upon the 
 enemy lines, grenades were used to throw a 
 barrage in advance of the attacking soldiers so 
 as to sweep the ground ahead clear of the 
 enemy. 
 
 The French paid particular attention to the 
 training of grenadiers. A man had to be a 
 good, cool-headed pitcher before he could be 
 classed as a grenadier. He must be able to 
 throw his grenade with perfect accuracy up to 
 
HAND-GRENADES 27 
 
 a distance of seventy yards, and to maintain an 
 effective barrage. The grenadier carried his 
 grenades in large pockets attached -to his belt, 
 and he was attended by a carrier who brought 
 up grenades to him in baskets, so that he was 
 served with a continuous supply. 
 
 LONG-DISTANCE GRENADE-THROWING 
 
 All this relates to short-distance fighting, but 
 grenades were also used for ranges beyond the 
 reach of the pitcher's arm. Even back in the 
 sixteenth century, the range of the human arm 
 was not great enough to satisfy the combatants 
 and grenadiers used a throwing-implement, 
 something like a shovel, with which the grenade 
 was slung to a greater distance, in much the 
 same way as a lacrosse ball is thrown. Later, 
 grenades were fitted with light, flexible wooden 
 handles and were thrown, handle and all, at the 
 enemy. By this means they could be slung to 
 a considerable distance. Such grenades were 
 used in the recent war, particularly by the Ger- 
 mans. The handle was provided with streamers 
 so as to keep the grenade head-on to the enemy, 
 and it was usually exploded by percussion on 
 striking its target. These long-handled gre- 
 
28 INVENTIONS OF THE GREAT WAR 
 
 nades, however, were clumsy 
 and bulky, and the grenadier re- 
 quired a good deal of elbow- 
 room when throwing them. 
 
 A much better plan was to 
 hurl them with the aid of a gun. 
 A rifle made an excellent short- 
 distance mortar. With it gre- 
 nades could be thrown from 
 three to four hundred yards. 
 The grenade was fastened on a 
 rod which was inserted in the 
 barrel of the rifle and then it was 
 fired out of the gun by the ex- 
 plosion of a blank cartridge. 
 The butt of the rifle was rested 
 on the ground and the rifle was 
 tilted so as to throw the grenade 
 up into the air in the way that 
 a mortar projects its shell. 
 
 FIG. 3. 
 
 STRIKING A LIGHT 
 
 The lighting of the grenade 
 fuses with a cigarette did very 
 A rifle grenade we n f or the early tin-can gre- 
 
 fitted to the 
 
 muzzle of a rifle nades, but the cigarettes were 
 
HAND-GRENADES 29 
 
 not always handy, particularly in the heat 
 of battle, and something better had to be de- 
 vised. One scheme was to use a safety- 
 match composition on the end of a fuse. This 
 was covered with waxed paper to protect 
 it from the weather. The grenadier wore 
 an armlet covered with a friction compo- 
 sition such as is used on a safety-match box. 
 Before the grenade was thrown, the waxed 
 paper was stripped off and the fuse was lighted 
 by being scratched on the armlet. In another 
 type the fuse was lighted by the twisting of a 
 cap which scratched a match composition on a 
 friction surface. A safety-pin kept the cap 
 from turning until the grenadier was ready to 
 throw the grenade. 
 
 The Mills hand-grenade, which proved to be 
 the most popular type used by the British Army, 
 was provided with a lever which was normally 
 strapped down and held by means of a safety- 
 pin. Fig. 4 shows a sectional view of this 
 grenade. Just before the missile was thrown, 
 it was seized in the hand so that the lever was 
 held down. Then the safety-pin was removed 
 and when the grenade was thrown, the lever 
 would spring up under pull of the spring A. 
 
30 INVENTIONS OF THE GREAT WAR 
 
 This would cause the pin B to strike the per- 
 cussion cap C, which would light the fuse D. 
 The burning fuse would eventually carry the fire 
 to the detonator E, which would touch off the 
 main explosive, shattering the shell of the gre- 
 nade and scattering its fragments in all direc- 
 
 Fia. 4. Details of the Mills hand grenade 
 
 tions. The shell of the grenade was indented 
 so that it would break easily into a great many 
 small pieces. 
 
 There were some advantages in using gre- 
 nades lighted by fuse instead of percussion, 
 and also there were many disadvantages. If 
 too long a time-fuse were used, the enemy might 
 
HAND-GRENADES 
 
 31 
 
 catch the grenade, as you would a baseball and 
 hurl it back before it exploded. This was a 
 hazardous game, but it was often done. 
 
 Among the different 
 types of grenades which 
 the Germans used was 
 one provided with a par- 
 achute as shown in Fig. 
 5. The object of the par- 
 achute was to keep the 
 head of the grenade to- 
 ward the enemy, so that 
 when it exploded it would 
 expend its energies for- 
 ward and would not cast 
 fragments back toward 
 the man who had thrown 
 it. This was a very sen- 
 sitive grenade, arranged 
 to be fired by percussion, 
 but it was so easily ex- 
 ploded that the firing- 
 mechanism was not re- 
 leased until after the 
 grenade had been thrown. 
 In the handle of this gre- 
 
 SAFETY CORD 
 
 FIG. 5. A German para- 
 chute grenade 
 
32 INVENTIONS OF THE GREAT WAR 
 
 nade there was a bit of cord about twenty feet 
 long. One end of this was attached to a safety- 
 needle, A, while the other end, formed into a 
 loop, was held by the grenadier when he threw 
 the grenade. Not until the missile had reached 
 a height of twelve or thirteen feet would the 
 pull of the string withdraw the needle A. This 
 would permit a safety-hook, B, to drop out of 
 a ring, C, on the end of a striker pellet, D. 
 When the grenade struck, the pellet D would 
 move forward and a pin, E, would strike a cap 
 on the detonator F, exploding the missile. This 
 form of safety-device was used on a number of 
 German grenades. 
 
 The British had another scheme for locking 
 the mechanism until after the grenade had 
 traveled some distance through the air. De- 
 tails of this grenade, which was of the type 
 adopted to be fired from a rifle, are shown in 
 Fig. 6. The striker A is retained by a couple 
 of bolts, B, which in turn are held in place by 
 a sleeve, C. On the sleeve is a set of wind- 
 vanes, D. As the grenade travels through the 
 air, the wind-vanes cause the sleeve C to re- 
 volve, screwing it down clear of the bolts B, 
 which then drop out, permitting the pin A to 
 
uiiiiiiiii/imii 
 
 FIG. 6. British riile grenade with a safety-device which is 
 unlocked by the rush of air against a set of inclined vanes, 
 D, when the missile is in flight 
 
 33 
 
34 INVENTIONS OF THE GREAT WAR 
 
 strike the detonator E upon impact of the gre- 
 nade with its target. 
 The Germans had one peculiar type which 
 
 FIG. 7. Front, side, and sectional views of a disk-shaped 
 German grenade 
 
 was in the shape of a disk. In the disk were 
 six tubes, four of which carried percussion caps 
 so that the grenade was sure to explode no mat- 
 ter on which tube it fell. The disk was thrown 
 
 FlQ. 8. A curious German hand grenade shaped like a hair 
 
 brush 
 
 with the edge up, and it would roll through the 
 air. Another type of grenade was known as 
 the hair-brush grenade because it had a rectan- 
 
HAND-GRENADES 35 
 
 gular body of tin about six inches long and two 
 and three quarter inches wide and deep, which 
 was nailed to a wooden handle. 
 
 MINIATURE ARTILLERY 
 
 Hand-artillery was very effective as far as 
 it went, but it had its limitations. Grenades 
 could not be made heavier than two pounds in 
 weight if they were to be thrown by hand; in 
 fact, most of them were much lighter than that. 
 If they were fired from a rifle, the range was 
 increased but the missile could not be made very 
 much heavier. TNT is a very powerful ex- 
 plosive, but there is not room for much of it 
 in a grenade the size of a large lemon. Trench 
 fighting was a duel between forts, and while the 
 hand-artillery provided a means of attacking 
 the defenders of a fort, it made no impression on 
 the walls of the fort. It corresponded to shrap- 
 nel fire on a miniature scale, and something 
 corresponding to high-explosive fire on a small 
 scale was necessary if the opposing fortifica- 
 tions were to be destroyed. To meet this prob- 
 lem, men cast their thoughts back to the primi- 
 tive artillery of the Eomans, who used to hurl 
 great rocks at the enemy with catapults. And 
 
36 INVENTIONS OF THE GREAT WAR 
 
 the trench fighters actually rigged up catapults 
 with which they hurled heavy bombs at the 
 enemy lines. All sorts of ingenious catapults 
 were built, some modeled after the old Roman 
 machines. In some of these stout timbers were 
 used as springs, in others there were powerful 
 coil springs. It was not necessary to cast the 
 bombs far. For distant work the regular ar- 
 tillery could be used. What was needed was a 
 short-distance gun for heavy missiles and that 
 is what the catapult was. 
 
 But the work of the catapult was not really 
 satisfactory. The machine was clumsy ; it occu- 
 pied too much space, and it could not be aimed 
 very accurately. It soon gave way to a more 
 modern apparatus, fashioned after the old 
 smooth-bore mortars. This was a miniature 
 mortar, short and wide-mouthed. A rifled bar- 
 rel was not required, because, since the missile 
 was not to be hurled far, it was not necessary to 
 set it spinning by means of rifling so as to hold 
 it head-on to the wind. 
 
 GIANT PEA-SHOOTEBS 
 
 Better aim was secured when a longer-bar- 
 reled trench mortar came to be used. In the 
 
Press Illustrating Service 
 
 A 3-inch Stokes mortar and two of its shells 
 
 
 Press Illustrating Service 
 
 Dropping a shell into a 6-inch trench mortar 
 
1 J 
 
 is- s 
 
 U 
 
HAND-GRENADES 37 
 
 trench, weight was an important item. There 
 was no room in which to handle heavy guns, and 
 the mortar had to be portable so that it could 
 be carried forward by the infantry in a charge. 
 As the walls of a light barrel might be burst 
 by the shock of exploding powder, compressed 
 air was used instead. The shell was virtually 
 blown out of the gun in the same way that a boy 
 blows missiles out of a pea-shooter. That the 
 shell might be kept from tumbling, it was fitted 
 with vanes at the rear. These acted like the 
 feathers of an arrow to hold the missile head-on 
 to its course. 
 
 The French in particular used this type of 
 mortar and the air-pump was used to compress 
 the air that propelled the shell or aerial torpedo, 
 or else the propelling charge was taken from 
 a compressed-air tank. Carbon-dioxide, the 
 gas used in soda water, is commonly stored in 
 tanks under high pressure and this gas was 
 sometimes used in place of compressed air. 
 When the gas in the tank was exhausted the lat- 
 ter could be recharged with air by using a hand- 
 pump. Two or three hundred strokes of the 
 pump would give a pressure of one hundred and 
 twenty to one hundred and fifty pounds per inch, 
 
38 INVENTIONS OF THE GREAT WAK 
 
 and would supply enough air to discharge a 
 number of shell. The air was let into the bar- 
 rel of the mortar in a single puff sufficient to 
 launch the shell; then the tank was cut off at 
 once, so that the air it contained would not 
 escape and go to waste. 
 
 THE STOKES MORTAR 
 
 However, the most useful trench mortar de- 
 veloped during the war was invented by Wilfred 
 Stokes, a British inventor. In this a compara- 
 tively slow-acting powder was used to propel 
 the missile, and so a thin-walled barrel could 
 be used. The light Stokes mortar can easily 
 be carried over the shoulder by one man. It 
 has two legs and the barrel itself serves as 
 a third leg, and the mortar stands like a tripod. 
 The two legs are adjustable, so that the barrel 
 can be inclined to any desired angle. It took 
 but a moment to set up the mortar for action in 
 a trench or shell-hole. 
 
 Curiously enough, there is no breech-block, 
 trigger or fire-hole in this mortar. It is fired 
 merely by the dropping of the missile into the 
 mouth of the barrel. The shell carries its own 
 propelling charge, as shown in Fig. 9. This 
 
HAND-GRENADES 39 
 
 is in the form of rings, A, which are fitted on 
 a stem, B. At the end of the stem are a de- 
 tonating cap and a cartridge, to ignite the 
 propellant, A. At the bottom of the mortar 
 barrel, there is a steel point, E, known as the 
 
 FIG. 9. Sectional view of a 3-inch Stokes mortar showing a 
 shell at the instant of striking the anvil 
 
 "anvil." When the shell is dropped into the 
 mortar, the cap strikes the anvil, exploding the 
 cartridge and touching off the propelling 
 charge, A. The gases formed by the burning 
 charge hurl the shell out of the barrel to a 
 distance of several hundred yards. 
 
40 INVENTIONS OF THE GREAT WAR 
 
 The first Stokes mortar was made to fire a 
 3-inch shell, but the mortar grew in size until 
 
 it could hurl shell of 6- 
 inch and even 8y 2 -mch 
 size. Of course, the 
 larger mortars had to 
 have a very substantial 
 base. They were not so 
 readily portable as the 
 smaller ones and they 
 could not be carried by 
 one man; but compared 
 with ordinary artillery of 
 the same bore they were 
 immeasurably lighter 
 and could be brought to 
 advanced positions and 
 set up in a very short 
 6-inch trench time. The larger shell 
 have tail-vanes, as shown 
 in Fig. 10, to keep them 
 
 FIG. 10. A 
 mortar shell fitted with 
 tail-vanes 
 
 from tumbling when in flight. 
 
CHAPTER III 
 
 GUNS THAT FIRE THEMSELVES 
 
 MANY years ago a boy tried his hand at 
 firing a United States Army service 
 rifle. It was a heavy rifle of the Civil War 
 period, and the lad did not know just how to 
 hold it. He let the butt of the gun rest un- 
 certainly against him, instead of pressing it 
 firmly to his shoulder, and, in consequence, when 
 the gun went off he received a powerful kick. 
 
 That kick made a deep impression on the 
 lad, not only on his flesh but on his mind as 
 well. It gave him a good conception of the 
 power of a rifle cartridge. 
 
 Years afterward, when he had moved to Eng- 
 land, the memory of that kick was still with 
 him. It was a useless prank of the gun, he 
 thought, a waste of good energy. Why could 
 not the energy be put to use? And so he set 
 himself the task of harnessing the kick of the 
 gun. 
 
 41 
 
42 INVENTIONS OF THE GREAT WAR 
 
 A very busy program he worked out for that 
 kick to perform. He planned to have the gun 
 use up its exuberant energy in loading and fir- 
 ing itself. So he arranged the cartridges on a 
 belt and fed the belt into the gun. When the 
 gun was fired, the recoil would unlock the breech, 
 take out the empty case of the cartridge just 
 fired, select a fresh cartridge from the belt, and 
 cock the main spring ; then the mechanism would 
 return, throwing the empty cartridge-case out 
 of the gun, pushing the new cartridge into the 
 barrel, closing the breech, and finally pulling 
 the -trigger. All this was to be done by the 
 energy of a single kick, in about one tenth of a 
 second, and the gun would keep on repeating the 
 operation as long -as the supply of cartridges 
 was fed to it. The new gun proved so successful 
 that the inventor was knighted, and became Sir 
 Hiram Maxim. 
 
 But Maxim's was by no means the first ma- 
 chine-gun. During the Civil War a Chicago 
 physician brought out a very ingenious ten- 
 barreled gun, the barrels of which were fired 
 one after the other by the turning of a hand- 
 
GUNS THAT FIKE THEMSELVES 43 
 
 crank. Although Dr. Galling was a graduate 
 of a medical school, he was far more fond of 
 tinkering with machinery than of doling out 
 pills. He invented a number of clever mechan- 
 isms, but the -one that made him really famous 
 was that -machine-gun. At first our government 
 did not take the invention seriously. The gun 
 was tried out in the war, but whenever it went 
 into battle it was fired not by soldiers but by a 
 representative of Dr. (ratling's company, who 
 went into the army to demonstrate the worth of 
 the invention. Not until long after was the 
 Gatling gun officially adopted by our army. 
 Then it was taken up by many of the European 
 armies as well. 
 
 Although many other machine-guns were in- 
 vented, the Gatling was easily the best and most 
 serviceable, until the Maxim invention made its 
 appearance, and even then it held its own for 
 many years ; but eventually it had to succumb. 
 The Maxim did not have to be cranked: it 
 fired itself, which was a distinct advantage; 
 and then, instead of being a bundle of guns 
 all bound up into a single machine, Maxim's 
 was a single-barreled gun and hence was much 
 lighter and could be handled much more easily. 
 
44 INVENTIONS OF THE GREAT WAR 
 
 A GUN AS A GAS-ENGINE 
 
 Another big advance was made by a third 
 American, Mr. John M. Browning, who is re- 
 sponsible for the Colt gun. It was not a kick 
 that set Browning to thinking. He looked upon 
 a gun as an engine of the same order as an 
 automobile engine, and really the resemblance 
 is very close. The barrel of the gun is the 
 cylinder of the engine; the bullet is the piston; 
 and for fuel gunpowder is used in place of gaso- 
 lene. As in the automobile engine, the charge 
 is fired by a spark; but in the case of the gun 
 the spark is produced by a blow of the trigger 
 upon a bit of fulminate of mercury in the end of 
 the cartridge. 
 
 Explosion is the same thing as burning. The 
 only way that the explosion of gunpowder dif- 
 fers from the burning of a stick of wood is that 
 the latter is very slow, while the former goes 
 like a flash. In both cases the fuel turns into 
 great volumes of gas. In the case of the gun 
 the gas is formed almost instantly and in such 
 quantity that it has to drive the bullet out of 
 the barrel to make room for itself. In the cart- 
 ridge that our army uses, only about a tenth 
 
(C) Committee on Public Information 
 
 Browning Machine Rifle, weight only 15 pounds 
 
 (C) Committee on Public Information 
 
 Browning Machine Gun, weighing 34^ pounds 
 
GUNS THAT FIRE THEMSELVES 45 
 
 of an ounce of smokeless powder is used, but 
 this builds up so heavy a pressure of gas that 
 the bullet is sent speeding out of the gun at a 
 rate of half a mile a second. It travels so fast 
 that it will plow -through four feet of solid wood 
 before coming to a stop. 
 
 Now it occurred to Browning that it wouldn't 
 really be stealing to take a little of that gas- 
 power and use it to work the mechanism of his 
 machine-gun. It was ever so little he wanted, 
 and the bullet would never miss it. The 
 danger was not that he might take too much. 
 His problem was to take any power at all with- 
 out getting more than his mechanism could 
 stand. What he did was to bore a hole through 
 the side of the gun-barrel. When the gun was 
 fired, nothing happened until the bullet passed 
 this hole; then some of the gas that was push- 
 ing the bullet before it would blow out through 
 the hole. But this would be a very small 
 amount indeed, for the instant that the bullet 
 passed out of the barrel the gases would rush 
 out after it, the pressure in the gun would drop, 
 and -the gas would stop blowing through the 
 hole. With the bullet traveling at the rate of 
 about half a mile in a second, imagine how short 
 
46 INVENTIONS OF THE GREAT WAR 
 
 a space of time elapses after it passes the hole 
 before it emerges from the muzzle, and what a 
 small amount of gas can pass through the hole 
 in that brief interval! 
 
 The gas that Browning got in this way he 
 led into a second cylinder, fitted with a piston. 
 This piston was given a shove, and that gave 
 a lever a kick which set going the mechanism 
 that extracted the empty cartridge-case, in- 
 serted a fresh cartridge, and fired it. 
 
 GETTING BID OF HEAT 
 
 The resemblance of a machine-gun to a gaso- 
 lene-engine can be demonstrated still further. 
 One of the most important parts of an auto- 
 mobile engine is the cooling-system. The gaso- 
 lene burning in the cylinders would soon make 
 them red-hot, were not some means provided 
 to carry off the heat. The same is true of a 
 machine-gun. In fact, the heat is one of the 
 biggest problems that has to be dealt with. In 
 a gasolene-engine the heat is carried off in one 
 of three ways: (1) by passing water around 
 the cylinders; (2) by building flanges around 
 the cylinders to carry the heat off into the air; 
 and (3) by using a fan to blow cool air against 
 
GUNS THAT FIKE THEMSELVES 47 
 
 the cylinders. All of these schemes are used 
 in the machine-gun. In Dr. Gatling's gun 'the 
 cooling-problem was very simple. As there 
 were ten barrels, one barrel could be cooling 
 while the rest were taking their turn in the 
 firing. In other words, each barrel received 
 only a tenth of the heat that the whole gun was 
 producing; and yet Gatling found it advisable 
 to surround the barrels for about half their 
 length with a water-jacket. 
 
 In the Maxim gun a water-jacket is used that 
 extends the full length of the barrel, and into 
 this waiter-jacket seven and a half pints of water 
 are poured. Yet in a minute and a half of 
 steady firing at a moderate rate, or before six 
 hundred rounds are discharged, the water will 
 be boiling. After that, with every thousand 
 rounds of continuous fire a pint and a half of 
 water will be evaporated. Now the water and 
 the water-jacket add a great deal of weight to 
 the gun, and this Browning decided to do away 
 with in his machine-gun. Instead of water he 
 used air to carry off the heat. The more sur- 
 face the air touches, the more heat will it carry 
 away; and so the Golt gun was at first made 
 with a very thick- walled barrel. But later the 
 
48 INVENTIONS OF THE GREAT WAR 
 
 Colt was formed with flanges, like the flanges 
 on a motor-cycle engine, so as to increase the 
 surface of the barrel. Of course, air-cooling is 
 not so effective as water-cooling, but it is 
 claimed for this gun, and for other machine- 
 guns of the same class, that the barrel is 
 sufficiently cooled for ordinary service. Al- 
 though a machine-gun may be capable of firing 
 many hundred shots per minute, it is seldom 
 that such a rate is kept up very long in battle. 
 Usually, only a few rounds are fired at a time 
 and then there is a pause, and there is plenty 
 of time for the barrel to cool. Once in a while, 
 however, the gun has to be fired continuously 
 for several minutes, and then the barrel grows 
 exceedingly hot. 
 
 EFFECT OF OVERHEATING 
 
 But what if the gun-barrel does become hot? 
 The real trouble is not that the cartridge will 
 explode prematurely, but that the barrel will 
 expand as it grows hot, so that the bullet will 
 fit too loosely in the bore. Inside the barrel 
 the bore is rifled; that is, there are spiral 
 grooves in it which give a twist to the bullet 
 as it passes through, setting it spinning like a 
 
GUNS THAT FIRE THEMSELVES 49 
 
 top. The spin of the bullet keeps its nose point- 
 ing forward. If it were not for the rifling, the 
 bullet would tumble over and over, every which 
 way, and it could not go very far through the 
 air, to say nothing of penetrating steel armor. 
 To gain the spinning-motion the bullet must 
 fit into the barrel snugly enough to squeeze 
 into the spiral grooves. Now there is another 
 American machine-gun known as the Hotchkiss, 
 which was used to a considerable extent by the 
 French Army. It is a gas-operated gun, some- 
 thing like the Colt, and it is air-cooled. It was 
 found in tests of the Hotchkiss gun that in from 
 three to four minutes of firing the barrel was 
 expanded so much that the shots began to be a 
 little uncertain. In seven minutes of con- 
 tinuous firing the barrel had grown so large that 
 the rifling failed to grip the bullet at all. The 
 gun was no better than an old-fashioned 
 smooth-bore. The bullets would not travel 
 more than three hundred yards. It is because 
 of this danger of overheating that the Colt and 
 the Hotchkiss guns are always furnished with a 
 spare barrel. As soon as a barrel gets hot it is 
 uncoupled and the spare one is inserted in its 
 place. Our men are trained to change the 
 
50 INVENTIONS OF THE GREAT WAR 
 
 barrel of a colt in the dark in a quarter of a 
 minute. 
 
 But a gun that has to have a spare barrel 
 and that has to have its barrel changed in the 
 midst of a hot engagement is not an ideal 
 weapon, by any means. And this brings us to 
 still another invention that, too, by an Amer- 
 ican. Colonel I. N. Lewis, of the United States 
 Army, conceived of a machine-gun that would be 
 cooled not by still air but by air in motion. This 
 would do away with all the bother of water- 
 jackets. It would keep the gun light so that 
 it could be operated by one man, and yet it 
 would not have to be supplied with a spare 
 barrel. 
 
 Like the Colt and the Hotchkiss, the Lewis 
 gun takes its power from the gas that comes 
 through a small port in the barrel, near the 
 muzzle. In the plate facing page 44 the port 
 may be seen leading into a cylinder that lies 
 under the barrel. It takes about one ten- 
 thousandth part of a second for a bullet to 
 pass out of the barrel after clearing the port, 
 but in that brief interval there is a puff of 
 gas in the cylinder which drives back a pis- 
 ton. This piston has teeth on it which en- 
 
GUNS THAT FIRE THEMSELVES 51 
 
 gage a small gear connected with a main- 
 spring. When the piston moves back, it winds 
 the spring, and it is this spring that operates 
 the mechanism of the gun. The cartridges, in- 
 stead of being taken from a belt or a clip, are 
 taken from a magazine that is round and flat. 
 There are forty-seven cartridges in the maga- 
 zine and they are arranged like the spokes of a 
 wheel, but in two layers. As soon as forty- 
 seven rounds have been fired, the shooting must 
 stop while a new magazine is inserted. But to 
 insert it takes only a couple of seconds. 
 
 USING THE BULLET TO FAN THE GUN 
 
 The most ingenious part of the Lewis gun 
 is the cooling-system. On the barrel of the gun 
 aro sixteen flanges or fins. These, instead of 
 running around the gun, run lengthwise of the 
 barrel. They are very light fins, being made 
 of aluminum, and are surrounded by a cas- 
 ing of the same metal. The casing is open at 
 each end so that the air can flow through it, 
 but it extends beyond the muzzle of the barrel, 
 and there it is narrowed down. At the end of 
 the barrel there is a mouthpiece so shaped that 
 the bullet, as it flies through, sucks a lot of air 
 
52 INVENTIONS OF THE GREAT WAR 
 
 in its wake, making a strong current flow 
 through the sixteen channels formed between 
 the fins inside the casing. This air flows at the 
 rate of about seventy miles per hour, which is 
 enough to carry off all the heat that is generated 
 by the firing of the cartridges. The gun may 
 be regulated to fire between 350 and 750 rounds 
 per minute, and its total weight is only 25% 
 pounds. 
 
 America can justly claim the honor of invent- 
 ing and developing the machine-gun, although 
 Hiram Maxim did give up his American citizen- 
 ship and become a British subject. By the way, 
 he is not to be confused with his younger 
 brother, Hudson Maxim, the inventor of high 
 explosives, who has always been an American 
 to the core. Of course we must not get the im- 
 pression that only Americans have invented 
 machine-guns. There have been inventors of 
 such weapons in various countries of Europe, 
 and even in Japan. Our own army for a while 
 used a gun known as the Benet-Mercie, which 
 is something like the Hotchkiss. This was in- 
 vented by L. V. Benet, an American, and H. A. 
 Mercie, a Frenchman, both living in St. Denis, 
 France. 
 
Lewis Machine-guns in action at the front 
 
GUNS THAT FIRE THEMSELVES 53 
 
 THE BROWNING MACHINE-GUN 
 
 When we entered the war, it was expected 
 that we would immediately equip our forces 
 with the Lewis gun, because the British and the 
 Belgians had found it an excellent weapon and 
 also because it was invented by an American 
 officer, who very patriotically offered it to our 
 government without charging patent royalties. 
 But the army officials would not accept it, 
 although many Lewis guns were bought by the 
 navy. This raised a storm of protest through- 
 out the country until finally it was learned that 
 there was another gun for which the army was 
 waiting, which it was said would be the very 
 best yet. The public was skeptical and finally 
 a test was arranged in Washington at which the 
 worth of the new gun was demonstrated. 
 
 It was a new Browning model; or, rather, 
 there were two distinct models. One of them, 
 known as the heavy model, weighed only 34% 
 pounds, this with its water-jacket filled; for it 
 was a water-cooled gun. Without its charge of 
 water the machine weighed but 22% pounds and 
 could be rated as a very light machine-gun. 
 However, it was classed as a heavy gun and was 
 
54 INVENTIONS OF THE GREAT WAR 
 
 operated from a tripod. The new machine used 
 recoil to operate its mechanism. The construc- 
 tion was simple, there were few parts, and the 
 gun could very quickly be taken apart in case 
 of breakage or disarrangement of the mechan- 
 ism. But the greatest care was exercised to 
 prevent jamming of cartridges, which was one 
 of the principal defects in the other types of 
 machine-guns. In the test this new weapon 
 fired twenty thousand shots at the rate of six 
 hundred per minute, with interruptions of only 
 four and a half seconds, due partly to defective 
 cartridges. 
 
 There was no doubt that the new Browning 
 was a remarkable weapon. But if that could 
 be said of the heavy gun, the light gun was a 
 marvel. It weighed only fifteen pounds and 
 was light enough to be fired from the shoulder 
 or from the hip, while the operator was walk- 
 ing or running. In fact, it was really a ma- 
 chine-rifle. The regular .30-caliber service 
 cartridges were used, and these were stored in 
 a clip holding twenty cartridges. The cart- 
 ridges could be fired one at a time, or the entire 
 clip could be fired in two and a half seconds. It 
 took but a second to drop an empty clip out of 
 
GUNS THAT FIRE THEMSELVES 55 
 
 the gun and replace it with a fresh one. The 
 rifle was gas-operated and air-cooled, but no 
 special cooling-device was supplied because it 
 would seldom be necessary to fire a shoulder 
 rifle fast enough and long enough for the barrel 
 to become overheated. 
 
 After the Browning machine-rifle was demon- 
 strated it was realized that the army had been 
 perfectly justified in waiting for the new 
 weapon. Like the heavy Browning, the new 
 rifle was a very simple mechanism, with few 
 parts which needed no special tools to take them 
 apart or reassemble them ; a single small wrench 
 served this purpose. Both the heavy and the 
 light gun were proof against mud, sand, and 
 dust of the battle-field. But best of all, a man 
 did not have to have highly specialized training 
 before he could use the Browning rifle. It did 
 not require a crew to operate one of these guns. 
 Each soldier could have his own machine-gun 
 and carry it in a charge as he would a rifle. 
 The advantage of the machine-rifle was that the 
 operator could fire as he ran, watching where 
 the bullets struck the ground by noting the dust 
 they kicked up and in that way correcting his 
 aim until he was on the target. Very accurate 
 
56 INVENTIONS OF THE GREAT WAR 
 
 shooting was thus made possible, and the ma- 
 chine-rifle proved invaluable in the closing 
 months of the war. 
 
 Browning is unquestionably the foremost in- 
 ventor of firearms in the world. He was born 
 of Mormon parents, in Ogden, Utah, in 1854, 
 and his father had a gun shop. As a boy 
 Browning became familiar with the use of fire- 
 arms and when he was but fourteen years of 
 age he invented an improved breech mechanism 
 which was later used in the Winchester repeater. 
 Curiously enough, it was a Browning pistol that 
 was used by the assassin at Serajevo who killed 
 the Archduke of Austria and precipitated the 
 great European war, -and it was with the Brown- 
 ing machine-gun and rifle that our boys swept 
 the Germans back through the Argonne For- 
 est and helped to bring the war to a successful 
 end. 
 
 THE MACHINE-GUN IN SERVICE 
 
 Although the machine-gun has been used ever 
 since the Civil War, it was not a vital factor in 
 warfare until the recent great conflict. Army 
 officials were very slow to take it up, because 
 they did not understand it. They used to think 
 
GUNS THAT FIRE THEMSELVES 57 
 
 of it as an inferior piece of light artillery, in- 
 stead of a superior rifle. The Gatling was so 
 heavy that it had to be mounted on wheels, and 
 naturally it was thought of as a cannon. In 
 the Franco-Prussian War the French had a ma- 
 chine-gun by which they set great store. It was 
 called a mitrailleuse, or a gun for firing grape- 
 shot. It was something like the Gatling. The 
 French counted on this machine to surprise 
 and overwhelm the Germans. But they made 
 the mistake of considering it a piece of artil- 
 lery and fired it from long range, so that it did 
 not have a chance to show its worth. Only on 
 one or two occasions was it used at close 
 range, and then it did frightful execution. 
 However, it was a very unsatisfactory machine, 
 and kept getting out of order. It earned the 
 contempt of the Germans, and later when the 
 Maxim gun was offered to the German Army 
 they would have none of it. They did not want 
 to bother with "a toy cannon." 
 
 It really was not until the war between Eus- 
 sia and Japan that military men began to real- 
 ize the value of the machine-gun. As the war 
 went on, both the Eussians and the Japanese 
 bought up all the machine-guns they could se- 
 
58 INVENTIONS OF THE GREAT WAR 
 
 cure. They learned what could be done with 
 the aid of barbed wire to retard the enemy while 
 the machine-guns mowed them down as they 
 were trying to get through. 
 
 A man with a machine-gun is worth a hun- 
 dred men with rifles; such is the military esti- 
 mate of the weapon. The gun fires so fast that 
 after hitting a man it will hit him again ten 
 times while he is falling to the ground. And 
 so it does not pay to fire the gun continuously 
 in one direction, unless there is a dense mass of 
 troops charging upon it. Usually the machine- 
 gun is swept from side to side so as to cover 
 as wide a range as possible. It is played upon 
 the enemy as you would play the hose upon the 
 lawn, scattering a shower of lead among the 
 advancing hosts. 
 
 MACHINE-GUN FOETS 
 
 It used to be thought that the Belgian forts of 
 armored steel and concrete, almost completely 
 buried in the ground, would hold out against 
 any artillery. But when the Germans brought 
 up their great howitzers and hurled un- 
 dreamed-of quantities of high explosives on 
 these forts, they broke and crumbled to pieces. 
 
GUNS THAT FIRE THEMSELVES 59 
 
 Then it was predicted that the day of the fort 
 was over. But the machine-gun developed a 
 new type of warfare. Instead of great forts, 
 mounting huge guns, little machine-gun forts 
 were built, and, they were far more troublesome 
 than the big fellows. 
 
 To the Germans belongs the credit for the new 
 type of fort, which consisted of a small concrete 
 structure, hidden from view as far as possible, 
 but commanding some important part of the 
 front. " Pill-boxes, " the British call them, be- 
 cause the first ones they ran across were round 
 in shape and something like a pill-box in ap- 
 pearance. These pill-boxes were just large 
 enough to house a few men and a couple of 
 machine-guns. Concealment was of the utmost 
 importance; safety depended upon it. Air- 
 planes were particularly feared, because a ma- 
 chine-gun emplacement was recognized to be 
 so important that a whole battery of artillery 
 would be turned upon a suspected pill-box. 
 
 Some of the German machine-gun forts were 
 very elaborate, consisting of spacious under- 
 ground chambers where a large garrison of 
 gunners could live. These forts were known 
 as Mebus, a word made from the initials of 
 
60 INVENTIONS OF THE GREAT WAR 
 
 "Maschinengewehr Eisen-Bettungs Unter- 
 stand," meaning a machine-gun iron-bedded 
 foundation. 
 
 It was the machine-gun that was responsible 
 for the enormous expenditure of ammunition in 
 the war. Before a body of troops dared to 
 make a charge, the ground had to be thoroughly 
 searched by the big guns for any machine-gun 
 nests. Unless these were found and destroyed 
 by shell-fire, the only way that remained to get 
 the best of them was to crush them down with 
 tanks. It was really the machine-gun that 
 drove the armies into trenches and under the 
 ground. 
 
 But a machine-gun did not have to be housed 
 in a fort, particularly a light gun of the Lewis 
 type. To be sure, the Lewis gun is a little 
 heavy to be used as a rifle, but it could easily 
 be managed with a rest for the muzzle in the 
 crotch of a- tree, and a strong man could actually 
 fire the piece from the shoulder. The light ma- 
 chine-gun could go right along with a charging 
 body of troops and do very efficient service, par- 
 ticularly in fighting in a town or village, but it 
 had to be kept moving or it would be a target 
 for the artillery. In a certain village fight a 
 
GUNS THAT FIRE THEMSELVES 61 
 
 machine-gunner kept changing his position. 
 He would fire for a few minutes from one build- 
 ing and then shift over to some other. He did 
 this no less than six times, never staying more 
 than five minutes at a time in the same spot. 
 But each one of the houses was shelled within 
 fifteen minutes of the time he opened fire from 
 it, which shows the importance that the Ger- 
 mans attached to machine-gun fire. 
 
CHAPTEE IV 
 
 GUNS AND SUPER-GUNS 
 
 WHEN the news came that big shells were 
 dropping into Paris from a gun which 
 must be at least seventy miles away, the world 
 at first refused to believe; then it imagined 
 that some brand-new form of gun or shell 
 or powder had been invented by the Germans. 
 However, while the public marveled, ordnance 
 experts were interested but not astonished. 
 They knew that it was perfectly feasible to build 
 a gun that would hurl a shell fifty, or seventy- 
 five, or even a hundred miles, without involving 
 anything new in the science of gunnery. 
 
 SHOOTING ABOUND THE EDGE OF THE EAKTH 
 
 But if such ranges were known to be possible, 
 why was no such long-distance gun built before? 
 Simply because none but the Germans would 
 ever think of shooting around the edge of the 
 earth at a target so far away that it would 
 
 62 
 
GUNS AND SUPER-GUNS 63 
 
 have- to be as big as a whole city to be hit at 
 all. In a distance of seventy miles, the curve 
 of ihe earth is considerable. Paris is far be- 
 low the horizon of a man standing at St. Go- 
 bain, where the big German gun was located. 
 And if a hole were bored from St. Gobain 
 straight to Paris, so that you could see the city 
 from the gun, it would pass, midway of its 
 course, -three- thousand, seven hundred and fifty 
 feet below the surface of the earth. With the 
 target so far off, it was impossible to aim at any 
 particular fort, ammunition depot, or other 
 point of military importance. There is always 
 some uncertainty as to just where a shell will 
 fall, due to slight differences in quality and 
 quantity of the powder used, in the density of 
 the air, the direction of the wind, etc. This 
 variation is bad enough when a shell is to be 
 fired ten miles, but when the missile has to 
 travel seventy miles, it is out of the question 
 to try to hit a target that is not miles in extent. 
 Twenty years before the war our Ordnance 
 Department had designed a fifty-mile gun, but 
 it was not built, because we could see no possi- 
 ble use for it. Our big guns were built for fight- 
 ing naval battles or for the defense of our coasts 
 
64 INVENTIONS OF THE GREAT WAR 
 
 from naval attacks, and there is certainly no use 
 in firing at a ship that is so far below the horizon 
 that we cannot even see the tips of its masts; 
 and so our big guns, though they were capable 
 of firing a shell twenty-seven miles, if aimed 
 high enough, were usually mounted in carriages 
 that would not let them shoot more than twelve 
 or fifteen miles. 
 
 The distance to which a shell can be hurled 
 depends to a large extent upon the angle of the 
 gun. If the gun is tilted up to an angle of 15 
 degrees, the shell will go only about half as 
 far as if it were tilted up to 43 V degrees, which 
 is the angle that will carry a shell to its great- 
 est distance. If the long-range German gun 
 was fired at that angle, the shell must have 
 risen to a height of about twenty-four miles. 
 
 BEYOND THE EARTH ? S ATMOSPHERE 
 
 Most of the air that surrounds our globe lies 
 within four miles of the surface. Few airplanes 
 can rise to a greater height than this, because 
 the air is so thin that it gives no support to the 
 wings of the machine. The greatest height to 
 which a man has ever ascended is seven miles. 
 A balloon once carried two men to such a height. 
 
GUNS AND SUPER-GUNS 65 
 
 One of them lost consciousness, and the other, 
 who was nearly paralyzed, succeeded in pulling 
 the safety-valve rope with his teeth. That 
 brought the balloon down, and their instruments 
 showed that they had gone up thirty-six, thou- 
 sand feet. What the ocean of air contains above 
 that elevation, we do not know, but judging by 
 the way the atmosphere thins out as we rise 
 from the surface of the earth, we reckon that 
 nine tenths of the air lies within ten miles of 
 the surface of the earth. At twenty-four miles, 
 or the top of the curve described by the shell 
 of the German long-range guns, there must be 
 an almost complete vacuum. 
 
