file which includes the original illustrations4 ,see #debfi-;h4htm or #debfi-;h4zip3 7https3_/_/www4gutenberg4org_/cache_/epu b_/#debfi_/pg#debfi-;images4html7 or 7https3_/_/www4gutenberg4org_/files_/#de bfi_/debfi-;h4zip7 ,images of the original pages are available through ,internet ,archive4 ,see https3_/_/archive4org_/details_/inventio nsofgrea#jj;bondrich ,illustration3 ,oil-tempering the lining of a ,big ,gun 7,see page #gf7 ,,inventions ,,of ,,the ,,great ,,war by ,a4 ,,russell ,,bond ,managing ,editor of ,scientific ,american1 ,author of ,on the ,battle-,front of ,engineering1 etc4 ,with ,many ,illustrations ,illustration ,new ,york ,the ,century ,co4 #aiai ,copyright1 #aiah1 #aiai1 by ,the ,century ,co4 ,published1 ,june1 #aiai ,,preface ,the great ,world ,war was more than two-thirds over when ,america entered the struggle1 and yet in a sense this country was in the war from its very beginning4 ,three great inventions controlled the character of the fighting and made it different from any other the world has ever seen4 ,these three inventions were ,american4 ,the submarine was our invention2 it carried the war into the sea4 ,the airplane was an ,american invention2 it carried the war into the sky4 ,we invented the machine-gun2 it drove the war into the ground4 ,it is not my purpose to boast of ,american genius but1 rather1 to show that we entered the war with heavy responsibilities4 ,the inventions we had given to the world had been developed marvelously in other lands4 ,furthermore they were in the hands of a determined and unscrupulous foe1 and we found before us the task of overcoming the very machines that we had created4 ,yankee ingenuity was faced with a real test4 ,the only way of overcoming the airplane was to build more and better machines than the enemy possessed4 ,this we tried to do1 but first we had to be taught by our allies the latest refinements of this machine1 and the war was over before we had more than started our arial program4 ,the machine-gun and its accessory1 barbed wire 7also an ,american invention71 were overcome by the tank2 and we may find what little comfort we can in the fact that its invention was inspired by the sight of an ,american farm tractor4 ,but the tank was a ,british creation and was undoubtedly the most important invention of the war4 ,on the sea we were faced with a most baffling problem4 ,the ,u-boat could not be coped with by the building of swarms of submarines4 ,the essential here was a means of locating the enemy and destroying him even while he lurked under the surface4 ,two ,american inventions1 the hydrophone and the depth bomb1 made the lot of the ,u-boat decidedly unenviable and they hastened if they did not actually end ,german frightfulness on the sea4 ,but these were by no means the only inventions of the war4 ,great ,britain showed wonderful ingenuity and resourcefulness in many directions2 ,france did marvels with the airplane and showed great cleverness in her development of the tank and there was a host of minor inventions to her credit2 while ,italy showed marked skill in the creation of large airplanes and small seacraft4 ,the ,central ,powers1 on the other hand1 were less originative but showed marked resourcefulness in developing the inventions of others4 ,forts were made valueless by the large portable ,austrian guns4 ,the long range gun that shelled ,paris was a sensational achievement1 but it cannot be called a great invention because it was of little military value4 ,the great ,german ,zeppelins were far from a success because they depended for their buoyancy on a highly inflammable gas4 ,it is interesting to note that while the ,germans were acknowledging the failure of their dirigibles the ,british were launching an airship program1 and here in ,america we had found an economical way of producing a non-inflammable balloon gas which promises a great future for arial navigation4 ,the most important ,german contribution to the war--it cannot be classed as an invention--was poison gas1 and it was not long ere they regretted this infraction of the rules of civilized warfare adopted at the ,hague ,conference2 for the ,allies soon gave them a big dose of their own medicine and before the war was over1 fairly deluged them with lethal gases of every variety4 ,many inventions of our own and of our allies were not fully developed when the war ended1 and there were some which1 although primarily intended for purposes of war1 will be most serviceable in time of peace4 ,for this war was not one of mere destruction4 ,it set men to thinking as they had never thought before4 ,it intensified their inventive faculties1 and as a result1 the world is richer in many ways4 ,lessons of thrift and economy have been taught us4 ,manufacturers have learned the value of standardization4 ,the business man has gained an appreciation of scientific research4 ,the whole story is too big to be contained within the covers of a single book1 but ,i have selected the more important and interesting inventions and have endeavored to describe them in simple language for the benefit of the reader who is not technically trained4 ,a4 ,,russell ,,bond ,new ,york1 ,may1 #aiai ,,contents ,,chapter ,,page ,i ,,the ,,war ,,in ,,and ,,under ,,the ,,ground #c ,,ii ,,hand-,,grenades ,,and ,,trench ,,mortars #bj ,,iii ,,guns ,,that ,,fire ,,themselves #da ,,iv ,,guns ,,and ,,super-,,guns #fb ,v ,,the ,,battle ,,of ,,the ,,chemists #he ,,vi ,,tanks #ajg ,,vii ,,the ,,war ,,in ,,the ,,air #abc ,,viii ,,ships ,,that ,,sail ,,the ,,skies #adh ,,ix ,,getting ,,the ,,range #afi ,x ,,talking ,,in ,,the ,,sky #ahd ,,xi ,,warriors ,,of ,,the ,,paint-,,brush #bji ,,xii ,,submarines #bcb ,,xiii ,,getting ,,the ,,best ,,of ,,the ,u-,,boat #bec ,,xiv ,,devil',s ,,eggs #bgf ,,xv ,,surface ,,boats #bih ,,xvi ,,reclaiming ,,the ,,victims ,,of ,,the ,,submarines #caj ,,index #cci ,,list ,,of ,,illustrations ,oil-tempering the lining of a big gun ,frontispiece ,,facing ,,page ,lines of zig-zag trenches as viewed from an aroplane #h ,french sappers using stethoscopes to detect the mining operations of the enemy #i ,a #c-;inch ,stokes mortar and two of its shells #cf ,dropping a shell into a #f-;inch trench mortar #cf ,the ,maxim machine-gun operated by the energy of the recoil #cg ,colt machine-gun partly broken away to show the operating mechanism #cg ,the ,lewis gun which produces its own cooling current #dd ,the ,bent-,merci gun operated by gas #dd ,browning machine-gun1 weighing #cd-a_/b pounds #de ,browning machine-rifle1 weight only #ae pounds #de ,lewis machine-guns in action at the front #eb ,an elaborate ,german machine-gun fort #ec ,comparative diagram of the path of a projectile from the ,german super-gun #fj ,one of our #af-;inch coast defence guns on a disappearing mount #fa ,height of gun as compared with the ,new ,york ,city ,hall #fa ,the #aba-mile gun designed by ,american ordnance officer #fh ,american #af-;inch rifle on a railway mount #fi ,a long-distance sub-calibered ,french gun on a railway mount #gf ,inside of a shrapnel shell and details of the fuse cap #gg ,search-light shell and one of its candles #gg ,putting on the gas-masks to meet a gas cloud attack #hd ,even the horses had to be masked #he ,portable flame-throwing apparatus #he ,liquid fire streaming from fixed flame-throwing apparatus #ib ,cleaning up a dugout with the fire-broom #ic ,british tank climbing out of a trench at ,cambrai #aab ,even trees were no barrier to the ,british tank #aac ,the ,german tank was very heavy and cumbersome #aac ,the speedy ,british ,whippet tank that can travel at a speed of twelve miles per hour #abj ,the ,french high-speed baby tank #abj ,section through our ,mark ,,viii tank showing the layout of the interior #aba ,a ,handley-,page bombing plane with one of its wings folded back #abh ,how an object dropped from the ,woolworth ,building would increase its speed in falling #abi ,machine-gun mounted to fire over the blades of the propeller #acf ,mechanism for firing between the blades of the propeller #acf ,it would take a hundred horses to supply the power for a small airplane #acg ,the flying-tank #add ,an ,n-,c 7,navy-,curtiss7 seaplane of the type that made the first flight across the ,atlantic #ade ,a big ,german ,zeppelin that was forced to come down on ,french soil #adh ,observation car lowered from a ,zeppelin sailing above the clouds #adi ,giant ,british dirigible built along the lines of a ,zeppelin #aef ,one of the engine cars or power eggs of a ,british dirigible #aef ,crew of the ,c-#e 7,american coastal dirigible7 starting for ,newfoundland to make a transatlantic flight #aeg ,the curious tail of a kite balloon #afj ,observers in the basket of an observation balloon #afj ,enormous range-finders mounted on a gun turret of an ,american warship #afa ,british anti-aircraft section getting the range of an enemy aviator #agf ,a ,british aviator making observations over the ,german lines #agg ,radio headgear of an airman #aib ,carrying on conversation by radio with an aviator miles away #aib ,long distance radio apparatus at the ,arlington 7,va47 station #aic ,a giant gun concealed among trees behind the ,french lines #bab ,observing the enemy from a papier-mch replica of a dead horse #bac ,camouflaged headquarters of the ,american #bfth ,division in ,france #bbj ,a camouflaged ship in the ,hudson ,river on ,victory ,day #bba ,complex mass of wheels and dials inside a ,german submarine #bdj ,surrendered ,german submarines1 showing the net cutters at the bow #bda ,forward end of a ,u-boat #bef ,a depth bomb mortar and a set of ash cans at the stern of an ,american destroyer #beg ,a depth bomb mortar in action and a depth bomb snapped as it is being hurled through the air #bfj ,airplane stunning a ,u-boat with a depth bomb #bfa ,the false hatch of a mystery ship #bfh ,the same hatch opened to disclose the #c-;inch gun and crew #bfh ,a ,french hydrophone installation with which the presence of submarines was detected #bfi ,section of a captured mine-laying ,u-boat #bgb ,a paravane hauled up with a shark caught in its jaws #bgc ,a ,dutch mine-sweeper engaged in clearing the ,north ,sea of ,german mines #bhh ,hooking up enemy anchored mines #bhi ,an ,italian sea tank climbing over a harbor boom #cjj ,deck of a ,british aircraft mothership or hush ship #cja ,electrically propelled boat or surface torpedo1 attacking a warship #cjd ,hauling a seaplane up on a barge so that it may be towed #cje ,climbing into an armored diving suit #cbj ,lowering an armored diver into the water #cbj ,a diver's sea sled ready to be towed along the bed of the sea #cba ,the sea sled on land showing the forward horizontal and after vertical rudders #cba ,the diving sphere built for deep sea salvage operations #cbd ,the pneumatic breakwater #cbe ,,inventions ,,of ,,the ,,great ,,war ,,chapter ,i ,,the ,,war ,,in ,,and ,,under ,,the ,,ground ,for years the ,germans had been preparing for war4 ,the whole world knew this1 but it had no idea how elaborate were their preparations1 and how these were carried out to the very minutest detail4 ,when the call to arms was sounded1 it was a matter of only a few hours before a vast army had been assembled--fully armed1 completely equipped1 ready to swarm over the frontiers into ,belgium and thence into ,france4 ,it took much longer for the ,french to raise their armies of defense1 and still longer for the ,british to furnish ,france with any adequate help4 ,despite the heroic resistance of ,belgium1 the ,entente ,allies were unprepared to stem the tide of ,german soldiers who poured into the northern part of ,france4 ,so easy did the march to ,paris seem1 that the ,germans grew careless in their advance and then suddenly they met with a reverse that sent them back in full retreat4 ,however1 the military authorities of ,germany had studied not only how to attack but also how to retreat and how to stand on the defensive4 ,in this1 as in every other phase of the conflict1 they were far in advance of the rest of the world1 and after their defeat in the ,first ,battle of the ,marne1 they retired to a strong position and hastily prepared to stand on the defensive4 ,when the ,allies tried to drive them farther back1 they found that the ,german army had simply sunk into the ground4 ,the war of manoeuver had given way to trench warfare1 which lasted through long1 tedious months nearly to the end of the great conflict4 ,the ,germans found it necessary to make the stand because the ,russians were putting up such a strong fight on ,germany's eastern frontier4 ,men had to be withdrawn from the western front to stem the ,russian tide1 which meant that the western armies of the kaiser had to cease their offensive activities for the time being4 ,the delay was fatal to the ,germans1 for they had opposed to them not only brave men but intelligent men who were quick to learn4 ,and when the ,germans were ready to resume operations in the ,west1 they found that the ,allies also had sunk into the ground and had learned all their tricks of trench warfare1 adding a number of new ones of their own4 ,the whole character of the war was changed4 ,the opposing forces were dead-locked and neither could break through the other's lines4 ,the idea of digging into the ground did not originate with this war1 but never before had it been carried out on so extensive a scale4 ,the inventive faculties of both sides were vainly exercised to find some way of breaking the dead-lock4 ,hundreds of new inventions were developed4 ,the history of war from the days of the ancient ,romans up to the present time was searched for some means of breaking down the opposing lines4 ,however1 the dead-lock was not broken until a special machine had been invented1 a traveling fort4 ,but the story of that machine is told in another chapter4 ,at the outset the ,allies dug very shallow ditches1 such as had been used in previous wars4 ,when it was found that these burrows would have to be occupied for weeks and months1 the ,french and ,british imitated the ,germans and dug their trenches so deep that men could walk through them freely1 without danger of exposing their heads above ground2 and as the ditches grew deeper1 they had to be provided with a firing-step on which the riflemen could stand to fire over the top of the trenches4 ,the trenches were zig-zagged so that they could not be flanked1 otherwise they would have made dangerous traps for the defenders2 for had the enemy gained one end of the trench1 he could have fired down the full length of it1 killing or wounding every man it contained4 ,but zig-zagging made it necessary to capture each turn separately4 ,there were lines upon lines of these trenches4 ,ordinarily there were but three lines1 several hundred feet apart1 with communicating trenches connecting them1 and then several kilometers#a farther back were reserve trenches1 also connected by communicating trenches with the front lines4 #a ,a kilometer is1 roughly1 six tenths of a mile2 or six miles would equal ten kilometers4 ,men did not dare to show themselves out in the open near the battle-front for a mile or more behind