 If only we could accompany a shell on its 
 course, we should find a strange condition of 
 affairs. The higher we rose, the darker would 
 the heavens become, until the sun would shine 
 like a fiery ball in a black sky. All around, the 
 stars would twinkle, and below would be the 
 glare of light reflected from the earth's surface 
 and its atmosphere, while the cold would be far 
 more intense than anything suffered on earth. 
 Up at that height, there would be nothing to in- 
 dicate that the shell was moving no rush of 
 air against the ears. We should seem detached 
 
66 INVENTIONS OF THE GREAT WAR 
 
 from earth and out in the endless reaches of 
 space. 
 
 It seems absurd to think that a shell weighing 
 close to a quarter of a ton could be retarded 
 appreciably by mere air. But when we realize 
 that the shell left the gun at the rate of over 
 half a mile a second traveling about thirty 
 times faster than an express-train we know 
 that the air-pressure mounts up to a respectable 
 figure. The pressure is the same whether a 
 shell is moving through the air or the air is 
 blowing against the shell. When the wind 
 blows at the rate of 100 to 120 miles per hour, 
 it is strong enough to lift houses off their foun- 
 dations, to wrench trees out of the ground, to 
 pick up cattle and carry them sailing through 
 the air. Imagine what it would do if its ve- 
 locity were increased to 1,800 miles per hour. 
 That is what the shell of a big gun has to con- 
 tend with. As most of the air lies near the 
 earth, the shell of long-range guns meet with 
 less and less resistance the higher they rise, 
 until they get up into such thin air that there 
 is virtually no obstruction. The main trouble 
 is to pierce the blanket of heavy air that lies 
 near the earth. 
 
GUNS AND SUPER-GUNS 67 
 
 WAYS OF INCREASING THE BANGE 
 
 The big 16-inch guns that protect our coasts 
 fire a shell that weighs 2,400 pounds. Nine 
 hundred pounds of smokeless powder is used to 
 propel the shell, which leaves the muzzle of the 
 gun with a speed of 2,600 feet per second. Now, 
 the larger the diameter of the shell, the greater 
 will be its speed at the muzzle of the gun, be- 
 cause there will be a greater surface for the 
 powder gases to press against. On the other 
 hand, the larger the shell, the more will it be 
 retarded by the air, because there will be a 
 larger surface for the air to press against. It 
 has been proposed by some ordnance experts 
 that a shell might be provided with a disk at 
 each end, which would make it fit a gun of larger 
 caliber. A 10-inch shell, for instance, could 
 then be fired from a 16-inch gun. Being lighter 
 than the 16-inch shell, it would leave the muzzle 
 of the gun at a higher speed. The disks could 
 be so arranged that as soon as the shell left 
 the gun they would be thrown off, and then the 
 10-inch shell, although starting with a higher 
 velocity than a 16-inch shell, would offer less 
 resistance to the air. In that way it could be 
 
68 INVENTIONS OF THE GREAT WAR 
 
 made to cover a much greater range. By the 
 way, the shell of the German long-range gun 
 was of but 8.2-inch caliber. 
 
 Another way of increasing the range is to 
 lengthen the gun. Eight here we must become 
 acquainted with the word " caliber. " Caliber 
 means the diameter of the shell. A 16-inch gun, 
 for instance, fires a shell of 16-inch caliber ; but 
 when we read that the gun is a 40- or 50-caliber 
 gun, it means that the length of the gun is forty 
 or fifty times the diameter of the shell. Our 
 biggest coast-defense guns are 50-caliber 16- 
 inch guns, which means that they are fifty times 
 16 inches long, or 66% feet in length. When a 
 gun is as long as that, care has to be taken to 
 prevent it from sagging at the muzzle of its own 
 weight. These guns actually do sag a little, 
 and when the shell is fired through the long 
 barrel it straightens up the gun, making the 
 muzzle "whip" upward, just as a drooping 
 garden hose does when the water shoots through 
 it. 
 
 Now the longer the caliber length of a gun, 
 the farther it will send a shell, because the pow- 
 der gases will have a longer time to push the 
 shell. But we cannot lengthen our big guns 
 
GUNS AND SUPER,GUNS 69 
 
 much more without using some special support 
 for the muzzle end of the gun, to keep it from 
 " whipping " too much. It is likely that the 
 long-range German gun was provided with a 
 substantial support at the muzzle to keep it 
 from sagging. 
 
 Every once in a while a man comes forth with 
 a "new idea" for increasing the range. One 
 plan is to increase the powder-pressure. We 
 have powders that will produce far more pres- 
 sure than an ordinary gun can stand. But we 
 have to use powders that will burn compara- 
 tively slowly. We do not want too sudden a 
 shock to start with, but we wish the powder 
 to give off an enormous quantity of gas which 
 will keep on pushing and speeding up the shell 
 until the latter emerges from the muzzle. The 
 fifty-mile gun that was proposed twenty years 
 ago was designed to stand a much higher pres- 
 sure than is commonly used, and it would have 
 fired a 10-inch shell weighing 600 pounds with 
 a velocity of 4,000 feet per second at the muzzle. 
 
 The Allies built no "super-guns," because 
 they knew that they could drop a far greater 
 quantity of explosives with much greater ac- 
 curacy from airplanes, and at a much lower 
 
70 INVENTIONS OF THE GREAT WAR 
 
 cost. The German gun at St. Gobain was spec- 
 tacular and it did some damage, but it had no 
 military value and it did not intimidate the 
 French as the Germans had hoped it would. 
 
 A GUN WITH A RANGE OF A HUNDRED AND 
 TWENTY MILES 
 
 But although we built no such gun, after the 
 Germans began shelling Paris our Ordnance 
 Department designed a gun that would fire a 
 shell to a distance of over 120 miles! There 
 was no intention of constructing the gun, but 
 the design was worked out just as if it were 
 actually to be built. It was to fire a shell of 
 10-inch caliber, weighing 400 pounds. Now, an 
 Elswick standard 10-inch gun is 42 feet long 
 and its shell weighs 500 pounds. Two hundred 
 pounds of powder are used to propel the shell, 
 which leaves the muzzle with a velocity of 3,000 
 feet per second. If the gun is elevated to the 
 proper angle, it will send the shell 25 miles, and 
 it will take the shell a minute and thirty-seven 
 seconds to cover that distance. But the long- 
 range gun our ordnance experts designed would 
 have to be charged with 1,440 pounds of powder 
 and the shell would leave the muzzle of the gun 
 
GUNS AND SUPER-GUNS 71 
 
 with a velocity of 8,500 feet per second. It 
 would be in the air four minutes and nine sec- 
 onds and would travel 121.3 miles. Were the 
 gun fired from the Aberdeen Proving Grounds, 
 near Baltimore, Maryland, its shell would travel 
 across three states and fall into New York Bay 
 at Perth Amboy. At the top of its trajectory 
 it would rise 46 miles above the earth. 
 
 But the most astonishing part of the design 
 was the length of the gun, which worked out to 
 225 feet. An enormous powder-chamber would 
 have to be used, so that the powder gases would 
 keep speeding up the shell until it reached the 
 required velocity at the muzzle. The weight 
 of the barrel alone was estimated at 325 tons. 
 
 It would have to be built up in four sections 
 screwed together and because of its great 
 length and weight it would have to be supported 
 on a steel truss. The gun would be mounted 
 like a roller lift-bridge with a heavy counter- 
 weight at its lower end so that it could be ele- 
 vated or depressed at will and a powerful hy- 
 draulic jack would be required to raise it. 
 
 The recoil of a big gun is always a most im- 
 portant matter. Unless a gun can recoil, it 
 will be smashed by the shock of the powder ex- 
 
72 INVENTIONS OF THE GREAT WAR 
 
 plosion. Usually, heavy springs are used to 
 take up the shock, or cylinders filled with oil in 
 which pistons slide. The pistons have small 
 holes in them through which the oil is forced 
 as the piston moves and this retards the gun 
 in its recoil. But this " super-gun " was de- 
 signed to be mounted on a carriage running 
 on a set of tracks laid in a long concrete pit. 
 On the recoil the gun would run back along 
 the tracks, and its motion would be retarded by 
 friction blocks between the carriage and the 
 tracks and also by a steel cable attached to the 
 forward end of the carriage and running over 
 a pulley on the front wall of the pit, to a fric- 
 tion drum. 
 
 The engraving facing page 68 gives some idea 
 of the enormous size of the gun. Note the man 
 at the breech of the gun. The hydraulic jack 
 is collapsible, so that the gun may be brought 
 to the horizontal position for loading, as shown 
 by the dotted lines. The cost of building this 
 gun is estimated at two and a half million dol- 
 lars and its 400-pound shell would land only 
 about sixty pounds of high explosives on the 
 target. A bombing-plane costing but thirty 
 thousand dollars could land twenty-five times 
 
GUNS AND SUPER-GUNS 73 
 
 as big a charge of high explosives with far 
 greater accuracy. Aside from this, the gun 
 lining would soon wear out because of the tre- 
 mendous erosion of the powder gases. 
 
 THE THREE-SECOND LIFE OF A GUN 
 
 Powder gases are very hot indeed hot 
 enough to melt steel. The greater the pressure 
 in the gun, the hotter they are. It is only be- 
 cause they pass through the gun so quickly, 
 that they do not melt it. As a matter of fact, 
 they do wear it out rapidly because of their 
 heat and velocity. They say that the life of a 
 big gun is only three seconds. Of course, a shell 
 passes through the gun in a very minute part 
 of a second, but if we add up these tiny periods 
 until we have a total of three seconds, during 
 which the gun may have fired two hundred 
 rounds, we shall find that the lining of the barrel 
 is so badly eroded that the gun is unfit for ac- 
 curate shooting, and it must go back to the shops 
 for a new inner tube. 
 
 ELASTIC GUNS 
 
 We had better go back with it and learn 
 something about the manufacture of a big gun. 
 
74 INVENTIONS OF THE GREAT WAR 
 
 Guns used to be cast as a solid chunk of metal. 
 Now they are built up in layers. To under- 
 stand why this is necessary, we must realize 
 that steel is not a dead mass, but is highly elas- 
 tic far more elastic than rubber, although, of 
 course, it does not stretch nor compress so far. 
 When a charge of powder is exploded in the 
 barrel of a gun, it expands in all directions. 
 Of course, the projectile yields to the pressure 
 of the powder gases and is sent kiting out of the 
 muzzle of the gun. But for an instant before 
 the shell starts to move, an enormous force is 
 exerted against the walls of the bore of the 
 gun, and, because steel is elastic, the barrel is 
 expanded by this pressure, and the bore is ac- 
 tually made larger for a moment, only to spring 
 back in the next instant. You can picture this 
 action if you imagine a gun made of rubber; 
 as soon as the powder was fired, the rubber 
 gun would bulge out around the powder-cham- 
 ber, only to collapse to its normal size when 
 the pressure was relieved by the discharge of 
 the bullet. 
 
 Now r every elastic body has what is called its 
 elastic limit. If you take a coil spring, you can 
 pull it out or you can compress it, and it will 
 
GUNS AND SUPER-GUNS 75 
 
 always return to its original shape, unless you 
 pull it out or compress it beyond a certain 
 point ; that point is its elastic limit. The same 
 is true of a piece of steel : if you stretch it be- 
 yond a certain point, it will not return to its 
 original shape. When the charge of powder 
 in a cannon exceeds a certain amount, it 
 stretches the steel beyond its elastic limit, so 
 that the bore becomes permanently larger. 
 Making the walls of the gun heavier would not 
 prevent this, because steel is so elastic that the 
 inside of the walls expands beyond its elastic 
 limit before the outside is affected at all. 
 
 Years ago an American inventor named 
 Treadwell worked out a scheme for allowing the 
 bore to expand more without exceeding its elas- 
 tic limit. He built up his gun in layers, and 
 shrunk the outer layers upon the inner layers, 
 just as a blacksmith shrinks a tire on a wheel, 
 so that the inner tube of the gun would be 
 squeezed, or compressed. When the powder 
 was fired, this inner layer could expand farther 
 without danger, because it was compressed to 
 start with. The built-up gun was also indepen- 
 dently invented by a British inventor. All 
 modern big guns are built up. 
 
76 INVENTIONS OF THE GREAT WAK 
 
 HOW BIG GUNS ABE MADE 
 
 The inside tube, known as the lining, is cast 
 roughly to shape, then it is bored out, after 
 which it is forged by the blows of a powerful 
 steam-hammer. Of course, while under the 
 hammer, the tube is mounted on a mandrel, or 
 bar, that just fits the bore. The metal is then 
 softened in an annealing furnace, after which 
 it is turned down to the proper diameter and re- 
 bored to the exact caliber. The diameter of 
 the lining is made three ten-thousandths of an 
 inch larger than the inside of the hoop or sleeve 
 that fits over it. This sleeve, which is formed 
 in the same way, is heated up to 800 degrees, 
 or until its inside diameter is eight tenths of an 
 inch larger than the outside diameter of the 
 lining. The lining is stood up on end and the 
 sleeve is fitted over it. Then it is cooled by 
 means of water, so that it grips the lining and 
 compresses it. In this way, layer after layer 
 is added until the gun is built up to the proper 
 size. 
 
 Instead of having a lining that is compressed 
 by means of sleeves or jackets, many big guns 
 are wound with wire which is pulled so tight as 
 
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GUNS AND SUPER-GUNS 77 
 
 to compress the lining. The gun-tube is placed 
 in a lathe, and is turned so as to wind up the wire 
 upon it. A heavy brake on the wire keeps it 
 drawn very tight. This wire, also, is put on in 
 layers, so that each layer can expand consid- 
 erably without exceeding its elastic limit. Our 
 big 16-inch coast-defense guns are wound with 
 wire that is one -tenth of an inch square. The 
 length of wire on one gun is sufficient to reach 
 all the way from New York to Boston with fifty 
 or sixty miles of wire left over. 
 
 GUNS THAT PLAY HIDE-AND-SEEK 
 
 A very ingenious invention is the disappear- 
 ing-mount which is used on our coast fortifica- 
 tions. By means of this a gun is hidden beyond 
 its breastworks so that it is absolutely invisible 
 to the enemy. In this sheltered position it is 
 loaded and aimed. It is not necessary to sight 
 the gun on the target as you would sight a rifle. 
 The aiming is done mathematically. Off at 
 some convenient observation post, an observer 
 gets the range of the target and telephones this 
 range to the plotting-room, where a rapid cal- 
 culation is made as to how much the gun should 
 be elevated and swung to the right or the left. 
 
78 INVENTIONS OF THE GREAT WAR 
 
 This calculation is then sent on to the gunners, 
 who adjust the gun accordingly. When all is 
 ready, the gun is raised by hydraulic pressure, 
 and just as it rises above the parapet it is auto- 
 matically fired. The recoil throws the gun back 
 to its crouching position behind the breastworks. 
 All that the enemy sees, if anything, is the flash 
 of the discharge. 
 
 Now that airplanes have been invented, the 
 disappearing-mount has lost much of its useful- 
 ness. Big guns have to be hidden from above. 
 They are usually located behind a hill, five or six 
 miles back of the trenches, where the enemy can- 
 not see them from the ground, and they are care- 
 fully hidden under trees or a canopy of foliage 
 or are disguised with paint. 
 
 The huge guns recently built to defend our 
 coasts are intended to fire a shell that will pierce 
 the heavy armor of a modern dreadnought. 
 The shell is arranged to explode after it has 
 penetrated the armor, and the penetrating- 
 power is a very important matter. About 
 thirty years ago the British built three battle- 
 ships, each fitted with two guns of 1614-inch cali- 
 ber and 30-caliber length. In order to test the 
 penetrating-power of this gun a target was 
 
GUNS AND SUPER-GUNS 79 
 
 built, consisting first of twenty inches of steel 
 armor and eight inches of wrought-iron ; this 
 was backed by twenty feet of oak, five feet of 
 granite, eleven feet of concrete, and six feet 
 of brick. When the shell struck this target it 
 passed through the steel, the iron, the oak, the 
 granite, and the concrete, and did not stop until 
 it had penetrated three feet of the brick. We 
 have not subjected our 16-inch gun to such a 
 test, but we know that it would go through two 
 such targets and still have plenty of energy left. 
 Incidentally, it costs us $1,680 each time the big 
 gun is -fired. 
 
 THE FAMOUS FORTY-TWO-CENTIMETER GUN 
 
 One of the early surprises of the war was the 
 huge gun used by the Germans to destroy the 
 powerful Belgian forts. Properly speaking, 
 this was not a gun, but a howitzer; and right 
 here we must learn the difference between mor- 
 tars, howitzers, and guns. What we usually 
 mean by "gun" is a piece of long caliber which 
 is designed to hurl its shell with a flat trajec- 
 tory. But long ago it was found advantageous 
 to throw a projectile not at but upon a fortifica- 
 tion, and for this purpose short pieces of large 
 
80 INVENTIONS OP THE GREAT WAR 
 
 bore were built. These would fire at a high 
 angle, so that the projectile would fall almost 
 vertically on the target. 
 
 As we have said, the bore of a gun is rifled; 
 that is, it is provided with spiral grooves that 
 will set the shell spinning, so as to keep its 
 nose pointing in the direction of its flight. 
 Mortars, on the other hand, were originally in- 
 tended for short-range firing, and their bore 
 was not rifled. In recent years, however, mor- 
 tars have been made longer and with rifled 
 bores, so as to increase their range, and such 
 long mortars are called ' ' howitzers. ' ' The Ger- 
 man 42-centimeter howitzer fired a shell that was 
 2,108 pounds in weight and was about 1% yards 
 long. The diameter of the shell was 42 centi- 
 meters, which is about 16% inches. It carried 
 an enormous amount of high explosive, which 
 was designed to go off after the shell had 
 penetrated its target. The marvel of this how- 
 itzer was not that it could fire so big a shell but 
 that so large a piece of artillery could be trans- 
 ported over the highroads and be set for use in 
 battle. But although the 42-centimeter gun was 
 widely advertised, the real work of smashing 
 the Belgian forts was done by the Austrian 
 
GUNS AND SUPER-GUNS 81 
 
 "Skoda" howitzers, which fired a shell of 30.5- 
 centimeter (12-inch) caliber, and not by the 42- 
 centimeter gun. The Skoda howitzer could be 
 taken apart and transported by three motor- 
 cars of 100 horse-power each. The cars trav- 
 eled at a rate of about twelve miles per hour. 
 It is claimed the gun could be put together in 
 twenty-four minutes, and would fire at the rate 
 of one shot per minute. 
 
 FIELD-GUNS 
 
 So far, we have talked only of the big guns, 
 but in a modern battle the field-gun plays a very 
 important part. This fires a shell that weighs 
 between fourteen and eighteen pounds and is 
 about three inches in diameter. The shell and 
 the powder that fires it are contained in a cart- 
 ridge that is just like the cartridge of a shoul- 
 der rifle. These field-pieces are built to be fired 
 rapidly. The French 75-millimeter gun, which 
 is considered one of the best, will fire at the 
 rate of twenty shots per minute, and its effective 
 range is considerably over three miles. Tbe 
 French supplied us with all 75-millimeter guns 
 we needed in the war, while we concentrated 
 our efforts on the manufacture of ammunition. 
 
82 INVENTIONS OF THE GREAT WAR 
 
 GUNS THAT FIEE GUNS 
 
 During the War of the Bevolution, cannon 
 were fired at short range, and it was the cus- 
 tom to load them with grape-shot, or smalliron 
 balls, when firing against a charging enemy, be- 
 cause the grape would scatter like the shot of 
 a shot-gun and tear a bigger gap in the ranks of 
 the enemy than would a single solid cannon-ball. 
 In modern warfare, guns are fired from a 
 greater distance, so that there will be little dan- 
 ger of their capture. It is impossible for them 
 to fire grape, because the ranges are far too 
 great ; besides, it would be impossible to aim a 
 charge of grape-shot over any considerable dis- 
 tance, because the shot would start spreading as 
 soon as they left the muzzle of the gun and 
 would scatter too far and wide to be of much 
 service. But this difficulty has been overcome 
 by the making of a shell which is really a gun in 
 itself. Within this shell is the grape-shot, 
 which consists of two hundred and fifty half- 
 inch balls of lead. The shell is fired over the 
 lines of the enemy, and just at the right moment 
 it explodes and scatters a hail of leaden balls 
 over a fairly wide area. 
 
GUNS AND SUPER-GUNS 83 
 
 It is not a simple matter to time a shrapnel 
 shell so that it will explode at just the right mo- 
 ment. Spring-driven clockwork has been tried, 
 which would explode a cap after the lapse of a 
 certain amount of time ; but this way of timing 
 shells has not proved satisfactory. Nowadays 
 a train of gunpowder is used. When the shell 
 is fired, the shock makes a cap (see drawing fac- 
 ing page 77) strike a pin, E, which ignites the 
 train of powder, A. The head of the shell is 
 made of two parts, in each of which there is a 
 powder-fuse. There is a vent, or short cut, 
 leading from one fuse to the other, and, by the 
 turning of one part of the fuse-head with respect 
 to the other, this short cut is made to carry the 
 train of fire from the upper to the lower fuse 
 sooner or later, according to the adjustment. 
 The fire burns along one powder-train A, and 
 then jumps through the short cut B to the other, 
 or movable train, as it is called, until it finally 
 reaches, through hole C, the main charge F, in 
 the shell. The movable part of the fuse-head is 
 graduated so that the fuse may be set to explode 
 the shell at any desired distance. In the fuse- 
 head there is also a detonating-pin K, which 
 will strike the primer L and explode the shell 
 
84 INVENTIONS OF THE GREAT WAR 
 
 when the latter strikes the ground, if the time- 
 fuse has failed to act. 
 
 When attacking airplanes, it is important to 
 be able to follow the flight of the shell, so some 
 shrapnel shell are provided with a smoke-pro- 
 ducing mixture, which is set on fire when the 
 shell is discharged, so as to produce a trail of 
 smoke. 
 
 In meeting the attack of any enemy at night, 
 search-light shell are sometimes used. On ex- 
 ploding they discharge a number of "candles," 
 each provided with a tiny parachute that lets 
 the candle drop slowly to the ground. Their 
 brilliant light lasts fifteen or twenty minutes. 
 Obviously, ordinary search-lights could not be 
 used on the battle-field, because the lamp would 
 at once be a target for enemy batteries, but with 
 search-light shell the gun that fires them can 
 remain hidden and one 's own lines be shrouded 
 in darkness while the enemy lines are brilliantly 
 illuminated. 
 
CHAPTEE V 
 
 THE BATTLE OF THE CHEMISTS 
 
 SOME years ago the nations of the world 
 gathered at the city of The Hague, in Hol- 
 land, to -see what could be done to put an end to 
 war. They did not accomplish much in that di- 
 rection, but they did draw up certain rules of 
 warfare which they agreed to abide by. There 
 were some practices which were considered too 
 horrible for any civilized nation to indulge in. 
 Among these was the use of poisonous gases, 
 and Germany was one of the nations that took 
 a solemn pledge not to use gas in war. 
 
 Eighteen years later the German Army had 
 dug itself into a line of trenches reaching from 
 the English Channel to Switzerland, and facing 
 them in another line of trenches were the armies 
 of France and England, determined to hold back 
 the invaders. Neither side could make an ad- 
 vance without frightful loss of life. But 1 a 
 German scientist came forth with a scheme for 
 
 85 
 
86 INVENTIONS OF THE GREAT WAR 
 
 breaking the dead-lock. This was Professor 
 Nernst, the inventor of a well-known electric 
 lamp and a man who had always violently hated 
 the British. His plan was to drown out the 
 British with a flood of poisonous gas. To be 
 sure, there was the pledge taken at The Hague 
 Conference, but why should that stand in Ger- 
 many's way? What cared the Germans for 
 promises now? Already they had broken a 
 pledge in their violation of Belgium. Already 
 they had rained explosives from the sky on un- 
 fortified British cities (thus violating another 
 pledge of The Hague Conference) ; already they 
 had determined to war on defenseless merchant- 
 men. To them promises meant nothing, if such 
 promises interfered with the success of German 
 arms. They led the world in the field of chem- 
 istry ; why, they reasoned, should n't they make 
 use of this advantage? 
 
 POURING GAS LIKE WATER 
 
 It was really a new mode of warfare that the 
 Germans were about to launch and it called for 
 much study. In the first place, they had to de- 
 cide what sort of gas to use. It must be a gas 
 that could be obtained in large quantities. It 
 
THE BATTLE OF THE CHEMISTS 87 
 
 must be a very poisonous gas, that would act 
 quickly on the enemy; it must be easily com- 
 pressed and liquefied so that it could be carried 
 in containers that were not too bulky; it must 
 vaporize when the pressure was released; and 
 it must be heavier than air, so that it would not 
 be diluted by the atmosphere but would hug the 
 ground. You can pour gas just as you pour 
 water, if it is heavier than air. A heavy gas 
 will stay in the bottom of an unstoppered bottle 
 and can be poured from one bottle into another 
 like water. If the gas is colored, you can see 
 it flowing just as if it were a liquid. On the 
 other hand, a gas which is much lighter than 
 air can also be kept in unstoppered bottles if 
 the bottles are turned upside down, and the gas 
 can be poured from one bottle into another ; but 
 it flows up instead of down. 
 
 Chlorine gas was selected because it seemed 
 to meet all requirements. For the gas attack 
 a point was chosen where the ground sloped 
 gently toward the opposing lines, so that the 
 gas would actually flow down hill into them. 
 Preparations were carried out with the utmost 
 secrecy. Just under the parapet of the trenches 
 deep pits were dug, about a yard apart on a 
 
88 INVENTIONS OF THE GREAT WAR 
 
 front of fifteen miles, or over twenty-five thou- 
 sand pits. In these pits were placed the chlo- 
 rine tanks, each weighing about ninety pounds. 
 Each pit was then closed with a plank and this 
 was covered with a quilt filled with peat moss 
 soaked in potash, so that in case of any leakage 
 the chlorine would be taken up by the potash 
 and rendered harmless. Over the quilts sand- 
 bags were piled to a considerable height, to 
 protect the tanks from shell-fragments. 
 
 Liquid chlorine will boil even in a tempera- 
 ture of 28 degrees below zero Fahrenheit, but 
 in tanks it cannot boil because there is no room 
 for it to turn into a gas. Upon release of the 
 pressure at ordinary temperatures, the liquid 
 boils violently and big clouds of gas are pro- 
 duced. If the gas were tapped off from the top 
 of the cylinder, it would freeze on pouring out, 
 because any liquid that turns into a gas has to 
 draw heat from its surroundings. The greater 
 the expansion, the more heat the gas absorbs, 
 and in the case of the chlorine tanks, had the 
 nozzles been set in the top of the tank they 
 would very quickly have been crusted with frost 
 and choked, stopping the flow. 
 
 But the Germans had anticipated this diffi- 
 
THE BATTLE OF THE CHEMISTS 89 
 
 culty, and instead of drawing off the gas from 
 tfre top of the tank, they drew off the liquid 
 from the bottom in small leaden tubes which 
 passed up through the liquid in the tank and 
 were kept as warm as the surrounding liquid. 
 In fact, it was not gas from the top of the tank, 
 but liquid from the bottom, that was streamed 
 out and this did not turn into gas until it had 
 left the nozzle. 
 
 WAITING FOB THE WIND 
 
 Everything was ready for the attack on the 
 British in April, 1915. A point had been chosen 
 where the British lines made a juncture with 
 the French. The Germans reckoned that a 
 joint of this sort in the opponent's lines would 
 be a spot of weakness. Also, they had very 
 craftily picked out this particular spot because 
 the French portion of the line was manned by 
 Turcos, or Algerians, who would be likely to 
 think there was something supernatural about 
 a death-dealing cloud. On the left of the Afri- 
 cans was a division of Canadians, but the main 
 brunt of the- gas was designed to fall upon the 
 Turcos. Several times the attack was about 
 to be made, but was abandoned because the 
 
90 INVENTIONS OF THE GREAT WAR 
 
 wind was not just right. The Germans wished 
 to pick out a time when the breeze was blowing 
 steadily not so fast as to scatter the gas, but 
 yet so fast that it would overtake men who at- 
 tempted to run away from it. It was not until 
 April 22 that conditions were ideal, and then 
 the new mode of warfare was launched. 
 
 Just as had been expected, the Turcos were 
 awe-struck when they saw, coming out of the 
 German trenches, volumes of greenish-yellow 
 gas, which rolled toward them, pouring down 
 into shell-holes and flowing over into the 
 trenches as if it were a liquid. They were 
 seized with superstitious fear, particularly when 
 the gas overcame numbers of them, stifling 
 them and leaving them gasping for breath. Im- 
 mediately there was a panic and they raced 
 back, striving to out-speed the pursuing 
 cloud. 
 
 For a stretch of fifteen miles the Allied 
 trenches were emptied, and the Germans, who 
 followed in the wake of the gas, met with no op- 
 position except in the sector held by the Cana- 
 dians. Here, on the fringe of the gas cloud, so 
 determined a fight was put up that the Germans 
 faltered, and the brave Canadians held them 
 
THE BATTLE OF THE CHEMISTS 91 
 
 until reinforcements arrived and the gap in the 
 line was closed. 
 
 The Germans themselves were new at the 
 game or they could have made a complete suc- 
 cess of this surprise attack. Had they made the 
 attack on a broader front, nothing could have 
 kept them from breaking through to Calais. 
 The valiant Canadians who struggled and 
 fought without protection in the stifling clouds 
 of chlorine, were almost wiped out. But many 
 of them who were on the fringe of the cloud es- 
 caped by wetting handkerchiefs, socks, or other 
 pieces of cloth, and wrapping them around their 
 mouths and noses. 
 
 The world was horrified when it read of this 
 German gas attack, but there was no time to be 
 lost. Immediately orders went out for gas- 
 masks, and in all parts of England, and of 
 France as well, women were busy sewing the 
 masks. These were very simple affairs 
 merely a pad of cotton soaked in washing-soda 
 and arranged to be tied over the mouth and nose. 
 But when the next attack came, not long after 
 the first, the men were prepared in some meas- 
 ure for it, and again it failed to bring the Ger- 
 mans the success they had counted upon. 
 
92 INVENTIONS OF THE GREAT WAR 
 
 One thing that the Germans had not counted 
 upon was the fact that the prevailing winds in 
 Flanders blow from west to east. During the 
 entire summer and autumn of 1915, the winds 
 refused to favor them, and no gas attacks were 
 staged from June to December. This gave the 
 British a long respite and enabled them not only 
 to prepare better gas-masks, but also to make 
 plans to give the Hun a dose of his own medi- 
 cine. 
 
 WHEN THE WIND PLAYED A TRICK ON THE GERMANS 
 
 There were many disadvantages in the use 
 of gas clouds, which developed as the Germans 
 gathered experience. The gas started from 
 their own lines in a very dense cloud, but the 
 cloud grew thinner and thinner as it traveled 
 toward the enemy, and lost a great deal of its 
 strength. If the wind were higher than fifteen 
 miles an hour, it would swirl the gas around and 
 dissipate it before it did much harm to the op- 
 posing fighters. If the wind were light, there 
 were other dangers. On one occasion in 1916 
 a cloud of gas was released upon an Irish regi- 
 ment. The wind was rather fickle. It carried 
 the gas toward the British trenches, but before 
 

 Courtesy of "Scientific American " 
 
 Cleaning Up a Dugout with the "Fire Broom 
 
THE BATTLE OF THE CHEMISTS 93 
 
 reaching them the cloud hesitated, the wind 
 veered around, and soon the gas began to pour 
 back upon the German lines. The Germans 
 were entirely unprepared for this boomerang 
 attack. Many of the Huns had no gas-masks 
 on, and those who had, found that the masks 
 were not in proper working-order. As a result 
 of this whim of the winds, eleven thousand Ger- 
 mans were killed. 
 
 While chlorine was the first gas used, it was 
 evident that it was not the only one that could 
 be employed. British chemists had suspected 
 that the Germans would use phosgene, which 
 was a much more deadly gas, and in the long in- 
 terval between June and December, 1915, masks 
 were constructed which would keep out not only 
 the fumes of chlorine but also the more poison- 
 ous phosgene. In one of their sorties the Brit- 
 ish succeeded in capturing some valuable notes 
 on gas attacks, belonging to a German general, 
 which showed that the Germans were actually 
 preparing to use phosgene. This deadly gas is 
 more insidious in its action than chlorine. The 
 man who inhales phosgene may not know that 
 he is gassed. He may experience no ill effects, 
 but hours afterward, particularly if he has ex- 
 
94 INVENTIONS OF THE GREAT WAR 
 
 ercised in the meantime, he may suddenly fall 
 dead, owing to its paralyzing action on the heart. 
 
 FREEING THE BKITISH TRENCHES OF RATS 
 
 Phosgene was not used alone, but had to be 
 mixed with chlorine, and the deadly combina- 
 tion of the two destroyed all life for miles be- 
 hind the trenches. However, the British were 
 ready for it. They had been drilled to put on 
 their masks in a few seconds' time, on the first 
 warning of a gas attack. When the clouds of 
 chlorine and phosgene came over No Man's 
 Land, they were prepared, and, except for cas- 
 ualties among men whose masks proved defec- 
 tive, the soldiers in the trenches came through 
 with very few losses. .All animal life, however, 
 was destroyed. This was a blessing to the Brit- 
 ish Tommy, whose trenches had been overrun 
 with rats) The British had tried every known 
 method to get rid of these pests, and now, thanks 
 to the Germans, their quarters were most effec- 
 tively fumigated with phosgene and every rat 
 was killed. If only the "cooties" could have 
 been destroyed in the same way, the Germans 
 might have been forgiven many of their offenses. 
 
 The disadvantages in the use of gas clouds 
 
THE BATTLE OF THE CHEMISTS 95 
 
 became increasingly apparent. What was 
 wanted was some method of placing the gas 
 among the opponents in concentrated form, 
 without wasting any of it on its way across from 
 one line to the other. This led to the use of 
 shell filled with materials which would produce 
 gas. There were many advantages in these 
 shell. They could be thrown exactly where it 
 was desired that they should fall, without the 
 help of the fickle winds. When the shell landed 
 and burst, the full effect of its contents was 
 expended upon the enemy. A gas cloud would 
 rise over a wood, but with shell the wood could 
 be filled with gas, which, once there, would lurk 
 among the trees for days. Chemicals could be 
 used in shell which could not be used in a cloud 
 attack. The shell could be filled with a liquid, 
 or even with a solid, because when it burst the 
 filling would be minutely pulverized. And so 
 German chemists were set to work devising all 
 sorts of fiendish schemes for poisoning, chok- 
 ing, or merely annoying their opponents. 
 
 GAS THAT MADE ONE WEEP 
 
 One of the novel shell the Germans used was 
 known as the "tear-gas" shell. This was filled 
 
96 INVENTIONS OF THE GREAT WAR 
 
 with a liquid, Hie vapor of which was very irri- 
 tating to the eyes. The liquid vaporized very 
 slowly and so its effect would last a long time. 
 However, the vapor did not permanently injure 
 the eyes ; it merely filled them with tears to such 
 an extent that a soldier was unable to see and 
 consequently was confused and retarded in his 
 work. The ' ' tear-gas ' ' shell were marked with 
 a "T" by the Germans and were known as 
 "T-shell." 
 
 Another type of shell, known as the 
 "K-shell," contained a very poisonous liquid, 
 the object of which was to destroy the enemy 
 quickly. The effect of this shell was felt at 
 once, but it left no slow vapors on the ground, 
 and so it could be followed up almost immedi- 
 ately by an attack. Later on, the Germans de- 
 veloped three types of gas shell one known as 
 the " Green Cross, " another as the "Yellow 
 Cross," and the third as the "Blue Cross.' 7 
 The Green Cross shell was filled with diphos- 
 gene, or a particularly dangerous combination 
 of phosgene in liquid form, which would remain 
 in pools on the ground or soak into the ground 
 and would vaporize when it became warm. Its 
 vapors were deadly. One had always to be on 
 
THE BATTLE OF THE CHEMISTS 97 
 
 his guard against them. In the morning, when 
 the sun warmed the earth and vapors were seen 
 to rise from the damp soil, tests were made of 
 the vapors to see whether it was mere water 
 vapor or diphosgene, before men were allowed 
 to walk through it. 
 
 These vapors were heavier than air and would 
 flow down into a trench, filling every nook and 
 cranny. If phosgene entered a trench by a di- 
 rect hit, the liquid would remain there for days, 
 rendering that part of the trench uninhabitable 
 except by men in gas-masks. The infected part 
 of the trench, however, was cut off from the 
 rest of the trench by means of gas-locks. In 
 other words, blankets were used to keep the gas 
 out, and usually two blankets were hung so that 
 a man in passing from one part of the trench 
 to another could lift up the first blanket, pass 
 under it, and close it carefully behind him be- 
 fore opening the second blanket which led into 
 the portion of the trench that was not infected. 
 
 The Germans had all sorts of fiendish schemes 
 for increasing the discomfort of the Allies. 
 For instance, to some of their diphosgene Shell 
 they added a gas which caused intense vomit- 
 ing. 
 
98 INVENTIONS OF THE GREAT WAR 
 
 The Yellow Cross shell was another fiendish 
 invention of the Huns. It was popularly known 
 as "mustard gas" and was intended not to 
 kill but merely to discomfort the enemy. The 
 gas had a peculiar penetrating smell, some- 
 thing like garlic, -and its fumes would burn the 
 flesh wherever it was exposed to them, produc- 
 ing great blisters and sores that were most 
 distressing. The material in the shell was a 
 liquid which was very hard to get rid of because 
 it would vaporize so slowly. On account of the 
 persistence of this vapor, lasting as it did for 
 days, these gas shell were usually not fired 
 by the Germans on lines that they expected to 
 attack immediately. 
 
 THE SNEEZING-SHELL 
 
 The Blue Cross shell was comparatively 
 harmless, although very annoying. It con- 
 tained a solid which was atomized by the ex- 
 plosion of the shell, and which, after it got 
 into the nostrils, caused a violent sneezing. 
 The material, however, was not poisonous and 
 did not produce any casualties to speak of, 
 although it was most unpleasant. A storm of 
 Blue Cross shell could be followed almost im- 
 
THE BATTLE OF THE CHEMISTS 99 
 
 mediately by an attack, because the effect of 
 the shell would have been dissipated before 
 the attackers reached the enemy who were still 
 suffering from the irritation of their nostrils. 
 
 GAS-MASKS 
 
 As the different kinds of gas shell were de- 
 veloped, the gas-masks were improved to meet 
 them. In every attack there were "duds" or 
 unexploded shell, which the chemists of the 
 Allies analyzed. Also, they were constantly 
 experimenting with new gases, themselves, and 
 often could anticipate the Germans. The Allies 
 were better able to protect themselves against 
 gas attacks than the Germans, because 
 there was a scarcity of rubber in Germany 
 for the manufacture of masks. When it was 
 found that phosgene was going to be used, the 
 simple cotton-wad masks had to give way to 
 more elaborate affairs with chemicals that 
 would neutralize this deadly gas. And later 
 when the mustard gas was used which attacked 
 the eyes, and the sneezing-gas that attacked the 
 nose, it was found necessary to cover the face 
 completely, particularly the eyes; and so hel- 
 mets of rubber were constructed which were 
 
100 INVENTIONS OF THE GREAT WAR 
 
 tightly fitted around the neck under the coat 
 collar. The inhaled aid was purified by pas- 
 sage through a box or can filled with chemicals 
 and charcoal made of various materials, such as 
 cocoanut shells, peach pits, horse-chestnuts, and 
 the like. Because the Germans had no rubber 
 to spare, they were obliged to use leather, which 
 made their masks stiff and heavy. 
 
 GLASS THAT WILL NOT SHATTER 
 
 One of the greatest difficulties that had to be 
 contended with was the covering of the eyes. 
 There was danger in the use of glass, because 
 it was liable to be cracked or broken, letting in 
 the deadly fumes and gassing the wearer. Ex- 
 periments were made with celluloid and similar 
 materials, but the finest gas-masks produced 
 in the war were those made for our own soldiers, 
 .in which the goggles were of glass, built up in 
 layers, with a celluloid-like material between, 
 which makes a tough composition that will 
 stand up against a very hard blow. Even if 
 it cracks, this glass will not shatter. 
 
 The glasses were apt to become coated on 
 the inside with moisture coming from the per- 
 spiration of the face, and some means had to be 
 
THE BATTLE OF THE CHE-MISTS * Ifcl 
 
 provided for wiping them off. The French hit 
 upon a clever scheme of having the inhaled air 
 strike the glasses in a jet which would dry off 
 the moisture and keep the glasses clear. Be- 
 fore this was done, the masks were provided 
 with little sponges on the end of a finger-piece, 
 with which the glasses could be wiped dry with- 
 out taking the masks off. 
 
 But all this time, the Allies were not merely 
 standing on the defensive. No sooner had the 
 Germans launched their first attack than the 
 British and French chemists began to pay back 
 the Hun in kind. More attention was paid to 
 the shell than the cloud attack, and soon gas 
 shell began to rain upon the Germans. Not 
 only were the German shell copied, but new 
 gases were tried. Gas shell were manufac- 
 tured in immense quantities. 
 
 Then America took a hand in the war and 
 our chemists added their help, while our fac- 
 tories turned out steady streams of shell. If 
 Germany wanted gas warfare, the Allies were 
 determined that she should have it. Our chem- 
 ists were not afraid to be pitted against the 
 German chemists and the factories of the Allies 
 were more than a match for those of the Cen- 
 
,102 , .INY^XTIONS OF THE GREAT WAR 
 
 tral Powers. When the Germans first started 
 the use of gas, apparently they counted only 
 their own success, which they thought would 
 be immediate and overwhelming. They soon 
 learned that they must take what they gave. 
 The Allies set them a pace that they could not 
 keep up with. 
 
 When the armistice brought the war to a 
 sudden stop, the United States alone was mak- 
 ing each day two tons of gas for every mile of 
 the western front. If the war had continued, 
 the Germans would have been simply deluged. 
 As it was, they were getting far more gas than 
 they could possibly produce in their own fac- 
 tories and they had plenty of reason to regret 
 their rash disregard of their contract at The 
 Hague Conference. One gas we were making 
 was of the same order as mustard gas but far 
 more volatile, and had we had a chance to use 
 it against the Germans they would have found 
 it very difficult to protect themselves against its 
 penetrating fumes. 
 
 BATTLING WITH LIQUID FIBE 
 
 Somewhat associated with gas warfare was 
 another form of offensive which was introduced 
 
THE BATTLE OF THE CHEMISTS 103 
 
 with the purpose of breaking up the dead-lock 
 of trench warfare. A man could protect him- 
 self against gas by using a suitable mask and 
 clothing, but what could he do against fire! 
 It looked as if trench defenders would have to 
 give up if attacked with fire, and so, early in the 
 war, the Germans devised apparatus for shoot- 
 ing forth streams of liquid fire, and the Allies 
 were not slow to copy the idea. 
 
 The apparatus was either fixed or portable, 
 but it was not often that the fixed apparatus 
 could be used to advantage, because at best the 
 range of the flame-thrower was limited and in 
 few places were the trenches near enough for 
 flaming oil to be thrown across the intervening 
 gap. For this reason portable apparatus was 
 chiefly used, with which a man could send out a 
 stream for from a hundred to a hundred and 
 fifty feet. On his back he carried the oil-tank, 
 in the upper part of which there was a charge 
 of compressed air.. A pipe led from the tank 
 to a nozzle which the man held in his hand, 
 using it to direct the spray. 
 
 There was some danger to the operator in 
 handling a highly inflammable oil. The blaze 
 might flare back and burn him, particularly 
 
104 INVENTIONS OF THE GREAT WAR 
 
 when he was lighting the stream, and so a 
 special way of setting fire to the spray had to be 
 devised. Of course, the value of the apparatus 
 lay in its power to shoot the stream as far as 
 possible. The compressed air would sent the 
 stream to a good distance, but after lighting, 
 the oil might be consumed before it reached the 
 desired range. Some way had to be found of 
 igniting the oil stream far from the nozzle or 
 as near the limit of its range as possible. And 
 so two nozzles were used, one with a small open- 
 ing so that it would send out a fine jet of long 
 range, while the main stream of oil issued from 
 the second nozzle. The first nozzle was mov- 
 able with respect to the second and the two 
 streams could be regulated to come together at 
 any desired distance from the operator within 
 the range of the apparatus. The fine stream 
 was ignited and carried the flame out to the 
 main stream, setting fire to it near the limit of 
 its range. In this way a flare-back was avoided 
 and the oil blazed where the flame was needed. 
 The same sort of double nozzle was used on the 
 stationary apparatus and because weight was 
 not a consideration, heavier apparatus was used 
 which shot the stream to a greater distance. 
 
THE BATTLE OF THE CHEMISTS 105 
 
 But flame-throwing apparatus had its draw- 
 backs: there was always the danger that the 
 tank of highly inflammable oil might be burst 
 open by a shell or hand-grenade and its con- 
 tents set on fire. The fixed apparatus was 
 buried under bags of sand, but the man who 
 carried flame-throwing apparatus on his back 
 had to take his chances, not knowing at what 
 instant the oil he carried might be set ablaze, 
 turning him into a living, writhing, human 
 torch. Because of this hazard, liquid fire did 
 not play a very important part in trench war- 
 fare; to set fire to the spray at its source with 
 a well directed hand-grenade was too easy. 
 
 There were certain situations, however, in 
 which liquid fire played a very important part. 
 After a line of trenches had been captured it 
 was difficult to clear out the enemy who lurked 
 in dugouts and underground passages. They 
 would not surrender, and from their hidden 
 recesses they could pour out a deadly machine- 
 gun fire. The only way of dislodging them 
 was to use the "fire broom. " In other words, 
 a stream of liquid fire was poured into the dug- 
 
106 INVENTIONS OF THE GREAT WAR 
 
 out, burning out the men trapped in it. If 
 there were a second exit, they would come tum- 
 bling out in a hurry. If not, they would be 
 burned to death. After the first sweep of the 
 " broom, " if there were any survivors, there 
 would not be any fight left in them, and they 
 would be quick to surrender before being sub- 
 jected to a second dose of fire. 
 
CHAPTEE VI 
 TANKS 
 
 r 1 1 HEBE is no race-horse that can keep up 
 A with an automobile, no deer that can out- 
 run a locomotive. A bicyclist can soon tire out 
 the hardiest of hounds. Why? Because ani- 
 mals run on legs, while machines run on wheels. 
 
 As wheels are so much more speedy than legs, 
 it seems odd that we do not find this form of 
 locomotion in nature. There are many animals 
 that owe their very existence to the fact that 
 they can run fast. Why hasn't nature put 
 them on wheels so that when their enemy ap- 
 pears they can roll away, sedately, instead of 
 having to jerk their legs frantically back and 
 forth at the rate of a hundred strokes a minute I 
 
 But one thing we must not overlook. Our 
 wheeled machines must have a special road 
 prepared for them, either a macadam highway 
 or a steel track. They are absolutely helpless 
 
 107 
 
108 INVENTIONS OF THE GREAT WAR 
 
 when they are obliged to travel over rough 
 country. No wheeled vehicle can run through 
 fields broken by ditches and swampy spots, or 
 over ground obstructed with boulders and tree- 
 stumps. 
 
 But it is not always possible or practicable 
 to build a road for the machines to travel upon, 
 and it is necessary to have some sort of self- 
 propelled vehicle that can travel over all kinds 
 of ground. 
 
 Some time ago a British inventor developed 
 a machine with large wheels on which were 
 mounted the equivalent of feet. As the wheels 
 revolved, these feet would be planted firmly on 
 the ground, one after the other, and the machine 
 would proceed step by step. It could travel 
 over comparatively rough ground, and could 
 actually walk up a flight of stairs. We have a 
 very curious walking-machine in this country. 
 It is a big dredge provided with two broad 
 feet and a "swivel chair. " The machine 
 makes progress by alternately planting its feet 
 on the ground, lifting itself up, chair and all, 
 pushing itself forward, and sitting down again. 
 
 Although many other types of walking-ma- 
 chines have been patented, none of them has 
 
TANKS 109 
 
 amounted to very much. Clearly, nature hope- 
 lessly outclasses us in this form of propulsion. 
 
 Years ago it occured to one ingenious man 
 that if wheeled machines must have tracks or 
 roads for their wheels to run on, they might be 
 allowed to lay their own tracks. And so he 
 arranged his track in the form of an endless 
 chain of plates that ran around the wheels of 
 his machine. The wheels merely rolled on this 
 chain, and as they progressed, new links of the 
 track were laid down before them and the links 
 they had passed over were picked up behind 
 them. A number of inventors worked on this 
 idea, but one man in particular, Benjamin Holt, 
 of Peoria, Illinois, brought the invention to a 
 high state of perfection. He arranged a series 
 of wheels along the chain track, each carrying 
 a share of the load of the machine, and each 
 mounted on springs so that it would yield to 
 any unevenness of the ground, just as a cater- 
 pillar conforms itself to the hills and dales of 
 the surface it creeps over. In fact, the ma- 
 chine was called a " caterpillar " tractor be- 
 cause of its crawling locomotion. 
 
 But it was no worm of a machine. In power 
 it was a very elephant. It could haul loads 
 
110 INVENTIONS OF THE GREAT WAR 
 
 that would tax the strength of scores of horses. 
 Stumps and boulders were no obstacles in its 
 path. Even ditches could not bar its progress. 
 The machine would waddle down one bank 
 and up the other without the slightest diffi- 
 culty. It was easily steered; in fact, it could 
 turn around in its own length by traveling for- 
 ward on one of its chains, or traction-belts, 
 and backward on the other. The machine was 
 particularly adapted to travel on soft or plowed 
 ground, because the broad traction-belts gave 
 it a very wide bearing and spread its weight 
 over a large surface. It was set to work on 
 large farms, hauling gangs of plows and culti- 
 vators. Little did Mr. Holt think, as he 
 watched his powerful mechanical elephants at 
 work on the vast Western wheat-fields, that 
 they, or rather their offspring, would some day 
 play a leading role in a war that would rack the 
 whole world. 
 
 But we are getting ahead of our story. To 
 start at the very beginning, we must go back 
 to the time when the first savage warrior used 
 a plank of wood to protect himself from the 
 rocks hurled by his enemy. This was the start 
 
TANKS 111 
 
 of the never-ending competition between arms 
 and armor. As the weapons of offense de- 
 veloped from stone to spear, to arrow, to arque- 
 bus, the wooden plank developed into a shield 
 of brass and then of steel; and then, since a 
 separate shield became too bothersome to 
 carry, it was converted into armor that the 
 warrior could wear and so have both hands free 
 for battle. For every improvement in arms 
 there was a corresponding improvement in 
 armor. 
 
 After gunpowder was invented, the idea of 
 armor for men began to wane, because no armor 
 could be built strong enough to ward off the 
 rifle-bullet and at the same time light enough 
 for a man to wear. The struggle between arms 
 and armor was then confined to the big guns 
 and the steel protection of forts and war-ships. 
 
 But not so long ago the machine-gun was in- 
 vented, and this introduced a new phase of war- 
 fare. Not more than one rifle-bullet in a thou- 
 sand finds its mark on the battle-field. The 
 Boers in the battle of Colenso established a 
 record with one hit in six hundred shots. In 
 the excitement of battle men are too nervous to 
 take careful aim and they are apt to fire either 
 
112 INVENTIONS OF THE GREAT WAR 
 
 too high or too low, so that the mortality is 
 not nearly so great as some would expect. But 
 with the machine-gun there is not this waste of 
 ammunition, because it fires a stream of 
 bullets, the effect of which can readily be deter- 
 mined by the man who operates the volley. The 
 difference between the machine-gun fire and 
 rifle fire is something like the difference between 
 hitting a tin can with a stone or with a stream of 
 water. It is no easy matter to score a hit with 
 the stone; but any one can train a garden hose 
 on the can, because he can see where the water is 
 striking and move his hose accordingly until he 
 covers the desired spot. In the -same way, 
 with the machine-gun, it is much easier to train 
 the stream of bullets upon the mark, and, having 
 once found the mark, to hold the aim. That is 
 one reason why the destruction of a machine- 
 gun is so tremendous ; another, of course, being 
 that it will discharge so many more shots per 
 minute than the common rifle. 
 
 In the Eusso-Japanese War, the Eussians 
 played havoc with the attacking Japanese at 
 Port Arthur by using carefully concealed ma- 
 chine-guns, and the German military attaches 
 were quick to note the value of the machine- 
 
(C) Underwood & Underwood 
 
 Even Trees were no Barrier to the British Tank 
 
 Press Illustrating Service 
 
 The German Tank was very heavy and cumbersome 
 
TANKS 113 
 
 gun. Secretely they manufactured large num- 
 bers of machine-guns and established a special 
 branch of service to handle the guns, and they 
 developed the science of using them with telling 
 effect. And so, when the recent great war sud- 
 denly broke out, they surprised the world with 
 the countless number of machine-guns they pos- 
 sessed and the efficient use to which they put 
 them. Thousands of British soldiers in the 
 early days of the war fell victims to these death- 
 dealing machines. Two or three men with a 
 machine-gun could defy several companies of 
 soldiers, especially when the attackers had to 
 cut their way through barbed-wire entangle- 
 ments. It was clearly evident that something 
 must be done to defend the men against the 
 machine-gun; for to charge against it meant, 
 simply, wholesale slaughter. 
 
 At first the only means of combating the ma- 
 chine-guns seemed to be to destroy them with 
 shell-fire; but they were carefully concealed, 
 and it was difficult to search them out. Only 
 by long-continued bombardment was it possible 
 to destroy them and tear away the barbed wire 
 sufficiently to permit of a charge. Before an 
 enemy position was stormed it was subjected to 
 
114 INTENTIONS OF THE GREAT WAR 
 
 the fire of thousands -of guns of all calibers for 
 hours and even days. 
 
 But this resulted in notifying the enemy that 
 a charge was ere long to be attempted at a 
 certain place, and he could assemble his reserves 
 for a counter-attack. Furthermore, the Ger- 
 mans learned to conceal their machine-guns in 
 dugouts twenty or thirty feet underground, 
 where they were safe from the fire of the big 
 guns, and then, when the fire let up, the weapons 
 would be dragged up to the surface in time to 
 mow down the approaching infantry. 
 
 It was very clear that something would have 
 to be done to combat the machine-gun. If the 
 necessary armor was too heavy for the men 
 to carry, it must carry itself. Armored auto- 
 mobiles were of no service at all, because they 
 could not possibly travel over the shell-pitted 
 ground of No Man's Land. The Eussians 
 tried a big steel shield mounted on wheels, 
 which a squad of soldiers would push ahead 
 of them, but their plan failed because the wheels 
 would get stuck in shell-holes. A one-man 
 shield on wheels was tried by the British. Un- 
 der its shelter a man could steal up -to the barbed 
 wire and cut it and even crawl up to a machine- 
 
TANKS 115 
 
 gun emplacement and destroy it with a hand- 
 grenade. But this did not prove very success- 
 ful, either, because the wheels did not take 
 kindly to the rough ground of the battle-field. 
 
 And here is where we come back to Mr. 
 Holt's mechanical elephants. Just before the 
 great war broke out, Belgium poor unsus- 
 pecting Belgium was holding an agricultural 
 exhibit. An American tractor was on exhi- 
 bition. It was the one developed by Mr. 
 Holt, and its remarkable performances gained 
 for it a reputation that spread far and 
 wide. Colonel E. D. Swinton of the British 
 Army heard of the peculiar machine, and im- 
 mediately realized the advantages of an ar- 
 mored tractor for battle over torn ground. 
 But in the first few months of the war that 
 ensued, this idea was forgotten, until the ef- 
 fectiveness of the machine-gun and the neces- 
 sity for overcoming it recalled the matter 
 to his mind. At his suggestion a caterpillar 
 tractor was procured, and the military engi- 
 neers set themselves to the task of designing an 
 armored body to ride on the caterpillar-trac- 
 tor belts, Of course the machine had to be 
 
116 INVENTIONS OF THE GREAT WAR 
 
 entirely re-designed. The tractor was built for 
 hauling loads, and not to climb out of deep shell- 
 holes; but by running the traction-belts over 
 the entire body of the car, and running the 
 forward part of the tractor up at a sharp an- 
 gle the engineers overcame that difficulty. 
 
 In war, absolute secrecy is essential to the 
 success of any invention, and the British en- 
 gineers were determined to let no inkling of 
 the new armored automobiles reach the enemy. 
 Different parts of the machines were made in 
 different factories, so that no one would have 
 an idea of what the whole would look like. At 
 first the new machine was known as a " land- 
 cruiser " or " land-ship "; but it was feared that 
 this very name would give a clue to spies, and 
 so any descriptive name was forbidden. Many 
 of the parts consisted of rolled steel plates 
 which might readily be used in building up ves- 
 sels to hold water or gasolene ; and to give the 
 impression that such vessels were being con- 
 structed the name "tank" was adopted. The 
 necessity of guarding even the name of the ma- 
 chines was shown later, when rumors leaked 
 out that the tanks were being built to carry 
 water over the desert regions of Mesopotamia 
 
TANKS 117 
 
 and Egypt. Another curious rumor was that 
 the machines were snow-plows for use in Rus- 
 sia. To give some semblance of truth to this 
 story, the parts were carefully labeled, "For 
 Petrograd." 
 
 Probably never was a military secret so well 
 guarded as this one, and when, on September 
 15, 1916, the waddling steel tractors loomed up 
 out of the morning mists, the German fighters 
 were taken completely by surprise. Two days 
 before, their airmen had noticed some peculiar 
 machines which they supposed were armored 
 automobiles. They had no idea, however, that 
 such formidable monsters were about to de- 
 scend upon them. 
 
 The tanks proceeded leisurely over the shell- 
 torn regions of No Man's Land, wallowing 
 down into shell-holes and clambering up out of 
 them with perfect ease. They straddled the 
 trenches and paused to pour down them streams 
 of machine-gun bullets. Wire entanglements 
 were nothing to them ; under their weight steel 
 wire snapped like thread. The big brutes 
 marched up and down the lines of wire, treading 
 them down into the ground and clearing the way 
 for the infantry. Even trees were no barrier 
 
118 INVENTIONS OF THE GREAT WAR 
 
 to these tanks. Of course they did not attack 
 large ones, but the smallish trees were simply 
 broken down before their onslaughts. As for 
 concrete emplacements for machine-guns, the 
 tanks merely rode over them and crushed them. 
 Those who attempted to defend themselves in 
 the ruins of buildings found that the tanks 
 could plow right through walls and bring them 
 down in a shower of bricks and stone. There 
 was no stopping these monsters, and the Ger- 
 mans fled in consternation before them. 
 
 There were two sizes of tanks. The larger 
 ones aimed to destroy the machine-gun emplace- 
 ments, and they were fitted up with guns for fir- 
 ing a shell. The smaller tanks, armed with 
 machine-guns, devoted themselves to fighting 
 the infantry. British soldiers following in the 
 wake of the bullet-proof tank were protected 
 from the shots of the enemy and were ready to 
 attack him with bayonets when the time was 
 ripe. But the tanks also furnished an indirect 
 protection for the troops. It was not necessary 
 for the men to conceal themselves behind the 
 big tractors. Naturally, every Hun who stood 
 his ground and fought, directed all his fire upon 
 the tanks, leaving the British infantry free to 
 
TANKS 119 
 
 charge virtually unmolested. The success of 
 the tank was most pronounced. 
 
 In the meantime the French had been in- 
 formed of the plans of their allies, and they set 
 to work on a different design of tractor. It 
 was not until six months later that their ma- 
 chines saw service. The French design dif- 
 fered from the British mainly in having the 
 tractor belt confined to the wheels instead of 
 running over the entire body of the tank. It 
 was more blunt than the British and was pro- 
 vided at the forward end with a steel cutting- 
 edge, which adapted it to break its way through 
 wire entanglements. At each end there are two 
 upward-turning skids which helped the tank 
 to lift itself out of a hole. The larger machines 
 carried a regular 75-millimeter (3-inch) field- 
 gun, which is a very formidable weapon. They 
 carried a crew of one officer and seven men. 
 
 Life in a tank is far from pleasant. The heat 
 and the noise of machinery and guns are terrific. 
 Naturally, ventilation is poor and the fumes and 
 gases that accumulate are most annoying, to 
 say the least. Sometimes the men were over- 
 come by them. But war is war, and such dis- 
 comforts had to be endured, 
 
120 INVENTIONS OF THE GREAT WAR 
 
 But the tank possessed one serious defect 
 which the Germans were not slow to discover. 
 Its armor was proof against machine-gun fire, 
 but it could not ward off the shells of field- 
 guns, and it was such a slow traveler that the 
 enemy did not find it a very difficult task to 
 hit it with a rapid-fire gun if the gunner could 
 see his target. And so the Germans ordered up 
 their guns to the front lines, where they could 
 score direct hits. Only light guns were used 
 for this purpose, especially those whose rifling 
 was warn down by long service, because 
 long range was not necessary for tank 
 fighting. 
 
 When the Germans began their final great 
 drive, it was rumored that they had built some 
 monster tanks that were far more formidable 
 than anything the Allies had produced. Un- 
 like the British, they used the tanks not to lead 
 the army but to follow and destroy small nests 
 of French and British that were left behind. 
 When the French finally did capture one of the 
 German tanks, which had fallen into a quarry, 
 it proved to be a poor imitation. It was an 
 ugly-looking affair, very heavy and cumber- 
 some. Owing to the scarcity of materials for 
 
(C) Underwood & Underwood 
 
 The Speedy British "Whippet" Tank that can travel at a 
 speed of twelve miles per hour 
 
 CO Underwood & Underwood 
 
 The French High-Speed "Baby" Tank 
 
sl 
 ' 
 
 <L> ., 
 C 
 
 II 
 
 .si 
 
 g 
 
 r rt o 
 
 . 
 
TANKS 121 
 
 producing high-grade armor, it had to make 
 up in thickness of plating what it lacked in 
 quality of steel. The tank was intended to 
 carry a crew of eighteen men and it fairly 
 bristled with guns, but it could not manceuver 
 as well as the British tank; for when some 
 weeks later a fleet of German tanks encountered 
 a fleet of heavy British tanks, the Hun machines 
 were completely routed. 
 
 It was then that the British sprang another 
 surprise upon the Germans. After the big 
 fellows had done their work, a lot of baby tanks 
 appeared on the scene and chased the German 
 infantry. These little tanks could travel at a 
 speed of twelve miles an hour, which is about 
 as fast as an ordinary man can run. " Whip- 
 pets, " the British called them, because they 
 were like the speedy little dogs of that name. 
 They carried but two men, one to guide the tank 
 and the other to operate the machine-gun. The 
 French, too, built a light ." mosquito" tank, 
 which was even smaller than the British tank, 
 and fully as fast. It was with these machines, 
 which could dart about quickly on the battle- 
 field and dodge the shell of the field-guns, and 
 which were immune to the fire of the machine- 
 
122 INVENTIONS OF THE GREAT "WAR 
 
 gun, that the Allies were able to make progress 
 against the Germans. 
 
 When the Germans retired, they left behind 
 them nests of machine-guns to cover the with- 
 drawal of their armies. These gunners were 
 ordered to fight to the very end. They looked 
 for no mercy and expected no help. Had it 
 not been for the light tanks, it would have been 
 well nigh impossible to overcome these deter- 
 mined bodies of men without frightful losses. 
 
 Since America invented the machine-gun and 
 also barbed wire, and since America furnished 
 the inspiration for the tank with which to tram- 
 ple down the wire entanglements and stamp out 
 the machine-guns, naturally people expected 
 our army to come out with something better 
 than anything produced by our allies. We did 
 turn out a number of heavy machines patterned 
 after the original British tank, with armor that 
 could stand up against heavy fire, and we also 
 produced a small and very speedy tank similar 
 to the French "baby" tank, but before we could 
 put these into service the war ended. The 
 tanks we did use so effectively at St.-Mihiel 
 and in the Argonne Forest were supplied by 
 the French. 
 
CHAPTER VII 
 THE WAB IN THE AIR 
 
 WE Americans are a peace-loving people, 
 which is the very reason why we went 
 into the war. We had to help down the 
 power that was disturbing the peace of the 
 world. We do not believe in conquests at 
 least of the type that Germany tried to force 
 and yet there are certain conquests that we 
 do indulge in once in a while. 
 
 Eleven years before Germany undertook to 
 conquer Europe two young Americans made the 
 greatest conquest that the world has ever seen. 
 The Wright brothers sailed up into the heavens 
 and gained the mastery of the air. They of- 
 fered their conquest to the United States; but 
 while we accepted their offering with enthusi- 
 asm at first, we did not know what to do with 
 the new realm after we got it. There seemed 
 to be no particular use in flying. It was just 
 
 123 
 
124 INVENTIONS OF THE GREAT WAR 
 
 a bit too risky to be pleasant sport, and about 
 all we could see in it was an exhibition for the 
 circus or the county fair. 
 
 Not so in Europe, however. Flying meant 
 something over there there where the fron- 
 tiers have ever bristled with big guns and 
 strong fortifications, and where huge military 
 forces have slept on their arms, never knowing 
 what dreadful war the morning would bring 
 forth. The war-lovers hailed the airplane as 
 a new instrument with which to terrorize their 
 neighbors; the peace-lovers saw in it another 
 menace to their homes ; it gave them a new fron- 
 tier to defend. And so the military powers of 
 Europe took up the airplane seriously and 
 earnestly and developed it. 
 
 At first military authorities had rated the 
 airplane chiefly as a flying scout. Some bomb- 
 dropping experiments had been made with it, 
 but it proved very difficult to land the bombs 
 near the target, and, besides, machines of those 
 days were not built to carry very heavy loads, 
 so that it did not seem especially profitable to 
 attack the enemy from the skies. As for actual 
 battles up among the clouds, they were dreamed 
 of only by the writers of fiction. But wild 
 
THE WAR IN THE AIR 125 
 
 dreams became stern realities in the mighty 
 struggle between the great powers of the world. 
 
 EYES IN THE SKY 
 
 As a scouting-machine the airplane did 
 prove to be far superior to mounted patrols 
 which used to perform scout-work. In fact, it 
 changed completely the character of modern 
 warfare. From his position high up in the 
 heavens the flying scout had an unobstructed 
 view of the country for miles and he could see 
 just what the enemy was doing. He could see 
 whether large forces of men were collecting for 
 an attack. He could watch the course of sup- 
 ply-trains, and judge of their size. He could 
 locate the artillery of the enemy and come back 
 with information which in former times a scout 
 posted in a tall tree or even in a captive balloon 
 could not begin to acquire. Surprise attacks 
 were impossible, with eyes in the sky. The 
 aviator could help his own batteries by signal- 
 ing to them where to send their shell, and when 
 the firing began he would spot the shots as they 
 landed and signal back to the battery how to 
 correct its aim so as to drop the shell squarely 
 on the target. 
 
126 INVENTIONS OF THE GREAT WAR 
 
 The French sprang a surprise on the Ger- 
 mans by actually attacking the infantry from 
 the sky. The idea of attack from overhead 
 was so novel that armies did not realize the 
 danger of exposing themselves behind the bat- 
 tle-front. Long convoys of trucks and masses 
 of infantry moved freely over the roads 
 behind the lines and they were taken by sur- 
 prise when the French began dropping steel 
 darts upon them. These were about the size 
 of a pencil, with pointed end and fluted tail, 
 so that they would travel through the air like 
 an arrow. The darts were dropped by the 
 hundred wherever the airmen saw a large 
 group of the enemy, and they struck with suf- 
 ficient velocity to pierce a man from head to 
 foot. But steel darts were not used very long. 
 The enemy took to cover and then the only way 
 to attack him was to drop explosives which 
 would blow up his shelter. 
 
 At the outset, air scouts were more afraid of 
 the enemy on the ground than in the sky. The 
 Germans had anti-aircraft guns that were fired 
 with accuracy and accounted for many Allied 
 planes. In those days, airplanes flew at com- 
 paratively low altitudes and they were well 
 
THE WAft IN THE AIB 127 
 
 within the reach of the enemy's guns. But it 
 was not long before the airplanes began to fight 
 one another. Each side was very much an- 
 noyed by the flying scouts of its opponents and 
 after a number of pistol duels in the sky the 
 French began to arm their planes with machine- 
 guns. 
 
 Two months after the war started the first 
 airplane was sent crashing to earth after a bat- 
 tle in the sky. The fight took place five thou- 
 sand feet above the earth, between a French 
 and a German machine. The German pilot was 
 killed and the plane fell behind the French 
 lines, carrying with it a Prussian nobleman 
 who died before he could be pulled out of the 
 wreckage. The war had been carried into the 
 skies. But if scouts were to fight one another, 
 they could not pay much attention to scouting 
 and spotting and it began to be realized that 
 there were four distinct classes of work for the 
 airplane to do scouting, artillery-spotting, bat- 
 tling, and bombing. Each called for special 
 training and its own type of machine. As air 
 fighting grew more specialized these classes 
 were further subdivided, but we need not go into 
 such refinements. 
 
128 INVENTIONS OF THE GREAT WAR 
 
 AIR SCOUTS AND THEIE DANGERS 
 
 The scouting-airplane usually carried two 
 men, one- to drive -the machine and the other to 
 make observations. The observer had to carry 
 a camera, to take photographs of what lay be- 
 low, and he was usually equipped with a wire- 
 less outfit, with which he could send important 
 information back to his own base. The camera 
 was sometimes fitted with a stock like that of 
 a gun, so that it could be aimed from the 
 shoulder. Some small cameras were shaped so 
 that they could be held in the hand like a pistol 
 and aimed over the side of the fuselage, or body, 
 of the airplane ; but the best work was done with 
 large cameras fitted with telescopic lenses, or 
 "telephoto" lenses, as they are called. Some 
 of these were built into the airplane, with the 
 lens opening down through the bottom of the 
 fuselage. 
 
 The scouting-airplane carried a machine-gun, 
 not for attack, but for defense. It had to be a 
 quick climber and a good dodger, so that it 
 could escape from an attacking plane. Usually 
 it did not have to go very far into the enemy 
 country, and it was provided with a large wing- 
 
How an object dropped from the Woolworth Building would 
 increase its speed in falling 
 
THE WAfc IN THE AIR 
 
 spread, so that if anything happened to the 
 engine, it could volplane, or glide back, to its 
 own lines. As the scouting-planes were large, 
 they offered a big target to anti-aircraft guns, 
 and so the work of the air scout was to swoop 
 down upon the enemy, when, of course, the 
 machine would be traveling at high velocity, 
 because it would have all the speed of falling 
 added to that which its own propeller gave it. 
 
 It was really a very difficult matter to hit a 
 rapidly moving airplane; and even if it were 
 hit, there were few spots in which it could be 
 mortally wounded. Hundreds of shots could go 
 through the wings of an airplane without im- 
 pairing its flying in the least. The engine, too, 
 could be pretty well peppered with ordinary 
 bullets without being disabled. As for -the men 
 in the machine, they furnished small targets, 
 and even they could be hit in many places with- 
 out being put entirely out of business. And so 
 the dangers of air scouting were not so great 
 as might at first be supposed. 
 
 One of the most vulnerable spots in the air- 
 plane was the gasolene tank. If that were 
 punctured so that the fuel would run out, the 
 airplane would have to come to the ground. 
 
130 INVENTIONS OF THE GREAT WAR 
 
 Worse still, the gasolene might take fire and 
 there was nothing the aviator dreaded more 
 than fire. There were occasions in which he had 
 to choose between leaping to earth and burn- 
 ing to death, and the former was usually pre- 
 ferred as a quicker and less painful death. 
 In some of the later machines the gasolene-tank 
 could be pitched overboard if it took fire, by the 
 throwing of a lever, and then the aviator could 
 glide to earth in safety. 
 
 THE SELF-HEALING GASOLENE-TANK 
 
 One of the contributions which we made to 
 military aeronautics was a gasolene-tank that 
 was puncture-proof. It was made of soft rub- 
 ber with a thin lining of copper. There are 
 some very soft erasers on the market through 
 which you can pass a lead pencil and never find 
 the hole after it has passed through, because 
 the rubber has closed in and healed the wound. 
 Such was the rubber used in the gasolene-tank. 
 It could be peppered with bullets and yet would 
 not leak a drop of gasolene, unless the bullet 
 chanced to plow along the edge of the tank 
 and open a long gash. 
 
 The Germans used four different kinds of 
 
THE WAR IN THE AIR 131 
 
 cartridges in their aircraft guns. The first 
 carried the ordinary bullet, a second type had 
 for its bullet a shell of German silver filled with 
 a phosphor compound. This was automatically 
 ignited through a small opening in the base of 
 the shell when it was fired from the gun and it 
 left a trail of smoke by which the gunner could 
 trace its course through the air and correct his 
 aim. At night the bright spot of light made 
 by the burning compound would serve the same 
 purpose. Such a bullet, if it hit an ordinary 
 gasolene-tank, would set fire to its contents. 
 The bullet would plow through the tank and out 
 at the opposite side and there, at its point of 
 exit, is where the gasolene would be set on 
 fire. Such incendiary bullets were repeatedly 
 fired into or through the rubber tanks and the 
 hole would close behind the bullet, preventing 
 the contents from taking fire. The two other 
 types of bullets referred to were an explosive 
 bullet or tiny shell which would explode on 
 striking -the target and a perforating steel bul- 
 let which was intended to pierce armor or pene- 
 trate into vital parts of an airplane engine. 
 
 Machines with which artillery-spotting was 
 done were usually manned by a pilot and an ob- 
 
132 INVENTIONS OF THE GREAT WAR 
 
 server, so that the latter could devote his entire 
 attention to noting the fire of the guns and 
 signaling ranges without being hampered by 
 having to drive the machine. These machines 
 were usually of the pusher type, so that the ob- 
 server could have an unobstructed view. They 
 did not have to be fast machines. It was really 
 better for them to move slowly. Had it been 
 possible for them to stop altogether and hover 
 over the spot that was being shelled, it would 
 have been a distinct advantage. That would 
 have given the observer a chance to note with 
 better accuracy the fall of the shell. Like the 
 scout, -the spotter had to be a fast climber, so 
 that it could get out of the range of enemy guns 
 and run away from attacking planes. 
 
 GIANTS OF THE SKY 
 
 The largest war-planes were the bomb-drop- 
 ping machines. They had to be capable of 
 carrying heavy loads of explosives. They were 
 usually slow machines, speed being sacrificed 
 in carrying-capacity. 
 
 The Germans paid a great deal of attention 
 to big bomb-dropping machines, particularly 
 after their Zeppelins proved a failure. Their 
 
THE WAR IN THE AIR 133 
 
 huge Gothas were built to make night raids on 
 undefended cities. The Italians and the British 
 retaliated with machines that were even larger. 
 At first the French were inclined to let giant 
 planes alone. They did not care to conduct 
 long-distance bombing-raids on German cities 
 because their own important cities were so near 
 the battle-front that the Germans could have 
 done those places more harm than the French 
 could have inflicted. Later they built some 
 giant machines, although not so large as those 
 of the Italians and the British. 
 
 The large triplane Capronis built by the 
 Italians held a crew of three men. They were 
 armed with three guns and carried 2750 pounds 
 of explosives. That made a useful load of 4000 
 pounds. The machine was driven by three en- 
 gines with a total of 900 horse-power. 
 
 The big British plane was the Handley-P-age, 
 which had a wing-spread of 125 feet and could 
 carry a useful load of three tons. These enor- 
 mous machines conducted their raids at night 
 because they were comparatively slow and could 
 not defend themselves against speedy battle- 
 planes. The big Italian machines used * i search- 
 light " bombs to help them locate important 
 
134 INVENTIONS OF THE GREAT WAR 
 
 points on the ground beneath. These were 
 brilliant magnesium torches suspended from 
 parachutes so that they would fall slowly and 
 give a broad illumination, while the airplane it- 
 self was shielded from the light by the para- 
 chute. 
 
 But these giants were not the only bombing- 
 machines. There were smaller machines that 
 operated over the enemy's battle-line and 
 dropped bombs on any suspicious object behind 
 the enemy lines. These machines had to be con- 
 voyed by fast battle-planes which fought off 
 hostile airmen. 
 
 HOW FAST IS A HUNDRED AND FIFTY MILES 
 PER HOUR? 
 
 In naval warfare the battle-ship is the big- 
 gest and heaviest ship of the fleet, but in the 
 air the battle-planes are the lightest and the 
 smallest of the lot. They are one-man ma- 
 chines, as a rule, little fellows, but enormously 
 speedy. Speed is such an important factor in 
 aerial warfare that there was a continuous 
 struggle between the opposing forces to pro- 
 duce the faster machine. Airplanes were con- 
 stantly growing speedier, until a speed of 150 
 
THE WAR IN THE AIR 135 
 
 miles per hour was not an uncommon rate of 
 travel. It is hard to imagine such a speed as 
 that, but we may gain some idea if we consider 
 a falling object. The observation platform of 
 the Woolworth Building, in New York, is about 
 750 feet above 'the ground. If you should drop 
 an object from this platform you would start 
 it on a journey that would grow increasingly 
 speedy, particularly as it neared the ground. 
 By the time it had dropped from the sixtieth 
 story to the fifty-ninth it would have attained a 
 speed of nearly 20 miles per hour. (We are not 
 making any allowances for the resistance of the 
 air and what it would do to check the speed.) As 
 it passed the fiftieth story it would be traveling 
 as fast as an express-train, or 60 miles per hour. 
 It would finally reach the ground with a speed 
 equal to that of a fast battle-plane 150 miles 
 per hour. 
 
 The battle-plane was usually fitted with a 
 single machine-gun that was fixed to the air- 
 plane, so that it was brought to bear on the 
 target by aiming the entire machine. In this the 
 plane was something like a submarine, which 
 must point its bow at its intended victim in or- 
 der to aim its torpedo. The operator of the bat- 
 
136 INVENTIONS OF THE GREAT WAR 
 
 tie-plane simply drove his machine at the enemy 
 and touched a button on his steering-lever to 
 start his machine-gun going. 
 
 SHOOTING THROUGH THE PROPELLER 
 
 Now, the fleetest machines and the most easily 
 maneuvered are those of the tractor type, that 
 is, the ones which have the propeller in front; 
 but having the propeller in front is a handicap 
 for a single-seater machine, for the gun has to 
 be fired through the propeller and the bullets 
 are sure to hit the propeller-blades. Neverthe- 
 less the French did fire right through the pro- 
 peller, regardless of whether or not the blades 
 were hit; but at the point where they came in 
 line with the fire of the gun they were armored 
 with steel, so that there was no danger of their 
 being cut by the bullets. It was calculated that 
 not more than one bullet in eighteen would strike 
 the propeller-blade and be deflected from its 
 course, which was a very trifling loss ; neverthe- 
 less, it was a loss, and on this account a mechan- 
 ism was devised which would time the opera- 
 tions of the machine-gun so that the shots would 
 come only when the propeller-blades were clear 
 of the line of fire. 
 
Machine Gun mounted to Fire over the Blades of the Propeller 
 
 Courtesy of "Scientific American " 
 
 Mechanism for Firing Between the Blades of the Propeller 
 
 The cam B on the propeller shaft lifts the rod C, rocking the angle 
 lever D which moves the rod E and operates the firing-piece F. 
 Firing may be stopped by means of lever Hand Bowden wire G. 
 I is the ejection-tube for empty cartridges. 
 