the front-line trenches1 for the enemy's sharp-shooters were always on the watch for a target4 ,the men had to stay in the trenches day and night for two or more weeks at a time1 and sleeping-accommodations of a very rough sort were provided for them in dugouts which opened into the trenches4 ,the dugouts of the ,allies were comparatively crude affairs1 but the ,germans spent a great deal of time upon their burrows4 ,,underground ,,villages ,when the ,french first swept the ,germans back out of their trenches along the ,aisne1 they were astonished to find how elaborate were these underground dwellings4 ,they found that the ground was literally honeycombed with rooms and passageways4 ,often the dugouts were two stories in depth and extended as much as sixty feet below the level of the ground4 ,in fact1 all along this part of the front1 the ,germans had a continuous underground village in which thousands of men were maintained4 ,the officers' quarters were particularly well fitted up1 and every attention was given to the comfort of their occupants4 ,there were steel door-mats at the entrances of the quarters4 ,the walls were boarded and even papered4 ,the bedrooms were fitted with spring beds1 chiffoniers1 and wash-stands1 and all the rooms were lighted with electric lamps4 ,there were spacious quarters for the men1 with regular underground mess halls and elaborate kitchens4 ,there were power-plants to furnish steam for the operation of pumps and for the lighting-plants and for other purposes4 ,illustration3 7,c7 ,underwood ,underwood ,lines of ,zig-,zag ,trenches as viewed from an ,airplane ,there was a chalk formation here in which were many large natural caves4 ,one enormous cave was said to have held thirty thousand soldiers1 and in this section the ,germans kept large reserve forces4 ,by digging far into the ground1 the ,german troops secured protection from shell-fire2 in fact1 the horrible noise of battle was heard only as a murmur1 down in these depths4 ,with characteristic thoroughness1 the ,germans built their trench system for a long stay2 while the ,allies1 on the other hand1 looked upon their trenches as merely temporary quarters1 which would hold the enemy at bay until they could build up armies large enough to drive the invaders out of the country4 ,the construction of the trenches along some parts of the battle-line was particularly difficult1 because of the problem of drainage4 ,this was especially true in ,flanders1 where the trenches in many cases were below water-level1 and elaborate pumping-systems had to be installed to keep them dry4 ,some of them were concrete-lined to make them waterproof4 ,in the early stages of the war1 before the trenches were drained1 the men had to stand in water for a good part of the time1 and the only way they could get about at all in the miry trenches was by having duck-boards in them4 ,duck-boards are sections of wooden sidewalk such as we find in small villages in this country1 consisting of a couple of rails on which crosspieces of wood are nailed4 ,these duck-boards fairly floated in the mud4 ,illustration3 ,courtesy of ,scientific ,american ,french ,sappers using ,stethoscopes to detect the ,mining ,operations of the ,enemy ,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 trench4 ,these gates were swung up out of the way1 but when lowered they were kept closed with a rather complicated system of bolts which the enemy would be unable to unfasten without some delay2 and while he was struggling to get through the gate1 he would be a target for the bullets of the defenders4 ,,hiding ,,railroads ,,in ,,ditches ,because of the elaborate system of trenches1 and the distance from the front line to that part of the country where it was safe to operate in the open1 it was necessary to build railways which would travel through tunnels and communicating trenches to the front lines4 ,these were narrow-gage railroads and a special standard form of track section was designed1 which was entirely of metal1 something like the track sections of toy railroads4 ,the tracks were very quickly laid and taken up at need4 ,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 miniature railroads to the front lines4 ,usually the trench railroads did not come to the very front of the battle-line1 but their principal use was to carry shell to the guns which were located in concealed positions4 ,railroad or tramway trenches could not be sharply zig-zagged but had to have easy curves1 which were apt to be recognized by enemy airplanes1 and so they were often concealed under a covering of wire strewn with leaves4 ,,periscopes ,,and ,,sniperscopes ,but while the armies were buried underground1 it was necessary for them to keep their eyes upon each other so that each might be ready for any sudden onslaught of the other4 ,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 themselves4 ,a trench periscope was a very simple affair1 consisting of a tube with two mirrors1 one at the top and one at the bottom1 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 top4 ,observation posts were established wherever there was a slight rise in the ground4 ,sometimes these posts were placed far in advance of the trenches and sometimes even behind the trenches where it was possible to obtain a good view of the opposing lines4 ,sometimes a tunnel would be dug forward1 leading to an outlet close to the enemy's lines1 and here an observer would take his position at night to spy with his ears upon the activities of the enemy4 ,observers who watched the enemy by day would often not dare to use periscopes1 which might be seen by the enemy and draw a concentrated fire of rifles and even shell4 ,so that every manner of concealment was employed to make the observation posts invisible and to have them blend with their surroundings4 ,observers even wore veils so that the white of their skin would not betray them4 ,illustration3 ,redrawn from ,military ,map ,reading by permission of ,e4 ,c4 ,mc,kay ,,fig4 #a4 ,a sniperscope with which a sharpshooter could take aim without showing his head above the parapet ,snipers were equally ingenious in concealing themselves4 ,they frequently used rifles which were connected with a dummy butt and had a periscope sighting-attachment4 ,this attachment was called a sniperscope4 ,the rifle-barrel could be pushed through a loophole in the parapet and the sniper standing safely below the parapet could hold the dummy butt to his shoulder and aim his rifle with perfect accuracy by means of the periscope4 ,it was next to impossible to locate a sniper hidden in this way4 ,one method of doing it was to examine rubbish1 tin cans1 or any object that had been penetrated by a bullet and note the direction taken by the bullet4 ,this would give a line leading toward the source of the shot1 and when a number of such lines were traced1 they would cross at a spot where the sniper or his gun was stationed1 and a few shell would put the man out of business4 ,dummy heads of papier mch were sometimes stuck above the parapet to draw the fire of enemy snipers and the bullet-holes which quickly appeared in them were studied to discover the location of the snipers4 ,illustration3 ,redrawn from ,military ,map ,reading by permission of ,e4 ,c4 ,mc,kay ,,fig4 #b4 ,a fixed rifle stand arranged to be fired after dark ,sometimes fixed rifles were used4 ,these were set on stands so that they could be very accurately trained upon some important enemy post4 ,then they could be fired in the dark1 without aiming1 to disturb night operations of the enemy4 ,often a brace of rifles1 as many as six1 would be coupled up to be fired simultaneously1 and by operating a single lever each gun would throw out the empty cartridge shell and bring a fresh one into position4 ,,steel ,,brier ,,patches ,the most important defense of a trench system consisted in the barbed wire entanglements placed before it4 ,barbed wire1 by the way1 is an ,american invention1 but it was originally intended for the very peaceful purpose for keeping cattle within bounds4 ,long ago it was used in war1 but never to the extent to which it was employed in this world struggle4 ,the entanglements 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 directions1 so as to make an impenetrable tangle4 ,where it was possible to prepare the entanglements without disturbance and the position was an important one1 the mass of barbed wire often extended for a hundred yards or more in depth4 ,just beyond the entanglements trip-wires were sometimes used4 ,a trip-wire was a slack wire which was laid on the ground4 ,before being laid1 the wire was tightly coiled so that it would not lie flat1 but would catch the feet of raiders and trip them up4 ,each side had gates in the line through which this wire could quickly be removed to let its own raiding-parties through4 ,sometimes raiders used tunnels1 with outlets beyond the barbed wire1 but they had to cut their way through the metal brier patches of their opponents4 ,early in the war1 various schemes were devised for destroying the entanglements4 ,there were bombs in the form of a rod about twelve feet long1 which could be pushed under the wire and upon exploding would tear it apart4 ,another scheme was to fire a projectile formed like a grapnel4 ,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 shore4 ,then the cable would be wound up on a winch and the grapnel hooks would tear the wire from its fastenings4 ,such schemes1 however1 did not prove very practicable1 and it was eventually found that a much better way of destroying barbed wire was to bombard it with high-explosive shell1 which would literally blow the wire apart4 ,but it required a great deal of shelling to destroy these entanglements1 and it was really not until the tank was invented that such obstructions could be flattened out so that they formed no bar to the passage of the soldiers4 ,the ,germans not only used fixed entanglements1 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 obstruction4 ,,mines ,,and ,,counter-,,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 mines4 ,tunnels were dug reaching out under the enemy's lines and large quantities of explosives were stored in them4 ,at the moment when it was intended to make an assault1 there would be a heavy cannonading to disconcert the enemy1 and then the mine would be touched off4 ,in the demoralizing confusion that resulted1 the storming-party would sweep over the enemy4 ,such mines were tried on both sides1 and the only protection against them was to out-guess the other side and build counter-mines4 ,if it were suspected1 from the importance of a certain position and the nature of the ground1 that the enemy would probably try to undermine it1 the defenders would dig tunnels of their own toward the enemy at a safe distance beyond their own lines and establish listeners there to see if they could hear the mining-operations of their opponents4 ,very delicate microphones were used1 which the listeners would place on the ground or against the walls of their tunnel4 ,then they would listen for the faintest sound of digging1 just as a doctor listens through a stethoscope to the beating of a patient's heart or the rush of air through his lungs4 ,when these listening-instruments picked up the noise of digging1 the general direction of the digging could be followed out by placing the instrument at different positions and noting where the noise was loudest4 ,then a counter-mine would be extended in that direction1 far enough down to pass under the enemy's tunnel1 and at the right moment1 a charge of ,,tnt 7trinitrotoluol7 would be exploded1 which would destroy the enemy's sappers and put an end to their ambitious plans4 ,a very interesting case of mining was furnished by the ,british when they blew up the important post of ,messines ,ridge4 ,this was strongly held by the ,germans and the only way of dislodging the enemy was to blow off the top of the ridge4 ,before work was started1 geologists were called upon to determine whether or not the ground were suitable for mining-operations4 ,they picked out a spot where the digging was good from the ,british side1 but where1 if counter-mines were attempted from the ,german side1 quicksands would be encountered and tunneling of any sort would be difficult4 ,the ,british sappers could1 therefore1 proceed with comparative safety4 ,the ,germans suspected that something of the sort was being undertaken1 but they found it very difficult to dig counter-mines4 ,however1 one day their suspicions were confirmed1 when the whole top of the hill was blown off1 with a big loss of ,german lives4 ,in the assault that followed the ,british captured the position and it was annexed to the ,british lines4 ,,chapter ,,ii ,,hand-,,grenades ,,and ,,trench ,,mortars ,in primitive times battles were fought hand-to-hand4 ,the first implements of war were clubs and spears and battle-axes1 all intended for fighting at close quarters4 ,the bow and arrow enabled men to fight at a distance1 but shields and armor were so effective a defense that it was only by hand-to-hand fighting that a brave enemy could be defeated4 ,even the invention of gunpowder did not separate the combatants permanently1 for although it was possible to hurl missiles at a great distance1 cannon were so slow in their action that the enemy could rush them between shots4 ,shoulder firearms also were comparatively slow in the early days1 and liable to miss fire1 and it was not until the automatic rifle of recent years was fully developed that soldiers learned to keep their distance4 ,when the great ,european war started1 military authorities had come to look upon war at close quarters as something relegated to bygone days4 ,even the bayonet was beginning to be thought of little use4 ,rifles could be charged and fired so rapidly and machine-guns could play such a rapid tattoo of bullets1 that it seemed impossible for men to come near enough for hand-to-hand fighting1 except at a fearful cost of life4 ,in developing the rifle1 every effort was made to increase its range so that it could be used with accuracy at a distance of a thousand yards and more4 ,but when the ,germans1 after their retreat in the ,first ,battle of the ,marne1 dug themselves in behind the ,aisne1 and the ,french and ,british too found it necessary to seek shelter from machine-gun and rifle fire by burrowing into the ground1 it became apparent that while rifles and machine-guns could drive the fighting into the ground1 they were of little value in continuing the fight after the opposing sides had buried themselves4 ,the trenches were carried close to one another1 in some instances being so close that the soldiers could actually hear the conversation of their opponents across the intervening gap4 ,under such conditions long-distance firearms were of very little practical value4 ,what was needed was a short-distance gun which would get down into the enemy trenches4 ,to be sure1 the trenches could be shelled1 but the shelling had to be conducted from a considerable distance1 where the artillery would be immune to attack1 and it was impossible to give a trench the particular and individual attention which it would receive at the hands of men attacking it at close quarters4 ,before we go any farther we must learn the meaning of the word trajectory4 ,no bullet or shell travels in a straight line4 ,as soon as it leaves the muzzle of the gun1 it begins to fall1 and its course through the air is a vertical curve that brings it eventually down to the ground4 ,this curve is called the trajectory4 ,no gun is pointed directly at a target1 but above it1 so as to allow for the pull of gravity4 ,the faster the bullet travels1 the flatter is this curve or trajectory1 because there is less time for it to fall before it reaches its target4 ,modern rifles fire their missiles at so high a speed that the bullets have a very flat trajectory4 ,but in trench warfare a flat trajectory was not desired4 ,what was the use of a missile that traveled in a nearly straight line1 when the object to be hit was hiding in the ground8 ,trench fighting called for a missile that had a very high trajectory1 so that it would drop right into the enemy trench4 ,,hand-,,artillery ,trench warfare is really a close-quarters fight of fort against fort1 and the soldiers who manned the forts had to revert to the ancient methods of fighting an enemy intrenched behind fortifications4 ,centuries ago1 not long after the first use of gunpowder in war1 small explosive missiles were invented which could be thrown by hand4 ,these were originally known as flying mortars4 ,the missile was about the size of an orange or a pomegranate1 and it was filled with powder and slugs4 ,a small fuse1 which was ignited just before the device was thrown1 was timed to explode the missile when it reached the enemy4 ,because of its size and shape1 and because the slugs it contained corresponded1 in a manner1 to the pulp-covered seeds with which a pomegranate is filled1 the missile was called a grenade4 ,grenades had fallen out of use in modern warfare1 although they had been revived to a small extent in the ,russo-,japanese war1 and had been used with some success by the ,bulgarians and the ,turks in the ,balkan wars4 ,and yet they had not been taken very seriously by the military powers of ,europe1 except ,germany4 ,germany was always on the lookout for any device that might prove useful in war1 and when the ,germans dug themselves in after the ,first ,battle of the ,marne1 they had large quantities of hand-grenades for their men to toss over into the trenches of the ,allies4 ,these missiles proved very destructive indeed4 ,they took the place of artillery1 and were virtually hand-thrown shrapnel4 ,the ,french and ,british were entirely unprepared for this kind of fighting1 and they had hastily to improvise offensive and defensive weapons for trench warfare4 ,their hand-grenades were at first merely tin cans filled with bits of iron and a high explosive in which a fuse-cord was inserted4 ,the cord was lighted by means of a cigarette and then the can with its spluttering fuse was thrown into the enemy lines4 ,as time went on and the art of grenade fighting was learned1 the first crude missiles were greatly improved upon and grenades were made in many forms for special service4 ,there was a difference between grenades hurled from sheltered positions and those used in open fighting4 ,when the throwers were sheltered behind their own breastworks1 it mattered not how powerful was the explosion of the grenade4 ,we must remember that in hand-artillery the shell is far more powerful in proportion to the distance it is thrown than the shell fired from a gun1 and many grenades were so heavily charged with explosives that they would scatter death and destruction farther than they could be thrown by hand4 ,the grenadier who cast one of these grenades had to duck under cover or hide under the walls of his trench1 else the fragments scattered by the exploding missile might fly back and injure him4 ,some grenades would spread destruction to a distance of over three hundred feet from the point of explosion4 ,for close work1 grenades of smaller radius were used4 ,these were employed to fight off a raiding-party after it had invaded a trench1 and the destructive range of these grenades was usually about twenty-five feet4 ,hand-grenades came to be used in all the different ways that artillery was used4 ,there were grenades which were filled with gas1 not only of the suffocating and tear-producing types1 but also of the deadly poisonous variety4 ,there were incendiary grenades which would set fire to enemy stores1 and smoke grenades which would produce a dense black screen behind which operations could be concealed from the enemy4 ,grenades were used in the same way that shrapnel was used to produce a barrage or curtain of fire1 through which the enemy could not pass without facing almost certain death4 ,curtains of fire were used not only for defensive purposes when the enemy was attacking1 but also to cut off a part of the enemy so that it could not receive assistance and would be obliged to surrender4 ,in attacks upon the enemy lines1 grenades were used to throw a barrage in advance of the attacking soldiers so as to sweep the ground ahead clear of the enemy4 ,the ,french paid particular attention to the training of grenadiers4 ,a man had to be a good1 cool-headed pitcher before he could be classed as a grenadier4 ,he must be able to throw his grenade with perfect accuracy up to a distance of seventy yards1 and to maintain an effective barrage4 ,the grenadier carried his grenades in large pockets attached to his belt1 and he was attended by a carrier who brought up grenades to him in baskets1 so that he was served with a continuous supply4 ,,long-,,distance ,,grenade-,,throwing ,all this relates to short-distance fighting1 but grenades were also used for ranges beyond the reach of the pitcher's arm4 ,even back in the sixteenth century1 the range of the human arm was not great enough to satisfy the combatants and grenadiers used a throwing-implement1 something like a shovel1 with which the grenade was slung to a greater distance1 in much the same way as a lacrosse ball is thrown4 ,later1 grenades were fitted with light1 flexible wooden handles and were thrown1 handle and all1 at the enemy4 ,by this means they could be slung to a considerable distance4 ,such grenades were used in the recent war1 particularly by the ,germans4 ,the handle was provided with streamers so as to keep the grenade head-on to the enemy1 and it was usually exploded by percussion on striking its target4 ,these long-handled grenades1 however1 were clumsy and bulky1 and the grenadier required a good deal of elbow-room when throwing them4 ,illustration3 ,,fig4 #c4 ,a rifle grenade fitted to the muzzle of a rifle ,a much better plan was to hurl them with the aid of a gun4 ,a rifle made an excellent short-distance mortar4 ,with it grenades could be thrown from three to four hundred yards4 ,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 explosion of a blank cartridge4 ,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 shell4 ,,striking ,a ,,light ,the lighting of the grenade fuses with a cigarette did very well for the early tin-can grenades1 but the cigarettes were not always handy1 particularly in the heat of battle1 and something better had to be devised4 ,one scheme was to use a safety-match composition on the end of a fuse4 ,this was covered with waxed paper to protect it from the weather4 ,the grenadier wore an armlet covered with a friction composition such as is used on a safety-match box4 ,before the grenade was thrown1 the waxed paper was stripped off and the fuse was lighted by being scratched on the armlet4 ,in another type the fuse was lighted by the twisting of a cap which scratched a match composition on a friction surface4 ,a safety-pin kept the cap from turning until the grenadier was ready to throw the grenade4 ,the ,mills hand-grenade1 which proved to be the most popular type used by the ,british ,army1 was provided with a lever which was normally strapped down and held by means of a safety-pin4 ,fig4 #d shows a sectional view of this grenade4 ,just before the missile was thrown1 it was seized in the hand so that the lever was held down4 ,then the safety-pin was removed and when the grenade was thrown1 the lever would spring up under pull of the spring ,a4 ,this would cause the pin ,b to strike the percussion cap ,c1 which would light the fuse ,d4 ,the burning fuse would eventually carry the fire to the detonator ,e1 which would touch off the main explosive1 shattering the shell of the grenade and scattering its fragments in all directions4 ,the shell of the grenade was indented so that it would break easily into a great many small pieces4 ,illustration3 ,,fig4 #d4 ,details of the ,mills hand grenade ,there were some advantages in using grenades lighted by fuse instead of percussion1 and also there were many disadvantages4 ,if too long a time-fuse were used1 the enemy might catch the grenade1 as you would a baseball and hurl it back before it exploded4 ,this was a hazardous game1 but it was often done4 ,illustration3 ,,fig4 #e4 ,a ,german parachute grenade ,among the different types of grenades which the ,germans used was one provided with a parachute as shown in ,fig4 #e4 ,the object of the parachute was to keep the head of the grenade toward the enemy1 so that when it exploded it would expend its energies forward and would not cast fragments back toward the man who had thrown it4 ,this was a very sensitive grenade1 arranged to be fired by percussion1 but it was so easily exploded that the firing-mechanism was not released until after the grenade had been thrown4 ,in the handle of this grenade there was a bit of cord about twenty feet long4 ,one end of this was attached to a safety-needle1 ,a1 while the other end1 formed into a loop1 was held by the grenadier when he threw the grenade4 ,not until the missile had reached a height of twelve or thirteen feet would the pull of the string withdraw the needle ,a4 ,this would permit a safety-hook1 ,b1 to drop out of a ring1 ,c1 on the end of a striker pellet1 ,d4 ,when the grenade struck1 the pellet ,d would move forward and a pin1 ,e1 would strike a cap on the detonator ,f1 exploding the missile4 ,this form of safety-device was used on a number of ,german grenades4 ,illustration3 ,,fig4 #f4 ,british rifle grenade with a safety-device which is unlocked by the rush of air against a set of inclined vanes1 ,d1 when the missile is in flight ,the ,british had another scheme for locking the mechanism until after the grenade had traveled some distance through the air4 ,details of this grenade1 which was of the type adopted to be fired from a rifle1 are shown in ,fig4 #f4 ,the striker ,a is retained by a couple of bolts1 ,b1 which in turn are held in place by a sleeve1 ,c4 ,on the sleeve is a set of wind-vanes1 ,d4 ,as the grenade travels through the air1 the wind-vanes cause the sleeve ,c to revolve1 screwing it down clear of the bolts ,b1 which then drop out1 permitting the pin ,a to strike the detonator ,e upon impact of the grenade with its target4 ,illustration3 ,,fig4 #g4 ,front1 side1 and sectional views of a disk-shaped ,german grenade ,illustration3 ,,fig4 #h4 ,a curious ,german hand grenade shaped like a hair brush ,the ,germans had one peculiar type which was in the shape of a disk4 ,in the disk were six tubes1 four of which carried percussion caps so that the grenade was sure to explode no matter on which tube it fell4 ,the disk was thrown with the edge up1 and it would roll through the air4 ,another type of grenade was known as the hair-brush grenade because it had a rectangular body of tin about six inches long and two and three quarter inches wide and deep1 which was nailed to a wooden handle4 ,,miniature ,,artillery ,hand-artillery was very effective as far as it went1 but it had its limitations4 ,grenades could not be made heavier than two pounds in weight if they were to be thrown by hand2 in fact1 most of them were much lighter than that4 ,if they were fired from a rifle1 the range was increased but the missile could not be made very much heavier4 ,,tnt is a very powerful explosive1 but there is not room for much of it in a grenade the size of a large lemon4 ,trench fighting was a duel between forts1 and while the hand-artillery provided a means of attacking the defenders of a fort1 it made no impression on the walls of the fort4 ,it corresponded to shrapnel fire on a miniature scale1 and something corresponding to high-explosive fire on a small scale was necessary if the opposing fortifications were to be destroyed4 ,to meet this problem1 men cast their thoughts back to the primitive artillery of the ,romans1 who used to hurl great rocks at the enemy with catapults4 ,and the trench fighters actually rigged up catapults with which they hurled heavy bombs at the enemy lines4 ,all sorts of ingenious catapults were built1 some modeled after the old ,roman machines4 ,in some of these stout timbers were used as springs1 in others there were powerful coil springs4 ,it was not necessary to cast the bombs far4 ,for distant work the regular artillery could be used4 ,what was needed was a short-distance gun for heavy missiles and that is what the catapult was4 ,illustration3 ,press ,illustrating ,service ,a #c-;inch ,stokes mortar and two of its shells ,illustration3 ,press ,illustrating ,service ,dropping a shell into a #f-;inch trench mortar ,but the work of the catapult was not really satisfactory4 ,the machine was clumsy2 it occupied too much space1 and it could not be aimed very accurately4 ,it soon gave way to a more modern apparatus1 fashioned after the old smooth-bore mortars4 ,this was a miniature mortar1 short and wide-mouthed4 ,a rifled barrel was not required1 because1 since the missile was not to be hurled far1 it was not necessary to set it spinning by means of rifling so as to hold it head-on to the wind4 ,,giant ,,pea-,,shooters ,better aim was secured when a longer-barreled trench mortar came to be used4 ,in the trench1 weight was an important item4 ,there was no room in which to handle heavy guns1 and the mortar had to be portable so that it could be carried forward by the infantry in a charge4 ,as the walls of a light barrel might be burst by the shock of exploding powder1 compressed air was used instead4 ,the shell was virtually blown out of the gun in the same way that a boy blows missiles out of a pea-shooter4 ,that the shell might be kept from tumbling1 it was fitted with vanes at the rear4 ,these acted like the feathers of an arrow to hold the missile head-on to its course4 ,illustration3 ,courtesy of ,scientific ,american ,the ,maxim ,machine-gun ,operated by the ,energy of the ,recoil ,illustration3 ,courtesy of ,scientific ,american ,colt ,machine-gun partly broken away to show the ,operating ,mechanism ,gas from port ,a pushes down piston ,b1 rocking lever ,c1 which compresses coil-spring ,d4 ,the cartridge fed into the gun by wheel ,e1 is extracted by ,f1 raised by ,g to breech ,h1 and rammed in by bolt ,i4 ,j1 piston firing-hammer4 ,the ,french in particular used this