I 
 
 Si 
 
THE WAR IN THE AIR 137 
 
 A cam placed on the propeller-shaft worked 
 the trigger of the machine-gun. This did not 
 slow up the fire of the machine-gun. Quite the 
 contrary. We are apt to think of the fire of the 
 machine-guns as very rapid, but they usually 
 fire only about five hundred rounds per minute, 
 while an airplane propeller will make something 
 like twelve hundred revolutions per minute. 
 And so the mechanism was arranged to pull the 
 trigger only once for every two revolutions of 
 the propeller. 
 
 FIGHTING AMONG THE CLOUDS 
 
 There was no service of the war that began to 
 compare with that of the sky fighter. He had 
 to climb to enormous heights. Air battles took 
 place at elevations of twenty thousand feet. 
 The higher the battle-plane could climb, the bet- 
 ter, because the man above had a tremendous 
 advantage. Clouds were both a haven and a 
 menace to him. At any moment an enemy plane 
 might burst out of the cloufds upon him. He 
 had to be ready to go through all the thrilling 
 tricks of a circus performer so as to dodge the 
 other fellow and get a commanding position. 
 Jf he were getting ttye worst of it, he might 
 
138 INVENTIONS OF THE GREAT WAR 
 
 feign death and let his machine go tumbling and 
 fluttering down for a thousand feet or so, only 
 to recover his equilibrium suddenly and dart 
 away when the enemy was thrown off his guard. 
 He might escape into some friendly cloud, but 
 he dared not hide in it very long, lest he get 
 lost. 
 
 It is a peculiar sensation that comes over an 
 aviator when he is flying through a thick mass 
 of clouds. He is cut off from the rest of the 
 world. He can hear nothing but the terrific 
 roar of his own motor and the hurricane rush 
 of the wind against his ears. He can see 
 nothing but the bluish fog of the clouds. He 
 begins to lose all sense of direction. His com- 
 pass appears to swing violently to and fro, when 
 really it is his machine that is zig-zagging under 
 his unsteady guidance. The more he tries to 
 steady it, the worse becomes the swing of the 
 compass. As he turns he banks his machine 
 automatically, just as a bicyclist does when 
 rounding a corner. He does this unconsciously, 
 and he may get to spinning round and round, 
 with his machine standing on its side. In some 
 cases aviators actually emerged from the clouds 
 with their machines upside down. To be sure, 
 
THE WAR IN THE AIR 139 
 
 this was not an alarming position for an expe- 
 rienced aviator ; at the same time, it was not al- 
 together a safe one. A machine was some- 
 times broken by its operator's effort to right it 
 suddenly. And so while the clouds made handy 
 shelters, they were not always safe harbors. 
 
 To the battle-plane fell the task of clearing 
 the air of the enemy. If the enemy's battle- 
 planes were disposed of, his bombing-planes, 
 his spotters, and his scouts could not operate, 
 and he would be blind. And so each side tried 
 to beat out the other with speedier, more power- 
 ful, and more numerous battle-planes. Fast 
 double-seaters were built with guns mounted so 
 that they could turn in any direction. 
 
 THE FLYING TANK 
 
 The Germans actually built an armored bat- 
 tle-plane known as the flying tank. It was a 
 two-seater intended mainly for attacking in- 
 fantry and was provided with two machine- 
 guns that pointed down through the floor of the 
 fuselage. A third gun mounted on a revolving 
 wooden ring could be used to fight off hostile 
 planes. The bottom and sides of the fuselage 
 or body of the airplane from the gunner's cock- 
 
140 INVENTIONS OF THE GREAT WAK 
 
 pit forward were sheathed with plates of steel 
 armor. The machine was a rather cumbersome 
 craft and did not prove very successful. A fly- 
 ing tank was brought down within the American 
 lines just before the signing of the armistice. 
 
 AMERICA'S HELP 
 
 Our own contribution to the war in the air 
 was considerable, but we had hardly started be- 
 fore the armistice brought the fighting to an 
 end. Before we entered the war we did not 
 give the airplane any very serious considera- 
 tion. To be sure, we built a large number of 
 airplanes for the British, but they were not 
 good enough to be sent to the front ; they were 
 used merely as practice planes in the British 
 training-schools. We knew that we were hope- 
 lessly outclassed, but we did not care very 
 much. Then we stepped into the conflict. 
 
 "What, can we do to help?" we asked our 
 allies, and their answer gave us a shock. 
 
 " Airplanes !" they cried. " Build us air- 
 planes thousands of them so that we can 
 drive the enemy out of the air and blind his 
 armies!" 
 
 It took us a while to recover from our sur- 
 
THE WAR IN THE AIR 141 
 
 prise, and then we realized why we had been 
 asked to build airplanes. The reputation of the 
 United States as a manufacturer of machinery 
 had spread throughout the world. We Ameri- 
 cans love to take hold of a machine and turn it 
 out in big quantities. Our allies were sure that 
 we could turn out first-class airplanes, and many 
 of them, if we tried. 
 
 Congress made an appropriation of six hun- 
 dred and forty million dollars for aeronautics, 
 and then things began to hum. 
 
 A BIRTHDAY PRESENT TO THE NATION 
 
 The heart of an airplane is its engine. We 
 know a great deal about gasolene-engines, es- 
 pecially automobile engines ; but an airplane en- 
 gine is a very different thing. It must be tre- 
 mendously powerful, and at the same time ex- 
 tremely light. Every ounce of unnecessary 
 weight must be shaved off. It must be built 
 with the precision of a watch; its vital parts 
 must be true x o a ten-thousandth part of an inch. 
 It takes a very powerful horse to develop one 
 horse-power for a considerable length of time. 
 It would take a hundred horses to supply the 
 power for even a small airplane, and they would 
 
142 INVENTIONS OF THE GREAT WAR 
 
 weigh a hundred and twenty thousand pounds. 
 An airplane motor of the same power would 
 weigh less than three hundred pounds, which is 
 a quarter of the weight of a single horse. It 
 was this powerful, yet most delicate, machine 
 that we were called upon to turn out by the thou- 
 sand. There was no time to waste; a motor 
 must be designed that could be built in the 
 American way, without any tinkering or fussy 
 hand-work. 
 
 Two of our best engineers met in a hotel in 
 Washington on June 3, 1917, and worked for 
 five days without once leaving their rooms. 
 They had before them all the airplane knowl- 
 edge of our allies. American engine-builders 
 offered up their trade secrets. Everything was 
 done to make this motor worthy of America's 
 reputation. There was a race to have the mo- 
 tor finished by the Fourth of July. Sure 
 enough, on Independence Day the finished motor 
 was there in Washington the "Liberty mo- 
 tor, " a birthday present to the nation. 
 
 Of course that did not mean that we were 
 ready at once to turn out Liberty motors by the 
 thousand. The engine had to undergo many 
 tests and a large number of alterations before it 
 
THE WAR IN THE AIR 143 
 
 was perfectly satisfactory and then special ma- 
 chinery had to be constructed before it could 
 be manufactured in quantity. It was Thanks- 
 giving Day before the first manufactured Lib- 
 erty was turned out and even after that change 
 upon change was made in this little detail and 
 that. It was not until a year after we went to 
 war that the engine began to be turned out in 
 quantity. 
 
 There was nothing startlingly new about the 
 engine. It was a composite of a number of 
 other engines, but it was designed to be turned 
 out in enormous quantities, and it was remark- 
 ably efficient. It weighed only 825 pounds and 
 it developed over 420 horse-power. Some ma- 
 chines went up as high as 485 horse-power. An 
 airplane engine weighing less than 2 pounds per 
 horse-power is wonderfully efficient. Of course 
 the Liberty was too heavy for a light battle- 
 plane (a heavy machine, no matter how power- 
 ful, cannot make sharp turns), but it was ex- 
 cellent for other types of airplanes and large 
 orders for Liberty engines were made by our 
 allies. Of course we made other engines as 
 well, and the planes to carry them. We built 
 large Caproni and Handley-Page machines, and 
 
144 INVENTIONS OF THE GEEAT WAR 
 
 we were developing some remarkably swift and 
 powerful planes of our own when the Germans 
 thought it about time to stop fighting. 
 
 FLYING BOATS 
 
 So far we have said nothing about the sea- 
 planes which were used in large numbers to 
 watch for submarines. These were big flying 
 boats in which speed was not a very important 
 matter. One of the really big machines we de- 
 veloped, but which was not finished until after 
 the war, was a giant with a 110-foot span and 
 a body or hull 50 feet long. During the war 
 seaplanes carried wireless telephone apparatus 
 with which they could call to destroyers and sub- 
 marine-chasers when they spotted a submarine. 
 They also carried bombs which they could drop 
 on U-boats, and even heavy guns with which 
 they could fire shell. 
 
 A still later development are the giant planes 
 of. the N. C. type with a wing-spread of 126 
 feet and driven by four Liberty motors. They 
 carry a useful load of four and a half tons. 
 
 Early in the war, large guns were mounted 
 on airplanes, but the shock of the recoil proved 
 too much for the airplane to stand. However, 
 
C) Uriderwood & Underwood 
 
 The Flying-tank an Armored German Airplane designed 
 for firing on troops on the march 
 
THE WAR IN THE AIR 145 
 
 an American inventor produced a gun which 
 had no recoil. This he accomplished by using 
 a double-end gun, which was fired from the mid- 
 dle. The bullet or shell was shot out at the 
 forward end of the gun and a dummy charge 
 of sand was shot out at the rear end. The sand 
 spread out and did no damage at a short dis- 
 tance from the gun, but care had to be taken 
 not to come too close. These non-recoil guns 
 were made in different sizes, to fire 1%-inch to 
 3-inch shell. 
 
 THE AUTOMATIC SEAPLANE 
 
 Another interesting development was the tar- 
 get airplane used for the training of aerial gun- 
 ners. This was a small seaplane with a span 
 of only 18y 2 feet, driven by a 12-horse-power 
 motor, the whole machine weighing but 175 
 pounds. This was sent up without a pilot and 
 it would fly at the rate of forty to fifty miles 
 per hour until its supply of gasolene gave out, 
 when it would drop down into the sea. It af- 
 forded a real target for gunners in practice 
 machines. 
 
 Early in the war an American inventor pro- 
 posed that seaplanes be provided with torpedoes 
 
146 INVENTIONS OF THE GREAT WAR 
 
 which they could launch at an enemy ship. The 
 seaplane would swoop down out of the sky to 
 within a short distance of the ship, drop its pro- 
 jecticle, and fly off again, and the torpedo would 
 continue on its course until it blew up the vessel. 
 It was urged that a fleet of such seaplanes pro- 
 tected by a convoy of fast battle-planes could 
 invade the enemy harbors and destroys its pow- 
 erful fleet. It seemed like a rather wild idea, 
 but the British actually built such torpedo- 
 planes and tested them. However, the German 
 fleet surrendered before it was necessary to 
 blow it up in such fashion. 
 
 AIRPLANES AFTER THE WAR 
 
 With the war ended, all the Allied powers 
 have large numbers of airplanes on their hands 
 and also large numbers of trained aviators. 
 Undoubtedly airplanes will continue to fill the 
 skies in Europe and we shall see more and more 
 of them in this country. Even during the war 
 they were used for other purposes than fighting. 
 There were ambulances on wings machines 
 with the top of the fuselage removable so that 
 a patient on a stretcher could be placed inside. 
 A French machine was furnished with a com- 
 
THE WAR IN THE AIR 147 
 
 plete hospital equipment for emergency treat- 
 ment and even for performing an operation in 
 case of necessity. The flying hospital could 
 carry the patient back to the field or base hos- 
 pital after treatment. 
 
 Mail-carrying airplanes are already an old 
 story. In Europe the big bombing-machines 
 are being used for passenger service between 
 cities. There is an air line between Paris and 
 London. The airplanes carry from a dozen to 
 as many as fifty passengers on a single trip. In 
 some cities here, as well as abroad, the police 
 are being trained to fly, so that they can police 
 the heavens when the public takes to wings. 
 Evidently the flying-era is here. 
 
CHAPTER VIII 
 
 SHIPS THAT SAIL THE SKIES 
 
 SHORTLY after the Civil War broke out, 
 Thaddeus S. C. Lowe, an enthusiastic 
 American aeronaut, conceived the idea of send- 
 ing up scout balloons to reconnoiter the posi- 
 tion of the enemy. These balloons were to be 
 connected by telegraph wires with the ground, 
 so that they could direct the artillery fire. The 
 idea was so novel to the military authorities of 
 that day that it was not received with favor. 
 Balloons were looked upon as freak inventions, 
 entirely impracticable for the stern realities 
 of war ; and as for telegraphing from a balloon, 
 no one had ever done that before. 
 
 But this enthusiast was not to be daunted, 
 and he made a direct appeal to President Lin- 
 coln, offering to prove the practicability of this 
 means of scouting. So he took his balloon to 
 Washington and made an ascent from the 
 grounds of the Smithsonian Institution, while 
 
 148 
 
eourtesy ot "Scientific American " 
 
 Observation Car lowered from a Zeppelin sailing 
 above the clouds 
 
SHIPS THAT SAIL THE SKIES 149 
 
 the President came out on the lawn south of the 
 White House to watch the demonstration. In 
 order to test him, Mr. Lincoln took off his hat, 
 waved his handkerchief, and made other signals. 
 Lowe observed each act through his field-glasses 
 and reported it to the President by telegraph. 
 Mr. Lincoln was so impressed by the demonstra- 
 tion that he ordered the army to use the ob- 
 servation balloon, and so with some reluctance 
 the gas-bag was introduced into military serv- 
 ice, Professor Lowe being made chief aeronautic 
 engineer. Under Lowe's direction the observa- 
 tion balloons played an important part in the 
 operations of the Union Army. 
 
 On one occasion a young German military 
 attache begged the privilege of making an as- 
 cent in the balloon. Permission was given and 
 when the German officer returned to earth he 
 was wildly enthusiastic in praise of this aerial 
 observation post. He had had a splendid view 
 of the enemy and could watch operations 
 through his field-glasses which were of utmost 
 importance. Realizing the military value of 
 the aircraft, he returned to Germany and urged 
 military authorities to provide themselves with 
 captive balloons. This young officer was Count 
 
150 INVENTIONS OF THE GREAT WAR 
 
 Ferdinand von Zeppelin, who was destined later 
 to become the most famous aeronautic authority 
 in the world and who lived to see Germany 
 equipped with a fleet of balloons which were 
 self-propelling and could travel over land and 
 sea to spread German frightfulness into Eng- 
 land. He also lived to see the virtual failure 
 of this type of war-machine in the recent great 
 conflict, and it was possibly because of his deep 
 disappointment at having his huge expensive 
 airships bested by cheap little airplanes that 
 Count von Zeppelin died in March, 1917. How- 
 ever, he was spared the humiliation of seeing a 
 fleet of Zeppelins lose their way in a fog and 
 fall into France, one of them being captured be- 
 fore it could be destroyed, so that all its secrets 
 of construction were learned by the French. 
 
 THE WEIGHT OF HYDROGEN 
 
 Before we describe the Zeppelin airships and 
 the means by which they were eventually over- 
 come, we must know something about the prin- 
 ciples of balloons. Every one knows that bal- 
 loons are kept up in the air by means of a very 
 light gas, but somehow the general public fails 
 to understand why the gas should hold it up. 
 
SHIPS THAT SAIL THE SKIES 151 
 
 Some people have a notion that there is some- 
 thing, mysterious about hydrogen gas which 
 makes it resist the pull of gravity, and that the 
 more hydrogen you crowd into the balloon the 
 more weight it will lift. But hydrogen has 
 weight and feels the pull of gravity just as air 
 does, or water, or lead. The only reason the 
 balloon rises is because it weighs less than the 
 air it displaces. It is hard to think of air 
 as having weight, but if we weigh air, hydrogen, 
 coal-gas, or any other gas, in a vacuum, it will 
 tip the scales just as a solid would. A thousand 
 cubic feet of air weighs 80 pounds. In other 
 words, the air in a room ten feet square with a 
 ceiling ten feet high, weighs just about 80 
 pounds. The same amount of coal-gas weighed 
 in a vacuum would register only 40 pounds; 
 while an equal volume of hydrogen would weigh 
 only 51/2 pounds. But when we speak of vol- 
 umes of gas we must remember that gas, unlike 
 a liquid or a solid, can be compressed or ex- 
 panded to almost any dimensions. For in- 
 stance, we could easily fill our room with a ton 
 of air if the walls would stand the pressure ; or 
 we could pump out the air, until there were but 
 a few ounces of air left. But in one case the 
 
152 INVENTIONS OF THE GREAT WAR 
 
 air would be so highly compressed that it would 
 exert a pressure of about 375 pounds on every 
 square inch of the wall of the room, while in 
 the other case its pressure would be almost in- 
 finitesimal. But 80 pounds of air in a room 
 of a thousand cubic feet would exert the same 
 pressure as the atmosphere, or 15 pounds on 
 every square inch. And when we say that a 
 thousand cubic feet of hydrogen weighs only a 
 little over 5 pounds, we are talking about hydro- 
 gen at the same pressure as the atmosphere. 
 
 Since the hydrogen is sixteen times lighter 
 than air, naturally it will float in the air, just as 
 a piece of wood will float in water because it is 
 lighter than the same volume of water. If we 
 surrounded the thousand cubic feet of hydro- 
 gen with a bag so that the gas will not diffuse 
 into the air and mix with it, we shall have a 
 balloon which would float in air provided the bag 
 and the hydrogen it contains do not weigh more 
 than eighty pounds. As we rise from the sur- 
 face of the earth, the air becomes less and less 
 dense, or, in other words, it becomes lighter, 
 and the balloon will keep on rising through the 
 atmosphere until it reaches a point at which its 
 
SHIPS THAT SAIL THE SKIES 153 
 
 weight, gas-bag and all, is exactly the same as 
 that of an equal volume of air. 
 
 But there are many conditions that affect the 
 height to which the balloon will ascend. The 
 higher we rise, the colder it is apt to become, 
 and cold has a tendency to compress the hydro- 
 gen, collapsing the balloon and making it rela- 
 tively heavier. When the sun beats upon a bal- 
 loon, it heats the hydrogen, expanding it and 
 making it relatively lighter, and if there is 
 no room for this expansion to take place in the 
 bag, the bag will burst. For this reason, a big 
 safety-valve must be provided and the ordinary 
 round balloon is open at the bottom so that the 
 hydrogen can escape when it expands too much 
 and the balloonist carries ballast in the form of 
 sand which he can throw over to lighten the 
 balloon when the gas is contracted by a sudden 
 draft of cold air. 
 
 Although a round balloon carries no engine 
 and no propeller, it can be guided through the 
 air to some degree. When an aeronaut wishes 
 to go in any particular direction, he sends up 
 his balloon by throwing out ballast or lowers it 
 by letting out a certain amount of gas, until 
 
154 INVENTIONS OF THE GKEAT WAR 
 
 he reaches a level at which he finds a breeze 
 blowing in the desired direction. Such was 
 the airship of Civil War times, but for mili- 
 tary purposes it was not advisable to use free 
 balloons, because of the difficulty of controlling 
 them. They were too liable to fall into the 
 hands of the enemy. All that was needed was 
 a high observation post from which the enemy 
 could be watched, and from which observations 
 could be reported by telegraph. The balloon 
 was not looked upon as a fighting-machine. 
 
 ZEPPELIN'S FAILURES AND SUCCESSES 
 
 But Count Zeppelin was a man of vision. He 
 dreamed of a real ship of the air a machine 
 that would sail wherever the helmsman chose, 
 regardless of wind and weather. Many years 
 elapsed before he actually began to work out 
 his dreams, and then he met with failure after 
 failure. He believed in big machines and the 
 loss of one of his airships meant the waste of 
 a large sum of money, but he persisted, even 
 though he spent all his fortune, and had to go 
 heavily in debt. Every one thought him a crank 
 until he built his third airship and proved its 
 worth by making a trip of 270 miles. At once 
 
SHIPS THAT SAIL THE SKIES 155 
 
 the German Government was interested and saw 
 wonderful military possibilities in the new craft. 
 The Zeppelin was purchased by the government 
 and money was given the inventor to further his 
 experiments. 
 
 That was not the end of his failures. Before 
 the war broke out, thirteen Zeppelins had been 
 destroyed by one accident or another. Evi- 
 dently the building of Zeppelin airships was not 
 a paying undertaking, although they were used 
 to carry passengers on short aerial voyages. 
 But the government made up money losses and 
 Zeppelin went on developing his airships. 
 
 Of course, he was not the only one to build 
 airships, nor even the first -to build a dirigible. 
 The French built some large dirigibles, but 
 they failed to see any great military advantage 
 in ships that could sail through the air, par- 
 ticularly after the airplane was invented, and 
 so it happened that when the war started the 
 French were devoting virtually all their ener- 
 gies to the construction of speedy, powerful 
 airplanes. As for the British, they did not pay 
 much attention to airships. The idea that their 
 isles might be attacked from the sky seemed an 
 exceedingly remote possibility. 
 
156 INVENTIONS OF THE GKEAT WAR 
 
 MOID, SEMI-RIGID, AND FLEXIBLE BALLOONS 
 
 Count Zeppelin always held that the dirigible 
 balloons must be rigid, so that they could be 
 driven through the air readily and would hold 
 their shape despite variations in the pressure of 
 the hydrogen. The French, on the other hand, 
 used a semi-rigid airship ; that is, one in which a 
 flexible balloon is attached to a rigid keel or 
 body. The British clung to the idea of an en- 
 tirely flexible balloon and they suspended their 
 car from the gas-bag without any rigid frame- 
 work to hold the gas-bag in shape. In every 
 case, the balloons were kept taut or distended 
 by means of air-bags or ballonets. These air- 
 bags were placed inside the gas-bags and as the 
 hydrogen expanded it would force the air out 
 through valves, but the hydrogen itself would 
 not escape. When the hydrogen contracted, the 
 air-bags were pumped full of air so as to main- 
 tain the balloon in its fully distended condition. 
 Additional supplies of compressed hydrogen 
 were kept in metal tanks. 
 
 In the Zeppelin balloon, however, the gas was 
 contained in separate bags which were placed in 
 a framework of aluminum covered over with 
 
(C) Underwood & Underwood 
 
 Giant British Dirigible built along the lines of a Zeppelin 
 
 (C) Underwood & Underwood 
 
 One of the engine cars or "power eggs" of a British Dirigible 
 
SHIPS THAT SAIL THE SKIES 157 
 
 fabric. Count Zeppelin did not believe in plac- 
 ing all his eggs in one basket. If one of these 
 balloons burst or was injured in any way, there 
 was enough buoyancy in the rest of the gas-bags 
 to hold up the airship. As the Zeppelins were 
 enormous structures, the framework had to be 
 made strong and light, and it was built up of a 
 latticework of aluminum alloy. Aluminum it- 
 self was not strong enough for the purpose, but 
 a mixture of aluminum and zinc and later an- 
 other alloy known as duralumin, consisting of 
 aluminum with three per cent of copper and 
 one per cent of nickel, provided a very rigid 
 framework that was exceedingly light. Dura- 
 lumin is four or five times as strong as alum- 
 inum and yet weighs but little more. 
 
 The body of the Zeppelin is not a perfect cir- 
 cle in section, but is made up in the form of a 
 polygon with sixteen sides, and the largest of the 
 Zeppelins used during the war contained sixteen 
 compartments, in each of which was placed a 
 large hydrogen gas-bag. A super-Zeppelin, as 
 the latest type is called, was about seventy-five 
 feet in diameter and seven hundred and sixty 
 feet long, or almost as long as three New 
 York street blocks. In its gas-bags it carried 
 
158 INVENTIONS OF THE GREAT WAR 
 
 two million cubic feet of hydrogen and although 
 the whole machine with its fuel, stores, and pas- 
 sengers weighed close to fifty tons, it was so 
 much lighter than the air it displaced that it 
 had a reserve buoyancy of over ten tons. 
 
 KEEPING ENGINES CLEAB OF THE INFLAMMABLE 
 HYDROGEN 
 
 As hydrogen is a very inflammable gas, it is 
 extremely dangerous to have an internal-com- 
 bustion engine operating very near the gas- 
 bags. In the super-Zeppelins the engines were 
 placed in four cars suspended from the balloon. 
 There was one of these cars forward, and one 
 at the stern, while near the center were two cars 
 side by side. In the rear car there were two 
 engines, either of which could be used to drive 
 the propeller. By means of large steering rud- 
 ders and horizontal rudders, the machine could 
 be forced to dive or rise or turn in either direc- 
 tion laterally. The pilot of the Zeppelin had 
 an elaborate operating-compartment from 
 which he could control the rudders, and he also 
 had control of the valves in the ballonets so that 
 by the touch of a button he could regulate the 
 pressure of gas in any part of the dirigible. 
 
SHIPS THAT SAIL THE SKIES 
 
 There were nineteen men in the crew of the 
 Zeppelin two in the operating-compartment, 
 and two in each of the cars containing engines, 
 except for the one at the stern in which there 
 were three men. The other men were placed 
 in what was known as the "cat walk" or pass- 
 ageway running inside the framework under 
 the gas-bags. These men were given various 
 tasks and were supposed to get as much sleep 
 as they could, so as to be ready to replace the 
 other men at need. 
 
 The engine cars at each side of the balloon 
 were known as power eggs because of their gen- 
 eral egg shape. At the center of the Zeppelin 
 the bombs were stored, and there were electro- 
 magnetic releasing-devices operated from the 
 pilot's room by which the pilot could drop the 
 bombs whenever he chose. The Zeppelin also 
 carried machine-guns to fight off airplanes. 
 Gasolene was stored in tanks which were placed 
 in various parts of the machine, any one of 
 which could feed one or all of the engines, and 
 they were so arranged that they could be thrown 
 overboard when the gasolene was used up, so 
 as to lighten the load of the Zeppelin. Water 
 ballast was used instead of sand, and alcohol 
 
160 INVENTIONS OF THE GREAT WAR 
 
 was mixed with the water to keep it from freez- 
 ing. The machine which came down in French 
 territory and was captured before it could be 
 destroyed by the pilot, found itself unable to 
 rise because in the intense cold of the upper 
 air the water ballast had frozen, and it could 
 not be let out to lighten the load of the Zep- 
 pelin. 
 
 THE ZEPPELIN'S TINY ANTAGONISTS 
 
 The one thing above all others that the Zep- 
 pelin commander feared was the attack of air- 
 planes. In the early stages of the war, it was 
 considered unsafe for airplanes to fly by night 
 because of the difficulty of making a landing in 
 the dark. Later this difficulty was overcome by 
 the use of search-lights at the landing-fields. 
 The airplane would signal its desire to land and 
 the search-lights would point out the proper 
 landing-field for it. So that after the first few 
 months of the war Zeppelins were subjected to 
 the danger of airplane attack. Of course, on a 
 dark night it was very difficult for an airplane 
 to locate a Zeppelin, because the huge machine 
 could not be seen and the throb of its engines 
 was drowned out by the engines of the airplane 
 

SHIPS THAT SAIL THE SKIES 161 
 
 itself. Nevertheless, Zeppelins were occa- 
 sionally located and destroyed by airplanes. 
 
 The danger of the Zeppelin lay in the fact 
 that it was supported by an enormous volume 
 of very inflammable gas and the airplane needed 
 but to set fire to this gas to cause the destruc- 
 tion of the giant of the air. And so the ma- 
 chine-guns carried by airplanes were provided 
 with explosive, flaming bullets. A burst of 
 flame within the gas-bag would not set the gas 
 on fire, because there would be no air inside 
 to feed the fire, but surrounding the gas-bag 
 there was always a certain leakage of hydro- 
 gen which would mix with the air in the com- 
 partment and this would produce an explosive 
 mixture which needed but the touch of fire to 
 set it off. The Zeppelin w r as provided with a 
 ventilating-system to carry off these explosive 
 gases, but they could never be disposed of very 
 effectively, and, as a consequence, a number of 
 Zeppelins were destroyed by the tiny antagon- 
 ists that were sent up by the British and the 
 French. To fight off these assailants the Ger- 
 mans provided their Zeppelins with guns which 
 would fire shrapnel shell. It is difficult for a 
 Zeppelin to use machine-guns against an air- 
 
162 INVENTIONS OF THE GREAT WAR 
 
 plane because the latter would merely climb 
 above the Zeppelin and would be shielded by 
 the balloon itself. And so the Germans put a 
 gun emplacement on top of the balloon both 
 forward and aft. There was a deck extending 
 along the top of the balloon which was reached 
 by a ladder running up through the center of 
 the airship. But it was impossible to ward off 
 the fleet little antagonists, once the dirigible wa-s 
 discovered. True, a Zeppelin could make as 
 much as seventy miles per hour, but the fast- 
 est airplanes could travel twice as fast as that. 
 
 SUSPENDING AN OBSERVER BELOW THE ZEPPELIN 
 
 One ingenious scheme that was tried was to 
 suspend an observation car under the Zeppelin. 
 The car was about fourteen feet long and five 
 feet in diameter, fitted with a tail to keep it 
 headed in the direction it was towed. It had 
 glass windows forward and there was plenty of 
 room in it for a man to lie at full length and 
 make observations of things below. The car 
 with its observer could be lowered a few thou- 
 sand feet below the Zeppelin, so that the ob- 
 server could watch proceedings below, while the 
 airship remained hidden among the clouds. 
 
SHIPS THAT SAIL THE SKIES 163 
 
 The observer was connected by telephone with 
 the chart-room of the Zeppelin and could report 
 his discoveries or even act as a pilot to direct 
 the course of the ship. 
 
 But despite everything that could be done, 
 the Zeppelin eventually proved a failure as a 
 war-vessel because it was so very costly to con- 
 struct and operate and could so easily be de- 
 stroyed, and the Germans began to build huge 
 airplanes with which bombing-raids could be 
 continued. 
 
 Strange to say, however, although the Ger- 
 mans were ready to admit the failure of their 
 big airship, when the war stopped the Allies 
 were actually building machines patterned after 
 the Zeppelin, but even larger, and expected to 
 use them for bombing-excursions over Ger- 
 many. This astonishing turn of the tables was 
 due to the fact that America had made a con- 
 tribution to aeronautics that solved the one 
 chief drawback of the Zeppelin. 
 
 A BALLOON GAS THAT WILL NOT BURN 
 
 When we entered the war against Germany, 
 our allies placed before us all their problems 
 and among them was this one of the highly in- 
 
164 INVENTIONS OP THE GREAT WAR 
 
 flammable airship. Could we not furnish a sub- 
 stitute for hydrogen that would not burn? It 
 was suggested to us that helium would do if we 
 could produce thai gas cheaply and in sufficient 
 quantity. Now, helium has a history of its own 
 that is exceedingly interesting. 
 
 Every now and then the moon bobs its head 
 into our light and we have a solar eclipse. But 
 our satellite is not big enough to cut off all 
 the light of the big luminary and the fiery at- 
 mosphere of the sun shows us a brilliant halo 
 all around the black disk of the moon. Long 
 ago, astronomers analyzed this flaming atmos- 
 phere with the spectroscope, and by the differ- 
 ent bands of light that appeared they were able 
 to determine what gases were present in the 
 sun's atmosphere. But there was one band of 
 bright yellow which they could not identify. 
 Evidently this was produced by a gas unknown 
 on earth, and they called it "helium" or "sun" 
 gas. 
 
 For a quarter of a century this sun gas re- 
 mained a mystery; then one day, in 1895, Sir 
 William Ramsay discovered the same band of 
 light when studying the spectrum of the mineral 
 cleveite. The fact that astronomers had been 
 
SHIPS THAT SAIL THE SKIES 165 
 
 able to single out an element on the sun ninety 
 million miles away before our chemists could 
 find it right here on earth, produced a mild sen- 
 sation, but the general public attached no spe- 
 cial importance to the gas itself. It proved 
 to be a very light substance, next to hydrogen 
 the lightest of gases, and for years it resisted 
 all attempts at liquefaction. Only when Onnes, 
 the Dutch scientist, succeeded in getting it down 
 to a temperature of 450 degrees below zero, Fah- 
 renheit, did the gas yield to the chill and con- 
 dense into a liquid. The gas would not burn; 
 it would not combine with any other elements, 
 and apparently it had no use on earth, and it 
 might have remained indefinitely a lazy member 
 of the chemical fraternity had not the great 
 world conflict stirred us into frenzied activity 
 in all branches of science in our effort to beat 
 the Hun. 
 
 Because the gas had no commercial value, 
 there was only a small amount of helium to be 
 found in the whole world. Not a single labora- 
 tory in the United States had more than five 
 cubic feet of it and its price ranged from 
 $1,500 to $6,000 per cubic foot. At the lowest 
 price it would cost $3,000,000,000 to provide gas 
 
166 INVENTIONS OP THE GREAT WAR 
 
 enough for one airship of Zeppelin dimensions 
 and it seemed absurd even to think of a helium 
 airship. 
 
 AMERICAN CHEMISTS TO THE RESCUE 
 
 Just before the war it was discovered that 
 there is a considerable amount of helium in the 
 natural gas of Oklahoma, Texas, and Kansas, 
 and Sir William Ramsey suggested that our 
 chemists might study some method of getting 
 helium from this source. The only way of sep- 
 arating it out was to liquefy the gases by sub- 
 jecting them to extreme cold. All gases turn 
 to liquid if they are cooled sufficiently, and then 
 further cold will freeze them solid. But helium 
 can stand more cold than any other and this 
 fact gave the clue to its recovery from natu- 
 ral gas. The latter was frozen and one after 
 another the different elements condensed into 
 liquid, until finally only helium was left. 
 This sounds simple, but it is a difficult mat- 
 ter to get such low temperature as that on a 
 large scale and do it economically. To be of 
 any real service in aeronautics helium would 
 have to be reduced in cost from fifteen hun- 
 dred dollars to less than ten cents per cubic 
 
SHIPS THAT SAIL THE SKIES 167 
 
 foot. Several different kinds of refrigerating- 
 machinery were tried and finally just before the 
 war was brought to a close by the armistice we 
 had succeeded in producing helium at the rate 
 of eight cents per cubic foot, with the prospect 
 of reducing its cost still further. A large plant 
 for recovering helium was being built. The 
 plant will have been completed before this book 
 is published, and it will be turning out helium 
 for peaceful instead of military airships. 
 
 The reduction in the cost of helium is really 
 one of the most important developments of this 
 war. By removing the fire risk from airships 
 we can safely use these craft for aerial cruises 
 or for quick long-distance travel over land and 
 sea. For, even in time of peace, sailing under 
 millions of cubic feet of hydrogen is a serious 
 matter. Although no incendiary bullets are to 
 be feared, there is always the danger of setting 
 fire to the gas within the exhaust of the engines. 
 Engines have had to be hung in cars well below 
 the balloon proper. But with helium in the gas- 
 bags the engines can be placed inside the bal- 
 loon envelop and the propellers can operate on 
 the center line of the car. 
 
 In the case of one Zeppelin, the hydrogen was 
 
168 INVENTIONS OF THE GREAT WAR 
 
 set on fire by an electric spark produced by fric- 
 tion on the fabric of one of the gas-bags, and so 
 even with the engine exhausts properly screened 
 there is danger. The helium airship, however, 
 would be perfectly safe from fire and passen- 
 gers could smoke on deck or in their cabins 
 within the balloon itself without any more fear 
 of fire than they would have on shipboard. 
 Wonderful possibilities have been opened by the 
 production of helium on a large and economical 
 scale, and the airship seems destined to play 
 an important part in transportation very soon. 
 As this book is going to press, we learn of enor- 
 mous dirigibles about to be built in England for 
 passenger service, which will have half again as 
 great a lifting-power as the largest Zeppelins. 
 The final chapter of the story of dirigibles is yet 
 to be written, but in concluding this chapter it 
 is interesting to note that the world's greatest 
 aeronautic expert got his first inspiration from 
 America and finally that America has now fur- 
 nished the one element which was lacking to 
 make the dirigible balloon a real success. 
 
CHAPTER IX 
 GETTING THE RANGE 
 
 EVERY person with a good pair of eyes in 
 his head is a range-finder. He may not 
 know it, but he is, just the same, and the way to 
 prove it is to try a little range-finding on a small 
 scale. 
 
 Use the top of a table for your field of opera- 
 tions, and pick out some spot within easy reach 
 of your hand for the target whose range you 
 wish to find. The target may be a penny or a 
 small circle drawn on a piece of white paper. 
 Take a pencil in your hand and imagine it is 
 a shell which you are going to land on the 
 target. It is not quite fair to have a bird's-eye 
 view of the field, so get down -on your knees and 
 bring your eyes within a few inches of the top 
 of the table. Now close one eye and making 
 your hand describe an arc through the air, like 
 the arc that a shell would describe, see how 
 nearly you can bring the pencil-point down on 
 
 169 
 
170 INVENTIONS OP THE GREAT WAR 
 
 the center of the target. Do it slowly, so that 
 your eye may guide the hand throughout its 
 course. You will be surprised to find out how 
 far you come short, or overreach the mark. 
 You will have actually to grope for the target. 
 If by any chance you should score a hit on the 
 first try, you may be sure that it is an accident. 
 
 Have a friend move the target around to a 
 different position, and try again. Evidently, 
 with one eye you are not a good range-finder; 
 but now use two eyes and you will score a hit 
 every time. Not only can you land the pencil 
 on the penny, but you will be able to bring it 
 down on the very center of the target. 
 
 The explanation of this is. that when you 
 bring your eyes to bear upon any object that 
 is near by, they have to be turned in slightly, so 
 that both of them shall be aimed directly at 
 that object. The nearer the object, the more 
 they are turned in, and the farther the object, 
 the more nearly parallel are the eyes. Long 
 experience has taught you to gage the distance 
 of an object by the feel of the eyes that is, by 
 the effort your muscles have to make to pull 
 the eyes to a focus and in this way the eyes 
 give you the range of an object. You do not 
 
GETTING THE RANGE 171 
 
 know what the distance is in feet or inches, but 
 you can tell when the pencil-point has moved 
 out until it is at the same focus as the target. 
 The experiment can be tried on a larger scale 
 with the end of a fishing-rod, but here you will 
 probably have to use a larger target. However, 
 there is a limit to which you can gage the range. 
 At a distance of, say, fifteen or twenty feet, a 
 variation of a few inches beyond or this side 
 of the target makes scarcely any change in the 
 focus of the eyes. That is because the eyes are 
 so close together. If they were farther apart, 
 they could tell the range at much greater dis- 
 tances. 
 
 SPREADING THE EYES FAE APART 
 
 Now the ordinary range-finder, used in the 
 army and in the navy, is an arrangement for 
 spreading the eyes apart to a considerable dis- 
 tance. Of course the -eyes are not actually 
 spread, but their vision is. The range-finder is 
 really a double telescope. The barrel is not 
 pointed at an object, but it is held at right angles 
 to it. You look into the instrument at the mid- 
 dle of the barrel and out of it at the two ends. 
 A system of mirrors or prisms makes this pos- 
 
172 INVENTIONS OF THE GREAT WAR 
 
 sible. The range-finder may be a yard or more 
 in length, which is equivalent to spreading your 
 eyes a yard or more apart. Now, the prisms or 
 object-glasses at the ends of the tube are ad- 
 justable, so that they will turn in until they 
 focus directly on the target whose range you 
 wish to find, and the angle through which these 
 glasses are turned gives a measure of the dis- 
 tance of the target. The whole thing is cal- 
 culated out so that the distance in feet, yards, 
 or meters, or whatever the measure may be, is 
 registered on a scale in the range-finder. Ordi- 
 narily only one eye is used to look through the 
 range-finder, because the system of mirrors is 
 set to divide the sight of that one eye and make 
 it serve the purposes of two. That leaves the 
 other eye free to read the scale, which comes 
 automatically into view as the range-finder is 
 adjusted for the different ranges. 
 