type of mortar and the air-pump was used to compress the air that propelled the shell or arial torpedo1 or else the propelling charge was taken from a compressed-air tank4 ,carbon-dioxide1 the gas used in soda-water1 is commonly stored in tanks under high pressure and this gas was sometimes used in place of compressed air4 ,when the gas in the tank was exhausted the latter could be recharged with air by using a hand-pump4 ,two or three hundred strokes of the pump would give a pressure of one hundred and twenty to one hundred and fifty pounds per inch1 and would supply enough air to discharge a number of shell4 ,the air was let into the barrel of the mortar in a single puff sufficient to launch the shell2 then the tank was cut off at once1 so that the air it contained would not escape and go to waste4 ,,the ,,stokes ,,mortar ,however1 the most useful trench mortar developed during the war was invented by ,wilfred ,stokes1 a ,british inventor4 ,in this a comparatively slow-acting powder was used to propel the missile1 and so a thin-walled barrel could be used4 ,the light ,stokes mortar can easily be carried over the shoulder by one man4 ,it has two legs and the barrel itself serves as a third leg1 and the mortar stands like a tripod4 ,the two legs are adjustable1 so that the barrel can be inclined to any desired angle4 ,it took but a moment to set up the mortar for action in a trench or shell-hole4 ,illustration3 ,,fig4 #i4 ,sectional view of a #c-;inch ,stokes mortar showing a shell at the instant of striking the anvil ,illustration3 ,,fig4 #aj4 ,a #f-;inch trench mortar shell fitted with tail-vanes ,curiously enough1 there is no breech-block1 trigger or fire-hole in this mortar4 ,it is fired merely by the dropping of the missile into the mouth of the barrel4 ,the shell carries its own propelling charge1 as shown in ,fig4 #i4 ,this is in the form of rings1 ,a1 which are fitted on a stem1 ,b4 ,at the end of the stem are a detonating cap and a cartridge1 to ignite the propellant1 ,a4 ,at the bottom of the mortar barrel1 there is a steel point1 ,e1 known as the anvil4 ,when the shell is dropped into the mortar1 the cap strikes the anvil1 exploding the cartridge and touching off the propelling charge1 ,a4 ,the gases formed by the burning charge hurl the shell out of the barrel to a distance of several hundred yards4 ,the first ,stokes mortar was made to fire a #c-;inch shell1 but the mortar grew in size until it could hurl shell of #f-;inch and even #h-a_/b-;inch size4 ,of course1 the larger mortars had to have a very substantial base4 ,they were not so readily portable as the smaller ones and they could not be carried by one man2 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 time4 ,the larger shell have tail-vanes1 as shown in ,fig4 #aj1 to keep them from tumbling when in flight4 ,,chapter ,,iii ,,guns ,,that ,,fire ,,themselves ,many years ago a boy tried his hand at firing a ,united ,states ,army service rifle4 ,it was a heavy rifle of the ,civil ,war period1 and the lad did not know just how to hold it4 ,he let the butt of the gun rest uncertainly against him1 instead of pressing it firmly to his shoulder1 and1 in consequence1 when the gun went off he received a powerful kick4 ,that kick made a deep impression on the lad1 not only on his flesh but on his mind as well4 ,it gave him a good conception of the power of a rifle cartridge4 ,years afterward1 when he had moved to ,england1 the memory of that kick was still with him4 ,it was a useless prank of the gun1 he thought1 a waste of good energy4 ,why could not the energy be put to use8 ,and so he set himself the task of harnessing the kick of the gun4 ,a very busy program he worked out for that kick to perform4 ,he planned to have the gun use up its exuberant energy in loading and firing itself4 ,so he arranged the cartridges on a belt and fed the belt into the gun4 ,when the gun was fired1 the recoil would unlock the breech1 take out the empty case of the cartridge just fired1 select a fresh cartridge from the belt1 and cock the main spring2 then the mechanism would return1 throwing the empty cartridge-case out of the gun1 pushing the new cartridge into the barrel1 closing the breech1 and finally pulling the trigger4 ,all this was to be done by the energy of a single kick1 in about one tenth of a second1 and the gun would keep on repeating the operation as long as the supply of cartridges was fed to it4 ,the new gun proved so successful that the inventor was knighted1 and became ,sir ,hiram ,maxim4 ,a ,,doctor',s ,,ten-,,barreled ,,gun ,but ,maxim's was by no means the first machine-gun4 ,during the ,civil ,war a ,chicago physician brought out a very ingenious ten-barreled gun1 the barrels of which were fired one after the other by the turning of a hand-crank4 ,although ,dr4 ,gatling was a graduate of a medical school1 he was far more fond of tinkering with machinery than of doling out pills4 ,he invented a number of clever mechanisms1 but the one that made him really famous was that machine-gun4 ,at first our government did not take the invention seriously4 ,the gun was tried out in the war1 but whenever it went into battle it was fired not by soldiers but by a representative of ,dr4 ,gatling's company1 who went into the army to demonstrate the worth of the invention4 ,not until long after was the ,gatling gun officially adopted by our army4 ,then it was taken up by many of the ,european armies as well4 ,although many other machine-guns were invented1 the ,gatling was easily the best and most serviceable1 until the ,maxim invention made its appearance1 and even then it held its own for many years2 but eventually it had to succumb4 ,the ,maxim did not have to be cranked3 it fired itself1 which was a distinct advantage2 and then1 instead of being a bundle of guns all bound up into a single machine1 ,maxim's was a single-barreled gun and hence was much lighter and could be handled much more easily4 ,a ,,gun ,,as ,a ,,gas-,,engine ,another big advance was made by a third ,american1 ,mr4 ,john ,m4 ,browning1 who is responsible for the ,colt gun4 ,it was not a kick that set ,browning to thinking4 ,he looked upon a gun as an engine of the same order as an automobile engine1 and really the resemblance is very close4 ,the barrel of the gun is the cylinder of the engine2 the bullet is the piston2 and for fuel gunpowder is used in place of gasolene4 ,as in the automobile engine1 the charge is fired by a spark2 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 cartridge4 ,illustration3 ,courtesy of ,scientific ,american ,the ,lewis ,gun which produces its own cooling current ,illustration3 ,courtesy of ,scientific ,american ,the ,bent-,merci ,gun operated by gas ,explosion is the same thing as burning4 ,the only way that the explosion of gunpowder differs from the burning of a stick of wood is that the latter is very slow1 while the former goes like a flash4 ,in both cases the fuel turns into great volumes of gas4 ,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 itself4 ,in the cartridge that our army uses1 only about a tenth of an ounce of smokeless powder is used1 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 second4 ,it travels so fast that it will plow through four feet of solid wood before coming to a stop4 ,illustration3 7,c7 ,committee on ,public ,information ,browning ,machine ,rifle1 weight only #ae pounds ,illustration3 7,c7 ,committee on ,public ,information ,browning ,machine-,gun1 weighing #cd-a_/b pounds ,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-gun4 ,it was ever so little he wanted1 and the bullet would never miss it4 ,the danger was not that he might take too much4 ,his problem was to take any power at all without getting more than his mechanism could stand4 ,what he did was to bore a hole through the side of the gun-barrel4 ,when the gun was fired1 nothing happened until the bullet passed this hole2 then some of the gas that was pushing the bullet before it would blow out through the hole4 ,but this would be a very small amount indeed1 for the instant that the bullet passed out of the barrel the gases would rush out after it1 the pressure in the gun would drop1 and the gas would stop blowing through the hole4 ,with the bullet traveling at the rate of about half a mile in a second1 imagine how short a space of time elapses after it passes the hole before it emerges from the muzzle1 and what a small amount of gas can pass through the hole in that brief interval6 ,the gas that ,browning got in this way he led into a second cylinder1 fitted with a piston4 ,this piston was given a shove1 and that gave a lever a kick which set going the mechanism that extracted the empty cartridge-case1 inserted a fresh cartridge1 and fired it4 ,,getting ,,rid ,,of ,,heat ,the resemblance of a machine-gun to a gasolene-engine can be demonstrated still further4 ,one of the most important parts of an automobile engine is the cooling-system4 ,the gasolene burning in the cylinders would soon make them red-hot1 were not some means provided to carry off the heat4 ,the same is true of a machine-gun4 ,in fact1 the heat is one of the biggest problems that has to be dealt with4 ,in a gasolene-engine the heat is carried off in one of three ways3 7#a7 by passing water around the cylinders2 7#b7 by building flanges around the cylinders to carry the heat off into the air2 and 7#c7 by using a fan to blow cool air against the cylinders4 ,all of these schemes are used in the machine-gun4 ,in ,dr4 ,gatling's gun the cooling-problem was very simple4 ,as there were ten barrels1 one barrel could be cooling while the rest were taking their turn in the firing4 ,in other words1 each barrel received only a tenth of the heat that the whole gun was producing2 and yet ,gatling found it advisable to surround the barrels for about half their length with a water-jacket4 ,in the ,maxim gun a water-jacket is used that extends the full length of the barrel1 and into this water-jacket seven and a half pints of water are poured4 ,yet in a minute and a half of steady firing at a moderate rate1 or before six hundred rounds are discharged1 the water will be boiling4 ,after that1 with every thousand rounds of continuous fire a pint and a half of water will be evaporated4 ,now the water and the water-jacket add a great deal of weight to the gun1 and this ,browning decided to do away with in his machine-gun4 ,instead of water he used air to carry off the heat4 ,the more surface the air touches1 the more heat will it carry away2 and so the ,colt gun was at first made with a very thick-walled barrel4 ,but later the ,colt was formed with flanges1 like the flanges on a motor-cycle engine1 so as to increase the surface of the barrel4 ,of course1 air-cooling is not so effective as water-cooling1 but it is claimed for this gun1 and for other machine-guns of the same class1 that the barrel is sufficiently cooled for ordinary service4 ,although a machine-gun may be capable of firing many hundred shots per minute1 it is seldom that such a rate is kept up very long in battle4 ,usually1 only a few rounds are fired at a time and then there is a pause1 and there is plenty of time for the barrel to cool4 ,once in a while1 however1 the gun has to be fired continuously for several minutes1 and then the barrel grows exceedingly hot4 ,,effect ,,of ,,overheating ,but what if the gun-barrel does become hot8 ,the real trouble is not that the cartridge will explode prematurely1 but that the barrel will expand as it grows hot1 so that the bullet will fit too loosely in the bore4 ,inside the barrel the bore is rifled2 that is1 there are spiral grooves in it which give a twist to the bullet as it passes through1 setting it spinning like a top4 ,the spin of the bullet keeps its nose pointing forward4 ,if it were not for the rifling1 the bullet would tumble over and over1 every which way1 and it could not go very far through the air1 to say nothing of penetrating steel armor4 ,to gain the spinning-motion the bullet must fit into the barrel snugly enough to squeeze into the spiral grooves4 ,now there is another ,american machine-gun known as the ,hotchkiss1 which was used to a considerable extent by the ,french ,army4 ,it is a gas-operated gun1 something like the ,colt1 and it is air-cooled4 ,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 uncertain4 ,in seven minutes of continuous firing the barrel had grown so large that the rifling failed to grip the bullet at all4 ,the gun was no better than an old-fashioned smooth-bore4 ,the bullets would not travel more than three hundred yards4 ,it is because of this danger of overheating that the ,colt and the ,hotchkiss guns are always furnished with a spare barrel4 ,as soon as a barrel gets hot it is uncoupled and the spare one is inserted in its place4 ,our men are trained to change the barrel of a colt in the dark in a quarter of a minute4 ,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 weapon1 by any means4 ,and this brings us to still another invention--that1 too1 by an ,american4 ,colonel ,i4 ,n4 ,lewis1 of the ,united ,states ,army1 conceived of a machine-gun that would be cooled not by still air but by air in motion4 ,this would do away with all the bother of water-jackets4 ,it would keep the gun light so that it could be operated by one man1 and yet it would not have to be supplied with a spare barrel4 ,like the ,colt and the ,hotchkiss1 the ,lewis gun takes its power from the gas that comes through a small port in the barrel1 near the muzzle4 ,in the plate facing page #dd the port may be seen leading into a cylinder that lies under the barrel4 ,it takes about one ten-thousandth part of a second for a bullet to pass out of the barrel after clearing the port1 but in that brief interval there is a puff of gas in the cylinder which drives back a piston4 ,this piston has teeth on it which engage a small gear connected with a main-spring4 ,when the piston moves back1 it winds the spring1 and it is this spring that operates the mechanism of the gun4 ,the cartridges1 instead of being taken from a belt or a clip1 are taken from a magazine that is round and flat4 ,there are forty-seven cartridges in the magazine and they are arranged like the spokes of a wheel1 but in two layers4 ,as soon as forty-seven rounds have been fired1 the shooting must stop while a new magazine is inserted4 ,but to insert it takes only a couple of seconds4 ,,using ,,the ,,bullet ,,to ,,fan ,,the ,,gun ,the most ingenious part of the ,lewis gun is the cooling-system4 ,on the barrel of the gun are sixteen flanges or fins4 ,these1 instead of running around the gun1 run lengthwise of the barrel4 ,they are very light fins1 being made of aluminum1 and are surrounded by a casing of the same metal4 ,the casing is open at each end so that the air can flow through it1 but it extends beyond the muzzle of the barrel1 and there it is narrowed down4 ,at the end of the barrel there is a mouthpiece so shaped that the bullet1 as it flies through1 sucks a lot of air in its wake1 making a strong current flow through the sixteen channels formed between the fins inside the casing4 ,this air flows at the