 On the battle-ships enormous range-finders 
 are used. Some of them are twenty feet long. 
 With the eyes spread as far apart as that and 
 with a microscope to read the scale, you can 
 imagine how accurately the range can be found, 
 even when the target is miles away. But on 
 land such big range-finders cannot conveniently 
 
GETTING THE RANGE 173 
 
 be used; they are too bulky. When it is neces- 
 sary to get the range of a very distant object, 
 two observers are used who are stationed sev- 
 eral hundred yards apart. These observers 
 have telescopes which they bear upon the ob- 
 ject, and the angle through which they have to 
 turn the telescope is reported by telephone to 
 the battery, where, by a rapid calculation, it is 
 possible to estimate the exact position of the 
 target. Then the gun is moved up or down, to 
 the right or to the left, according to the cal- 
 culation. The observers have to creep as near 
 to the enemy as possible and they must be up 
 high enough to command a good view of the 
 target. Sometimes they are placed on top of 
 telegraph poles or hidden up a tall tree, or in 
 a church steeple. 
 
 GETTING THE OBSERVER OFF THE GROUND 
 
 This was the method of getting the range in 
 previous wars and it was used to a considerable 
 extent in the war we have just been through. 
 But the great European conflict brought out 
 wonderful improvements in all branches of 
 fighting ; and range-finding was absolutely rev- 
 olutionized, because shelling was done at greater 
 
174 INVENTIONS OF THE GREAT WAR 
 
 ranges than ever before, but chiefly because the 
 war was carried up into the sky. 
 
 A bird's-eye observation is much more ac- 
 curate than any that can be obtained from the 
 ground. Even before this war, some observa- 
 tions were taken by sending a man up in a kite, 
 particularly a kite towed from a ship, and even 
 as far back as the Civil War captive balloons 
 were used to raise an observer to a good height 
 above the ground. They were the ordinary 
 round balloons, but the observation balloon of 
 to-day is a very different-looking object. It is 
 a sausage-shaped gas-bag that is held on a slant 
 to the wind like a kite, so that the wind helps 
 to hold it up. To keep it head-on to the wind, 
 there is a big air-bag that curls around the 
 lower end of the sausage. This acts like a rud- 
 der, and steadies the balloon. Some balloons 
 have a tail consisting of a series of cone-shaped 
 cups strung on a cable. A kite balloon will ride 
 steadily in a wind that would dash a common 
 round balloon in all directions. Observers in 
 these kite balloons are provided with telephone 
 instruments by which they can communicate in- 
 stantly with the battery whose fire they are di- 
 recting. But a kite balloon is a helpless object; 
 
GETTING THE RANGE 175 
 
 it cannot fight the enemy. The hydrogen gas 
 that holds it up will burn furiously if set on 
 fire. In the war an enemy airplane had merely 
 to drop a bomb upon it or fire an incendiary bul- 
 let into it, and the balloon would go up in smoke. 
 Nothing could save it, once it took fire, and all 
 the observers could do was to jump for their 
 lives as soon as they saw the enemy close by. 
 They always had parachutes strapped to them, 
 so they could leap without an instant 's delay in 
 case of sudden danger. At the very first ap- 
 proach of an enemy airplane, the kite balloon 
 had to be hauled down or it would surely be de- 
 stroyed, and so kite balloons were not very de- 
 pendable observation stations for the side 
 which did not control the air. 
 
 As stated in the preceding chapter, just be- 
 fore the fighting came to an end, our army was 
 preparing to use balloons that were not afraid 
 of flaming bullets, because they were to be filled 
 with a gas that would not burn. 
 
 MAKING MAPS WITH A CAMERA 
 
 Because airplanes filled the sky with eyes, 
 everything that the army did near the front 
 had to be carefully hidden from the winged 
 
176 INVENTIONS OF THE GREAT WAR 
 
 scouts. Batteries were concealed in the woods, 
 or under canopies where the woods were shot 
 to pieces, or they were placed in dugouts so that 
 they could not be located. Such targets could 
 seldom be found with a kite balloon. It was 
 the task of airplane observers to search out 
 these hidden batteries. The eye alone was not 
 depended upon to find them. Large cameras 
 were used with telescopic lenses which would 
 bring the surface of the earth near while the 
 airplane flew at a safe height. These were 
 often motion-picture cameras which would auto- 
 matically make an exposure every second, or 
 every few seconds. 
 
 When the machine returned from a photo- 
 graphing-expedition, the films were developed 
 and printed, and then pieced together to form a 
 photographic map. The map was scrutinized 
 very carefully for any evidence of a hidden bat- 
 tery or for any suspicious enemy object. As 
 the enemy was always careful to disguise its 
 work, the camera had to be fitted with color- 
 screens which would enable it to pick out de- 
 tails that would not be evident to the eye. As 
 new photographic maps were made from day to 
 day, they were carefully compared one with 
 
GETTING THE RANGE 177 
 
 the other so that it might be seen if there was the 
 slightest change in them which would indicate 
 some enemy activity. As soon as a suspicious 
 spot was discovered, its position was noted on 
 a large-scale military map and the guns were 
 trained upon it. 
 
 CORRECTING THE AIM 
 
 It is one thing to know where the target is and 
 another to get the shell to drop upon it. In the 
 firing of a shell a distance of ten or twenty miles, 
 the slightest variation in the gun will make a 
 difference of many yards in the point where the 
 shell lands. Not only that, but the direction of 
 the wind and the density of the air have a part 
 to play in the journey of the shell. If the shell 
 traveled through a vacuum, it would be a much 
 simpler matter to score a hit by the map alone. 
 But even then there would be some differences, 
 because a gun has to be " warmed up" before it 
 will fire according to calculation. That is why 
 it is necessary to have observers, or " spotters " 
 as they are called, to see where the shell actu- 
 ally do land and tell the gun-pointers whether 
 to elevate or depress the gun, and how much to 
 "traverse" it that is, move it sideways. This 
 
178 INVENTIONS OF THE GREAT WAR 
 
 would not be a very difficult matter if there 
 were only one gun firing, but when a large num- 
 ber of guns are being used, as was almost in- 
 variably the case in the war, the spotter had to 
 know which shell belonged to -the gun he was 
 directing. 
 
 One of the most important inventions of the 
 war was the wireless telephone, which airplanes 
 used and which were brought to such perfection 
 that the pilot of an airplane could talk to a 
 station on the earth without any difficulty, 
 from a distance of ten miles; and in some 
 cases he could reach a range of fifty miles. 
 With the wireless telephone, the observer could 
 communicate instantly with the gun-pointer, 
 and tell him when to fire. Usually -thirty sec- 
 onds were allowed after the signal sent by the 
 observer before the gun was fired, and on the in- 
 stant of firing, a signal was sent to the man in 
 the airplane to be on the lookout for the shell. 
 Knowing the position of the target, the gun- 
 pointer would know how long it would take the 
 shell to travel through the air, and he would 
 keep the man in the airplane posted, warning 
 him at ten seconds, five seconds, and so forth, 
 before the shell was due to land. 
 
GETTING THE RANGE 179 
 
 In order to keep the eyes fresh for observation 
 and not to have them distracted by other sights, 
 the observer usually gazed into space until just 
 before the instant the shell was to land. Then 
 he would look for the column of smoke pro- 
 duced by the explosion of the shell and report 
 back to the battery how far wide of the mark 
 the shell had landed. A number of shell would 
 be fired at regular intervals, say four or five per 
 minute, so that the observer would know which 
 shell belonged to the gun in question. 
 
 There are different kinds of shell. Some 
 will explode on the instant of contact with the 
 earth. These are meant to spread destruction 
 over the surface. There are other shell which 
 will explode a little more slowly and these pene- 
 trate the ground to some extent before going off ; 
 while a third type has a delayed action and is 
 intended to be buried de^ep in the ground before 
 exploding, so as to destroy dugouts and under- 
 ground positions. The bursts of smoke from 
 the delayed-action "shell and the semi-delayed- 
 action shell rise in a slender vertical column and 
 are not so easily seen from the sky. The instan- 
 taneous shell, however, produces a broad burst 
 of smoke which can be spotted much more 
 
180 INVENTIONS OF THE GREAT WAR 
 
 readily, and this enables the man in the air- 
 plane to determine the position of the shell with 
 greater accuracy. For this reason, instantan- 
 eous shell were usually used for spotting-pur- 
 poses, and after the gun had found its target, 
 other shell were used suited to the character of 
 the work that was to be done. 
 
 MINIATURE BATTLE-FIELDS 
 
 Observation of shell-fire from an airplane 
 called for a great deal of experience, and our 
 spotters were given training on a miniature 
 scale before they undertook to do spotting from 
 the air. A scaffolding was erected in the train- 
 ing-quarters over a large picture of a typical bit 
 of enemy territory. Men were posted at the 
 top of this scaffolding so that they could get a 
 bird's-eye view of the territory represented on 
 the map, and they were connected by telephone 
 or telegraph with men below who represented 
 the batteries. The instructor would flash a little 
 electric light here and there on the miniature 
 battle-field, and the observers had to locate these 
 flashes and tell instantly how far they were 
 from certain targets. This taught them to be 
 keen and quick and to judge distance accurately. 
 
GETTING THE RANGE 181 
 
 Airplane observing was difficult and dangerous, 
 and often impossible. On cloudy days the ob- 
 server might be unable to fly at a safe height 
 without being lost in the clouds. Then depend- 
 ence had to be placed upon observers stationed 
 at vantage-points near the enemy, or in kite 
 balloons. 
 
 SPOTTING BY SOUND 
 
 When there is no way of seeing the work of 
 a gun, it is still possible to correct the aim, be- 
 cause the shell can be made to do its own spot- 
 ting. Every time a shell lands, it immediately 
 announces the fact with a loud report. That 
 report is really a message which the shell sends 
 out in all directions with a speed of nearly 800 
 miles per hour 1,142 feet per second, to be 
 exact. This sound-message is picked up by a 
 recorder at several different receiving-stations. 
 Of course it reaches the nearest station a frac- 
 tion of a second before it arrives at the next 
 nearest one. The distance of each station from 
 the 'target is known by careful measurement on 
 the map, and the time it takes for sound to 
 travel from the target to each station is accur- 
 ately worked out. If the sound arrives at each 
 
182 INVENTIONS OF THE GREAT WAR 
 
 station on schedule time, the shell has scored a 
 hit ; but if it reaches one station a trifle ahead 
 of time and lags behind at another, that is evi- 
 dence that the shell has missed the target and a 
 careful measure of the distance in time shows 
 how far and in what direction it is wide of the 
 mark. In this way it was possible to come 
 within fifty or even twenty-five yards of the 
 target. 
 
 This sound-method was also used to locate 
 an enemy battery. It was often well nigh im- 
 possible to locate a battery in any other way. 
 With the use of smokeless powder, there is 
 nothing to betray the position of the gun, ex- 
 cept the flash at the instant of discharge, and 
 even the flash was hidden by screens from the 
 view of an airplane. Aside from this, when an 
 airplane came near enough actually to see one 
 of these guns, the gun would stop firing until the 
 airplane had been driven off. But a big gun 
 has a big voice, and it is impossible to silence 
 it. Often a gun whose position has remained 
 a secret for a long time was discovered because 
 the gun itself " peached. " 
 
 The main trouble with sound-spotting was 
 that there were usually so many shell and guns 
 
GETTING THE RANGE 183 
 
 going off at the same time that it was difficult 
 if not impossible to distinguish one from an- 
 other. Sometimes the voice of a hidden gun 
 was purposely drowned by the noise of a lot of 
 other guns. After all, the main responsibility 
 for good shooting had to fall on observers who 
 could actually see the target, and when we think 
 of the splendid work of our soldiers in the war, 
 we must not forget to give full credit to the 
 tireless men whose duty it was to watch, to 
 the men on wings who dared the fierce battle- 
 planes of the enemy, to the men afloat high in 
 the sky who must leap at a moment's notice 
 from under a blazing mass of hydrogen, and 
 finally to the men who crept out to perilous 
 vantage-points at risk of instant death, in order 
 to make the fire of their batteries tell. 
 
CHAPTER X 
 TALKING IN THE SKY 
 
 IN one field of war invention the United States 
 held almost a monopoly and the progress 
 Americans achieved was epoch-making. 
 
 Before the war, an aviator when on the wing 
 was both deaf and dumb. He could communi- 
 cate with other airplanes or with the ground 
 only by signal or, for short distances, by radio- 
 telegraphy, but he could not even carry on 
 conversation with a fellow passenger in the 
 machine without a speaking-tube fitted to mouth 
 and ears so as to cut out the terrific roar of 
 his own engine. Now the range of his voice 
 has been so extended that he can chat with fel- 
 low aviators miles away. This remarkable 
 achievement and many others in the field of 
 radio-communication hinge upon a delicate elec- 
 trical device invented by Deforest in 1906 and 
 known as the "audion." For years this in- 
 strument was used by radiotelegraphers with- 
 
 184 
 
TALKING IN THE SKY 185 
 
 out a real appreciation of its marvelous possi- 
 bilities, and, as a matter of fact, in its earlier 
 crude form it was not capable of performing the 
 wonders it has achieved since it was taken over 
 and developed by the engineers of the Bell Tele- 
 phone System. 
 
 THE AUDION 
 
 Although the audion is familiar to all ama- 
 teur radio-operators, we shall have to give a 
 brief outline of its construction and operation 
 for the benefit of those who have not had the 
 opportunity to dabble in wireless telegraphy. 
 
 The audion is a small glass bulb from which 
 the air is exhausted to a high degree of vacuum. 
 The bulb contains three elements. One is a 
 tiny filament which is heated to incandescence 
 by a battery, so that it emits negatively charged 
 electrons. The filament is at one side of the 
 bulb and at the opposite side there is a metal 
 plate. When the plate and the filament are 
 connected with opposite poles of a battery, there 
 is a flow of current between them, but because 
 only negative electrons are emitted by the 
 filament, the current will flow only in one di- 
 rection that is, from the plate to the filament 
 
186 INVENTIONS OF THE GREAT WAR 
 
 If the audion be placed in the circuit of an alter- 
 nating-current generator, it will let through 
 only the current running in one direction. 
 Thus it will "rectify" the current or convert 
 alternating current into direct current. 
 
 But the most important part of the audion, the 
 part for which Deforest is responsible, is the 
 third element, which is a grid or flat coil of 
 platinum wire placed between the filament and 
 the plate. This grid furnishes a very delicate 
 control of the strength of the electric current 
 between plate and filament. The slightest 
 change in electric power in the grid will pro- 
 duce large changes of power in the current 
 flowing through the audion. This makes it 
 possible to magnify or amplify very feeble elec- 
 tric waves, and the extent to which the ampli- 
 fying can be carried is virtually limitless, be- 
 cause a series of audions can be used, the cur- 
 rent passing through the first being connected 
 with the grid of the next, and so on. 
 
 TALKING FROM NEW YORK TO SAN FRANCISCO 
 
 There is a limit to which telephone conversa- 
 tions can be carried on over a wire, unless there 
 is some way of adding fresh energy along the 
 
TALKING IN THE SKY 187 
 
 line. For years all sorts of experiments were 
 tried with mechanical devices which would re- 
 ceive a telephone message and send it on with 
 a fresh relay of current. But these devices dis- 
 torted the message so that it was unintelligible. 
 The range of wire telephony was greatly in- 
 creased by the use of certain coils invented by 
 Pupin, which were placed in the line at inter- 
 vals; but still there was a limit to which con- 
 versation could be carried on by wire and it 
 looked as if it would never be possible to tele- 
 phone from one end of this big country of ours 
 to the 'other. But the audion supplied a 
 wonderfully efficient relay and one day we 
 awoke to hear San Francisco calling, " Hello, " 
 to New York. 
 
 Used as a relay, the improved audion made it 
 possible to pick up very faint wireless-tele- 
 graph messages and in that way increased the 
 range of radio outfits. Messages could be re- 
 ceived from great distances without any exten- 
 sive or elaborate aerials, and the audion could 
 be used at the sending-station to magnify the 
 signals transmitted and send them forth with 
 far greater power. 
 
 Having improved the audion and used it sue- 
 
188 INVENTIONS OF THE GREAT WAR 
 
 cessfully for long-distance telephone conversa- 
 tion over wires, the telephone company began 
 to experiment with wireless telephony. They 
 believed that it might be possible to use radio- 
 telephony in places where wires could not be 
 laid. For instance, it might be possible to talk 
 across the Atlantic. 
 
 But before we go farther, just a word of ex- 
 planation concerning radiotelegraphy and radio- 
 telephony for the benefit of those who have 
 not even an elementary knowledge of the 
 subject. 
 
 SIMPLE EXPLANATION OF RADIOTELEGRAPHY 
 
 Suppose we should set up two stakes in a pond 
 of water, at some distance from each other, and 
 around each we set a ring-shaped cork float. If 
 we should move one of these floats up and down 
 on its stake, it would produce ripples in the 
 water which would spread out in all directions 
 and finally would reach the opposite stake and 
 cause the float there to bob up and down in 
 exactly the same way as did the float moved 
 by hand. In wireless telegraphy the two stakes 
 are represented by antennae or aerials and the 
 cork floats are electric charges which are sent 
 
TALKING IN THE SKY 189 
 
 oscillating up and down the antennae. The os- 
 cillations produced at one aerial will set up 
 electro-magnetic waves which will spread out 
 in all directions in the ether until they reach a 
 receiving-aerial, and there they will produce 
 electric oscillations similar to the ones at the 
 transmitting-antenna. 
 
 Telegraph signals are sent by the breaking 
 up of the oscillations at the transmitting-station 
 into long and short trains of oscillations corre- 
 sponding to the dots and dashes of ordinary 
 wire telegraphy. In other words, while the 
 sending-key is held down for a dash, there will 
 be a long series of oscillations in the antenna, 
 and for the dot a short series, and these short 
 and long trains of waves will spread out to the 
 receiving-aerial where they will reproduce the 
 same series of oscillations. But only a small 
 part of the energy will act on the receiving- 
 aerial because the waves like those on the pond 
 spread in all directions and grow rapidly 
 weaker. Hence the advantage of an extremely 
 delicate instrument like the audion to amplify 
 the signals received. 
 
 The oscillations used in wireless telegraphy 
 these days are very rapid, usually entirely too 
 
190 INVENTIONS OF THE GREAT WAR 
 
 rapid, to affect an ordinary telephone receiver, 
 and if they did they would produce a note of 
 such high pitch that it could not be heard. So 
 it is customary to interrupt the oscillations, 
 breaking them up into short trains of waves, 
 and these successive trains produce a note of 
 low enough pitch to be heard in the telephone 
 receiver. Of course the interruptions are of 
 such high frequency that in the sending of a dot- 
 and-dash message each dot is made up of a great 
 many of the short trains of waves. 
 
 Now in radiotelephony it is not necessary to 
 break up the oscillations, but they are allowed to 
 run continuously at very high speed and act as 
 carriers for other waves produced by speaking 
 into the transmitter; that is, a single speech- 
 wave would be made up of a large number 
 of smaller waves. To make wireless tele- 
 phony a success it was necessary to find some 
 way of making perfectly uniform carrier-waves, 
 and then of loading on them waves of speech. 
 Of course, the latter are not sound-waves, be- 
 cause they are not waves of air, but they are 
 electro-magnetic waves corresponding exactly 
 to the sound-waves of air and at the receiving- 
 end they affect the telephone receiver in the 
 
TALKING IN THE SKY 191 
 
 same way that it is affected by the electric 
 waves which are sent over telephone wires. The 
 telephone engineers found that the audion 
 could be used to regulate the carrier-waves and 
 also to superpose the speech-waves upon them, 
 and -at the receiving- station the audion was used 
 to pick up these waves, no matter how feeble 
 they might be, 'and amplify them so that they 
 could be heard in a telephone receiver. 
 
 TALKING WITHOUT WIRES 
 
 Attempts at long-distance talking without 
 wires were made from Montauk Point, on the 
 tip of Long Island, to Wilmington, Delaware, 
 and they were successful. This was in 1915. 
 The apparatus was still further improved and 
 then the experiment was tried of talking from 
 the big Arlington station near Washington to 
 Darien, on the Isthmus of Panama. This was 
 a distance of twenty-one hundred miles, and 
 speech was actually transmitted through -space 
 over that great distance. That having proved 
 successful, the next attempt was to talk from 
 Arlington to Mare Island and San Diego, on the 
 Pacific Coast, a distance of over twenty-five 
 hundred miles. This proved a success, too, and 
 
192 INVENTIONS OF THE GREAT WAR 
 
 it was found possible even to talk as far as 
 Honolulu. 
 
 The engineers now felt confident that they 
 could talk across the Atlantic to Europe, and 
 so in October of 1915 arrangements were made 
 to conduct experiments between Arlington and 
 the Eiffel Tower in Paris. Although the war 
 was at its height, and the French were strain- 
 ing every effort to hold back the Germans at 
 that time, and although there were constant de- 
 mands for the use of radiatelegraphy, the 
 French showed such an appreciation of science 
 that they were willing to lend their aid to these 
 experiments. The Eiffel Tower could be used 
 only for short periods of time, and there was 
 much interference from other high-powered 
 stations. Nevertheless, the experiment proved 
 perfectly successful, and conversation was car- 
 ried on between our capital and that of France, 
 a distance of thirty-six hundred miles. At the 
 same time, an operator in Honolulu, forty-five 
 hundred miles away, heard the messages, and 
 so the voice at Arlington carried virtually one 
 third of the way around the globe. After that 
 achievement, there was a lull in the wireless- 
 telephone experiments because of the war. 
 
(C) G. V. Buck 
 
 Radio Head-gear of an Airman 
 
 (C) G. V. Buck 
 
 Carrying on Conversation by Radio with an Aviator 
 Miles Away 
 
TALKING IN THE SKY 193 
 
 But there soon came an opportunity to make 
 very practical use of all the experimental work. 
 As soon as there seemed to be a possibility that 
 we might be drawn into the war, the Secretary 
 of the Navy asked for the design of apparatus 
 that would make it possible for ships to converse 
 with one another and with shore stations. Of 
 course all vessels are equipped with wireless- 
 telegraph apparatus, but there is a decided ad- 
 vantage in having the captain of one ship talk 
 directly with the captain of another ship, or 
 take his orders from headquarters, with an 
 ordinary telephone receiver and transmitter. 
 A special equipment was designed for battle- 
 ships and on test it was found that ships could 
 easily converse with one another over a distance 
 of thirty-five miles and to shore stations from 
 a distance of a hundred and seventy-five miles. 
 The 'apparatus was so improved that nine con- 
 versations could be carried on at the same time 
 without any interference of one by the others. 
 
 When it became certain that we should have 
 to enter the war, there came a call for radio- 
 telephone apparatus for submarine-chasers, and 
 work was started on small, compact outfits for 
 these little vessels. 
 
194 INVENTIONS OF THE GREAT WAR 
 
 RADIOTELEPHONES FOB AIRPLANES 
 
 Then there was a demand for radiotelephone 
 apparatus to be used on airplanes. This was a 
 much more complicated matter and called for a 
 great deal of study. The way in which problem 
 after problem arose and was solved makes an 
 exceedingly interesting narrative. It seemed 
 almost absurd to think that a delicate radio- 
 telegraph apparatus could be made to work in 
 the terrific noise and jarring of an airplane. 
 The first task was to make the apparatus noise- 
 proof. A special sound-proof room was con- 
 structed in which a noise was produced exactly 
 imitating that of the engine exhaust of an air- 
 plane engine. In this room, various helmets 
 were tried in order to see whether they would 
 be proof against the noise, and finally a very 
 suitable helmet was designed, in which the tele- 
 phone receiver and transmitter were installed. 
 
 By summer-time the work had proceeded so 
 far that an airplane equipped with transmitting- 
 apparatus could send spoken messages to an 
 operator on the ground from a distance of two 
 miles. The antenna of the airplane consisted 
 of a wire with a weight on the lower end, which 
 
TALKING IN THE SKY 195 
 
 hung down about one hundred yards from the 
 body of the machine. But a trailing antenna 
 was a nuisance in airplane manoeuvers, and it 
 was also found that the helmet which was so 
 satisfactory in the laboratory was not just the 
 thing for actual service in an airplane. It had 
 to fit very tightly around the ears and the 
 mouth, and as the airplane went to high alti- 
 tudes where the air-pressure was much lower 
 than at the ground level, painful pressures were 
 produced in the ears which were most annoy- 
 ing. Aside from that, -in actual warfare air- 
 planes have to operate at extreme heights, 
 where the air is so rare that oxygen must be 
 supplied to the aviators, and it was difficult to 
 provide this supply of oxygen with the radio 
 helmet tightly strapped to the head of the op- 
 erator. But after considerable experiment, this 
 difficulty was overcome and also that of the 
 varying pressures on the ears. 
 
 Another great difficulty was to obtain a steady 
 supply -of power on the airplane to operate the 
 transmitting-apparatus. It has been the prac- 
 tice to supply current on airplanes for wireless- 
 telegraph apparatus by means of a small elec- 
 tric generator which is revolved by a little pro- 
 
196 INVENTIONS OF THE GREAT WAR 
 
 peller. The propeller in turn is revolved by 
 the rush of air as it is carried along by the plane. 
 But the speed of the airplane varies consider- 
 ably. At times, it may be traveling at only 
 forty miles per hour, and at other times as high 
 as one hundred and sixty miles per hour, so 
 that the little generator is subjected to great 
 variations of speed and consequent variations 
 of voltage. This made it impossible to produce 
 the steady oscillations -that are required in wire- 
 less telephony. After considerable experiment, 
 a generator was produced with two windings, 
 one of which operated through a vacuum tube, 
 somewhat like an audion, and to resist the in- 
 crease of voltage produced by the other winding. 
 Then another trouble developed. The sparks 
 produced by the magneto in the airplane motor 
 set up electro-magnetic waves which seriously 
 affected the receiving-instrument. There was 
 no way of getting rid of the magneto, but the 
 wires leading from it to the engine were in- 
 cased in metal tubes which were grounded at 
 frequent intervals, and in that way the trouble 
 was overcome to a large extent. The magnetos 
 themselves were also incased in such a way that 
 
TALKING IN THE SKY 197 
 
 electro-magnetic waves would not be radiated 
 from them. 
 
 Instead of using trailing wires which were 
 liable to become entangled in the propeller, the 
 antenna was extended from the upper plane to 
 the tail of the machine, and later it was found 
 that by using two short trailing antennae one 
 from each tip of the wings, the very best results 
 could be obtained. Still another development 
 was to embed the antenna wires in the wings 
 of the plane. 
 
 It was considered necessary, if the apparatus 
 was to be practicable, to be able to use it over 
 a distance of two thousand yards, but in experi- 
 ments conducted in October, 1917, a couple of 
 airplanes were able to talk to each other when 
 twenty-three miles apart, and conversations 
 were carried on with the ground from a distance 
 of forty-five miles. The conditions under which 
 these distances were attained were unusual, and 
 a distance of three miles was accepted as a 
 standard for communication between airplanes. 
 The apparatus weighed only fifty-eight pounds 
 and it was connected with both the pilot and the 
 observer so that they could carry on conversa- 
 
198 INVENTIONS OF THE GREAT WAR 
 
 tions with each other and could both hear 
 the conversation with other airplanes or the 
 ground. As a matter of fact, airplanes with 
 standard apparatus are able to talk clearly to a 
 distance of five miles and even to a distance of 
 ten miles when conditions are favorable, and 
 they can receive messages from the ground over 
 almost any distance. 
 
 A similar apparatus was constructed for sub- 
 marine-chasers with a standard range of con- 
 versation of over five miles. Apparatus was 
 manufactured in large quantities in this country 
 and all our submarine-chasers were equipped 
 with it, as well as a great many of our airplanes 
 and seaplanes, and we furnished radio-appa- 
 ratus sets to our allies which proved of im- 
 mense value in the war. This was particularly 
 so in the case of submarine detection, when it 
 was possible for a seaplane or a balloon to re- 
 port its findings at once to submarine-chasers 
 and destroyers, and to guide them in pursuit -of 
 submarines. 
 
 The improved audion holds out a wonder- 
 ful future for radiotelephony. For receiving, 
 at least, no elaborate aerial will be needed, and 
 with a small loop of wire, an audion or two, 
 
TALKING IN THE SKY 199 
 
 and simple tuning-apparatus any one can hear 
 the radio gossip of the whole world. 
 
 TELEGRAPHING TWELVE HTJNDKED WOBDS PEB 
 MINUTE 
 
 Some remarkable advances were made in 
 telegraphy also. During the war and since, 
 messages have been sent direct from Washing- 
 ton to all parts of the world. In the telegraph 
 room operators are connected by wire with the 
 different radio stations along the coast -and they 
 can control the radio transmitters, sending their 
 messages without any repeating at the radio 
 stations. Long messages are copied off on a 
 machine something like a type-writer, which, 
 however, does not make type impressions, but 
 cuts perforations in a long sheet of paper. The 
 paper is then run through a transmitter at a 
 high speed and the message is sent out at a rate 
 of as much as twelve hundred words a minute. 
 At the receiving-station, the message is received 
 photographically on a strip of paper. The re- 
 ceiving-instrument has a fine quartz thread in 
 it, which carries a tiny mirror. A beam of light 
 is reflected from the mirror upon the strip of 
 sensitized paper. The radio waves twist the 
 
200 INVENTIONS OF THE GREAT WAR 
 
 quartz thread ever so slightly, which makes the 
 beam of light play back and forth, but of course 
 the motion is greatly magnified. In this way 
 a perfect record is made of the message in dots 
 and dashes, which are translated into the corre- 
 sponding letters of the alphabet. 
 
 DETECTING BADIO SPIES 
 
 There is another radio invention which we 
 contributed during the war, that proved of ut- 
 most service in thwarting German spies and 
 which is going to prove equally valuable in time 
 of pe'ace. Although a war invention, its peace- 
 time service will be to save lives. It is a very 
 simple matter to rig up a wireless-telegraph 
 system that will send messages to a considerable 
 distance, and simpler still to rig up a receiving- 
 set. European governments have always dis- 
 couraged amateur radiotelegraphy, but in this 
 country restrictions used to be so slight that 
 almost any one could set up and use a radio 
 set, both for receiving and for transmitting. 
 When we entered the war we were glad that 
 amateurs had been encouraged to play with 
 wireless, because we had hundreds of good radio 
 
TALKING IN THE SKY 201 
 
 operators ready to work the sets which the army 
 and the navy needed. 
 
 But this was a disadvantage, too. Many 
 operators were either Germans or pro-Germans 
 and were only too willing to use their radio ex- 
 perience in the interest of our enemies. It was 
 a simple matter to obtain the necessary appa- 
 ratus, because there was plenty of it to be had 
 everywhere. They could send orders to fellow 
 workers and receive messages from them, or 
 they could listen to dispatches sent out by the 
 government and glean information of great mili- 
 tary and naval importance. The apparatus 
 could easily be concealed: a wire hung inside 
 a chimney, a water-pipe, even a brass bedstead 
 could be used for the receiving-aerial. It was 
 highly important that these concealed stations 
 be located, but how were they to be discovered? 
 
 THE WIRELESS COMPASS 
 
 This problem was solved very nicely. The 
 audion had made it possible to receive radio 
 signals on a very small aerial. In place of the 
 ordinary stationary aerial a frame five feet 
 square was set up so that it could be turned 
 
202 INVENTIONS OF THE GREAT WAR 
 
 to any point of the compass. A few turns of 
 copper-bronze wire were wound round it. This 
 was called the "wireless compass/' It was set 
 up on the roof of the radio station and concealed 
 within a cupola. The shaft on which it was 
 mounted extended down into the operating- 
 room and carried a wheel by which it could be 
 turned. On the shaft was a circular band of 
 aluminum engraved with the 360 degrees of the 
 circle, and a couple of fixed pointers indicated 
 true north and south. Now when a signal was 
 received by the aerial, if it struck the frame 
 edgewise the radio waves would reach one side 
 before they would the other. Taking a single 
 wave, as shown by the drawing, Fig. 11, we 
 see that while the crest of the wave is sweep- 
 ing over one side of the frame, the trough of the 
 wave is passing the other side. Two currents 
 are set up in the radio compass, one in the 
 wires at the near side of the compass, and an- 
 other in the wires at the far side of the com- 
 pass. As these currents are of the same direc- 
 tion, they oppose each other and tend to kill 
 each other off, but one of the currents is 
 stronger than the other because the crest of the 
 wave is sweeping over that side, while the 
 
Courtesy of th "Scientific American" 
 
 FIG. 11. The radio compass turned parallel to an oncoming 
 electro-magnetic wave 
 
 203 
 
204 INVENTIONS OF THE GREAT WAK 
 
 trough of the wave is passing over the other. 
 The length of the wave may be anything, but 
 always one side will be stronger than the other, 
 and a current equal in strength to the difference 
 between the two currents goes down into the 
 operating-room and affects the receiver. Now 
 when the compass is set at right angles to the 
 oncoming wave, both sides are affected simul- 
 taneously and with the same strength, so that 
 they kill each other off completely, and no 
 current goes down to the receiver. Thus the 
 strength of the signal received can be varied 
 from a maximum, when the compass is parallel 
 to the oncoming waves, to zero, when it is at 
 right angles to them. 
 
 To find out where a sending-station is, the 
 compass is turned until the loudest sound is 
 heard in the receiver and then the campass 
 dial shows from what direction the signals are 
 coming. At the same time, another line on the 
 signals will be found by a second station with 
 another compass. These directions are traced 
 on a map; and where they meet, the sending- 
 station must be located. 
 
 With this apparatus it was possible to locate 
 the direction of the station within a degree. 
 
TALKING IN THE SKY 205 
 
 After the station had been located as closely 
 as possible in this way, a motor-truck was sent 
 out in which there was a concealed radio com- 
 pass. The truck would patrol the region 
 located by the fixed compasses, and with it the 
 position of the concealed station could be de- 
 termined with perfect accuracy. The building 
 would be raided and its occupants jailed and the 
 radio equipment confiscated. 
 
 Even receiving-sets were discovered with the 
 portable compass, but to find them was a far 
 more difficult task. For the receiving of mes- 
 sages from distant points without a conspicuous 
 aerial an audion would have to be used and this 
 would set up feeble oscillations which could be 
 picked up under favorable conditions by the 
 portable compass. 
 
 PILOTING SHIPS INTO POET 
 
 And now for the peace-time application of all 
 this. If the compass could be used to find those 
 who tried to hide, why could it not also be used 
 to find those who wished to be found? 
 
 Every now and then a ship runs upon the 
 rocks because it has lost its bearings in the fog. 
 But there will be no excuse for such accidents 
 
206 INVENTIONS OF THE GREAT WAR 
 
 now. A number of radio-compass stations have 
 been located around the entrance and approach 
 to New York Harbor. Similar stations have 
 been, or soon will be, established at other ports. 
 As soon as a ship arrives within fifty or a 
 hundred miles of port she is required to call for 
 her bearings. The operator of the control sta- 
 tion instructs the ship to send her call letters 
 for thirty seconds, and at the same time notifies 
 each compass station to get a bearing on the 
 ship. This each does, reporting back to the con- 
 trol station. The bearings are plotted on a 
 chart and inside of two minutes from the time 
 the ship gives her call letters, her bearing is 
 flashed to her by radio from the control station. 
 The chart on which the plotting is done is 
 covered with a sheet of glass. Holes are 
 pierced through the glass at the location of each 
 compass station. See Fig. 12. On the chart, 
 around each station, there is a dial marked off 
 in the 360 degrees of the circle. A thread 
 passes through the chart and the hole in the 
 glass at each station. These threads are at- 
 tached to weights under the chart. When a 
 compass station reports a bearing, the thread 
 of that station is pulled out and extended across 
 
207 
 
208 INTENTIONS OF THE GREAT WAR 
 
 the corresponding degree on the dial. The 
 same is done as each station reports and where 
 the threads cross, the ship must be located. 
 
 Not only can the direction-finder be used to 
 pilot a ship into a harbor, but it will also serve 
 to prevent collisions at sea, because a ship 
 equipped with a radio compass can tell whether 
 another ship is coming directly toward her. 
 
 And so as one of the happy outcomes of the 
 dreadful war, we have an apparatus that will 
 rob sea-fogs of their terrors to navigation. 
 
CHAPTER XI 
 
 WARRIORS OF THE PAINT-BRUSH 
 
 WHEN the great European war broke out, 
 it was very evident that the Entente 
 Allies would have to exercise every resource 
 to beat the foe which had been preparing for 
 years to conquer the world. But who ever 
 imagined that geologists would be called in to 
 choose the best places for boring mines under 
 the enemy: that meteorologists would be sum- 
 moned to forecast the weather and determine 
 the best time to launch an offensive ; that psy- 
 cologists would be employed to pick out the men 
 with the best nerves to man the machine-guns 
 and pilot the battle-planes? Certainly no one 
 guessed that artists and the makers of stage 
 scenery would play an important part in the 
 conflict. 
 
 But the airplane filled the sky with eyes that 
 at first made it impossible for an army to con- 
 ceal its plans from the enemy. And then there 
 
 209 
 
210 INVENTIONS OF THE GREAT WAR 
 
 were eyes that swam in the sea cruel eyes that 
 belonged to deadly submarine monsters, eyes 
 that could see without being seen, eyes that 
 could pop up out of the water at unexpected 
 moments, eyes that directed deadly missies at 
 inoffensive merchantmen. They were cowardly 
 eyes, too, which gave the ship no opportunity 
 to strike back at the unseen enemy. A vessel's 
 only safety lay in the chance that out in the 
 broad reaches of the ocean it might pass beyond 
 the range of those lurking eyes. It was a game 
 of hide-and-seek in which the pursuer and not 
 the pursued was hidden. Something had to be 
 done to conceal the pursued as well, but in the 
 open sea there was nothing to hide behind. 
 
 HIDING IN PLAIN SIGHT 
 
 There is such a thing as hiding in plain sight. 
 You can look right at a tree-toad without see- 
 ing him, because his colors blend perfectly with 
 the tree to which he is clinging. You can watch 
 a green leaf curl up and shrivel without realiz- 
 ing that the curled edge is really a caterpillar, 
 cunningly veined and colored to look just like 
 a dying leaf; and out in the woods a speckled 
 bird or striped animal will escape observation 
 
WARRIORS OF THE PAINT-BRUSH 211 
 
 just because it matches the spotted light that 
 comes through the underbrush. Nature is 
 constantly protecting its helpless animals 
 with colored coats that blend with the sur- 
 roundings. 
 
 Long ago clumsy attempts at concealment 
 were made when war-vessels were given a coat 
 of dark-gray paint which was supposed to make 
 them invisible at a distance. Actually the 
 paint made them more conspicuous; but, then, 
 concealment did not count for very much be- 
 fore the present war. 
 
 It was the eyes of the submarines that 
 brought a hurry call for the artists, and up to 
 them was put the problem of hiding ships in 
 plain sight. A new name was coined for these 
 warriors of the paint-brush: camoufleurs they 
 were called, and their work was known as 
 camouflage. 
 
 MATCHING THE SKY 
 
 Of course, no paint will make a ship abso- 
 lutely invisible at a short distance, but a large 
 vessel may be made to disappear completely 
 from view at a distance of six or seven miles 
 if it is properly painted. 
 
212 INVENTIONS OF THE GREAT WAR 
 
 To be invisible, a ship must reflect as much 
 light and the same shade of light as do its sur- 
 roundings. If it is seen against the background 
 of the sea, it must be of a bluish or a greenish 
 tint, but a submarine lies so low in the water 
 that any object seen at a distance is silhouetted 
 against the sky, and so the ship must have a 
 coat of paint that will reflect the same colors 
 as does the sky. Now, the sky may be of almost 
 any color of the rainbow, depending upon the 
 position of the sun and the amount of vapor or 
 dust in the air. Fortunately in the North 
 Sea and the waters about the British Isles, 
 where most of the submarine attacks took place, 
 the weather is hazy most of the time, and the 
 ship had to be painted of such a color that it 
 would reflect the same light as that reflected by 
 a hazy sky. With a background of haze and 
 more or less haze between the ship and the 
 periscope of the U-boat, it was not a very diffi- 
 cult matter to paint a ship so that it would be 
 invisible six or seven miles away. One shade of 
 gray was used to conceal a ship in the North 
 Sea and an entirely different shade was used 
 for the brighter skies of the Mediterranean. 
 