rate of about seventy miles per hour1 which is enough to carry off all the heat that is generated by the firing of the cartridges4 ,the gun may be regulated to fire between #cej and #gej rounds per minute1 and its total weight is only #be-a_/b pounds4 ,illustration3 ,lewis ,machine-guns in action at the front ,america can justly claim the honor of inventing and developing the machine-gun1 although ,hiram ,maxim did give up his ,american citizenship and become a ,british subject4 ,by the way1 he is not to be confused with his younger brother1 ,hudson ,maxim1 the inventor of high explosives1 who has always been an ,american to the core4 ,of course we must not get the impression that only ,americans have invented machine-guns4 ,there have been inventors of such weapons in various countries of ,europe1 and even in ,japan4 ,our own army for a while used a gun known as the ,bent-,merci1 which is something like the ,hotchkiss4 ,this was invented by ,l4 ,v4 ,bent1 an ,american1 and ,h4 ,a4 ,merci1 a ,frenchman1 both living in ,st4 ,denis1 ,france4 ,,the ,,browning ,,machine-,,gun ,when we entered the war1 it was expected that we would immediately equip our forces with the ,lewis gun1 because the ,british and the ,belgians had found it an excellent weapon and also because it was invented by an ,american officer1 who very patriotically offered it to our government without charging patent royalties4 ,but the army officials would not accept it1 although many ,lewis guns were bought by the navy4 ,this raised a storm of protest throughout the country until finally it was learned that there was another gun for which the army was waiting1 which it was said would be the very best yet4 ,the public was skeptical and finally a test was arranged in ,washington at which the worth of the new gun was demonstrated4 ,illustration3 ,courtesy of ,scientific ,american ,an elaborate ,german ,machine-,gun ,fort ,it was a new ,browning model2 or1 rather1 there were two distinct models4 ,one of them1 known as the heavy model1 weighed only #cd-a_/b pounds1 this with its water-jacket filled2 for it was a water-cooled gun4 ,without its charge of water the machine weighed but #bb-a_/b pounds and could be rated as a very light machine-gun4 ,however1 it was classed as a heavy gun and was operated from a tripod4 ,the new machine used recoil to operate its mechanism4 ,the construction was simple1 there were few parts1 and the gun could very quickly be taken apart in case of breakage or disarrangement of the mechanism4 ,but the greatest care was exercised to prevent jamming of cartridges1 which was one of the principal defects in the other types of machine-guns4 ,in the test this new weapon fired twenty thousand shots at the rate of six hundred per minute1 with interruptions of only four and a half seconds1 due partly to defective cartridges4 ,there was no doubt that the new ,browning was a remarkable weapon4 ,but if that could be said of the heavy gun1 the light gun was a marvel4 ,it weighed only fifteen pounds and was light enough to be fired from the shoulder or from the hip1 while the operator was walking or running4 ,in fact1 it was really a machine-rifle4 ,the regular 4#cj-;caliber service cartridges were used1 and these were stored in a clip holding twenty cartridges4 ,the cartridges could be fired one at a time1 or the entire clip could be fired in two and a half seconds4 ,it took but a second to drop an empty clip out of the gun and replace it with a fresh one4 ,the rifle was gas-operated and air-cooled1 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 overheated4 ,after the ,browning machine-rifle was demonstrated it was realized that the army had been perfectly justified in waiting for the new weapon4 ,like the heavy ,browning1 the new rifle was a very simple mechanism1 with few parts which needed no special tools to take them apart or reassemble them2 a single small wrench served this purpose4 ,both the heavy and the light gun were proof against mud1 sand1 and dust of the battle-field4 ,but best of all1 a man did not have to have highly specialized training before he could use the ,browning rifle4 ,it did not require a crew to operate one of these guns4 ,each soldier could have his own machine-gun and carry it in a charge as he would a rifle4 ,the advantage of the machine-rifle was that the operator could fire as he ran1 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 target4 ,very accurate shooting was thus made possible1 and the machine-rifle proved invaluable in the closing months of the war4 ,browning is unquestionably the foremost inventor of firearms in the world4 ,he was born of ,mormon parents1 in ,ogden1 ,utah1 in #ahed1 and his father had a gun shop4 ,as a boy ,browning became familiar with the use of firearms and when he was but fourteen years of age he invented an improved breech mechanism which was later used in the ,winchester repeater4 ,curiously enough1 it was a ,browning pistol that was used by the assassin at ,serajevo who killed the ,archduke of ,austria and precipitated the great ,european war1 and it was with the ,browning machine-gun and rifle that our boys swept the ,germans back through the ,argonne ,forest and helped to bring the war to a successful end4 ,,the ,,machine-,,gun ,,in ,,service ,although the machine-gun has been used ever since the ,civil ,war1 it was not a vital factor in warfare until the recent great conflict4 ,army officials were very slow to take it up1 because they did not understand it4 ,they used to think of it as an inferior piece of light artillery1 instead of a superior rifle4 ,the ,gatling was so heavy that it had to be mounted on wheels1 and naturally it was thought of as a cannon4 ,in the ,franco-,prussian ,war the ,french had a machine-gun by which they set great store4 ,it was called a mitrailleuse1 or a gun for firing grape-shot4 ,it was something like the ,gatling4 ,the ,french counted on this machine to surprise and overwhelm the ,germans4 ,but they made the mistake of considering it a piece of artillery and fired it from long range1 so that it did not have a chance to show its worth4 ,only on one or two occasions was it used at close range1 and then it did frightful execution4 ,however1 it was a very unsatisfactory machine1 and kept getting out of order4 ,it earned the contempt of the ,germans1 and later when the ,maxim gun was offered to the ,german ,army they would have none of it4 ,they did not want to bother with a toy cannon4 ,it really was not until the war between ,russia and ,japan that military men began to realize the value of the machine-gun4 ,as the war went on1 both the ,russians and the ,japanese bought up all the machine-guns they could secure4 ,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 through4 ,a man with a machine-gun is worth a hundred men with rifles2 such is the military estimate of the weapon4 ,the gun fires so fast that after hitting a man it will hit him again ten times while he is falling to the ground4 ,and so it does not pay to fire the gun continuously in one direction1 unless there is a dense mass of troops charging upon it4 ,usually the machine-gun is swept from side to side so as to cover as wide a range as possible4 ,it is played upon the enemy as you would play the hose upon the lawn1 scattering a shower of lead among the advancing hosts4 ,,machine-,,gun ,,forts ,it used to be thought that the ,belgian forts of armored steel and concrete1 almost completely buried in the ground1 would hold out against any artillery4 ,but when the ,germans brought up their great howitzers and hurled undreamed-of quantities of high explosives on these forts1 they broke and crumbled to pieces4 ,then it was predicted that the day of the fort was over4 ,but the machine-gun developed a new type of warfare4 ,instead of great forts1 mounting huge guns1 little machine-gun forts were built1 and1 they were far more troublesome than the big fellows4 ,to the ,germans belongs the credit for the new type of fort1 which consisted of a small concrete structure1 hidden from view as far as possible1 but commanding some important part of the front4 ,pill-boxes1 the ,british call them1 because the first ones they ran across were round in shape and something like a pill-box in appearance4 ,these pill-boxes were just large enough to house a few men and a couple of machine-guns4 ,concealment was of the utmost importance2 safety depended upon it4 ,airplanes were particularly feared1 because a machine-gun emplacement was recognized to be so important that a whole battery of artillery would be turned upon a suspected pill-box4 ,some of the ,german machine-gun forts were very elaborate1 consisting of spacious underground chambers where a large garrison of gunners could live4 ,these forts were known as ,mebus1 a word made from the initials of ,maschinengewehr ,eisen-,bettungs ,unterstand1 meaning a machine-gun iron-bedded foundation4 ,it was the machine-gun that was responsible for the enormous expenditure of ammunition in the war4 ,before a body of troops dared to make a charge1 the ground had to be thoroughly searched by the big guns for any machine-gun nests4 ,unless these were found and destroyed by shell-fire1 the only way that remained to get the best of them was to crush them down with tanks4 ,it was really the machine-gun that drove the armies into trenches and under the ground4 ,illustration3 ,comparative diagram of the path of a projectile from the ,german ,super-gun ,but a machine-gun did not have to be housed in a fort1 particularly a light gun of the ,lewis type4 ,to be sure1 the ,lewis gun is a little heavy to be used as a rifle1 but it could easily be managed with a rest for the muzzle in the crotch of a tree1 and a strong man could actually fire the piece from the shoulder4 ,the light machine-gun could go right along with a charging body of troops and do very efficient service1 particularly in fighting in a town or village1 but it had to be kept moving or it would be a target for the artillery4 ,in a certain village fight a machine-gunner kept changing his position4 ,he would fire for a few minutes from one building and then shift over to some other4 ,he did this no less than six times1 never staying more than five minutes at a time in the same spot4 ,but each one of the houses was shelled within fifteen minutes of the time he opened fire from it1 which shows the importance that the ,germans attached to machine-gun fire4 ,illustration3 ,courtesy of ,scientific ,american ,one of our #af-;inch ,coast ,defence ,guns on a disappearing mount ,illustration3 ,height of gun as compared with the ,new ,york ,city ,hall ,,chapter ,,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 away1 the world at first refused to believe2 then it imagined that some brand-new form of gun or shell or powder had been invented by the ,germans4 ,however1 while the public marveled1 ordnance experts were interested but not astonished4 ,they knew that it was perfectly feasible to build a gun that would hurl a shell fifty1 or seventy-five1 or even a hundred miles1 without involving anything new in the science of gunnery4 ,,shooting ,,around ,,the ,,edge ,,of ,,the ,,earth ,but if such ranges were known to be possible1 why was no such long-distance gun built before8 ,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 have to be as big as a whole city to be hit at all4 ,in a distance of seventy miles1 the curve of the earth is considerable4 ,paris is far below the horizon of a man standing at ,st4 ,gobain1 where the big ,german gun was located4 ,and if a hole were bored from ,st4 ,gobain straight to ,paris1 so that you could see the city from the gun1 it would pass1 midway of its course1 three thousand1 seven hundred and fifty feet below the surface of the earth4 ,with the target so far off1 it was impossible to aim at any particular fort1 ammunition depot1 or other point of military importance4 ,there is always some uncertainty as to just where a shell will fall1 due to slight differences in quality and quantity of the powder used1 in the density of the air1 the direction of the wind1 etc4 ,this variation is bad enough when a shell is to be fired ten miles1 but when the missile has to travel seventy miles1 it is out of the question to try to hit a target that is not miles in extent4 ,twenty years before the war our ,ordnance ,department had designed a fifty-mile gun1 but it was not built1 because we could see no possible use for it4 ,our big guns were built for fighting naval battles or for the defense of our coasts from naval attacks1 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 masts2 and so our big guns1 though they were capable of firing a shell twenty-seven miles1 if aimed high enough1 were usually mounted in carriages that would not let them shoot more than twelve or fifteen miles4 ,the distance to which a shell can be hurled depends to a large extent upon the angle of the gun4 ,if the gun is tilted up to an angle of #ae degrees1 the shell will go only about half as far as if it were tilted up to #dc-a_/b degrees1 which is the angle that will carry a shell to its greatest distance4 ,if the long-range ,german gun was fired at that angle1 the shell must have risen to a height of about twenty-four miles4 ,,beyond ,,the ,,earth',s ,,atmosphere ,most of the air that surrounds our globe lies within four miles of the surface4 ,few airplanes can rise to a greater height than this1 because the air is so thin that it gives no support to the wings of the machine4 ,the greatest height to which a man has ever ascended is seven miles4 ,a balloon once carried two men to such a height4 ,one of them lost consciousness1 and the other1 who was nearly paralyzed1 succeeded in pulling the safety-valve rope1 with his teeth4 ,that brought the balloon down1 and their instruments showed that they had gone up thirty-six thousand feet4 ,what the ocean of air contains above that elevation1 we do not know1 but judging by the way the atmosphere thins out as we rise from the surface of the earth1 we reckon that nine tenths of the air lies within ten miles of the surface of the earth4 ,at twenty-four miles1 or the top of the curve described by the shell of the ,german long-range guns1 there must be an almost complete vacuum4 ,if only we could accompany a shell on its course1 we should find a strange condition of affairs4 ,the higher we rose1 the darker would the heavens become1 until the sun would shine like a fiery ball in a black sky4 ,all around1 the stars would twinkle1 and below would be the glare of light reflected from the earth's surface and its atmosphere1 while the cold would be far more intense than anything suffered on earth4 ,up at that height1 there would be nothing to indicate that the shell was moving--no rush of air against the ears4 ,we should seem detached from earth and out in the endless reaches of space4 ,it seems absurd to think that a shell weighing close to a quarter of a ton could be retarded appreciably by mere air4 ,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 figure4 ,the pressure is the same whether a shell is moving through the air or the air is blowing against the shell4 ,when the wind blows at the rate of #ajj to #abj miles per hour1 it is strong enough to lift houses off their foundations1 to wrench trees out of the ground1 to pick up cattle and carry them sailing through the air4 ,imagine what it would do if its velocity were increased to #a1hjj miles per hour4 ,that is what the shell of a big gun has to contend with4 ,as most of the air lies near the earth1 the shell of long-range guns meet with less and less resistance the higher they rise1 until they get up into such thin air that there is virtually no obstruction4 ,the main trouble is to pierce the blanket of heavy air that lies near the earth4 ,,ways ,,of ,,increasing ,,the ,,range ,the big #af-;inch guns that protect our coasts fire a shell that weighs #b1djj pounds4 ,nine hundred pounds of smokeless powder is used to propel the shell1 which leaves the muzzle of the gun with a speed of #b1fjj feet per second4 ,now1 the larger the diameter of the shell1 the greater will be its speed at the muzzle of the gun1 because there will be a greater surface for the powder gases to press against4 ,on the other hand1 the larger the shell1 the more will it be retarded by the air1 because there will be a larger surface for the air to press against4 ,it has been proposed by some ordnance experts that a shell might be provided with a disk at each end1 which would make it fit a gun of larger caliber4 ,a #aj-;inch shell1 for instance1 could then be fired from a #af-;inch gun4 ,being lighter than the #af-;inch shell1 it would leave the muzzle of the gun at a higher speed4 ,the disks could be so arranged that as soon as the shell left the gun they would be thrown off1 and then the #aj-;inch shell1 although starting with a higher velocity than a #af-;inch shell1 would offer less resistance to the air4 ,in that way it could be made to cover a much greater range4 ,by the way1 the shell of the ,german long-range gun was of but #h4b-;inch caliber4 ,another way of increasing the range is to lengthen the gun4 ,right here we must become acquainted with the word caliber4 ,caliber means the diameter of the shell4 ,a #af-;inch gun1 for instance1 fires a shell of #af-;inch caliber2 but when we read that the gun is a #dj-or #ej-;caliber gun1 it means that the length of the gun is forty or fifty times the diameter of the shell4 ,our biggest coast-defense guns are #ej-;caliber #af-;inch guns1 which means that they are fifty times #af inches long1 or #ff-b_/c feet in length4 ,when a gun is as long as that1 care has to be taken to prevent it from sagging at the muzzle of its own weight4 ,these guns actually do sag a little1 and when the shell is fired through the long barrel it straightens up the gun1 making the muzzle whip upward1 just as a drooping garden hose does when the water shoots through it4 ,illustration3 ,courtesy of ,scientific ,american ,the #aba-,mile ,gun designed by ,american ,ordnance ,officers ,now the longer the caliber length of a gun1 the farther it will send a shell1 because the powder gases will have a longer time to push the shell4 ,but we cannot lengthen our big guns much more without using some special support for the muzzle end of the gun1 to keep it from whipping too much4 ,it is likely that the long-range ,german gun was provided with a substantial support at the muzzle to keep it from sagging4 ,illustration3 7,c7 ,underwood ,underwood ,american #af-;,inch ,rifle on a ,railway ,mount ,every once in a while a man comes forth with a new idea for increasing the range4 ,one plan is to increase the powder-pressure4 ,we have powders that will produce far more pressure than an ordinary gun can stand4 ,but we have to use powders that will burn comparatively slowly4 ,we do not want too sudden a shock to start with1 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 muzzle4 ,the fifty-mile gun that was proposed twenty years ago was designed to stand a much higher pressure than is commonly used1 and it would have fired a #aj-;inch shell weighing #fjj pounds with a velocity of #d1jjj feet per second at the muzzle4 ,the ,allies built no super-guns1 because they knew that they could drop a far greater quantity of explosives with much greater accuracy from airplanes1 and at a much lower cost4 ,the ,german gun at ,st4 ,gobain was spectacular and it did some damage1 but it had no military value and it did not intimidate the ,french as the ,germans had hoped it would4 ,a ,,gun ,,with ,a ,,range ,,of ,a ,,hundred ,,and ,,twenty ,,miles ,but although we built no such gun1 after the ,germans began shelling ,paris our ,ordnance ,department designed a gun that would fire a shell to a distance of over #abj miles6 ,there was no intention of constructing the gun1 but the design was worked out just as if it were actually to be built4 ,it was to fire a shell of #aj-;inch caliber1 weighing #djj pounds4 ,now1 an ,elswick standard #aj-;inch gun is #db feet long and its shell weighs #ejj pounds4 ,two hundred pounds of powder are used to propel the shell1 which leaves the muzzle with a velocity of #c1jjj feet per second4 ,if the gun is elevated to the proper angle1 it will send the shell #be miles1 and it will take the shell a minute and thirty-seven seconds to cover that distance4 ,but the long-range gun our ordnance experts designed would have to be charged with #a1ddj pounds of powder and the shell would leave the muzzle of the gun with a velocity of #h1ejj feet per second4 ,it would be in the air four minutes and nine seconds and would travel #aba4c miles4 ,were the gun fired from the ,aberdeen ,proving ,grounds1 near ,baltimore1 ,maryland1 its shell would travel across three states and fall into ,new ,york ,bay at ,perth ,amboy4 ,at the top of its trajectory it would rise #df miles above the earth4 ,but the most astonishing part of the design was the length of the gun1 which worked out to #bbe feet4 ,an enormous powder-chamber would have to be used1 so that the powder gases would keep speeding up the shell until it reached the required velocity at the muzzle4 ,the weight of the barrel alone was estimated at #cbe tons4 ,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 truss4 ,the gun would be mounted like a roller lift-bridge with a heavy counter-weight at its lower end so that it could be elevated or depressed at will and a powerful hydraulic jack would be required to raise it4 ,the recoil of a big gun is always a most important matter4 ,unless a gun can recoil1 it will be smashed by the shock of the powder explosion4 ,usually1 heavy springs are used to take up the shock1 or cylinders filled with oil in which pistons slide4 ,the pistons have small holes in them through which the oil is forced as the piston moves and this retards the gun in its recoil4 ,but this super-gun was designed to be mounted on a carriage running on a set of tracks laid in a long concrete pit4 ,on the recoil the gun would run back along the tracks1 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 pit1 to a friction drum4 ,the engraving facing page #fh gives some idea of the enormous size of the gun4 ,note the man at the breech of the gun4 ,the hydraulic jack is collapsible1 so that the gun may be brought to the horizontal position for loading1 as shown by the dotted lines4 ,the cost of building this gun is estimated at two and a half million dollars and its #djj-pound shell would land only about sixty pounds of high explosives on the target4 ,a bombing-plane costing but thirty thousand dollars could land twenty-five times as big a charge of high explosives with far greater accuracy4 ,aside from this1 the gun lining would soon wear out because of the tremendous erosion of the powder gases4 ,,the ,,three-,,second ,,life ,,of ,a ,,gun ,powder gases are very hot indeed--hot enough to melt steel4 ,the greater the pressure in the gun1 the hotter they are4 ,it is only because they pass through the gun so quickly1 that they do not melt it4 ,as a matter of fact1 they do wear it out rapidly because of their heat and velocity4 ,they say that the life of a big gun is only three seconds4 ,of course1 a shell passes through the gun in a very minute part of a second1 but if we add up these tiny periods until we have a total of three seconds1 during which the gun may have fired two hundred rounds1 we shall find that the lining of the barrel is so badly eroded that the gun is unfit for accurate shooting1 and it must go back to the shops for a new inner tube4 ,,elastic ,,guns ,we had better go back with it and learn something about the manufacture of a big gun4 ,guns used to be cast as a solid chunk of metal4 ,now they are built up in layers4 ,to understand why this is necessary1 we must realize that steel is not a dead mass1 but is highly elastic--far more elastic than rubber1 although1 of course1 it does not stretch nor compress so far4 ,when a charge of powder is exploded in the barrel of a gun1 it expands in all directions4 ,of course1 the projectile yields to the pressure of the powder gases and is sent kiting out of the muzzle of the gun4 ,but for an instant before the shell starts to move1 an enormous force is exerted against the walls of the bore of the gun1 and1 because steel is elastic1 the barrel is expanded by this pressure1 and the bore is actually made larger for a moment1 only to spring back in the next instant4 ,you can picture this action if you imagine a gun made of rubber2 as soon as the powder was fired1 the rubber gun would bulge out around the powder-chamber1 only to collapse to its normal size when the pressure was relieved by the discharge of the bullet4 ,now1 every elastic body has what is called its elastic limit4 ,if you take a coil spring1 you can pull it out or you can compress it1 and it will always return to its original shape1 unless you pull it out or compress it beyond a certain point2 that point is its elastic limit4 ,the same is true of a piece of steel3 if you stretch it beyond a certain point1 it will not return to its original shape4 ,when the charge of powder in a cannon exceeds a certain amount1 it stretches the steel beyond its elastic limit1 so that the bore becomes permanently larger4 ,making the walls of the gun heavier would not prevent this1 because steel is so elastic that the inside of the walls expands beyond its elastic limit before the outside is affected at all4 ,years ago an ,american inventor named ,treadwell worked out a scheme for allowing the bore to expand more without exceeding its elastic limit4 ,he built up his gun in layers1 and shrunk the outer layers upon the inner layers1 just as a blacksmith shrinks a tire on a wheel1 so that the inner tube of the gun would be squeezed1 or compressed4 ,when the powder was fired1 this inner layer could expand farther without danger1 because it was compressed to start with4 ,the built-up gun was also independently invented by a ,british inventor4 ,all modern big guns are built up4 ,,how ,,big ,,guns ,,are ,,made ,the inside tube1 known as the lining1 is cast roughly to shape1 then it is bored out1 after which it is forged by the blows of a powerful steam-hammer4 ,of course1 while under the hammer1 the tube is mounted on a mandrel1 or bar1 that just fits the bore4 ,the metal is then softened in an annealing furnace1 after which it is turned down to the proper diameter and re-bored to the exact caliber4 ,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 it4 ,this sleeve1 which is formed in the same way1 is heated up to #hjj degrees1 or until its inside diameter is eight tenths of an inch larger than the outside diameter of the lining4 ,the lining is stood up on end and the sleeve is fitted over it4 ,then it is cooled by means of water1 so that it grips the lining and compresses it4 ,in this way1 layer after layer is added until the gun is built up to the proper size4 ,illustration3 ,photograph from ,underwood ,underwood ,a ,long-distance ,sub-calibered ,french ,gun on a ,railway ,mount ,instead of having a lining that is compressed by means of sleeves or jackets1 many big guns are wound with wire which is pulled so tight as to compress the lining4 ,the gun-tube is placed in a lathe1 and is turned so as to wind up the wire upon it4 ,a heavy brake on the wire keeps it drawn very tight4 ,this wire1 also1 is put on in layers1 so that each layer can expand considerably without exceeding its elastic limit4 ,our big #af-;inch coast-defense guns are wound with wire that is one tenth of an inch square4 ,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 over4 ,illustration3 ,courtesy of ,scientific ,american ,inside of a ,shrapnel ,shell and ,details of the ,fuse ,cap ,search-light ,shell and one of its ,candles ,,guns ,,that ,,play ,,hide-,,and-,,seek ,a very ingenious invention is the disappearing-mount which is used on our coast fortifications4 ,by means of this a gun is hidden beyond its breastworks so that it is absolutely invisible to the enemy4 ,in this sheltered position it is loaded and aimed4 ,it is not necessary to sight the gun on the target as you would sight a rifle4 ,the aiming is done mathematically4 ,off at some convenient observation post1 an observer gets the range of the target and telephones this range to the plotting-room1 where a rapid calculation is made as to how much the gun should be elevated and swung to the right or the left4 ,this calculation is then sent on to the gunners1 who adjust the gun accordingly4 ,when all is ready1 the gun is raised by hydraulic pressure1 and just as it rises above the parapet it is automatically fired4 ,the recoil throws the gun back to its crouching position behind the breastworks4 ,all that the enemy sees1 if anything1 is the flash of the discharge4 ,now that airplanes have been invented1 the disappearing-mount has lost much of its usefulness4 ,big guns have to be hidden from above4 ,they are usually located behind a hill1 five or six miles back of the trenches1 where the enemy cannot see them from the ground1 and they are carefully hidden under trees or a canopy of foliage or are disguised with paint4 ,the huge guns recently built to defend our coasts are intended to fire a shell that will pierce the heavy armor of a modern dreadnought4 ,the shell is arranged to explode after it has penetrated the armor1 and the penetrating-power is a very important matter4 ,about thirty years ago the ,british built three battle-ships1 each fitted with two guns of #af-a_/d-;inch caliber and #cj-;caliber length4 ,in order to test the penetrating-power of this gun a target was built1 consisting first of twenty inches of steel armor and eight inches of wrought-iron2 this was backed by twenty feet of oak1 five feet of granite1 eleven feet of concrete1 and six feet of brick4 ,when the shell struck this target it passed through the steel1 the iron1 the oak1 the granite1 and the concrete1 and did not stop until it had penetrated three feet of the brick4 ,we have not subjected our #af-;inch gun to such a test1 but we know that it would go through two such targets and still have plenty of energy left4 ,incidentally1 it costs us #a1fhj each time the big gun is fired4 ,,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 forts4 ,properly speaking1 this was