 In this way, the artists made it possible for 
 
WABRIORS OF THE PAINT-BRUSH 213 
 
 ships to sail in safety much nearer the pursuer 
 who was trying to find them, and by just so much 
 they reduced his powers of destruction. But 
 still the odds were too heavy against the mer- 
 chantman. Something must be done for him 
 when he found himself within the seven-mile 
 danger-zone. Here again the artists came to 
 the rescue. 
 
 Before merchant ships were armed, a sub- 
 marine would not waste a torpedo on them, but 
 would pound them into submission with shell. 
 Even after ships were provided with guns, sub- 
 marines mounted heavier guns and unless a 
 ship was speedy enough to show a clean pair 
 of heels, the pursuing U-boat would stand off 
 out of range of the ship's guns and pour a 
 deadly fire into it. But the ships, too, mounted 
 larger guns and the submarines had to fall back 
 upon their torpedoes. 
 
 GETTING THE RANGE FOE THE TORPEDO 
 
 In order to fire its torpedo with any certainty, 
 the U-boat had to get within a thousand yards 
 of its victim. A torpedo travels at from 
 thirty to forty miles per hour. It takes time 
 for it to reach its target and a target which 
 
214 INVENTIONS OF THE GREAT WAR 
 
 is moving at, say, fifteen knots, will travel 
 five hundred yards while a thirty-knot tor- 
 pedo is making one hundred yards. And so 
 before the U-boat commander could discharge 
 his torpedo, he had to know how fast the 
 ship was traveling and how far away it was 
 from him. He could not come to the surface 
 and make deliberate observations, but had to 
 stay under cover, not daring even to keep his 
 eye out of water, for fear that the long wake 
 of foam trailing behind -the periscope would 
 give him away. All he could do, then, was 
 to throw his periscope up for a momentary 
 glimpse and make his calculations very quickly ; 
 then he could move to the position he figured 
 that he should occupy and shoot up his peri- 
 scope for another glimpse to check up his calcu- 
 lations. On the glass of this periscope, there 
 were a number of graduations running verti- 
 cally and horizontally. If he knew his victim 
 and happened to know the height of its smoke- 
 stacks or the length of the boat, he noted how 
 many graduations they covered, and then by a 
 set formula he could tell how far he was from 
 the boat. At the same time he had to work out 
 its rate of travel and note carefully the course 
 
WARRIORS OF THE PAINT-BRUSH 215 
 
 it was holding before he could figure where 
 his torpedo must be aimed. 
 
 There was always more or less uncertainty 
 about such observations, because they had to be 
 taken hastily, and the camoufleurs were not slow 
 to take advantage of this weakness. They in- 
 creased the enemy's confusion by painting high 
 bow-waves which made the ship look as if it were 
 traveling at high speed. They painted the 
 bow to look like the stern, and the stern to look 
 like the bow, and the stacks were painted so that 
 they appeared to slant in the opposite direc- 
 tion, so that it would look as if the vessel were 
 headed the other way. U-boats came to have a 
 very wholesome respect for destroyers and 
 would seldom attack a ship if one of these 
 fast fighting-craft was about, and so destroyers 
 were painted on the sides of ships as scare- 
 crows to frighten off the enemy. 
 
 MAKING STRAIGHT LINES LOOK CEOOKED 
 
 We say that "seeing is believing," but it is 
 not very hard to deceive the eye. The lines in 
 Fig. 13 look absolutely parallel, and they are; 
 but cross-hatch the spaces between them, with 
 the hatching reversed in alternate spaces, as in 
 
FIG. 13. Parallel lines that look straight 
 
 FIG. 14. Parallel lines that do not look straight 
 
 ** n n r 
 
 F yipl 
 
 usa twU u \ 
 
 Lirt Lir 
 
 Courtesy of the Submarine Defense Association 
 FIG. 15. Letters that look all higgledy-piggledy, but are 
 really straight 
 
 216 
 
WARRIORS OF THE PAINT-BRUSH 217 
 
 Fig. 14, and they no longer look straight. 
 Take the letters on the left, Fig. 15. They 
 look all higgledy-piggledy, but they are really 
 straight and parallel, as one can prove by laying 
 a straight-edge against them, or by drawing 
 a straight line through each letter, as shown at 
 the right, Fig. 16. Such illusions were used on 
 ships. Stripes were painted on the hull that 
 tapered slightly, from bow to stern, so that the 
 vessel appeared to be headed off at an angle, 
 when it was really broadside to the watcher at 
 the other end of the periscope. 
 
 There are color illusions, too, that were tried. 
 If you draw a red chalk -mark and a blue one on 
 a perfectly clean blackboard, the red line will 
 seem to stand out and the blue one to sink into 
 the black surface of the board, because your eye 
 has to focus differently for the two colors, and 
 a very dazzling effect can be had with alternat- 
 ing squares of blue and red. Other colors give 
 even more dazzling effects, and some of them, 
 when viewed at a distance, will blend into the 
 very shade of gray that will make a boat invisi- 
 ble 'at six miles. When U-boat commanders 
 took observations on a ship painted with a 
 i 'dazzle" camouflage, they saw a shimmering 
 
218 INVENTIONS OF THE GREAT WAR 
 
 image which it was hard for them to measure on 
 the fine graduations of their periscopes. Some 
 ships were painted with heavy blotches of black 
 and white, and the enemy making a hasty ob- 
 servation would be apt to focus his attention 
 on the dark masses and overlook the white parts. 
 So he was likely to make a mistake in estimating 
 the height of the smoke-stack or in measuring 
 the apparent length of a vessel. 
 
 A JOKE ON THE PHOTOGBAPHEE 
 
 Early in the submarine campaign one of our 
 boats was given a coat of camouflage, and when 
 the vessel sailed from its pier in the North 
 Eiver, New York, the owners sent a photog- 
 rapher two or three piers down the river to 
 photograph the ship as she went by. He took 
 the picture, but when the negative was de- 
 veloped, much to his astonishment he found 
 that the boat was not all on the plate. In the 
 finder of his camera, he had mistaken a heavy 
 band of black paint for the stern of the ship, 
 quite overlooking the real stern, which was 
 painted a grayish white. The artist had fooled 
 the photographer and at a distance of not nrore 
 than two or thre hundred yards! 
 
WARRIORS OF THE PAINT-BRUSH 219 
 
 SEEING BEYOND THE HOBIZON 
 
 The periscope of a submarine that is running 
 awash can be raised about fifteen feet above 
 the water, which means that the horizon as 
 viewed from that elevation is about six miles 
 away, and if you draw a circle with a six- 
 mile radius on the map of the Atlantic, you 
 will find that it is a mere speck in the ocean; 
 but a U-boat commander could see objects 
 that lay far beyond his horizon because he was 
 searching for objects which towered many feet 
 above the water. The smoke-stacks of some 
 vessels rise a hundred feet above the water- 
 line, and the masts reach up to much greater 
 altitudes. Aside from this, in the early days 
 of the war steamers burned soft coal and their 
 funnels belched forth huge columns of smoke 
 which was visible from twenty to thirty miles 
 away. 
 
 When this was realized, efforts were made 
 to cut down the superstructure of a ship as much 
 as possible. Some vessels had their stacks 
 cut down almost to the deck-line, and air-pumps 
 were installed to furnish the draft necessary to 
 
220 INVENTIONS OF THE GREAT WAR 
 
 keep their furnaces going. They had no masts 
 except for slender iron pipes which could be 
 folded down against the deck and could be 
 erected at .a moment's notice, to carry the 
 aerials of the wireless system. Over the ship 
 from stem to stern was stretched a cable, 
 familiarly known as a " clothes-line, " upon 
 which were laid strips of canvas that com- 
 pletely covered the superstructure of the ship. 
 These boats lay so low that they could not be 
 seen at any great distance, and it was difficult 
 for the U-boats to find them. They were slow 
 boats; too slow to run away from a modern 
 submarine, but because of their lowly structure, 
 they managed to elude the German U-boats. 
 When they were seen, the U-boat commanders 
 were afraid of them. They were suspicious of 
 anything that looked out of the ordinary, and 
 preferred to let the " clothes-line ships " go. 
 
 THE BRITISH MYSTERY SHIPS 
 
 The Germans had some very unhealthy ex- 
 periences with the "Q-boats" or "mystery 
 ships " of the British. These were vessels 
 rigged up much like ordinary tramp steamers, 
 but they were loaded with wood, so that they 
 
WARRIORS OF THE PAINT-BRUSH 221 
 
 would not sink, and their hatches were arranged 
 to fall open at the touch of a button, exposing 
 powerful guns. They also were equipped with 
 torpedo-tubes, so that they could give the U-boat 
 a dose of its own medicine. These ships would 
 travel along the lanes frequented by submarines, 
 and invite attack. They would limp along as 
 if they had been injured by a storm or a U-boat 
 attack, and looked like easy prey. When a sub- 
 marine did attack them, they would send out 
 frantic calls for help, and they had so-called 
 1 panic ' ' parties which took to the boats. Mean- 
 time, a picked crew remained aboard, carefully 
 concealed from view, and the captain kept his 
 eye upon the enemy through a periscope dis- 
 guised as a small ventilator, waiting for the 
 U-boat to come within range of certain destruc- 
 tion. Sometimes the panic party would lure 
 the submarine into a favorable position by 
 rowing under the stern as if to hide around the 
 other side of the ship. At the proper moment, 
 up would go the white ensign the British 
 man-of-war flag the batteries would be un- 
 masked, and a hail of shell would break loose 
 over the Hun. Many a German submarine was 
 accounted for by such traps. 
 
222 INVENTIONS OF THE GREAT WAR 
 
 Submarines themselves used all sorts of 
 camouflage. They were frequently equipped 
 with sails which they would raise to disguise 
 themselves as peaceful sloops, and in this way 
 they were able to steal up on a victim without 
 discovery. Sometimes they would seize a ship 
 and hide behind it in order to get near their 
 prey. 
 
 CAMOUFLAGE ON LAND 
 
 But the call for the wielders of the paint- 
 brush came not only from the sea. Their ser- 
 vices were needed fully as much on land, and the 
 making of land camouflage was far more in- 
 teresting because it was more varied and more 
 successful. Besides, it called for more than 
 mere paint; all sorts of tricks with canvas, 
 grass, and branches were used. Of course, the 
 soldiers were garbed in dust-colored clothing 
 and shiny armor was discarded. The helmets 
 they wore were covered with a material that cast 
 no gleam of light. In every respect, they tried 
 to make themselves of the same shade as their 
 surroundings. Like the Indians, they painted 
 their faces. This was done when they made 
 their raids at night. They painted their faces 
 
WARRIORS OF THE PAINT-BRUSH 223 
 
 black so that they would not show the faintest 
 reflection of light. 
 
 A PAPEB HOESE 
 
 The most interesting camouflage work was 
 done for the benefit of snipers or for observers 
 at listening-posts close to the enemy trenches. 
 It was very important to spy on the enemy and 
 discover his plans, and so men were sent out 
 as near his lines as possible, to listen to the con- 
 versation and to note any signs of unusual ac- 
 tivity which would be likely to precede a raid. 
 These men were supplied with telephone wires 
 which they dragged over No Man's Land, and 
 by which they could communicate their dis- 
 coveries to headquarters. Some very ingenious 
 listening-posts were established. In one case 
 a papier-mache duplicate of a dead horse was 
 made, which was an exact facsimile of an ani- 
 mal that had been shot and lay between the two 
 lines. One night, the carcass of the horse was 
 removed and the papier-mache replica took its 
 place. In the latter a man was stationed with 
 telephone connection back to his own lines. 
 Here he had an excellent chance to watch the 
 enemy. 
 
224 INVENTIONS OF THE GREAT WAR 
 
 On another occasion a standing tree, whose 
 branches had been shot away, was carefully 
 photographed and an exact copy of it made, but 
 with a chamber inside in which an observer could 
 be concealed. One night while the noise of the 
 workmen was drowned by heavy cannonading, 
 this tree was removed and its facsimile was set 
 up instead, and it remained for many a day be- 
 fore the enemy discovered that it was a fake 
 tree-trunk. It provided a tall observation post 
 from which an observer could direct the fire of 
 his own artillery. 
 
 FOOLING THE WATCHERS IN THE SKY 
 
 In the early stages of the war, it seemed im- 
 possible to hide anything from the Germans. 
 They had eyes everywhere and were able to an- 
 ticipate everything the Allies did. But the 
 spies that infested the sky were the worst handi- 
 cap. Even when the Allies gained control of 
 the air, the control was more or less nominal 
 because every now and then an enemy observer 
 would slip over or under the patrolling aero- 
 planes and make photographs of the Allies' 
 lines. The photographs were carefully com- 
 
WARRIORS OF THE PAINT-BRUSH 225 
 
 pared with others previously taken, that the 
 slightest change in detail might be discovered. 
 Airplane observers not only would be ready 
 to drop bombs on any suspicious object or upon 
 masses of troops moving along the roads, but 
 would telephone back to their artillery to direct 
 its fire upon these targets. Of course, the 
 enemy knew where the roads were located and 
 a careful watch was kept of them. 
 
 The French did not try to hide the roads, but 
 they concealed the traffic on the roads by hang- 
 ing rows of curtains over them. As these cur- 
 tains hung vertically and were spaced apart, one 
 would suppose that they would furnish little 
 concealment, but they prevented an observer 
 in an aeroplane from looking down the length 
 of a road. All the road he could see was that 
 which lay directly under his machine, because 
 there he could look between the curtains; if 
 he looked obliquely at the road, the curtains 
 would appear to overlap one another and would 
 conceal operations going on under them. 
 
 In one case, the Germans completely covered 
 a sunken road with canvas painted to represent 
 a road surface. Under this canvas canopy, 
 
226 INVENTIONS OF THE GREAT WAK 
 
 troops were moved to an important strategic 
 point without the slightest indication of such a 
 movement. 
 
 HIDING BIG GUNS 
 
 Nature 's tricks of camouflage were freely used 
 in the hiding of the implements of war on land. 
 Our big guns were concealed by being painted 
 with leopard spots and tiger stripes, the color 
 and nature of the camouflage depending upon 
 the station they were to occupy. In many cases, 
 they were covered with branches of trees or 
 with rope netting overspread with leaves. So 
 careful was the observation of the air scouts 
 that even the grass scorched by the fire of the 
 gun had to be covered with green canvas to 
 prevent betrayal of the position of the gun. 
 
 BO ADS THAT LED NOWHERE 
 
 In the making of an emplacement for a gun 
 it was of the utmost importance that no fresh 
 upturned earth be disclosed to the aerial ob- 
 servers. Even foot-paths leading to it had to 
 be concealed. Plans were carefully made to 
 cover up all traces of the work before the work 
 was begun. Where it was impossible to conceal 
 
WARRIORS OF THE PAINT-BRUSH 227 
 
 the paths, they were purposely made to lead 
 well beyond the point where the emplacement 
 was building, and, still further to deceive the 
 enemy, a show of work was sometimes under- 
 taken at the end of the path. Wherever the 
 sod had to be upturned, it was covered over 
 with green canvas. The earth that was re- 
 moved had to be concealed somewhere and the 
 best place of concealment was found to be some 
 old shell-hole which would hold a great deal 
 of earth without any evidence that would be ap- 
 parent to an observer in an aeroplane. If no 
 shell-hole were handy, the excavated material 
 had to be hauled for miles before a safe dump- 
 ing-ground could be found. As far as possible 
 everything was sunk below the earth level. 
 Big pits were dug in which the mortars were 
 placed, or if a shell-hole were empty, this was 
 used instead. 
 
 SHADOWLESS BUILDINGS 
 
 Any projection above the ground was apt to 
 cast a shadow which would show up on the ob- 
 server's photographs. This was a difficulty 
 that was experienced in building the hangars 
 for airplanes. The roofs of these sheds were 
 
228 INVENTIONS OF THE GREAT WAR 
 
 painted green so as to match the sod around 
 them, but as they projected above their sur- 
 roundings, they cast shadows which made them 
 clearly evident to the enemy. This was over- 
 come by the building of shadowless hangars; 
 that is, hangars with roofs that extended all 
 the way to the ground at such an angle that they 
 would cause no shadow except when the sun was 
 low. In some cases, aeroplanes were housed 
 in underground hangars, the approach to which 
 was concealed by a canvas covering. As for 
 the machines themselves, they scorned the use 
 of camouflage. Paint was little protection to 
 them. Some attempt was made to use trans- 
 parent wings of cellon, a material similar to 
 celluloid, but this did not prove a success. 
 
 THE PHOTOGRAPHIC BYE 
 
 Although camoufleurs made perfect imitations 
 of natural objects and surroundings, they were 
 greatly concerned to find -that the flying observ- 
 ers could see through their disguises. To the 
 naked eye the landscape would not show the 
 slightest trace of any suspicious object, but by 
 the use of a color-screen to cut out certain rays 
 of light, a big difference would be shown between 
 
WARRIORS OF THE PAINT-BRUSH 229 
 
 the real colors of nature and the artist's copies 
 of them. For instance, if a roof painted to 
 look like green grass were viewed through a 
 red color-screen, it would look brown ; while the 
 real grass, which apparently was of exactly the 
 same shade as the roof, would look red. It 
 had not been realized by the artists who had 
 never studied the composition of light, that there 
 is a great deal of red in the green light reflected 
 by grass, and that if they were to duplicate 
 this shade of green, they must put a certain 
 amount of red paint in their imitation grass 
 roofs. Air scouts did not depend upon their 
 eyes alone, but used cameras so that they could 
 study their photographs at their leisure and by 
 fitting the cameras with different color-screens, 
 they could analyze the camouflage and undo the 
 patient work of the artist. 
 
 A CALL FOR THE PHYSICIST 
 
 To meet this situation, another man was sum- 
 moned to help the physicist, who looks upon 
 color merely as waves of ether; who can pick 
 a ray of light to pieces just as a chemist can 
 analyze a lump of sugar. Under his expert 
 guidance, colors of nature were imitated so that 
 
230 INVENTIONS OF THE GREAT WAR 
 
 they would defy detection. Aside from this, the 
 physicist helped to solve the tricks of the 
 enemy 's camoufleurs. 
 
 But the physicist had barely rolled up his 
 sleeves and got into the fray when the armis- 
 tice was signed which put an end to the shams 
 as well as to the realities of the great war. 
 While the work of camouflage was not com- 
 pleted, we owe an inestimable debt to the men 
 who knew how to fake scenery and to their 
 learned associates who count the wave lengths 
 of light, and although their trade was a trade of 
 deception and shams, there was no sham -about 
 the service they rendered. 
 
 MAKING SHIPS VISIBLE 
 
 While in war safety lies in invisibility, in 
 peace the reverse is true. Now that the war is 
 over, it may seem that the work of the camou- 
 fleurs can find no useful application; but it 
 was impossible to learn how to make objects 
 invisible without also learning how to make 
 them conspicuously visible. As a consequence, 
 we know now how to paint a ship so that it 
 will show up more clearly in foggy weather, 
 thereby reducing the danger of collision. We 
 
WARRIORS OF THE PAINT-BRUSH 231 
 
 know, too, how to paint light-ships, buoys, etc., 
 so that they will be much more conspicuous 
 and better guides to mariners, and how to color 
 railroad signals and road signs so that they 
 will be more easily seen by locomotive engineers 
 and automobile drivers. 
 
OHAPTEE XII 
 
 SUBMABIIOJS 
 
 IT was an American invention that dragged 
 America into the war an American inven- 
 tion in the hands of barbarians and put to un- 
 speakably barbarous use. 
 
 After seeing how the Huns used the sub- 
 marine we are not so sure that we can take much 
 pride in its invention. But if any blame at- 
 taches to us for developing the submarine, we 
 made amends by the way in which we fought the 
 German U-boat and put an end to German 
 frightfulness on the sea. Of course, the credit 
 for Germany's defeat is not for a moment 
 claimed by Americans alone, but it must be ad- 
 mitted that we played an important part in 
 overcoming the menace of the U-boat. 
 
 There is no question that the submarine was 
 an American invention. To be sure, we can look 
 into ancient books and find suggestions for navi- 
 gating under the surface of the sea, but the 
 
 232 
 
SUBMARINES 233 
 
 first man who did actually build a successful 
 submarine was David Bushnell, back in the 
 Revolutionary War. After him came Robert 
 Fulton, who carried the invention farther. He 
 built and operated a submarine for the French 
 Government, and, in more recent years, the sub- 
 marine became a practical vessel of war in the 
 hands of John P. Holland and Simon Lake, 
 both Americans. However, we are not inter- 
 ested, just now, in the history of the submarine, 
 but rather in the development of this craft 
 during the recent war. 
 
 With Great Britain as an enemy, Germany 
 knew that she was hopelessly outclassed on the 
 sea; but while "Britannia ruled the waves," she 
 did not rule the depths of the sea, and so Ger- 
 many decided to claim this realm for her own. 
 Little attention did she pay to surface vessels. 
 Except in the Dogger Bank engagement and the 
 Battle of Jutland, the German first-class ves- 
 sels did not venture out upon the open sea, and 
 even the lighter craft merely made occasional 
 raids under cover of fog or darkness, only 
 to cut and run as soon as the British vessels 
 appeared. The submarine boat, or untersee- 
 boot as the Germans called it, was virtually the 
 
234 INVENTIONS OF THE GREAT WAR 
 
 only boat that dared go out into the high seas ; 
 consequently, the Germans specialized upon 
 that type of craft and under their close atten- 
 tion it grew into a highly perfected war-vessel. 
 But the Germans were not the only ones to de- 
 velop the submarine, as we shall see. 
 
 CONSTRUCTION OF THE U-BOATS 
 
 When the great war broke out, the German U- 
 boat was a comparatively small craft, less than 
 150 feet long, with its main hull only 12 feet in 
 diameter. It could make a speed of 12 knots on 
 the surface and only 9 when submerged. But 
 as the war progressed, it grew larger and 
 larger, until it attained a length of over 300 
 feet and its speed was increased to 12 knots 
 when submerged and 18 knots on the surface. 
 
 Figs. 16 to 18 show the construction of one 
 of the early U-boats. The later boats were 
 built after the same general plan, but on a 
 bigger scale. 
 
 It is not always safe to judge a thing by its 
 name; to do so is apt to lead to sad mistakes. 
 One would naturally suppose, from its name, 
 that a submarine is a boat that lives under 
 water, like a fish. But i<t is not a fish; it is 
 
235 
 
236 INVENTIONS OF THE GREAT WAR 
 
 an air-breathing animal that prefers to stay 
 on the surface, only occasionally diving under to 
 hide from danger or to steal upon its prey. 
 During the war, the German U-boats did not 
 average three hours per day under the surface ! 
 Because they were intended to run on the sur- 
 face they had to be built in the form of a sur- 
 face vessel, so as to throw off the waves and 
 keep from rolling and pitching too much in a 
 seaway. But they also had to be built to with- 
 stand the crushing weight of deep water, and as 
 a cylinder is much stronger than a structure of 
 ordinary boat shape, the main hull was made cir- 
 cular in section and of heavy plating, strongly 
 framed, while around this was an outer hull 
 of boat shape, as shown in Fig. 18. 
 
 PUTTING HOLES IN A TANK TO KEEP IT FULL, 
 
 The space between the inner and outer 
 hulls was used for water ballast and for reser- 
 voirs of oil to drive the engines; and, strange 
 as it may seem, the oil-tanks were always kept 
 full by means of holes in the bottom of them. 
 As the oil was consumed by the engines, water 
 would flow into the reservoir to take its place, 
 and the oil, being lighter than water, would float 
 
:: _r-^r-r^-=j jr INNCB CIRCULAR j f^-=^=--=i^ 
 
 Courtesy of the "Scientific American" 
 
 FIG. 18. Transverse section through conning-tower, showing 
 the interior (circular) pressure-resisting hull and the 
 lighter exterior hull, which is open to the sea 
 
 237 
 
238 INVENTIONS OF THE GREAT WAR 
 
 on top. The false hull was of light metal, be- 
 cause as it was open to the sea, the pressure on 
 the inside was always the same as that on the 
 outside. The reservoirs of oil and the water- 
 ballast tanks protected the inner hull of the 
 vessel from accidental damage and from hostile 
 shell and bombs. There were water-ballast 
 tanks inside the inner hull as well, as shown in 
 the cross-sectional view, Fig. 18. The water 
 in the ballast-tanks was blown out by com- 
 pressed air to lighten the U-boat and the boat 
 was kept on an even keel by the blowing out 
 or the letting in of water in the forward and 
 after tanks. 
 
 A heavy lead keel was attached to the bottom 
 of the boat, to keep it from rolling too mudh. 
 In case of accident, if there were no other way of 
 bringing the boat to the surface, this keel could 
 be cast loose. 
 
 At the forward end, where the torpedo-tubes 
 were located, there was a torpedo-trimming 
 tank. Torpedoes are heavy missiles and every 
 time one was discharged the boat was lightened, 
 and the balance of the submarine was upset. 
 To make up for the loss of weight, water had 
 to be let into the torpedo-trimming tank. 
 
SUBMARINES 239 
 
 A submarine cannot float under-water "With- 
 out swimming ; in other words, it must keep its 
 propellers going to avoid either sinking to the 
 bottom of the sea or bobbing up to the surface. 
 To be sure, it can make itself heavier or lighter 
 by letting water into or blowing water out of 
 its ballast-tanks, but it is impossible to regulate 
 the water ballast so delicately that the sub- 
 marine will float submerged; and should the 
 boat sink to a depth of two hundred feet or so, 
 the weight of water above it would be suffi- 
 cient to crush the hull, so it is a case of sink 
 or swim. Usually enough ballast is taken on 
 to make the submarine only a little lighter than 
 the water it displaces ; and then to remain under, 
 the vessel must keep moving, with its hori- 
 zontal rudders tilted to hold it down. The hori- 
 zontal rudders or hydroplanes of the U-boat 
 are shown in Fig. 17, both at the bow and at 
 the stern. 
 
 The main hull of 'the vessel was literally filled 
 with machinery. In the after part of the boat 
 were the Diesel oil-engines with which the 
 U-boat was propelled when on the surface. 
 There were two engines, each driving a pro- 
 peller-shaft. It was impossible to use the en- 
 
240 INVENTIONS OF THE GREAT WAR 
 
 gines when the vessel was submerged, not be- 
 cause of the gases they produced these could 
 easily have been carried out of the boat but 
 because every internal-combustion engine cqn- 
 sumes enormous quantities of air. In a few 
 minutes the engines would devour all the air 
 in the hull of the submarine and would then 
 die of suffocation. And so the engines were 
 used only, when the submarine was running 
 awash or on the surface, and then the air con- 
 sumed by them would rush down the hatchway 
 like a hurricane to supply their mighty lungs. 
 
 ENGINES THAT BUEN HEAVY OIL. 
 
 The oil-engines were strictly a German in- 
 vention. In the earlier days of the submarine 
 gasolene-engines were used, but despite every 
 precaution, gasolene vapors occasionally would 
 leak out of the reservoirs and accumulate in 
 pockets or along the floors of the hull, and it 
 needed but a spark to produce an explosion 
 that would blow up the submarine. But 
 Eudolph Diesel, a German, invented an engine 
 which would burn 'heavy oils. 
 
 In the Diesel engine there are no spark-plugs 
 and no magneto: the engine fires itself with- 
 
SUBMARINES 241 
 
 out electrical help. Air is let into the cylinder 
 at ordinary atmospheric pressure, or fifteen 
 pounds per square inch. But it is compressed 
 by the upward stroke of the piston to about 
 five hundred pounds per square inch. When 
 air is compressed it develops heat and the sud- 
 den high compression to over thirty times its 
 normal pressure raises the temperature to some- 
 thing like 1000 degrees Fahrenheit. Just as 
 this temperature is reached, a jet of oil is blown 
 into the cylinder by air under still higher pres- 
 sure. Immediately the spray of oil bursts into 
 flame and the hot gases of combustion drive the 
 piston down. Because of the intense heat al- 
 most any oil, from light gasolene to heavy, al- 
 most tarlike oils, can be used. As heavy oils 
 do not throw off any explosive vapors unless 
 they are heated, they make a very safe fuel for 
 submarines. 
 
 To drive the U-boat when no air was to be had 
 for the engines, electric motors were used. 
 There was one on each propeller-shaft and the 
 shafts could be disconnected from the oil-en^ 
 gines when the motors were driving. The mo- 
 tors got their power from storage batteries in 
 the stern of the submarine and under the floors 
 
242 INVENTIONS OF THE GBEAT WAR 
 
 forward. The motors when coupled to and 
 driven by the engines generated current which 
 was stored in the storage batteries. The sub- 
 marine could not run on indefinitely under- 
 water. When its batteries were exhausted it 
 would have to come to the surface and run its 
 engines to store up a fresh charge of electricity. 
 The electric motors gave the boat a speed of 
 about nine knots. 
 
 In addition to the main engines and motors, 
 there was a mass of auxiliary machinery. 
 There were pumps for compressing air to blow 
 the ballast-tanks and to discharge the torpedoes. 
 There was a special mechanism for operating 
 the rudder and hydroplanes, and all sorts of 
 valves, indicators, speaking-tubes, signal lines, 
 etc. The tiny hull was simply crammed with 
 mechanism of all kinds and particularly in the 
 early boats there was little room for the accom- 
 modation of the officers and crew. The officers ' 
 quarters were located amidships, and forward 
 there were the folding berths of the crews. In 
 the later boats more space was given the men. 
 The large U-boats carried a crew of forty and 
 as the hazards of submarine warfare increased, 
 more attention had to be paid to the men. 
 
SUBMARINES 243 
 
 FAT MEN NOT WANTED 
 
 Oddly enough, small, slender men were pre- 
 ferred for submarine duty, not because of lack 
 of space, but because it was apt to be very cold 
 in a submarine, particularly in the winter-time. 
 The water cooled off the boat when the sub- 
 marine was traveling submerged, and the motors 
 gave off little heat; while when the vessel was 
 running on the surface the rush of wind to sup- 
 ply the engines kept the thermometer low. This 
 meant that the men had to pile on much clothing 
 to keep warm, which made them very bulky. 
 The hatchway was none too large -and a fat man, 
 were he bundled up with enough clothing to keep 
 him warm, would have a hard time squeezing 
 through. 
 
 In the center of the vessel was the main hatch- 
 way, leading up to the conning-tower, which 
 was large enough to hold from three to five men. 
 This was the navigating-room when the vessel 
 was running submerged, and above it was the 
 navigating-bridge, used when the -submarine 
 was on the surface. In the conning-tower there 
 was a gyroscopic compass ; a magnetic compass 
 would not work at all inside the -steel hull of 
 
244 INVENTIONS OF THE GREAT WAR 
 
 the U-boat. And here were .the periscopes or 
 eyes of the submarine, rising from fifteen to 
 twenty feet above the roof of the conning- 
 tower. There were usually two periscopes. 
 They could be turned around to give the 
 man at the wheel a view in any direction and 
 they were used sometimes even when the vessel 
 was running on the surface, to give a longer 
 range of vision. 
 
 THE BLINDNESS OF THE SUBMAKINE 
 
 Now, a submarine cannot see anything under- 
 water. The commander cannot even see the 
 bow of his boat from the conning-tower, and 
 until he gets near enough to the surface to 
 poke his periscope out of water he is absolutely 
 blind and must feel his way about with compass 
 and depth-gage. It was always an anxious mo- 
 ment for the U-boat commander, when he was 
 coming up, until his periscope broke out of the 
 water and he could get his bearings ; and even 
 that was attended with danger, for his peri- 
 scope might be seen. Of course a periscope 
 is a very insignificant object on the broad sea, 
 but when a submarine is moving its periscope 
 is followed by a wake which is very conspic- 
 
SUBMARINES 245 
 
 uous, and so the U-boat ran a chance of being 
 discovered and destroyed before it could dive 
 again to a safe depth. Later, telescoping peri- 
 scopes were used, which could be raised by 
 means of a hand-lever. The submarine would 
 run along just under the surface and every 
 now and then it would suddenly raise its peri- 
 scope for an observation and drop it down again 
 under cover if there was danger nigh. This 
 was much simpler and quicker than having a six- 
 or eight-hundred-ton boat -come up to the sur- 
 face and dive to safety. He might even collide 
 with a vessel floating on the surface, but to 
 lessen this danger submarines were furnished 
 with ears or big microphone diaphragms at each 
 side of the hull by which a ship could be located 
 by the noise of its propellers. 
 
 In the bow were the torpedo-tubes and the 
 magazine of torpedoes. At first there were only 
 two torpedo-tubes, but later the number was 
 increased to four. These were kept constantly 
 loaded, so that the projectiles could be launched 
 in rapid succession, if necessary, without a 
 p*ause for the insertion of a fresh torpedo. In 
 some submarines tubes were provided in the 
 stern also so that the boat could discharge a 
 
246 INVENTIONS OF THE GREAT WAR 
 
 torpedo at its enemy while running away from 
 him. 
 
 Each tube was closed at the outer end by a 
 cap and art the inside end by a breech-block. 
 The tube was blown clear of water by means of 
 compressed air, and of course the outer cap was 
 closed when the breech was open to let in a tor- 
 pedo. Then the breech was closed, the cap 
 opened, and the torpedo was discharged from 
 the tube by a blast of air. 
 
 THE TORPEDO 
 
 A torpedo is really a motor-boat, a won- 
 derfully constructed boat, fitted with an en- 
 gine of its own that is driven by compressed 
 air and which drives the torpedo through the 
 water at about forty miles per hour. The 
 motor-boat is shaped like a cigar and that 
 used by the Germans was about fifteen feet 
 long and fourteen inches in diameter. We 
 used much larger torpedoes, some of them 
 being twenty-two feet long. Ours have a large 
 compressed-air reservoir and will travel for 
 miles; but the Germans used their torpedoes 
 at short ranges of a thousand yards and under, 
 cutting down the air-reservoir as much as pos- 
 
SUBMARINES 247 
 
 sible and loading the torpedo with an extra 
 large explosive charge. 
 
 We found in the Diesel engine that when 
 air is highly compressed it becomes very 
 hot. When compressed air is expanded, the 
 reverse takes place, the air becomes very cold. 
 The air that drives the motor of the torpedo 
 grows so cold that were no precautions taken 
 it would freeze any moisture that might be 
 present and would choke up the engine with the 
 frost. And so an alcohol flame is used to heat 
 the air. The air-motor is started automatically 
 by release of a trigger as the torpedo is blown 
 out of the torpedo-tube. By means of gear- 
 ing, the motor drives two propellers. These run 
 in opposite directions, so as to balance each 
 other and prevent any tendency for the torpedo 
 to swerve from its course. The torpedo is 
 steered by a rudder which is controlled by a 
 gyroscope, and it is kept at the proper depth 
 under water by diving-rudders which are con- 
 trolled by a very sensitive valve worked by the 
 weight of the water above it. The deeper the 
 water, the greater the weight or pressure; and 
 the valve is so arranged that, should the tor- 
 pedo run too far under, the pressure will cause 
 
248 INVENTIONS OF THE GREAT WAR 
 
 the diving-rudders to tilt until the torpedo comes 
 up again ; then if the torpedo rises too high, the 
 valve will feel the reduction of pressure and 
 turn the rudders in the other direction. 
 
 The business end of a torpedo is a " war- 
 head " packed with about four hundred 
 pounds of TNT. At the nose of the tor- 
 pedo is a firing-pin, with which the war-head 
 is exploded. Ordinarily, the firing-pin does 
 not project from the torpedo, but there is a 
 little propeller at the forward end which is 
 turned by the rush of water as the torpedo 
 is driven on its course. This draws out the 
 firing-pin and gets everything ready for the 
 TNT to explode as soon as the firing-pin is 
 struck. But the firing-pin is not the only means 
 of exploding the torpedo. Inside there is a very 
 delicate mechanism that will set off the charge 
 at the least provocation. In one type of tor- 
 pedo a steel ball is provided which rests in a 
 shallow depression and the slightest shock, the 
 sudden stopping or even a sudden swerve of the 
 torpedo, would dislodge the ball and set off the 
 charge. Hence various schemes, proposed by 
 inventors, for deflecting a torpedo without 
 touching the firing pin, would have been of no 
 value at all. 
 
SUBMAKIKETS 5 249 
 
 GUNS ON SUBMABINES 
 
 As torpedoes are expensive things, the 
 U-boats were supplied with other means of 
 destroying their victims. The Germans sprang 
 a surprise by mounting guns on the decks of 
 their submarines. At first these were arranged 
 to be lowered into a hatch when the boat was 
 running submerged, but later they were per- 
 manently mounted on the decks so that they 
 would be ready for instant use. They were 
 heavily coated with grease and the bore was 
 swabbed out immediately when the boat came to 
 the surface, so that there was no danger of 
 serious rust and corrosion. The 3-inch gun of 
 the early months of the war soon gave way to 
 heavier pieces and the latest U-boats were sup- 
 plied with guns of almost 6-inch caliber and 
 there was a gun on the after deck as well as 
 forward. 
 
 The U-boats depended upon radiotelegraphy 
 to get their orders and although they did not 
 have a very wide sending-range, they could re- 
 ceive messages from the powerful German sta- 
 tion near Berlin. The masts which carried the 
 radio aerials could be folded down into pockets 
 
250 INVENTIONS OF THE GREAT WAR 
 
 in the deck. From stem to stern over the entire 
 boat a cable was stretched which was intended to 
 permit the U-boat to slide under nets protect- 
 ing harbor entrances, and in later boats -there 
 were keen-toothed knives at the bow which 
 would cut through a steel net. During the war 
 German and Austrian U-boats occupied so much 
 attention that the public did not realize the 
 part that the Entente Allies were playing under 
 the sea. America, Great Britain, France, and 
 Italy made good use of submarines, operating 
 them against enemy vessels, blockading enemy 
 ports, and actually fighting enemy submarines. 
 
 A STEAM-DRIVEN SUBMARINE 
 
 The British in particular did splendid work 
 with the submarine and developed boats that 
 were superior to anything turned out by the 
 Germans. For instance, they developed a sub- 
 marine which is virtually a submersible de- 
 stroyer. It is 340 feet long and it can make a 
 speed of 24 knots on the surface. The most 
 remarkable part of this boat is that its engines 
 are driven by steam. Its boilers are fired with 
 oil fuel. There are two smoke-stacks which fold 
 (Jown when it submerges. Of course when run- 
 
SUBMARINES 261 
 
 ning under-water the vessel is driven by elec- 
 tricity and it makes a speed of 10 knots. It 
 carries three 4^inch guns, two forward and one 
 aft, and its displacement submerged is 2700 tons 
 as against 800 tons for the largest German sub- 
 marines. 
 
 A SUBMARINE THAT MOUNTS A TWELVE-INCH 
 GUN 
 
 Still more remarkable is the big "super-sub- 
 marine" designed by the British to bombard the 
 forts of the Dardanelles, but unfortunately it 
 was built too late to be used there. This sub- 
 marine carries a gun big enough for a battle- 
 ship. It is of 12-inch caliber and weighs 50 
 tons. Of course a big gun like that could not 
 be fired athwart the submarine. It might bowl 
 the little vessel over, even though it was a 
 1700-ton submarine. The gun is mounted to 
 fire fore and aft, with a deviation of only a few 
 degrees to one side or the other, so that the 
 shock of the recoil is taken by the length in- 
 stead of the beam of the submarine. It fires a 
 shell weighing 620 pounds and a full charge is 
 not used, so that the extreme range is only 
 about 15,000 yards. This submarine monitor 
 
252 INVENTIONS OF THE GREAT WAR 
 
 would have been a very difficult target for the 
 Turkish gunners to hit. 
 
 When the war came to an end and the Ger- 
 man submarines surrendered to the Entente 
 Allies at Harwich, there was considerable 
 public curiosity as to whether or not an exami- 
 nation of the U-boats would disclose any 
 wonderful secrets. But they contained nothing 
 that the Allies did not already know, and one 
 British officer stated that the plans of the Ger- 
 man submarines had often fallen into their 
 hands long before a U-boat of the same type 
 was captured! 
 
CHAPTER XIH 
 
 GETTING THE BEST OF THE U-BoAT 
 
 THE U-boat commander who sallied forth 
 from the harbor of Wilhelmshaven in the 
 early days of the war had nothing to fear. He 
 was out to murder, not to fight. His prey was 
 always out in the open, while he could kill with- 
 out exposing more than his eye above water. 
 Not even a sporting chance was allowed his 
 victims, particularly when he chose unarmed 
 merchantmen for his targets. He could come 
 up boldly to the surface and shell a ship into 
 submission. This was cheaper than torpedo- 
 ing the vessel, because torpedoes are expensive. 
 If the ship were speedy it might run away; or 
 if the U-boat came up too close to its intended 
 prey, the latter might run it down. That hap- 
 pened occasionally and it was the only danger 
 that the Herr Kommandant had to fear. 
 
 If a destroyer suddenly appeared, the U-boat 
 could dive into the shelter of the sea. If the 
 
 253 
 
254 INVENTIONS OF THE GREAT WAR 
 
 water were not too deep, it could lie on the 
 bottom for two or more days if need be. There 
 was plenty of air in the hull to sustain life 
 for many hours and then the compressed air 
 used for blowing the ballast-tanks could be 
 drawn upon. In the U-boat there were potash 
 cartridges to take up the carbon-dioxide, and 
 tanks of pure oxygen to revitalize the air. If 
 the submarine were damaged, it was not neces- 
 sary for it to come to the surface to effect re- 
 pairs. There were air-locks through which a 
 diver could be let out of the boat. He was 
 fitted with oxygen and potash cartridges, so 
 that he did not need to be connected by an air- 
 hose with the boat, but could walk around it 
 freely to mend injured rudders or to clear the 
 propeller of entanglements. 
 
 Even the small submarines of those early 
 days were capable of taking long voyages. 
 Setting his course at a comfortable pace of 10 
 knots, the U-boat commander could count on 
 enough fuel to carry him 1600 miles, and if 
 need be he could slow down to 8 knots and by 
 using certain of his water-ballast tanks for 
 additional oil-reservoirs, extend his cruising- 
 radius to nearly 3000 miles. The big 800-ton 
 
GETTING THE BEST OF THE U-BOAT 255 
 
 U-boats that were built later had a radius of 
 5000 miles at an 8-knot speed. And so when 
 the British closed the English Channel with 
 nets and mines, Herr Kommandant was not at 
 all perturbed; he could sail around the British 
 Isles if he chose and make war upon trans- 
 atlantic shipping. When harbors were walled 
 off with nets, he could remain outside and sink 
 vessels that were leaving or entering them. 
 
 SUBMAKINE-CHASEES 
 
 A real menace came when the U-boat com- 
 mander popped his periscope out of the sea 
 and saw several little motor-boats bearing down 
 upon him. They seemed harmless enough, but 
 a moment's inspection showed them to be armed 
 with guns fully as powerful as those he carried. 
 It was useless to discharge a torpedo at so 
 speedy and small a foe. A torpedo has to have 
 a fairly deep covering of water, else its course 
 will be disturbed by surface waves; and the 
 submarine-chasers drew so little water that a 
 torpedo would pass harmlessly under them. 
 It was useless for the U-boat commander to 
 come up and fight them with his guns. They 
 would have been upon him before he could do 
 
256 INVENTIONS OF THE GREAT WAR 
 
 that, and their speed and diminutive size made 
 them very difficult targets to hit. Besides, he 
 dared not risk a duel of shell, for he knew that 
 if the precious inner hull of his boat were 
 punctured, he could not seek refuge under 
 water; and if he could not hide, he was lost. 
 The little armed mosquito craft swarmed about 
 the harbor entrances, ready to dash at any sub- 
 marine that showed itself. They could travel 
 twice as fast as the submarine when it was sub- 
 merged and half again as fast as when it was 
 running on the surface. 
 
 Submarines had to take to cover when these 
 chasers were about. Herr Kommandant did 
 not even dare to take a look around through 
 his periscope, because the streak of foam that 
 trailed in its wake would betray him and im- 
 mediately the speedy motor-boats would take 
 up the chase ; and they had a disagreeable way 
 of dropping bombs which, even if they did not 
 sink the submarine, might produce such a con- 
 cussion as to spring its seams. His foes had 
 discovered one of his most serious defects. He 
 was blind under-water and they were making 
 the most of this handicap. 
 
 Groping along under-water by dead-reckon- 
 
GETTING THE BEST OF THE U-BOAT 257 
 
 ing was not any too safe a procedure near land, 
 because he was liable at any moment to crash 
 into an uncharted rock or maybe into the wreck 
 of some submarine victim. He could not cor- 
 rect his bearings without coming to the surface, 
 and, in the black depths of the sea, a slight mis- 
 calculation might send him to his doom. As 
 was explained in the previous chapter, he had 
 to keep moving, because he could not remain 
 suspended under water. 
 
 He was more helpless than a ship sailing 
 in the densest of fogs. A ship can stop and 
 listen to sound-signals, or even to the beat- 
 ing of the surf on the shore, or it can take 
 soundings to locate its position; and yet it is 
 no uncommon occurrence for a ship to run 
 ashore in a fog. How much easier it is for a 
 submarine to lose its bearings when obliged to 
 travel by dead-reckoning, particularly in the 
 disconcerting excitement of the chase! To 
 avoid the danger of collision with surface ves- 
 sels, the commander chose to run at a depth of 
 sixty-five feet. That wa's the upper limit of his 
 safety-zone. A depth of -over two hundred feet 
 was his lower limit, because, as stated before, 
 the water-pressure at that depth would crush in 
 
258 INVENTIONS OF THE GREAT WAR 
 
 his hull or at least start its seams. If the bot- 
 tom were smooth and sandy, and not too deep, 
 he could settle gently upon it and wait for dark- 
 ness, to make his escape. 
 
 But while he lay on a sandy bottom, he was 
 still in danger. Trawlers were sweeping the 
 bottom with nets. He might be discovered ; 
 and then if he did not come up and surrender, 
 a bomb would let in the sea upon him. 
 
 A HINT FROM NATURE 
 
 While he could not see under water, his ad- 
 versaries could. They had taken a hint from 
 nature. The fish-hawk has no difficulty in spy- 
 ing his submarine prey. Flying high above the 
 water, he can see his victims at a considerable 
 depth, and wait his chance to pounce upon an 
 unwary fish that comes too near the surface. 
 It is said that the British trained sea-gulls to 
 hunt submarines. Sea-gulls will follow a ship 
 far out to sea for the sake of feeding on refuse 
 that is thrown overboard. British submarines 
 encouraged the birds to follow them, by throw- 
 ing out bait whenever they came to the surface. 
 Of course the birds could see the submarine 
 even when it was submerged, and if they pur- 
 
GETTING THE BEST OF THE U-BOAT 259 
 
 sued it, they were always rewarded with plenty 
 of food. The gulls drew no fine distinction 
 between Hun and Briton, and so it came that 
 Herr Kommandant often groped his way along 
 in the dark sea, totally oblivious of the fact that 
 he was attended by an escort of feathered folk 
 who kept the British chasers informed of his 
 presence. 
 
 In this connection it is interesting to note 
 that the British trained sea lions to hunt sub- 
 marines. The animals were taught at first to 
 swim to a friendly submarine, locating it by 
 the sound of its propellers. They were always 
 rewarded with fish. These sea lions were muz- 
 zled so that they could not go fishing on their 
 own account. Then they learned to locate 
 enemy submarines and pointed them out by 
 swimming directly toward them and diving 
 down to them. 
 
 But there were human eyes, as well, that spied 
 upon the U-boat. Fast seaplanes patrolled the 
 waters, searching constantly for any trace of 
 submarine. Its form could be vaguely outlined 
 to a depth of from fifty to seventy-five feet, 
 unless the sea were choppy, and once it was dis- 
 covered, chasers or trawlers were signaled to 
 
260 INVENTIONS OF THE GREAT WAR 
 
 destroy it with bombs or to entangle it in nets. 
 Often a submarine would be discovered by a 
 leak in its oil-tank which would leave a tell- 
 tale trail. Sometimes when the U-boat itself 
 could not be discerned, there would be slight 
 shimmer, such as may be seen above a hot stove, 
 caused by refraction of light in its wake. This 
 was easily recognized by trained observers. 
 
 Even better aerial patrols were the small 
 dirigibles known as Blimps. They are a cross 
 between a balloon and an airplane, for they 
 have the body and the power-plant of an air- 
 plane, but the planes are replaced by a gas- 
 bag. Blimps could cruise leisurely and search 
 the sea thoroughly. They could stop and hover 
 directly over a submarine and drop explosives 
 upon it with great accuracy. And so Herr 
 Kommandant could take no comfort in hiding 
 under a blanket of waves unless the blanket were 
 so thick as to conceal his form completely from 
 the eyes overhead. This made it imperative 
 to leave the shallower waters near shore and 
 push out into the deep sea, where the small 
 chasers could not pursue him. But he could 
 not shake off his pursuers. Stream-trawlers 
 
Courtesy of "Scientific American " 
 
 Airplane Stunning a U-boat with a Depth-bomb 
 
GETTING THE BEST OP THE U-BOAT 261 
 
 are built to ride the heaviest gales and they 
 took up the chase out into the ocean. 
 
 There was a decided advantage for the U- 
 boat in moving out to sea. It had a wider 
 field of activity and could more easily escape 
 from its pursuers. But on the other hand, its 
 prey also had an advantage. Out in the open 
 ocean they were not obliged to follow the usual 
 ship lanes and it was more difficult for a sub- 
 marine to intercept them. There it took more 
 U-boats to blockade a given area. 
 
 A GAME OF HIDE-AND-SEEK 
 
 Then, it ceased to be quite so one-sided a 
 game when merchantmen began to carry guns. 
 That made it necessary for the submarine com- 
 mander to creep up on his victims stealthily, 
 and depend upon his torpedoes. He had to 
 get within a thousand yards of the ship and 
 preferably within five hundred yards, in order 
 to be sure of hitting it. If the ship could travel 
 faster than he could, he had to do this without 
 betraying his presence. But ship-captains 
 soon learned that their safety lay in zig-zagging. 
 When Herr Kommandant reached the point 
 
262 INVENTIONS OF THE GREAT WAR 
 
 from which he had planned to attack, he would 
 raise his telescopic periscope out of the water, 
 expecting to see his victim within good torpedo 
 range, only to find it sailing safely on another 
 tack. Again, he would have to take observa- 
 tions and make another try, probably with no 
 better luck. It was a game of hide-and-seek 
 in which the merchant ship had a good chance 
 of making its escape, particularly when blotches 
 of camouflage paint made it difficult for him to 
 get the range, as described in Chapter XI. 
 
 Slower ships could be attacked without all 
 this maneuvering, provided the submarine's 
 guns outranged those of the ship. And so U- 
 boats were provided with larger and larger 
 guns, which made it possible for them to stand 
 off and pound the merchantmen while out of 
 reach of the vessel's guns. But ships found a 
 way of hiding on the surface of the sea. A 
 vessel would spout forth volumes of dense black 
 smoke which would obliterate it from view. 
 (See Fig. 19.) If the wind was quartering, 
 the ship would change its course and dodge be- 
 hind the sheltering pall of smoke. Not only 
 was the smoke produced on the vessel itself, 
 but smoke-boxes were cast overboard to form 
 
GETTING THE BEST OF THE U-BOAT 263 
 
 a screen behind the vessel. These smoke- 
 boxes contained a mixture of coal-tar and phos- 
 phorus and other chemicals which would pro- 
 duce incomplete combustion. They were ig- 
 
 Courtesy of the Submarine Defense Association 
 
 FIG. 19. How a ship hid behind smoke produced on its own 
 stern, with different directions of wind 
 
 nited by the rubbing of a phosphorus compound 
 on a priming-composition, and then cast adrift 
 to pour out dense volumes of heavy smoke. 
 (See Fig. 20.) Behind this screen, the ship 
 could dodge and zig-zag and if her speed were 
 
264 INVENTIONS OF THE GREAT WAR 
 
 greater than that of the submarine, her chances 
 of escape were very good. 
 
 Another annoyance that Herr Kommcmdant 
 experienced was, when he lifted his periscopic 
 
 Courtesy of the Submarine Defense Association 
 
 FIG. 20. How a ship hid behind a screen of smoke produeed 
 by throwing smoke boxes overboard 
 
 eye above water, to find it so smeared with a 
 sticky substance that he could not see. His 
 foes had strewn the water with tar-oil that had 
 spread in a thin film over a surface miles in 
 extent. This blinded him at first, but before 
 
GETTING THE BEST OF THE U-BOAT 265 
 
 long he was equipped with a jet for washing off 
 the periscope glass and that little annoyance 
 was overcome. 
 
 But the craft most dreaded by the U-boat 
 commander were the destroyers. These light, 
 high-powered, heavily armed vessels could 
 travel twice as fast as he could on the surface 
 and three times as fast as he could submerged, 
 Shells were invented which would not ricochet 
 from the surface of the sea, but would plow 
 right through the water, where they struck and 
 hit the submarine below water-level. 
 
 DEATH -DEALING "ASH CANS" 
 
 However, it was not shell-fire that he dreaded, 
 but the big "ash cans" loaded with TNT 
 which were timed to explode far under water, 
 and which would crush his boat or start its 
 seams. It was not necessary for these bombs 
 to hit the U-boat. When they went off they 
 would send out a wave of pressure that would 
 crush the boat or start its seams even if it were 
 a hundred feet and more from the point of the 
 explosion. Within limits, the deeper the explo- 
 sion the wider would its destructive area be. 
 
 The timing-mechanism of some depth bombs 
 
266 INVENTIONS OF THE GREAT WAR 
 
 consisted merely -of a float on the end of a cord. 
 When the bomb was thrown overboard this 
 float remained on the surface until the cord 
 was pulled out to its full length, when there 
 would be a yank on the firing-trigger and the 
 charge would explode. In other depth bombs 
 there was a valve operated by the pressure of 
 the water. When the bomb sank to the depth 
 for which the valve was set, the pressure of the 
 water would force the valve in, exploding a 
 cartridge which set off the charge. So power- 
 ful were these depth bombs that the destroyer 
 had to travel at high speed to get out of range 
 of the explosion. 
 
 Depth bombs were rolled off the stern of the 
 destroyer and also thrown out from the sides 
 of the vessel by means of mortars. Some of 
 the mortars were Y-shaped and held a depth 
 bomb in each arm of the Y. When a blank 3- 
 inch shell was exploded at the base of the gun, 
 both bombs would be hurled from the ship, one 
 to port and the other to starboard. In this way 
 the destroyer could drop the bombs in a " pat- 
 tern ' ' of wide area. Herr Kommandant gained 
 a wholesome respect for these terriers of the 
 sea. It was suicide to show himself anywhere 
 
GETTING THE BEST OF THE U-BOAT 267 
 
 near a destroyer. In a moment the speedy boat 
 would be upon him, sowing depth bombs along 
 his course. His chances of escaping through 
 this hail of high explosives were remote in- 
 deed. 
 
 The ships that he was most eager to destroy 
 were either too speedy for him to catch, unless 
 they happened to come his way, or else they 
 were herded in large convoys protected by these 
 dreaded destroyers. The convoy proved a most 
 baffling problem for Herr Kommandant. He 
 dared not attack the convoy by daylight. In a 
 fog he might take a chance at picking off one 
 of the ships, but even that was very risky. He 
 could trail the convoy until dusk and then under 
 cover of darkness draw near enough to dis- 
 charge a torpedo, but in the daytime he must 
 keep his distance because there were eyes in the 
 sky watching for him. At the van and rear of 
 the convoy there were kite balloons high in the 
 sky, with observers constantly watching for 
 periscopes, and for U-boats that might be lurk- 
 ing under the surface. 
 
 As the destroyers gained in experience, the 
 difficulties of the U-boat attack grew greater 
 and its work grew more and more perilous. 
 
268 INVENTIONS OF THE GREAT WAR 
 
 The crew grumbled and grew mutinous. The 
 morale of the men was shaken. We can 
 imagine the horror of plunging hurriedly into 
 the depths of the sea, and rushing along blindly 
 under the surface, dodging this way and that, 
 while terrific explosions of depth bombs stagger 
 the submarine and threaten to crush it, and 
 there is the constant expectation that the next 
 explosion will tear the thin shell of the U-boat 
 and let in the black hungry water. The tables 
 were turned. Now, if never before, Herr Kom- 
 mandant, the hunter, knew what it felt like to 
 be hunted. 
 
 It takes an exceptional man to go through 
 such a harrowing experience with unshattered 
 nerves. On at least one occasion, a submarine 
 that was being depth-bombed came suddenly to 
 the surface. The hatch flew open and the crew 
 rushed out, holding up their hands and crying, 
 "Kamerad." The U-boat was uninjured, but 
 the shock of a depth-bomb explosion had put 
 the electric-lighting system out of commission, 
 and the crew, unnerved by the explosion and ter- 
 rified by the darkness, had overpowered their 
 officers and brought the boat to the surface. 
 
(C) Underwood & Underwood 
 
 The False Hatch of a Mystery Ship and 
 
 JJJ: 
 
 The same Hatch opened to disclose the 3-Inch Gun and Crew 
 

GETTING THE BEST OF THE U-BOAT 269 
 
 EYES IN THE SEA 
 
 There were other craft that Herr Kommm- 
 dmt had to look out for. His were not the only 
 submarines in the sea. His foes also were 
 possessed of submarines. They could not see 
 under water any better than he could, but they 
 could fight on the surface as well as he, and 
 they could creep up on him even as he crept 
 up on his prey. As a French submarine com- 
 mander puts it: "The U-boats used to enjoy 
 the advantage of remaining themselves invisible 
 while all the surface and aerial craft which were 
 sent in pursuit of them were boldly outlined 
 against the sky and visible to them. This is 
 one of the reasons we used submarines to am- 
 bush U-boats." Submarines were also used to 
 accompany the convoys, so that the U-boat com- 
 mander had to watch not only for the eyes 
 of the ship's lookouts and the eyes in the kite 
 balloons, but also for the periscope eyes that 
 swam in the sea. 
 
 TRAILING U-BOATS BY SOUND 
 
 The troubles of the submarine-commander 
 were multiplying. All over the world inventors 
 
270 INVENTIONS OF THE GREAT WAR 
 
 were plotting Ms destruction. As long as we 
 depended upon our eyes to ferret him out, the 
 sea was a safe refuge, provided he dived deep 
 enough, but when we began to use our ears as 
 well, he found himself in a very serious predica- 
 ment. Although light is badly broken up in its 
 passage through water, sound-waves will travel 
 through water much better than in air. The 
 first listening-devices used were crude affairs 
 and did not amount to much, particularly when 
 the U-boats muffled their motors and engines 
 so that they were virtually noiseless. But the 
 French invented a very sensitive sound-de- 
 tector. It consisted of a lot of tiny diaphragms 
 set in a big hemisphere. There were two of 
 these hemispheres, one at each side of the boat. 
 When sound-waves struck these hemispheres, 
 the diaphragms would respond. At the focus 
 of each hemisphere there was a megaphone re- 
 ceiver; one of these carried the sound to the 
 operator's right ear and the other to his left. 
 He would turn a megaphone around until he 
 found the diaphragm that produced the loudest 
 sound. This gave him the direction of the 
 sound-wave. Then the boat would be steered 
 in that direction. He knew that it was aimed 
 
GETTING THE BEST OF THE U-BOAT 271 
 
 properly when the sound coming to his right ear 
 was just as loud as that which came into his left 
 ear. 
 
 A still better hydrophone was developed by a 
 group of American inventors. The details of 
 this cannot yet be disclosed, but we know that 
 it was adopted at once by our allies. A very 
 sensitive receiver was used which could detect 
 a U-boat miles away and determine its direction 
 accurately. Under ideal conditions the range 
 of the device was from fifteen to twenty-five 
 miles, but the average was from three to eight 
 miles. If two or more boats fitted with sound- 
 detectors were used, they could determine the 
 position of the U-boat perfectly. One draw- 
 back was that the vessel would have to stop 
 so that the noise of its own engines would not 
 disturb the listener, but this was largely over- 
 come by trailing the detector a hundred feet 
 or more from the stern of the ship. The sounds 
 were then brought in by an electric cable to the 
 listener in the ship. 
 
 These sound-detectors were placed on Allied 
 submarines as well as surface vessels and they 
 were actually tried out on balloons and dirigi- 
 bles, so that they could follow a U-boat after it 
 
272 INVENTIONS OF THE GREAT WAR 
 
 had submerged too deeply to be followed by 
 sight. 
 
 Many U-boats were chased to their doom by 
 the aid of the American hydrophone. Fig. 
 
 o Listening 
 * Depth Chorye 
 
 Courtesy of the "Scientific American" 
 
 FIG. 21. Chart of an actual pursuit of a U-boat which 
 ended in the destruction of the submarine 
 
 21 illustrates a very dramatic chase. The full 
 line shows the course of the U-boat as plotted 
 out by hydrophones and the broken line the 
 course of the submarine-chasers. The dots rep- 
 
GETTING THE BEST OF THE U-BOAT 273 
 
 resent patterns of depth bombs dropped upon 
 the U-boat. Try as he would, the Herr Com- 
 mandant could not shake off his pursuers. At 
 one time, as the listeners stopped to take obser- 
 vations, they heard hammering in the U-boat 
 as if repairs were being made. The motors of 
 the submarine would start and stop, showing 
 clearly that it was disabled. More depth bombs 
 were dropped and then there was perfect 
 silence, which was soon broken by twenty-five 
 revolver-shots. Evidently the crew, unable to 
 come to the surface, had given up in despair 
 and committed suicide. 
 
 The Adriatic Sea was an ideal place for the 
 use of the hydrophone. The water there is so 
 deep that submarines dared not rest on the 
 bottom, but had to keep moving, and so they 
 could easily be followed. Across the sea, at the 
 heel of the boot of Italy, a barrage of boats 
 was established. U-boats would come down to 
 this barrage at night and, when within two or 
 three miles of the boats, dive and pass under 
 them. But when hydrophones were used that 
 game proved very hazardous. Our listeners 
 would hear them coming when they were miles 
 away. Then they would hear them shift from 
 
274 INVENTIONS OF THE GREAT WAR 
 
 oil- to electric-drive ^nd plunge under the sur- 
 face. Darkness was no protection to the U- 
 boats. The sound-detector worked just as well 
 at night as in the daytime and a group of three 
 boats would drop a pattern of bombs that would 
 send the U-boat to the bottom. 
 
 On one occasion after an attack it was evident 
 that the submarine had been seriously injured. 
 Its motors were operating, but something must 
 have gone wrong with its steering-gear, or its 
 ballast-chambers may have been flooded, be- 
 cause it kept going down -and soon the listeners 
 heard a crunching noise as it was crushed by 
 the tremendous pressure of the water. 
 
 And so U-boat warfare grew more and more 
 terrible for Herr Kommandant. The depths of 
 the sea were growing even more dangerous than 
 the surface. On every hand he was losing out. 
 He had tried to master the sea without master- 
 ing the surface of the sea. But he can never 
 really master who dares not fight out in the 
 open. For a time, the German did prevail, but 
 his adversaries were quick to see his deficiencies 
 and, by playing upon these, to rob the terror 
 of the sea of his powers. And as Herr Kom- 
 mandant looks back at the time when he stepped 
 
GETTING THE BEST OF THE U-BOAT 275 
 
 into the lime-light as the most brutal destroyer 
 the world has ever seen, he cannot take much 
 satisfaction in reflecting that the sum total of 
 his efforts was to spread hatred of Germany 
 throughout the world, to summon into the con- 
 flict a great nation whose armies turned the tide 
 of victory against his soldiers, and finally to 
 subject his navy, second only to that of Great 
 Britain, to the most humiliating surrender the 
 world has ever seen. 
 
CHAPTER XIV 
 " DEVIL'S EGGS" 
 
 IN modern warfare a duel between fixed forts 
 and floating forts is almost certain to end 
 in a draw. Because the former -are fixed they 
 make good targets, while the war-ship, being 
 able to move about, can dodge the shell that are 
 fired against it. On the other hand, a fort on 
 land can stand a great deal of pounding and 
 each of its guns must be put out of action in- 
 dividually, before it is subdued, while the fort 
 that is afloat runs the risk of being sunk with 
 a few well-directed shots. 
 
 But fortifications alone will not protect a 
 harbor from a determined enemy. They can- 
 not prevent hostile ships from creeping by them 
 under cover of darkness or a heavy fog. To 
 prevent this, the harbor must be mined, and this 
 must be done in such a way that friendly ship- 
 ping can be piloted through the mine-field, 
 
 276 
 
"DEVIL'S EGGS" 277 
 
 while hostile craft will be sure to strike the 
 mines and be destroyed. 
 
 The mines may be arranged to be fired by 
 electricity from shore stations, in which case 
 they are anchored at such a depth that ships 
 can sail over them without touching them. If a 
 hostile vessel tried to dash into the harbor, the 
 touch of a button on shore would sink it when 
 it passed over one of the mines. But the suc- 
 cess of electrically fired mines would depend 
 upon the "seeing." In a heavy fog they would 
 prove no protection. 
 
 Another way of using electric mines is to 
 have telltale devices which a ship would strike 
 and which would indicate to the operator on 
 shore that a vessel was riding over the mines 
 and would also let him know over which par- 
 ticular mines it was at the moment passing. 
 No friendly vessel Wiould undertake to enter 
 the harbor in a fog or after dark and the oper- 
 ator would not hesitate to blow up the invader 
 even if he could not see him. 
 
 However, the ordinary method of mining a 
 harbor is to lay fields of anchored mines across 
 the channels and entrances to the harbor 
 sensitive mines that will blow up at the slight- 
 
278 INVENTIONS OF THE GREAT WAR 
 
 est touch of a ship's hull and leave tortuous 
 passages through the fields for friendly ship- 
 ping. Of course pilots have to guide the ships 
 through the passages and lest enemy spies learn 
 just where the openings are the mine-fields 
 must be shifted now and then. 
 
 The mines are, therefore, made so that they 
 can be -taken up by friendly mine-sweepers who 
 know just how to handle them, and planted else- 
 where. These are defensive mines, but there 
 are other mines that are not intended to be 
 moved. They are planted in front of enemy 
 harbors to block enemy shipping and they are 
 made so sensitive or of such design that they 
 will surely explode if tampered with. 
 
 THE MINE THAT DOES ITS OWN SOUNDING 
 
 A favorite type of mine used during the war 
 was one which automatically adjusted itself to 
 sink to the desired depth. Submerged mines 
 are more dangerous to the enemy because they 
 cannot be seen and avoided. They should float 
 far enough under the surface to remain hidden 
 and yet not so deep that a shallow-draft ship 
 can pass over them without hitting them. As 
 the sea bottom may be very irregular, it is im- 
 
"DEVIL'S EGGS" 279 
 
 possible to tell how long the anchor cable should 
 be without sounding the depth of the water at 
 every point at which a mine is planted. But 
 the automatic anchor takes care of this. Very 
 ingeniously it does its own sounding and holds 
 the mine down to the depth for which it is set. 
 The mine cable is wound up on a reel in the 
 anchor and the mine is held fast to the anchor 
 by a latch. The anchor is of box-shape or 
 cylindrical form, with perforations in it. At 
 first it sinks comparatively slowly, but as it 
 fills with water it goes down faster. Attached 
 to the anchor is a plummet or weight, connected 
 by a cord to the latch. The length of this cord 
 determines the depth at which the mine will 
 float. 
 
 The operation of the mine is shown in Fig. 
 22. When it is thrown overboard (1) it im- 
 mediately turns over so that the buoyant mine 
 A floats on the surface (2). While the anchor 
 is slowly filling and sinking, the plummet B 
 runs out (3). If the mines are to float at a 
 depth of, say, ten feet, this cord must be ten 
 feet long. As soon as it runs out to its full 
 length (4) it springs a latch, (7, releasing the 
 mine A. Then the mine cable D pays out, as 
 
280 INVENTIONS OF THE GREAT WAR 
 
 the anchor E sinks, until the plummet B strikes 
 bottom (5). As soon as the plummet cord 
 slackens a spring-pressed pawl is released and 
 locks the mine-cable reel, so that as the anchor 
 
 Courtesy of the "Scientific American" 
 
 Fio. 22. How the mine automatically adjusts itself to vari- 
 ous depths of water 
 
 continues to sink it draws the mine down with 
 it, until it touches bottom (6), and as the anchor 
 was ten feet from the bottom when the plummet 
 touched bottom and locked the reel, the mine 
 
" DEVIL'S EGGS" 281 
 
 must necessarily be dragged down to a depth 
 of ten feet below the surface. 
 
 The mine itself, -or the "devil's egg" as it 
 is called, is usually a big buoyant sphere of 
 metal filled with TNT or some other power- 
 ful explosive; and projecting from it are a 
 number of very fragile prongs which if broken 
 or even cracked will set off the mine. There 
 is a safety-lever or pin that makes the mine 
 harmless when it is being handled, and this 
 must be withdrawn just before the mine is to 
 be launched. In some mines the prongs are 
 little plungers that are withdrawn into the 
 mine-shell and held by a cement which softens 
 after the mine is submerged and lets the 
 plungers spring out. When the plungers are 
 broken, water enters and, coming in contact 
 with certain chemicals, produces enough heat to 
 set off a cartridge which fires the mine. 
 
 PICKING INFERNAL MACHINES OUT OF THE SEA 
 
 The enemy mine-fields were often located 
 by seaplanes and then mine-sweepers had to 
 undertake the extremely hazardous task of rais- 
 ing the mines or destroying them. If they 
 were of the offensive type, it was much better 
 
282 INVENTIONS OF THE GREAT WAR 
 
 to destroy them. But occasionally, when con- 
 ditions permitted, mine-sweepers undertook to 
 raise the mines and reclaim them for future use 
 against the enemy. The work of seizing a mine 
 and making it fast to the hoisting-cable of the 
 mine-sweeper was usually done from a small 
 rowboat. Raising the first mine was always 
 the most perilous undertaking, because no one 
 knew just what type of mine it was and how to 
 handle it with safety, or whether there was any 
 way in which it could be made harmless. There 
 were some mines, for instance, that contained 
 within them a small vial partly filled with 
 sulphuric acid. The mine carried no prongs, 
 but if it were tilted more than twenty degrees 
 the acid would spill out and blow up the mine. 
 Such a mine would be exceedingly difficult if 
 nrot impossible to handle from a boat that was 
 rocked about by the waves. 
 
 After the first mine of the field was raised 
 and its safety-mechanism studied, the task of 
 raising the rest was not so dangerous. A 
 water telescope was used to locate the mine and 
 to aid in hooking the hoisting-cable into the 
 shackle on the mine. The hook was screwed 
 to the end of a pole and after the mine was 
 
"DEVIL'S EGGS" 283 
 
 hooked, the pole was unscrewed and the cable 
 hauled in, bringing up the "devil's egg" 
 bristling with death. Care had to be taken to 
 keep the bobbing boat from touching the deli- 
 cate prongs until the safety-device could be 
 set. 
 
 However, this painstaking and careful 
 method of raising mines was not often em- 
 ployed. Shallow-draft mine-sweepers would 
 run over the mine-field, dragging a cable be- 
 tween them. The cable would be kept down by 
 means of hydrovanes or "water kites " deep 
 enough to foul the anchor cables of the mines. 
 The "water kites " were V-shaped structures 
 that were connected to the cable in such a way 
 that they would nose down as they were 
 dragged through the water and carry the cable 
 under. The action is just the reverse of a kite, 
 which is set to nose up into the wind and carry 
 the kite up when it is dragged through the air. 
 By means of the cable the anchor chain of the 
 mine was caught and then the mine with its 
 anchor was dragged up. If the mine broke 
 loose from its anchor it could be exploded with 
 a rifle-shot if it did not automatically explode 
 on fouling the cable. 
 
284 INVENTIONS OF THE GREAT WAR 
 
 FLOATING MINES 
 
 When England entered the war she mined her 
 harbors because, although she had the mastery 
 of the sea, she had to guard against raids of 
 enemy ships carried out in foggy and dark 
 weather. But the mines were no protection 
 against submarines. They would creep along 
 the bottom under the mines. Then cable nets 
 were stretched across the harbor channels to 
 bar the submarines, but the U-boats were 
 fitted with cutters which would tear through 
 the nets, and it became necessary to use mines 
 set at lower depths so that the submarines could 
 not pass under them; and nets were furnished 
 with bombs which would explode when fouled 
 by submarines. In fact, mines were set adrift 
 with nets stretched between them, to trap sub- 
 marines. Floating mines were also used by the 
 Germans for the destruction of surface vessels 
 and these were usually set adrift in pairs, with 
 a long cable connecting them, so that if a vessel 
 ran into the cable the mines would be dragged 
 in against its hull and blow it up. 
 
 The laws of war require that floating mines be 
 
' 'DEVIL'S EGGS" 285 
 
 of such a design that they will become inopera- 
 tive in a few hours; otherwise they might drift 
 about for weeks or months or years and be a 
 constant menace to shipping. Sometimes 
 anchored mines break away from their moor- 
 ings and are carried around by ocean currents 
 or are blown about by the winds. A year 
 after the Eusso-Japanese War a ship was 
 blown up by striking a mine that had been torn 
 from its anchorage and had drifted far from 
 the field in which it was planted. No doubt 
 there are hundreds of mines afloat in the 
 Atlantic Ocean which for many years to come 
 will hold out the threat of sudden destruction 
 to ocean vessels ; for the Germans knew no laws 
 of war and had no scruples against setting 
 adrift mines that would remain alive until they 
 were eaten up with rust. 
 
 The chart on the next page shows the course 
 of ocean currents in the North Atlantic as 
 plotted out by the Prince of Monaco, from which 
 it may be seen that German mines will prob- 
 ably make a complete circuit of the North 
 Atlantic, drifting down the western coast of 
 Europe, across the Atlantic, around the Azores, 
 
286 INVENTIONS OF THE GREAT WAR 
 
 and into the Gulf Stream, which will carry them 
 back to the North Sea, only to start all over. 
 (See Fig. 23.) Some of them will run up into 
 the Arctic Ocean, where they will be blown up 
 by striking icebergs and many will be trapped 
 in the mass of floating 
 seaweed in the Sargasso 
 Sea. But many years 
 will pass before all dan- 
 ger of mines will be re- 
 
 Courtosy of the "Scientific American" 
 
 Flo. 23. Ocean currents of the North Atlantic showing the 
 probable path of drifting mines 
 
 moved. In the meantime, the war has left a 
 tremendous amount of work to be done in rais- 
 ing anchored mines and destroying them. 
 
" DEVIL'S EGGS" 287 
 
 EGG-LAYING SUBMARINES 
 
 Early in the war the British were astonished 
 to find enemy mine-fields in their own waters, 
 far from any German ports. They could not 
 have been planted by surface mine-layers, un- 
 less these had managed to creep up disguised 
 as peaceful trawlers. This seemed hardly 
 likely, because these fields appeared in places 
 that were well guarded. Then it was dis- 
 covered that German U-boats were doing this 
 work. Special mine-laying U-boats had been 
 built and one of them was captured with its 
 cargo of "devil's eggs." 
 
 A sectional view of the mine-laying U-boat 
 is shown opposite page 272. In the after part 
 of the boat were mine-chutes in each of which 
 three mines were stored. A mine-laying sub- 
 marine would carry about a score of mines. 
 These could be released one at a time. The 
 mine with its anchor would drop to the bottom. 
 As soon as it struck, anchor-arms would be 
 tripped and spread out to catch in the sand or 
 mud, while the mine cable would be released 
 and the mine would rise as far as the cable 
 would allow it. The U-boat commander would 
 
288 INVENTIONS OF THE GREAT WAR 
 
 have to know the depth of water in which 
 the mines were to be laid and adjust the cables 
 to this depth in advance. This could not be 
 done while the U-boat was submerged With 
 the mines all set for the depth at a certain spot, 
 the U-boat commander had to find that very 
 spot to lay his "eggs," otherwise they would 
 either lie too deep to do any harm to shipping, 
 or else they would reach up to the surface, 
 where they might be discovered by the Allied 
 patrols. As he had to do his navigating blindly, 
 by dead-reckoning, it was very difficult for him 
 to locate his mine-fields properly. 
 
 But the Germans did not have a monopoly 
 on submarine mine-laying. The British also 
 laid mines by submarine within German har- 
 bors and channels, right under the guns of 
 Heligoland, and many a U-boat was destroyed 
 by such mines within its home waters. 
 
 PABAVA9E8 
 
 On the other hand, the Allies had a way of 
 sailing right through fields of enemy mines 
 with little danger. Our ships were equipped 
 with "paravanes" which are something like 
 the i4 water kites* 1 used by mine-sweepers, and 
 
\!ui< 
 
" DEVIL'S EGGS" 289 
 
 they are still used in the waters of the war zone. 
 Paravanes are steel floats with torpedo-shaped 
 bodies and a horizontal plane near the for- 
 ward end. At the tail of the paravane, there 
 are horizontal and vertical rudders which can be 
 set to make the device run out from the side of 
 the vessel that is towing it, and at the desired 
 depth below the surface. Two paravanes are 
 used, one at each side of the ship, and the tow- 
 ing-cables lead from the bow of the vessel. 
 Thus there are two taut cables that run out 
 from the ship in the form of a V and at such a 
 depth that they will foul the mooring-cable of 
 any mine that might be encountered. The mine 
 cable slides along the paravane cable and in 
 this way is carried clear of the ship's hull. 
 When it reaches the paravane it is caught in a 
 sharp-toothed jaw which cuts the mine cable and 
 lets the mine bob up to the surface. The mine 
 is then exploded by rifle or machine-gun lire. 
 In some forms of paravane there is a hinged 
 jaw which is operated from the ship to shear the 
 cable. The jaw is repeatedly opened and 
 closed by a line that runs to a winch on the ship. 
 This winch winds up the line until it is taut 
 and then the line is permitted to slip, letting 
 
290 INVENTIONS OF THE GREAT WAR 
 
 the jaw open, only to close again as the winch 
 keeps on turning and winding up the line. 
 
 Guarded by steel sharks on each side, their 
 jaws constantly working, a ship can plow right 
 through a field of anchored mines with little 
 danger. To be sure, the bow might chance to 
 hit a mine, when, of course, there would be an 
 explosion ; but the ship could stand damage here 
 better than anywhere else and unless the bow 
 actually hit the mine, one or other of the para- 
 vanes would take care of it and keep it from 
 being dragged in against the hull of the vessel. 
 
 PENNING IN THE U-BOATS 
 
 According to German testimony, mines were 
 responsible for the failure of the U-boat. How- 
 ever, it was not merely the scattered mine- 
 fields sown in German waters that brought the 
 U-boat to terms, but an enormous mine-field 
 stretching across the North Sea from the Orkney 
 Islands to the coast of Norway. Early in the 
 war, U-boats had been prevented from entering 
 the English Channel by nets and mines stretched 
 across the Straits of Dover. As the submarine 
 
 V 
 
 menace grew, it was urged that a similar net 
 be stretched across the North Sea to pen the 
 
"DEVIL'S EGGS" 291 
 
 U-boats in. But it seemed like a stupendous 
 task. The distance across at the narrowest 
 point is nearly two hundred and fifty miles. 
 It would not have been necessary to have the 
 net come to the surface. It could just as well 
 have been anchored so that its upper edge 
 would be covered with thirty feet of water. 
 Surface vessels could then have sailed over it 
 without trouble and submarines could not have 
 passed over it without showing themselves to 
 patrolling destroyers. It would not have been 
 necessary to carry the net to the bottom of the 
 sea. A belt of netting a hundred and fifty feet 
 wide would have made an effective bar to the 
 passage of U-boats. As U-boats might cut their 
 way through the net, it was proposed to mount 
 bombs or mines on them which would explode on 
 contact and destroy any submarine that tried to 
 pass. However, laying a net two hundred feet 
 long even when it is laid in sections, is no small 
 job, but when the net is loaded with contact 
 mines, the difficulty of the work may be well 
 imagined. 
 