not a gun1 but a howitzer2 and right here we must learn the difference between mortars1 howitzers1 and guns4 ,what we usually mean by gun is a piece of long caliber which is designed to hurl its shell with a flat trajectory4 ,but long ago it was found advantageous to throw a projectile not at but upon a fortification1 and for this purpose short pieces of large bore were built4 ,these would fire at a high angle1 so that the projectile would fall almost vertically on the target4 ,as we have said1 the bore of a gun is rifled2 that is1 it is provided with spiral grooves that will set the shell spinning1 so as to keep its nose pointing in the direction of its flight4 ,mortars1 on the other hand1 were originally intended for short-range firing1 and their bore was not rifled4 ,in recent years1 however1 mortars have been made longer and with rifled bores1 so as to increase their range1 and such long mortars are called howitzers4 ,the ,german #db-;centimeter howitzer fired a shell that was #b1ajh pounds in weight and was about #a-a_/b yards long4 ,the diameter of the shell was #db centimeters1 which is about #af-a_/b inches4 ,it carried an enormous amount of high explosive1 which was designed to go off after the shell had penetrated its target4 ,the marvel of this howitzer was not that it could fire so big a shell but that so large a piece of artillery could be transported over the highroads and be set for use in battle4 ,but although the #db-;centimeter gun was widely advertised1 the real work of smashing the ,belgian forts was done by the ,austrian ,skoda howitzers1 which fired a shell of #cj4e-;centimeter 7#ab-;inch7 caliber1 and not by the #db-;centimeter gun4 ,the ,skoda howitzer could be taken apart and transported by three motor-cars of #ajj horse-power each4 ,the cars traveled at a rate of about twelve miles per hour4 ,it is claimed the gun could be put together in twenty-four minutes1 and would fire at the rate of one shot per minute4 ,,field-,,guns ,so far1 we have talked only of the big guns1 but in a modern battle the field-gun plays a very important part4 ,this fires a shell that weighs between fourteen and eighteen pounds and is about three inches in diameter4 ,the shell and the powder that fires it are contained in a cartridge that is just like the cartridge of a shoulder rifle4 ,these field-pieces are built to be fired rapidly4 ,the ,french #ge-millimeter gun1 which is considered one of the best1 will fire at the rate of twenty shots per minute1 and its effective range is considerably over three miles4 ,the ,french supplied us with all #ge-millimeter guns we needed in the war1 while we concentrated our efforts on the manufacture of ammunition4 ,,guns ,,that ,,fire ,,guns ,during the ,war of the ,revolution1 cannon were fired at short range1 and it was the custom to load them with grape-shot1 or small iron balls1 when firing against a charging enemy1 because 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-ball4 ,in modern warfare1 guns are fired from a greater distance1 so that there will be little danger of their capture4 ,it is impossible for them to fire grape1 because the ranges are far too great2 besides1 it would be impossible to aim a charge of grape-shot over any considerable distance1 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 service4 ,but this difficulty has been overcome by the making of a shell which is really a gun in itself4 ,within this shell is the grape-shot1 which consists of two hundred and fifty half-inch balls of lead4 ,the shell is fired over the lines of the enemy1 and just at the right moment it explodes and scatters a hail of leaden balls over a fairly wide area4 ,it is not a simple matter to time a shrapnel shell so that it will explode at just the right moment4 ,spring-driven clockwork has been tried1 which would explode a cap after the lapse of a certain amount of time2 but this way of timing shells has not proved satisfactory4 ,nowadays a train of gunpowder is used4 ,when the shell is fired1 the shock makes a cap 7see drawing facing page #gg7 strike a pin1 ,e1 which ignites the train of powder1 ,a4 ,the head of the shell is made of two parts1 in each of which there is a powder-fuse4 ,there is a vent1 or short cut1 leading from one fuse to the other1 and1 by the turning of one part of the fuse-head with respect to the other1 this short cut is made to carry the train of fire from the upper to the lower fuse sooner or later1 according to the adjustment4 ,the fire burns along one powder-train ,a1 and then jumps through the short cut ,b to the other1 or movable train1 as it is called1 until it finally reaches1 through hole ,c1 the main charge ,f1 in the shell4 ,the movable part of the fuse-head is graduated so that the fuse may be set to explode the shell at any desired distance4 ,in the fuse-head there is also a detonating-pin ,k1 which will strike the primer ,l and explode the shell when the latter strikes the ground1 if the time-fuse has failed to act4 ,when attacking airplanes1 it is important to be able to follow the flight of the shell1 so some shrapnel shell are provided with a smoke-producing mixture1 which is set on fire when the shell is discharged1 so as to produce a trail of smoke4 ,illustration3 7,c7 ,committee on ,public ,information ,putting on the ,gas ,masks to ,meet a ,gas ,cloud ,attack ,in meeting the attack of any enemy at night1 search-light shell are sometimes used4 ,on exploding they discharge a number of candles1 each provided with a tiny parachute that lets the candle drop slowly to the ground4 ,their brilliant light lasts fifteen or twenty minutes4 ,obviously1 ordinary search-lights could not be used on the battle-field1 because the lamp would at once be a target for enemy batteries1 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 illuminated4 ,,chapter ,v ,,the ,,battle ,,of ,,the ,,chemists ,some years ago the nations of the world gathered at the city of ,the ,hague1 in ,holland1 to see what could be done to put an end to war4 ,they did not accomplish much in that direction1 but they did draw up certain rules of warfare which they agreed to abide by4 ,there were some practices which were considered too horrible for any civilized nation to indulge in4 ,among these was the use of poisonous gases1 and ,germany was one of the nations that took a solemn pledge not to use gas in war4 ,illustration3 7,c7 ,kadel ,herbert ,even the ,horses had to be ,masked ,illustration3 ,photograph by ,kadel ,herbert ,portable ,flame-throwing ,apparatus ,eighteen years later the ,german ,army had dug itself into a line of trenches reaching from the ,english ,channel to ,switzerland1 and facing them in another line of trenches were the armies of ,france and ,england1 determined to hold back the invaders4 ,neither side could make an advance without frightful loss of life4 ,but a ,german scientist came forth with a scheme for breaking the dead-lock4 ,this was ,professor ,nernst1 the inventor of a well-known electric lamp and a man who had always violently hated the ,british4 ,his plan was to drown out the ,british with a flood of poisonous gas4 ,to be sure1 there was the pledge taken at ,the ,hague ,conference1 but why should that stand in ,germany's way8 ,what cared the ,germans for promises now8 ,already they had broken a pledge in their violation of ,belgium4 ,already they had rained explosives from the sky on unfortified ,british cities 7thus violating another pledge of ,the ,hague ,conference72 already they had determined to war on defenseless merchantmen4 ,to them promises meant nothing1 if such promises interfered with the success of ,german arms4 ,they led the world in the field of chemistry2 why1 they reasoned1 shouldn't they make use of this advantage8 ,,pouring ,,gas ,,like ,,water ,it was really a new mode of warfare that the ,germans were about to launch and it called for much study4 ,in the first place1 they had to decide what sort of gas to use4 ,it must be a gas that could be obtained in large quantities4 ,it must be a very poisonous gas1 that would act quickly on the enemy2 it must be easily compressed and liquefied so that it could be carried in containers that were not too bulky2 it must vaporize when the pressure was released2 and it must be heavier than air1 so that it would not be diluted by the atmosphere but would hug the ground4 ,you can pour gas just as you pour water1 if it is heavier than air4 ,a heavy gas will stay in the bottom of an unstoppered bottle and can be poured from one bottle into another like water4 ,if the gas is colored1 you can see it flowing just as if it were a liquid4 ,on the other hand1 a gas which is much lighter than air can also be kept in unstoppered bottles if the bottles are turned upside down1 and the gas can be poured from one bottle into another2 but it flows up instead of down4 ,chlorine gas was selected because it seemed to meet all requirements4 ,for the gas attack a point was chosen where the ground sloped gently toward the opposing lines1 so that the gas would actually flow down hill into them4 ,preparations were carried out with the utmost secrecy4 ,just under the parapet of the trenches deep pits were dug1 about a yard apart on a front of fifteen miles1 or over twenty-five thousand pits4 ,in these pits were placed the chlorine tanks1 each weighing about ninety pounds4 ,each pit was then closed with a plank and this was covered with a quilt filled with peat moss soaked in potash1 so that in case of any leakage the chlorine would be taken up by the potash and rendered harmless4 ,over the quilts sandbags were piled to a considerable height1 to protect the tanks from shell-fragments4 ,liquid chlorine will boil even in a temperature of #bh degrees below zero ,fahrenheit1 but in tanks it cannot boil because there is no room for it to turn into a gas4 ,upon release of the pressure at ordinary temperatures1 the liquid boils violently and big clouds of gas are produced4 ,if the gas were tapped off from the top of the cylinder1 it would freeze on pouring out1 because any liquid that turns into a gas has to draw heat from its surroundings4 ,the greater the expansion1 the more heat the gas absorbs1 and in the case of the chlorine tanks1 had the nozzles been set in the top of the tank they would very quickly have been crusted with frost and choked1 stopping the flow4 ,but the ,germans had anticipated this difficulty1 and instead of drawing off the gas from the top of the tank1 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 liquid4 ,in fact1 it was not gas from the top of the tank1 but liquid from the bottom1 that was streamed out and this did not turn into gas until it had left the nozzle4 ,,waiting ,,for ,,the ,,wind ,everything was ready for the attack on the ,british in ,april1 #aiae4 ,a point had been chosen where the ,british lines made a juncture with the ,french4 ,the ,germans reckoned that a joint of this sort in the opponent's lines would be a spot of weakness4 ,also1 they had very craftily picked out this particular spot because the ,french portion of the line was manned by ,turcos1 or ,algerians1 who would be likely to think there was something supernatural about a death-dealing cloud4 ,on the left of the ,africans was a division of ,canadians1 but the main brunt of the gas was designed to fall upon the ,turcos4 ,several times the attack was about to be made1 but was abandoned because the wind was not just right4 ,the ,germans wished to pick out a time when the breeze was blowing steadily--not so fast as to scatter the gas1 but yet so fast that it would overtake men who attempted to run away from it4 ,it was not until ,april #bb that conditions were ideal1 and then the new mode of warfare was launched4 ,just as had been expected1 the ,turcos were awe-struck when they saw1 coming out of the ,german trenches1 volumes of greenish-yellow gas1 which rolled toward them1 pouring down into shell-holes and flowing over into the trenches as if it were a liquid4 ,they were seized with superstitious fear1 particularly when the gas overcame numbers of them1 stifling them and leaving them gasping for breath4 ,immediately there was a panic and they raced back1 striving to out-speed the pursuing cloud4 ,for a stretch of fifteen miles the ,allied trenches were emptied1 and the ,germans1 who followed in the wake of the gas1 met with no opposition except in the sector held by the ,canadians4 ,here1 on the fringe of the gas cloud1 so determined a fight was put up that the ,germans faltered1 and the brave ,canadians held them until reinforcements arrived and the gap in the line was closed4 ,the ,germans themselves were new at the game or they could have made a complete success of this surprise attack4 ,had they made the attack on a broader front1 nothing could have kept them from breaking through to ,calais4 ,the valiant ,canadians who struggled and fought without protection in the stifling clouds of chlorine1 were almost wiped out4 ,but many of them who were on the fringe of the cloud escaped by wetting handkerchiefs1 socks1 or other pieces of cloth1 and wrapping them around their mouths and noses4 ,the world was horrified when it read of this ,german gas attack1 but there was no time to be lost4 ,immediately orders went out for gas-masks1 and in all parts of ,england1 and of ,france as well1 women were busy sewing the masks4 ,these were very simple affairs--merely a pad of cotton soaked in washing-soda and arranged to be tied over the mouth and nose4 ,but when the next attack came1 not long after the first1 the men were prepared in some measure for it1 and again it failed to bring the ,germans the success they had counted upon4 ,one thing that the ,germans had not counted upon was the fact that the prevailing winds in ,flanders blow from west to east4 ,during the entire summer and autumn of #aiae1 the winds refused to favor them1 and no gas attacks were staged from ,june to ,december4 ,this gave the ,british a long respite and enabled them not only to prepare better gas-masks1 but also to make plans to give the ,hun a dose of his own medicine4 ,illustration3 7,c7 ,kadel ,herbert ,liquid ,fire ,streaming from ,fixed ,flame-throwing ,apparatus ,,when ,,the ,,wind ,,played ,a ,,trick ,,on ,,the ,,germans ,there were many disadvantages in the use of gas clouds1 which developed as the ,germans gathered experience4 ,the gas started from their own lines in a very dense cloud1 but the cloud grew thinner and thinner as it traveled toward the enemy1 and lost a great deal of its strength4 ,if the wind were higher than fifteen miles an hour1 it would swirl the gas around and dissipate it before it did much harm to the opposing fighters4 ,if the wind were light1 there were other dangers4 ,on one occasion in #aiaf a cloud of gas was released upon an ,irish regiment4 ,the wind was rather fickle4 ,it carried the gas toward the ,british trenches1 but before reaching them the cloud hesitated1 the wind veered around1 and soon the gas began to pour back upon the ,german lines4 ,the ,germans were entirely unprepared for this boomerang attack4 ,many of the ,huns had no gas-masks on1 and those who had1 found that the masks were not