 And yet had it been thought that the net would 
 be a success it would have been laid anyhow, 
 but it was argued that seaweed would clog the 
 
292 INVENTIONS OF THE GREAT WAR 
 
 meshes of the net and ocean currents would tear 
 gaps in it. Even if it had not been torn away, 
 the tidal currents would have swept it down and 
 borne it under so far that U-boats could have 
 passed over it in safety without coming to the 
 surface. 
 
 A WALL OF MINES 
 
 When America entered the war, we were very 
 insistent that something must be done to block 
 the North Sea, and we proposed that a barrage 
 of anchored mines be stretched across the sea 
 and that these mines be set at different levels 
 so as to make a "wall" that submarines could 
 not dive under. This would do away with all 
 the drawbacks of a net. Ocean currents and 
 masses of seaweed could not affect individual 
 mines as they would a net. Furthermore, an 
 American inventor had devised a new type of 
 mine which was peculiarly adapted to the pro- 
 posed mine barrage. It had a firing-mechan- 
 ism that was very sensitive and the mine 
 had twice the reach of any other. 
 
 At length the British mine-laying forces were 
 prevailed upon to join with us in laying this 
 enormous mine. It was one of the biggest and 
 
"DEVIL'S EGGS" 293 
 
 most successful undertakings of the war. It 
 was to be two hundred and thirty miles long 
 and twelve miles wide on the average, reaching 
 from the rocky shores of the Orkney Islands 
 to Norway. There was plenty of deep water 
 close to the coast of Norway and it was against 
 international law to lay mines within three miles 
 of the shores of a neutral nation, so that the U- 
 boats might have had a clear passage around the 
 end of the barrage. But as it was also against 
 the law for the U-boats to sail through neutral 
 waters, Norway laid a mine-field off its coast 
 to enforce neutrality, and this was to join with 
 that which the British and we were to lay. 
 Most of the mine-laying was to be done by the 
 United States and we were to furnish the mines. 
 The order to proceed with the work was given 
 in October, 1917, and it was a big order. A 
 hundred thousand mines were to be made and to 
 preserve secrecy, as well as to hurry the work 
 as much as possible, it was divided among five 
 hundred contractors and subcontractors. The 
 parts were put together in one plant and then 
 sent to another, where each mine was filled with 
 three hundred pounds of molten TNT. To 
 carry them across the ocean small steamers 
 
294 INVENTIONS OF THE GREAT WAR 
 
 were used, so that if one should be blown up 
 by a submarine the loss of mines would not be 
 very great. There were twenty-four of these 
 steamers, each carrying from twelve hundred to 
 eighteen hundred mines and only one of them 
 was destroyed by a submarine. The steamers 
 delivered their loads on the west coast of Scot- 
 land and the mines were taken across to the 
 east coast by rail and motor canal-boats. Here 
 the mines were finally assembled, ready for 
 planting. Seventy thousand mines were 
 planted, four fifths of them by American mine- 
 layers and the rest by the British. 
 
 MINE RAILROADS ON SHIPS 
 
 To handle the mines the ships were specially 
 fitted with miniature railroads for transporting 
 the mines to the launching-point, so that they 
 could be dropped at regular intervals without 
 interruption. Each anchor mine was provided 
 with flanged wheels that ran on rails. The 
 mines were carried on three decks and each 
 deck was covered with a network of rails, 
 switches, and turn-tables, while elevators were 
 provided to carry the mines from one deck to 
 another. The mines, like miniature railroad 
 
"DEVIL'S EGGS" 295 
 
 cars, were coupled up in trains of thirty or forty 
 and as each mine weighed fourteen hundred 
 pounds, steam winches had to be used to haul 
 them. At the launching-point the tracks ran out 
 over the stern of the boat and here a trap was 
 provided which would hold only one mine at a 
 time. By the pulling of a lever the jaws of the 
 trap would open and the mine would slide off the 
 rails and plunge into the sea. 
 
 The mines were dropped every three hundred 
 feet in lines five hundred feet apart, as it was 
 unsafe for the mine-layers to steam any closer 
 to one another than that. The mines were of 
 the type shown in Fig. 22 and automatically 
 adjusted themselves to various depths. The 
 depth of the water ran down to twelve hundred 
 feet near the Norwegian coast. Never before 
 had mines been planted at anywhere near that 
 depth. 
 
 It was dangerous work, because the enemy 
 knew where the mines were being planted, as 
 neutral shipping had to be warned months in ad- 
 vance. The mine-layers were in constant 
 danger of submarine attack, although they were 
 convoyed by destroyers to take care of the 
 U-boats. There was- even danger of a surface 
 
296 INVENTIONS OF THE GREAT WAR 
 
 attack and so battle-cruisers were assigned the 
 job of guarding the mine-layers. The mine- 
 layers steamed in line abreast, and had one of 
 them been blown up, the shock would probably 
 have been enough to blow up the others as well. 
 Enemy mines were sown in the path of the 
 mine-layers, so the latter had to be preceded by 
 mine-sweepers. Navigation buoys had to be 
 planted at the ends of the lines of mines and the 
 enemy had a habit of planting mines near the 
 buoys or of moving the buoys whenever he had 
 a chance. But despite all risks the work was 
 carried through. 
 
 The barrier was not an impassable one. With 
 the mines three hundred feet apart, a submarine 
 might get through, even though the field was 
 twenty-five miles broad, but the hazards were 
 serious. Before the first lines of mines had been 
 extended half-way across, its value was demon- 
 strated by the destruction of several U-boats, 
 and as the safety-lane was narrowed down the 
 losses increased. It is said that altogether 
 twenty-three German submarines met their 
 doom in the great mine barrage. U-boat com- 
 manders balked at running through it, and 
 U-boat warfare virtually came to a standstill. 
 
" DEVIL'S EGGS" 297 
 
 According to Captain Bartenbach, commander 
 of submarine bases in Flanders, three U-boats 
 were sunk by anchored mines for every one that 
 was destroyed by a depth bomb. 
 
CHAPTEE XV 
 
 SURFACE BOATS 
 
 THE war on the submarine was fought 
 mainly from the surface of the sea and 
 from the air above the sea, and naturally it 
 resulted in many interesting naval develop- 
 ments. 
 
 As described in Chapter XIII, the first offen- 
 sive measure against the U-boat was the build- 
 ing of swarms of speedy motor-boats which 
 drove the invaders away from harbors and into 
 the open sea. To follow the U-boats out into 
 rough water larger submarine-chasers were 
 built, but even they could not cope with the 
 enemy far from the harbors. 
 
 MOTOR TORPEDO-BOATS 
 
 The Italians made excellent use of speedy 
 motor-boats in the protected waters of the Adri- 
 atic Sea. One type of motor-boat was equipped 
 
 298 
 
SURFACE BOATS 299 
 
 with two torpedo-tubes in the bow. Small 14- 
 inch torpedoes were used, but as each torpedo 
 carried two hundred pounds of high explosive, 
 the motor-boat was a formidable vessel if it 
 crept in close enough to discharge one of these 
 missiles at its foe. 
 
 On one occasion, a patrol of these little boats 
 sighted a couple of Austrian dreadnoughts 
 headed down the coast, surrounded by a screen 
 of ten destroyers. Favored by the mist, two of 
 the motor-boats crept through the screen of de- 
 stroyers, and torpedoed the battle-ships. Then 
 they made good their escape. A destroyer that 
 pursued one of the boats decided that the game 
 was not worth while when it was suddenly 
 shaken up by the explosion of a depth bomb 
 dropped from the motor-boat. 
 
 THE SEA TANK 
 
 The Italians showed a great deal of naval in- 
 itiative. They were forever trying to trap the 
 Austrian fleet or to invade its harbors. Like 
 all other naval powers, the Austrians protected 
 their harbors with nets and mines. It was im- 
 possible for submarines to make an entrance and 
 the ports were too well fortified to permit an 
 
300 INVENTIONS OF THE GREAT WAB 
 
 open attack on the surface. Nevertheless, the 
 Italians did break through the harbor defenses 
 on one or two occasions and sank Austrian war- 
 vessels. Again it was with a small boat that 
 they did the trick. 
 
 The nets which the Austrians stretched across 
 their harbor entrance were supported on wooden 
 booms or logs which served as floats. These 
 booms offered an effective bar to small boats 
 which might attempt to enter the harbor under 
 cover of darkness. But the Italians found a 
 way to overcome this obstruction. They built 
 a flat-l>ottome<l motor-boat which drew very 
 little water. Running under the boat were two 
 endless chains, like the treads (if a tank. In 
 fact, the boat came to IK* known as a "sea tank." 
 The chains were motor-driven ami had spiked 
 sprockets, so that when a boom was encountered 
 they would bite into the wood and pull the boat 
 up over the log, or maybe they would drag the 
 log down under the boat. At any rate, with this 
 arrangement it was not very difficult to pass the 
 boom and enter the harbor. At the rear the 
 chains were carried back far enough to prevent 
 the propeller from striking when the boat had 
 passed over the log. 
 

SURFACE BOATS 301 
 
 THE AWKWARD " EAGLES " 
 
 A curious boat that we undertook to furnish 
 during^he war was a cross between a destroyer 
 and a submarine-chaser. After the submarine 
 had been driven out to sea its greatest foe was 
 undoubtedly the destroyer, and frantic efforts 
 were made to turn out as many destroyers as 
 possible. But it takes time to build destroyers 
 and so a new type of boat was designed, to be 
 turned out quickly in Inrge numbers. A hun- 
 dred and ten "Eagles" (as these boats are 
 called) were ordered, but the armistice was 
 signed before any of them were put into service ; 
 and it is just as well that such was the case, for 
 in their construction everything was sacrificed 
 to speed of production. As a consequence they 
 are very ugly boats, with none of the fine lines 
 of a destroyer, and they roll badly, even when 
 the sea is comparatively peaceful. They are 
 five-hundred-ton boats designed to make eight- 
 een knots, which would not have been fast 
 enough to cope with U-boats, because the latter 
 could make as high a speed as that themselves, 
 when traveling on the surface, and the two 
 4-inch guns of the Eagles would have been far 
 
302 INVENTIONS OP THE GREAT WAR 
 
 outranged by the 5.9-inch guns of the larger 
 U-boats. 
 
 SEAPLANE TOWING-BAKGES 
 
 When the war on the U-boat was earned up 
 into the sky, many new naval problems cropped 
 up, particularly when German submarines 
 chose to work far out at sea. Big seaplanes 
 were used, but they consumed a great deal of 
 fuel in flying out and back, cutting down by just 
 so much their flying-radius at the scene of activi- 
 ties. A special towing-barge was used. These 
 barges had trimming-tanks aft, which could be 
 flooded so that the stern of the barge would sub- 
 merge. A cradle was mounted to run on a pair 
 of rails on the barge. The body of the seaplane 
 was lashed to this cradle and then drawn up on 
 the barge by means of a windlass. This done, 
 the water was blown out of the trimming- tanks 
 by means of compressed air and the barge was 
 brought up to an even keel. The barge with 
 its load was now ready to be towed by a de- 
 stroyer or other fast boat to the scene of opera- 
 tions. There water was again let into the 
 trimming-tanks and the seaplane was let back 
 
SURFACE BOATS 303 
 
 into the water. From the water the seaplane 
 arose into the air in the usual way. 
 
 Unfortunately, when the sea is at all rough 
 it is exceedingly difficult for a seaplane to take 
 wing, ^Irticularly a large seaplane. A better 
 starting-platform than the sea had to be fur- 
 nished. At first some seaplanes were furnished 
 with wheels, so that they could be launched from 
 platforms on large ships; and then, to increase 
 the flying-radius, seaplanes were discarded in 
 favor of airplanes. Once these machines were 
 launched, there was no way for them to get 
 back to the ship. They had to get back to land 
 before their fuel was exhausted. 
 
 On the large war-vessels *a starting-platform 
 was built on a pair of long guns. Then the 
 war-ship would head into the wind and the com- 
 bined travel of the ship and of the airplane 
 along the platform gave speed -enough to raise 
 the plane off the platform before it had run the 
 full length of the guns. But as long as aviators 
 had no haven until they got back to land, there 
 were many casualties. Eager to continue their 
 patrol as long as possible, they would some- 
 times linger too long before heading for home 
 
304 INVENTIONS OF THE GREAT WAR 
 
 and then they would not have enough fuel left 
 to reach land. Many an aviator was lost in this 
 way, and finally mother-ships for airplanes had 
 to be built. 
 
 % 
 THE "HUSH SHIPS" 
 
 The British Navy had constructed a number of 
 very fast cruisers to deal with any raiders the 
 Germans might send out. These cruisers were 
 light vessels capable of such high speeds that 
 they could even overtake a destroyer. They 
 were 840 feet long and their turbines developed 
 90,000 horse-power. The construction of these 
 vessels was for a long time kept a profound 
 secret and it was not until the German fleet 
 surrendered that photographs of them were al- 
 lowed to be published. Because of this secrecy 
 the boats were popularly known as " hush- 
 ships. " They were not armored; it was not 
 necessary to load them down with armor plate, 
 because their protection lay in speed and they 
 were designed to fight at very long range. In 
 fact, they were to carry guns that would out- 
 range those of the most powerful dreadnoughts. 
 Our largest naval guns are of 16-inch caliber, 
 but the "hush ships M were each to carry two 
 
SURFACE BOATS 305 
 
 18-inch guns. The guns were monsters weigh- 
 ing 150 tons each and they fired a shell 18 inches 
 in diameter and 7 feet long to a distance of 30 
 miles when elevated to an angle of 45 degrees. 
 The weight of the shell was 3600 pounds and it 
 carried 500 pounds of high explosive or more 
 than is carried in the largest torpedoes. 
 
 At the 32-mile range the shell would pass 
 through 12 inches of face-hardened armor and 
 at half that range it would pass through armor 
 18 inches thick, and there is no armor afloat any 
 heavier than this. 
 
 MOTHER-BOATS FOB AIRPLANES 
 
 Armed with such powerful guns as these, the 
 "hush ships " would have been very formidable 
 indeed ; but when the guns were mounted on one 
 of the cruisers, the Furious, they were found 
 too powerful for the vessel. It was evident that 
 the monsters would very -seriously rack their 
 own ship. So the guns were taken off the 
 cruiser and it was turned into a mother-ship 
 for airplanes. A broad, unobstructed deck was 
 built on the ship which provided a runway from 
 which airplanes could be launched, and this run- 
 way was actually broad enough to permit air- 
 
306 INVENTIONS OF THE GREAT WAR 
 
 planes to land upon it. Under the runway were 
 the hangars in which the airplanes were housed. 
 Other "hush ships'* were also converted into 
 airplane mother-boats and there were special 
 boats built for this very purpose, although they 
 were not .able to make the speed of the "hush 
 ships. " One of these special boats had funnels 
 that turned horizontally to carry off the furnace 
 smoke over the stern and leave a perfectly clear 
 flying-deck, 330 feet long. 
 
 TOBPHDO-PBOOF MONSTERS 
 
 As for the 18-inch guns, they were put to an- 
 other use. Early in the war the British had 
 need for powerful shallow-draft vessels which 
 could operate off the Flanders coast and attack 
 the coast fortifications that were being built by 
 the Germans. The ships that were built to 
 meet this demand were known as monitors, be- 
 cause like the famous " monitor " of our Civil 
 War they carried a single turret. These moni- 
 tors were very broad for their length and were 
 very slow. At best they could make only seven 
 knots and in heavy weather they could not make 
 more than two or three knots. 
 
 To be made proof against torpedoes these 
 
SURFACE BOATS 307 
 
 boats were formed with "blisters" or hollow 
 rounded swells in the hull at each side which 
 extended out to a distance of twelve to fifteen 
 feet. The blisters were subdivided into com- 
 partments, so that if a torpedo struck the ship 
 it would explode against a blister at a consider- 
 able distance from the real hull of the ship and 
 the force of the explosion would be expended 
 in the compartments. The blisters were the 
 salvation of the monitors. Often were the boats 
 struck by torpedoes without being sunk. 
 
 Unfortunately, this form of protection could 
 not be applied to ordinary vessels, because it 
 would have interfered seriously with navigation. 
 The blisters made the monitors very difficult 
 to steer and hampered the progress of a ship, 
 particularly in a seaway. 
 
 With ships such as these the British bom- 
 barded Zeebrugge from a distance of twenty to 
 twenty-five miles. Of course, the range had to 
 be plotted out mathematically, as the target was 
 far beyond the horizon of the ship, and the 
 firing had to be directed by spotters in air- 
 planes. 
 
 At first guns from antiquated battle-ships 
 were used in the monitors; then larger guns 
 
308 INVENTIONS OF THE GREAT WAR 
 
 were used, until finally two of the monitors in- 
 herited the 18-inch guns of the Furious. A 
 single gun was mounted on the after deck of each 
 vessel and the gun was arranged to fire only 
 on the starboard side. No heavily armored 
 turret was provided, but merely a light housing 
 to shelter the gun. 
 
 AN ELECTRICALLY STEERED MOTOR-BOAT 
 
 The British war-vessels that operated in the 
 shallow waters off the coast of Flanders were a 
 constant source of annoyance to the Germans. 
 Because of the shallow water it was seldom pos- 
 sible for a submarine to creep up on them. A 
 U-boat required at least thirty-five feet of water 
 for complete submergence and it did not dare 
 to attack in the open. This led the Germans to 
 launch a motor-boat loaded with high explosive, 
 which was steered from shore. The motor- 
 boat carried a reel of wire which connected it 
 with an operator on shore. There was no pilot 
 in the boat, but the helm was controlled elec- 
 trically by the man at the shore station. As it 
 was diffcult for the helmsman to see just what 
 his boat was doing, or just how to steer it when 
 it was several miles off, an airplane flew high 
 
SURFACE BOATS 309 
 
 above it and directed the helmsman, by radio- 
 telegraphy, how to steer his boat. Of course, 
 radiotelegraphy might have been used to 
 operate the steering-mechanism of the boat, 
 but there was the danger that the radio oper- 
 ators of the British might send out disturbing 
 waves that would upset the control of the motor- 
 boat, and so direct wire transmission was used 
 instead. Fortunately, when the Germans tried 
 this form of attack, an alert British lookout dis- 
 covered the tiny motor-boat. The alarm was 
 given and a lucky shot blew up the boat with 
 its charge before it came near the British vessel. 
 
CHAPTER XVI 
 RECLAIMING THE VICTIMS OF THE SUBMARINE 
 
 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 dam- 
 aged 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 cer- 
 tain 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. 
 
 310 
 
VICTIMS OF THE SUBMARINE 311 
 
 To be sure, not all of the U-boat's victims 
 were sunk in deep water. Many torpedoed ves- 
 sels were beached or succeeded in reaching shal- 
 low water before they foundered. Some were 
 sunk in harbors while they lay at anchor, before 
 the precaution was taken of protecting the har- 
 bors 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 poison- 
 ous 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 sal- 
 yors, provided with complete equipment of appa- 
 ratus and machinery. 
 
 The majority of wrecks, however, are found 
 in the open sea, where it would have been foolish 
 
312 INVENTIONS OF THE GREAT WAR 
 
 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 com- 
 paratively 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. 
 
 IN THE DEPTHS OF THE SEA 
 
 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 reach- 
 ing 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 main- 
 tained in suspension, to be carried hither and 
 yon by every chance current. Indeed, it makes 
 a rather fantastic picture to think of these losl 
 ships drifting in endless procession, far down 
 
VICTIMS OP THE SUBMARINE 313 
 
 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 illu- 
 sion and bid us paint a very different picture. 
 Liquids are almost incompressible. The differ- 
 ence 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 be- 
 fore 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 vie- 
 
314 INVENTIONS OF THE GREAT WAR 
 
 tim 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 ves- 
 sel in suspension, but practically such a condi- 
 tion 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. 
 
 A SUBMARINE GRAVEYARD 
 
 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 turned 
 
VICTIMS OF THE SUBMARINE 315 
 
 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 rais- 
 ing of wrecked vessels is really a branch of en- 
 gineering. 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 single 
 
316 INVENTIONS OF THE GREAT WAR 
 
 wreck may be constructed with profit if a num- 
 ber of vessels demanding similar treatment are 
 to be salved. 
 
 The principal fields of German activities were 
 the Mediterranean Sea and the waters surround- 
 ing 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 ef- 
 ficient 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 western- 
 most extremity of France, we enclose an area 
 in which the German submarines were particu- 
 larly active. The soundings here run up to 
 about sixty fathoms in some places, but the pre- 
 vailing depth is less than fifty fathoms. In 
 
VICTIMS OF THE SUBMARINE 317 
 
 the North Sea, too, except for a comparatively 
 narrow lane along the Norwegian coast which, 
 by the way, marked the safety lane of the Ger- 
 man 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. 
 
 DIFFERENT WAYS OF SALVING A WRECK 
 
 There are four well-known methods of rais- 
 ing 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 ex- 
 tended to the surface to keep the water from 
 flowing in as fast as it is pumped out. It is 
 
318 INVENTIONS OF THE GREAT WAR 
 
 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 patriot- 
 ism 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 or- 
 ganized 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 cof- 
 fer-dam construction much repair work was nec- 
 oessary. Marvelous acts of devotion and hero- 
 
VICTIMS OF THE SUBMARINE 
 
 ism 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 actu- 
 ally 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 de- 
 votion ! 
 
 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 fol- 
 lowed 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 examina- 
 tion to determine what caused the destruction 
 of the vessel. Neither of these methods of sal- 
 vage will serve for raising a ship sunk in deep 
 water. 
 
 RAISING A SHIP OK AIR 
 
 A salvage system that has come into promin- 
 noe within recent years consists in pumping 
 
320 INVENTIONS OP THE GREAT WAR 
 
 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 air- 
 space 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 strength- 
 ening 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 impractic- 
 able because the deck itself cannot stand the 
 strain. 
 
 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, the 
 
Climbing into an Armored Diving Suit 
 
 Lowering an Armored Diver into the Water 
 
A Diver's Sea Sled ready to be towed along the bed of the sea 
 
 The Sea Sled on Land showing the forward horizontal and 
 after vertical rudders 
 
VICTIMS OF THE SUBMARINE 321 
 
 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. 
 
 SALVING THE U. S. SUBMARINE F-4 
 
 If the salvor could always be assured of clear 
 weather, his troubles would be reduced a hun- 
 dredfold, but at best it takes a long time 'to 
 perform any work dependent upon divers, and 
 the chances are very good when they are operat- 
 ing 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 and 
 
322 INVENTIONS OF THE GREAT WAR 
 
 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 be- 
 ing 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 com- 
 pressed air, they came up to the surface, bring- 
 ing 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 drag- 
 ging the wreck out of the clutches of a sandy or 
 muddy bottom. Imagine the work of building 
 
VICTIMS OF THE SUBMARINE 323 
 
 pontoons large enough to raise the Lusitania. 
 They would have to have a combined displace- 
 ment 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 be- 
 ing 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 lia- 
 ble 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 ves- 
 sel 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 a 
 
324 INVENTIONS OF THE GREAT WAR 
 
 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. 
 
 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 neces- 
 sarily be of the same pressure as the surrtiund- 
 ing 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. When 
 
( C) International Film Service 
 
 The Diving Sphere built for Deep Sea Salvage Operations 
 
o 
 
VICTIMS OF THE SUBMARINE 325 
 
 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." 
 
 A HUMAN SODA-WATER BOTTLE 
 
 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. But 
 
326 INVENTIONS OF THE GREAT WAR 
 
 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-ves- 
 sels. The griping pains that accompany the 
 "Caisson Disease' 7 are excruciating. The only 
 cure is to restore the blood to its original pres- 
 sure 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 decom- 
 pressing 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 re- 
 
VICTIMS OF THE SUBMARINE 327 
 
 cesses 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, it 
 
328 INVENTIONS OF THE GREAT WAR 
 
 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 per- 
 formed at the depth of 300 feet would not have 
 taken more than a few minutes on the surface. 
 
 A SUBMARINE REST-CHAMBER 
 
 The Germans have paid a great deal of atten- 
 tion 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 and 
 
VICTIMS OF THE SUBMARINE 329 
 
 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 in- 
 dependent 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 re- 
 turn 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 decom- 
 pressing. 
 
 CUTTING METAL UNDER WATEE WITH 
 A TOECH 
 
 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 under- 
 water use, with which the diver can cut metal 
 by burning through it. This is a-ccomplished 
 by using a cup- shaped nozzle through which a 
 blast of air is projected under such pressure 
 
330 INVENTIONS OF THE GREAT WAR 
 
 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. 
 
 EXPLORING THE SEA BOTTOM IN A DIVERTS SLED 
 
 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 with- 
 out any physical exertion, he can explore the 
 bottom of the sea and hunt for wrecks. 
 
 ARMORED DIVING-SUITS 
 
 From time to time attempts have been made 
 to construct a diver's suit that will not yield 
 
VICTIMS OF THE SUBMARINE 331 
 
 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 de- 
 pendent 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 the 
 
332 INVENTIONS OF THE GREAT WAR 
 
 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 Hexed it would not dis- 
 place 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 bo 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 ex- 
 tending 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. 
 
 THK SALVOR'S SUBMARINE 
 
 Other schemes have been devised to relieve 
 the diver of abnormally high air-pressure. 
 
VICTIMS OF THE SUBMARINE 333 
 
 One plan is to construct a large spherical work- 
 ing-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 ob- 
 serve 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 tele- 
 phonic 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 an- 
 other position, as directed by telephone and an- 
 other 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 f ram- 
 
334 INVENTIONS OF THE GREAT WAR 
 
 ing. 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 em- 
 ployed, but no one who has any idea of how 
 large and how heavy such magnets must be 
 would give these suggestions any serious consid- 
 eration. 
 
 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. 
 
 FIOHTINO THE WAVES WITH AIR 
 
 However, there has been another recent de- 
 velopment which may have a very important 
 bearing on this problem of deep-sea salvage 
 work. It has often been observed that a sub- 
 merged reef, twenty or thirty feet below the 
 surface, may act as a breakwater to stop the 
 storming waves. Ail inventor who studied this 
 phenomenon arrived at the theory that the 
 reefs set up eddies in the water which break 
 
VICTIMS OF THE SUBMARINE 335 
 
 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 f ury of the 
 
336 INVENTIONS OF THE GREAT WAR 
 
 waves on the surface; and the silent, remorse- 
 less 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 un- 
 armored divers. We have reached a very in- 
 teresting 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 dread- 
 ful 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 fright- 
 fully 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 only 
 
VICTIMS OF THE SUBMARINE 337 
 
 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. 
 
INDEX 
 
 Air, fighting wave*, 334 
 
 raiting ship, on, 310 
 
 war in, 123 
 Airplane, ambulance, 146 
 
 armored, 139 
 
 artillery potting, 131 
 
 camera. 173 
 
 cartridge*, 131 
 
 clause* of work, 127 
 
 fighting among clouds, 137 
 
 flying boaU. 144 
 
 gMolene tank. 130 
 
 giant, 132 
 
 hospital, 140 
 
 launching from whip, 303 
 
 Liberty motor, 142 
 
 scouting, 125 
 
 scout*. 128 
 
 speed of, 134 
 
 spotting, 177 
 
 training * potters, 180 
 
 wireless telephone, 194 
 
 See al*o Seaplane 
 Ambulance airplane, 146 
 Armored diving suit, 330 
 Arms and armor, 1 1 1 
 Artillery, hand, 23 
 Atmosphere, shooting beyond, 
 
 64 
 A ud ion, 185 
 
 Balloon, Blimp, 260 
 helium, 164 
 historical, 148 
 hydrogen, 150 
 
 Balloon, kite, 174 
 
 principles, 150 
 
 record flight, 66 
 Barbed wire, 15 
 
 cylinders, 17 
 
 gate, trench, 
 
 gates through, 15 
 
 shelling, 16 
 Barge for towing seaplanss, 
 
 302 
 Barrage, grenade, 27 
 
 mine, 292 
 
 Battle-fields, miniature, 180 
 Blimp, 260 
 
 Blisters on ships, 307 
 Boats, electric, 308 
 
 Eagle, 301 
 
 flying, 144 
 
 surface, 298 
 Bomb* to destroy barbsd 
 
 wire, 16 
 
 Breakwater, pneumatic, 335 
 Browning, John M., 56 
 Buildings, shadowless, 227 
 
 Caisson disease, 325 
 Caliber, 68 
 
 Camera, airplane, 173 
 Camouflage and camoufleurs, 
 211 
 
 buildings, 227 
 
 grass, 229 
 
 horse, 223 
 
 land, 222 
 
 roads, 225 
 
 339 
 
840 
 
 INDEX 
 
 Camouflage. hip. 21 1 
 
 Cartridge, aircraft gunt, 13! 
 
 CatapuiU, 30 
 
 Caterpillar tractor, 109 
 
 Caret. 8 
 
 Coffer-dam, talragt, 318 
 
 Color, analy/ing, 229 
 
 creeni. 229 
 Com pa u, irirele**, 201 
 Convoy, 267 
 Countermine*. 1? 
 
 Deep M-. condition* in, 312 
 Drep water diving. 327 
 Depth bomt. 205 
 Devil's egfr, j?fl 
 Diet engine. 240 
 Direction-fin ier. 205 
 Dirigible. < li n 
 
 DifAftr, it 1 "" X '. 
 
 Di\rr. arm! red auit. 33O 
 
 Fort*, machine gun, 68 
 FUM, grenade. 28 
 
 rr%t 
 
 led. 3.10 
 
 ulmnnr.e torch. 3'^ 
 
 ;iit. 3*4 
 Diving, dr p. 324 
 
 record d*-;,th. 327 
 Duck '*.-ard. V 
 
 Dumtr.v head* of papier 
 mich*. 13 
 
 K*j?!e t-xit*. 3'1 
 Kgg-la>:r.g u.:r.arine. 2b7 
 Kgg. Dev;;^. 276 
 Klcctr;c mutor >jt, 30 
 rlngine. Du-ei, 240 
 
 Kip Id punt. 81 
 Fire broom, 105 
 liquid, 103 
 
 . 92 
 
 Ga, 85 
 
 American. 102 
 Ga* attack, 
 
 fir.t. 89 
 Ga*. chbrine, 87 
 
 dipho^grne, 98 
 
 -.. a' jr raU. 94 
 
 grer.ade*. 20 
 
 h-'i- m. 104 
 
 hydrcgett. 1AO 
 
 lock. 07 
 
 rr * ' '* 
 
 mu!ard. 98 
 
 phogrne. 1*3 
 
 pouring ....r water. 88 
 
 hril. 66 
 
 ancej;:^-. 9H 
 
 tear. DA 
 
 Turr.il ;r.g. 9H 
 
 Ga^-lrr.r *ar.k. airplane, 130 
 Gate. a- i wire, trench. 9 
 Gate* ihrouxh 'ar *; wire, 
 
 15 
 
 Gat ling gun. 43 
 <<' ''r. ; r-.r. Ridgt, 19 
 . ."* non-thaf.enng. 100 
 (rapne! th]l. 16 
 Graveyard. ubmartM, 314 
 Grrr.i'>. dtk-haped. 33 
 
 fuM-. 2 
 
 g. 2C 
 
 bruth. 34 
 
 h:*cn- of. 23 
 
 Mint,*29 
 
 pararh::!e. 31 
 
 range of, 25 
 
 rtrV, 2? 
 
 throwing implement, 27 
 
INDEX 
 
 341 
 
 Grenade, wind-vane safety de- 
 vice, 32 
 Gun, aircraft, 131 
 
 American, 60-mile, 63 
 
 big, hiding, 226 
 
 caliber, 68 
 
 disappearing, 77 
 
 double-end, 145 
 
 18- inch, monitors, 906 
 
 elastic, 73 
 
 field. 81 
 
 42-centimeter, 79 
 
 how made, 76 
 
 120-mile, 70 
 
 long range, Herman, 62 
 
 non- recoil, 145 
 
 on submarine, 249 
 
 16 inch, coat defense, 78 
 
 Skoda. HI 
 
 spotting by ound, 181 
 
 three-e^onJ life, 73 
 
 12-inch, submarine. 251 
 
 way* of increasing range, 
 67 
 
 wire wound, 70 
 
 Hand-grenade, see Grenade 
 Heiivxn. 164 
 Ho*pital, airplane, 147 
 Hori/on, seeing beyond, 219 
 Howitzer, 79 
 Hush ships, 304 
 Hydroaeroplanes, *e Sea- 
 planes 
 
 Hydrogen, weight of, 150 
 Hydrophone, 270 
 
 Illusion*, optical, 215 
 
 Kilometer, length in miles, 6 
 Kite balloons, 174 
 Kite, water, 283 
 
 Liberty motor, 142 
 Liquid-fire, 103 
 Locomotives, gasolene, 10 
 Lutitania, 316 
 
 Machine-gun, 112 
 
 airplane, 127 
 
 Benet-Mercie, 52 
 
 Browning, 53 
 
 Colt, 44 
 
 forts, 58 
 
 Galling, 43 
 
 history. 41 
 
 Hotchkiss, 49 
 
 Lewis, 50 
 
 Maxim, 42 
 
 water-jacket, 47 
 
 worth in rifles, 58 
 Machine-rifle, "5 
 Magnets, lilting, salvage. 334 
 Map-, making with camera, 
 
 175 
 
 Marr". flr*t battle of, 4 
 Me*ines Ridge, mine, 19 
 Metal -cutting under water, 
 
 329 
 Microphone detectors, mines, 
 
 18 
 
 Mine-field, North Sea, 290 
 Mine laying, North Sea, 292 
 Mine-laying submarine, 287 
 Mine railroad, 294 
 Mine-sweeping, 281 
 Mines, 276 
 
 anchored, 278 
 
 and countermines, 17 
 
 automatic sounding, 278 
 
 drift of, 285 
 
 electric, 277 
 
 floating, 284 
 
 Messines Ridge, 19 
 
342 
 
 INDEX 
 
 pararane*. 288 
 Monitor*. 306 
 Mortars, 79 
 
 depth bomb, 266 
 flying, 23 
 Mortar*. 8e alao Trench 
 
 mortar* 
 Mother-ahip* for airplane*. 
 
 Motor- boat, electric. 308 
 
 aea Tank. 299 
 Motor torpedo boat*, 296 
 Mystery *hip. 220 
 
 Net, North Sea. 290 
 
 Ocean current*. 286 
 Optical illusion*. 21ft 
 Oxy hydrogen torch. *ubm* 
 rine. 329 
 
 Paint in war. 209 
 Papier mach* head*. 13 
 P*pier mAche hor*e. 223 
 Parachute. 175 
 
 gren*de. 31 
 
 earchltght *hell. 84 
 Paravane*. 288 
 Perirupe. ubmartne, 244 
 
 trench. 1 1 
 Pill boxen. 59- 
 
 Pneumatic breakwater, 335 
 Pontoon*. alvBge, 320 
 Propeller, "hooting through. 
 136 
 
 Radio. *ee Wirele** 
 Kailnmd. mine. 294 
 Railway*, trench. 10 
 Ranjre-flndcr. 170 
 Rang?, getting the. 169 
 
 Range of gun*, increasing. 67 
 Range, torpedo. 213 
 Rat*, freeing Kenche* of, 94 
 Rifle grenade, t8 
 
 afety device. 32 
 Rifle, machine. 56 
 Rifle *tand. fixed. 14 
 Road*, camouflage, 226 
 
 Salvage. 310 
 
 diving. 324 
 
 ice-tong*. 334 
 
 lifting magnet*. 314 
 
 method*. 317 
 
 pneumatic. 319 
 
 puntoun*. 320 
 
 hacklr on htp. 333 
 
 ubmarine K 4. 321 
 
 ubmarine *phere. 332 
 Scouu. airplane, 12H 
 Sea. deep, condition*. 312 
 Sra gull* finding ubmarina*. 
 
 25H 
 Sa lion* locating ubmarine*. 
 
 . 
 
 S*a tank. 299 
 Seaplane. 143 
 
 automatic. 145 
 
 ubmarine patrol, 259 
 
 torpedo. 145 
 
 towing bar ?r. 3<rj 
 Search light *heli. H4 
 Shackle*. *a)vaK. 333 
 ShadowlcA* building*. 227 
 Shell. ga. 115 
 
 grapnel. 16 
 
 earch li^ht. 84 
 
 hrapnrl. 83 
 
 Stoke* mortar. 39 
 Shield on wheel*. 114 
 Ship*, airplane. 3U4 
 
INDEX 
 
 343 
 
 Ships, blisters, 307 
 
 camouflage, 211 
 
 "clothes-line," 220 
 
 convoy, 267 
 
 hush, 304 
 
 making visible, 230 
 
 monitors, 306 
 
 mystery, 220 
 
 railroads on, 294 
 
 sunk by submarines, 310 
 Ship*, see also Salvage 
 Shrapnel shell, 83 
 Sled, submarine, 330 
 Smoke screen, 262 
 Sniper, locating, 13 
 Sniperscopes, 12 
 Sound, detecting submarines, 
 
 269 
 
 Sound detector*, mines, 18 
 Sound, spotting by, 181 
 Sphere, salvor's submarine, 
 
 332 
 
 Spotting by sound, Iftl 
 Spotting gun-fire, 177 
 Submarine, blindness, '244 
 
 chasers. 255 
 
 construction, 234 
 
 depth bombs. 265 
 
 egg-laying, 287 
 
 engines, 246 
 
 F4, salving, 321 
 
 getting bet of, 253 
 
 graveyard, 314 
 
 guns on, 249 
 
 history, 232 
 
 hydrophone, 270 
 
 mine-field, 290 
 
 mine-laying, 287 
 
 net, 290 
 
 oil-tank, 236 
 
 periscope, 244 
 
 Submarine, reclaiming vic- 
 tims of, 310 
 
 rest chamber, 328 
 
 saJvage vessel, 332 
 
 sea-gulls, 258 
 
 sea-lion*, 259 
 
 seaplanes, 259 
 
 ships sunk, 310 
 
 sled, 330 
 
 steam-driven, 250 
 
 torch, 329 
 
 torpedo. 246 
 
 12-inch gun, 251 
 
 vs. submarine, 269 
 Super-gun*, 62 
 
 Tank, 107 
 
 American, 122 
 
 flying, 139 
 
 French, 119 
 
 (ierman, 120 
 
 one-man, 114 
 
 sea, 299 
 
 small, 121 
 
 Telegraphy, rapid, 199 
 Telephone, New York to San 
 Francisco, 186 
 
 wirelesH. 178 
 Titanic, :H4 
 
 TNT (trinitrotoluol), 18 
 Torch, submarine, 329 
 Torpedo, 299 
 
 boats, motor, 298 
 
 electrically steered, 108 
 
 construction, 246 
 
 getting range, 213 
 
 proof ships, 306 
 
 seaplane, 145 
 
 Towing-barge, seaplane, 302 
 Trajectory, 22 
 
344 
 
 INDEX 
 
 Trench, gas-lock, 07 
 Trench mortar, 36 
 
 pneumatic, 37 
 
 Stoke*. 38 
 Trench railway*, 10 
 Trench warfare, 4 
 Trenches, 21 
 
 barbed wire gate*, 
 
 duck- board*, 9 
 Tunnel*, mine*, 17 
 
 to obaenration poet*, 12 
 
 U-boat*, *ee Submarine* 
 Village*, underground, 7 
 
 Walking machine. 108 
 
 War, paint. 209 
 
 Water kite*. 283 
 
 Wave*, fighting with air. 334 
 
 Wirele** compass, 201 
 
 *pj detector, 200 
 Wirele** telegraph, rapid, 199 
 Wirele** telegraphy explained. 
 
 188 
 Wirele** telephone, 178 
 
 airplane, 184 
 Wirele** telephony acroat At- 
 
 lantic, 198 
 Woolworth Building, falling 
 
 from, 135 
 Wreck*. *ee Salvage 
 
 Zeppelin and Lowe's 
 
 140 
 Zeppelin balloon, construc- 
 
 tion. 156 
 Zeppelin, suspended obeerver, 
 
 162 
 
 Zeppelin's failure* 
 154 
 
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