in proper working-order4 ,as a result of this whim of the winds1 eleven thousand ,germans were killed4 ,illustration3 ,courtesy of ,scientific ,american ,cleaning ,up a ,dugout with the ,fire ,broom ,while chlorine was the first gas used1 it was evident that it was not the only one that could be employed4 ,british chemists had suspected that the ,germans would use phosgene1 which was a much more deadly gas1 and in the long interval between ,june and ,december1 #aiae1 masks were constructed which would keep out not only the fumes of chlorine but also the more poisonous phosgene4 ,in one of their sorties the ,british succeeded in capturing some valuable notes on gas attacks1 belonging to a ,german general1 which showed that the ,germans were actually preparing to use phosgene4 ,this deadly gas is more insidious in its action than chlorine4 ,the man who inhales phosgene may not know that he is gassed4 ,he may experience no ill effects1 but hours afterward1 particularly if he has exercised in the meantime1 he may suddenly fall dead1 owing to its paralyzing action on the heart4 ,,freeing ,,the ,,british ,,trenches ,,of ,,rats ,phosgene was not used alone1 but had to be mixed with chlorine1 and the deadly combination of the two destroyed all life for miles behind the trenches4 ,however1 the ,british were ready for it4 ,they had been drilled to put on their masks in a few seconds' time1 on the first warning of a gas attack4 ,when the clouds of chlorine and phosgene came over ,no ,man's ,land1 they were prepared1 and1 except for casualties among men whose masks proved defective1 the soldiers in the trenches came through with very few losses4 ,all animal life1 however1 was destroyed4 ,this was a blessing to the ,british ,tommy1 whose trenches had been overrun with rats4 ,the ,british had tried every known method to get rid of these pests1 and now1 thanks to the ,germans1 their quarters were most effectively fumigated with phosgene and every rat was killed4 ,if only the cooties could have been destroyed in the same way1 the ,germans might have been forgiven many of their offenses4 ,the disadvantages in the use of gas clouds became increasingly apparent4 ,what was wanted was some method of placing the gas among the opponents in concentrated form1 without wasting any of it on its way across from one line to the other4 ,this led to the use of shell filled with materials which would produce gas4 ,there were many advantages in these shell4 ,they could be thrown exactly where it was desired that they should fall1 without the help of the fickle winds4 ,when the shell landed and burst1 the full effect of its contents was expended upon the enemy4 ,a gas cloud would rise over a wood1 but with shell the wood could be filled with gas1 which1 once there1 would lurk among the trees for days4 ,chemicals could be used in shell which could not be used in a cloud attack4 ,the shell could be filled with a liquid1 or even with a solid1 because when it burst the filling would be minutely pulverized4 ,and so ,german chemists were set to work devising all sorts of fiendish schemes for poisoning1 choking1 or merely annoying their opponents4 ,,gas ,,that ,,made ,,one ,,weep ,one of the novel shell the ,germans used was known as the tear-gas shell4 ,this was filled with a liquid1 the vapor of which was very irritating to the eyes4 ,the liquid vaporized very slowly and so its effect would last a long time4 ,however1 the vapor did not permanently injure the eyes2 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 work4 ,the tear-gas shell were marked with a ,t by the ,germans and were known as ,t-shell4 ,another type of shell1 known as the ,k-shell1 contained a very poisonous liquid1 the object of which was to destroy the enemy quickly4 ,the effect of this shell was felt at once1 but it left no slow vapors on the ground1 and so it could be followed up almost immediately by an attack4 ,later on1 the ,germans developed three types of gas shell--one known as the ,green ,cross1 another as the ,yellow ,cross1 and the third as the ,blue ,cross4 ,the ,green ,cross shell was filled with diphosgene1 or a particularly dangerous combination of phosgene in liquid form1 which would remain in pools on the ground or soak into the ground and would vaporize when it became warm4 ,its vapors were deadly4 ,one had always to be on his guard against them4 ,in the morning1 when the sun warmed the earth and vapors were seen to rise from the damp soil1 tests were made of the vapors to see whether it was mere water vapor or diphosgene1 before men were allowed to walk through it4 ,these vapors were heavier than air and would flow down into a trench1 filling every nook and cranny4 ,if phosgene entered a trench by a direct hit1 the liquid would remain there for days1 rendering that part of the trench uninhabitable except by men in gas-masks4 ,the infected part of the trench1 however1 was cut off from the rest of the trench by means of gas-locks4 ,in other words1 blankets were used to keep the gas out1 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 blanket1 pass under it1 and close it carefully behind him before opening the second blanket which led into the portion of the trench that was not infected4 ,the ,germans had all sorts of fiendish schemes for increasing the discomfort of the ,allies4 ,for instance1 to some of their diphosgene shell they added a gas which caused intense vomiting4 ,the ,yellow ,cross shell was another fiendish invention of the ,huns4 ,it was popularly known as mustard gas and was intended not to kill but merely to discomfort the enemy4 ,the gas had a peculiar penetrating smell1 something like garlic1 and its fumes would burn the flesh wherever it was exposed to them1 producing great blisters and sores that were most distressing4 ,the material in the shell was a liquid which was very hard to get rid of because it would vaporize so slowly4 ,on account of the persistence of this vapor1 lasting as it did for days1 these gas shell were usually not fired by the ,germans on lines that they expected to attack immediately4 ,,the ,,sneezing-,,shell ,the ,blue ,cross shell was comparatively harmless1 although very annoying4 ,it contained a solid which was atomized by the explosion of the shell1 and which1 after it got into the nostrils1 caused a violent sneezing4 ,the material1 however1 was not poisonous and did not produce any casualties to speak of1 although it was most unpleasant4 ,a storm of ,blue ,cross shell could be followed almost immediately by an attack1 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 nostrils4 ,,gas-,,masks ,as the different kinds of gas shell were developed1 the gas-masks were improved to meet them4 ,in every attack there were duds or unexploded shell1 which the chemists of the ,allies analyzed4 ,also1 they were constantly experimenting with new gases1 themselves1 and often could anticipate the ,germans4 ,the ,allies were better able to protect themselves against gas attacks than the ,germans1 because there was a scarcity of rubber in ,germany for the manufacture of masks4 ,when it was found that phosgene was going to be used1 the simple cotton-wad masks had to give way to more elaborate affairs with chemicals that would neutralize this deadly gas4 ,and later when the mustard gas was used which attacked the eyes1 and the sneezing-gas that attacked the nose1 it was found necessary to cover the face completely1 particularly the eyes2 and so helmets of rubber were constructed which were tightly fitted around the neck under the coat collar4 ,the inhaled air was purified by passage through a box or can filled with chemicals and charcoal made of various materials1 such as cocoanut shells1 peach pits1 horse-chestnuts1 and the like4 ,because the ,germans had no rubber to spare1 they were obliged to use leather1 which made their masks stiff and heavy4 ,,glass ,,that ,,will ,,not ,,shatter ,one of the greatest difficulties that had to be contended with was the covering of the eyes4 ,there was danger in the use of glass1 because it was liable to be cracked or broken1 letting in the deadly fumes and gassing the wearer4 ,experiments were made with celluloid and similar materials1 but the finest gas-masks produced in the war were those made for our own soldiers1 in which the goggles were of glass1 built up in layers1 with a celluloid-like material between1 which makes a tough composition that will stand up against a very hard blow4 ,even if it cracks1 this glass will not shatter4 ,the glasses were apt to become coated on the inside with moisture coming from the perspiration of the face1 and some means had to be provided for wiping them off4 ,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 clear4 ,before this was done1 the masks were provided with little sponges on the end of a finger-piece1 with which the glasses could be wiped dry without taking the masks off4 ,but all this time1 the ,allies were not merely standing on the defensive4 ,no sooner had the ,germans launched their first attack than the ,british and ,french chemists began to pay back the ,hun in kind4 ,more attention was paid to the shell than the cloud attack1 and soon gas shell began to rain upon the ,germans4 ,not only were the ,german shell copied1 but new gases were tried4 ,gas shell were manufactured in immense quantities4 ,then ,america took a hand in the war and our chemists added their help1 while our factories turned out steady streams of shell4 ,if ,germany wanted gas warfare1 the ,allies were determined that she should have it4 ,our chemists 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 ,central ,powers4 ,when the ,germans first started the use of gas1 apparently they counted only their own success1 which they thought would be immediate and overwhelming4 ,they soon learned that they must take what they gave4 ,the ,allies set them a pace that they could not keep up with4 ,when the armistice brought the war to a sudden stop1 the ,united ,states alone was making each day two tons of gas for every mile of the western front4 ,if the war had continued1 the ,germans would have been simply deluged4 ,as it was1 they were getting far more gas than they could possibly produce in their own factories and they had plenty of reason to regret their rash disregard of their contract at ,the ,hague ,conference4 ,one gas we were making was of the same order as mustard gas but far more volatile1 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 fumes4 ,,battling ,,with ,,liquid ,,fire ,somewhat associated with gas warfare was another form of offensive which was introduced with the purpose of breaking up the dead-lock of trench warfare4 ,a man could protect himself against gas by using a suitable mask and clothing1 but what could he do against fire8 ,it looked as if trench defenders would have to give up if attacked with fire1 and so1 early in the war1 the ,germans devised apparatus for shooting forth streams of liquid fire1 and the ,allies were not slow to copy the idea4 ,the apparatus was either fixed or portable1 but it was not often that the fixed apparatus could be used to advantage1 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 gap4 ,for this reason portable apparatus was chiefly used1 with which a man could send out a stream for from a hundred to a hundred and fifty feet4 ,on his back he carried the oil-tank1 in the upper part of which there was a charge of compressed air4 ,a pipe led from the tank to a nozzle which the man held in his hand1 using it to direct the spray4 ,there was some danger to the operator in handling a highly inflammable oil4 ,the blaze might flare back and burn him1 particularly when he was lighting the stream1 and so a special way of setting fire to the spray had to be devised4 ,of course1 the value of the apparatus lay in its power to shoot the stream as far as possible4 ,the compressed air would send the stream to a good distance1 but after lighting1 the oil might be consumed before it reached the desired range4 ,some way had to be found of igniting the oil stream far from the nozzle or as near the limit of its range as possible4 ,and so two nozzles were used1 one with a small opening so that it would send out a fine jet of long range1 while the main stream of oil issued from the second nozzle4 ,the first nozzle was movable 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 apparatus4 ,the fine stream was ignited and carried the flame out to the main stream1 setting fire to it near the limit of its range4 ,in this way a flare-back was avoided and the oil blazed where the flame was needed4 ,the same sort of double nozzle was used on the stationary apparatus and because weight was not a consideration1 heavier apparatus was used which shot the stream to a greater distance4 ,but flame-throwing apparatus had its drawbacks3 there was always the danger that the tank of highly inflammable oil might be burst open by a shell or hand-grenade and its contents set on fire4 ,the fixed apparatus was buried under bags of sand1 but the man who carried flame-throwing apparatus on his back had to take his chances1 not knowing at what instant the oil he carried might be set ablaze1 turning him into a living1 writhing1 human torch4 ,because of this hazard1 liquid fire did not play a very important part in trench warfare2 to set fire to the spray at its source with a well directed hand-grenade was too easy4 ,,the ,,fire ,,broom ,there were certain situations1 however1 in which liquid fire played a very important part4 ,after a line of trenches had been captured it was difficult to clear out the enemy who lurked in dugouts and underground passages4 ,they would not surrender1 and from their hidden recesses they could pour out a deadly machine-gun fire4 ,the only way of dislodging them was to use the fire broom4 ,in other words1 a stream of liquid fire was poured into the dugout1 burning out the men trapped in it4 ,if there were a second exit1 they would come tumbling out in a hurry4 ,if not1 they would be burned to death4 ,after the first sweep of the broom1 if there were any survivors1 there would not be any fight left in them1 and they would be quick to surrender before being subjected to a second dose of fire4 ,,chapter ,,vi ,,tanks ,there is no race-horse that can keep up with an automobile1 no deer that can out-run a locomotive4 ,a bicyclist can soon tire out the hardiest of hounds4 ,why8 ,because animals run on legs1 while machines run on wheels4 ,as wheels are so much more speedy than legs1 it seems odd that we do not find this form of locomotion in nature4 ,there are many animals that owe their very existence to the fact that they can run fast4 ,why hasn't nature put them on wheels so that when their enemy appears they can roll away1 sedately1 instead of having to jerk their legs frantically back and forth at the rate of a hundred strokes a minute8 ,but one thing we must not overlook4 ,our wheeled machines must have a special road prepared for them1 either a macadam highway or a steel track4 ,they are absolutely helpless when they are obliged to travel over rough country4 ,no wheeled vehicle can run through fields broken by ditches and swampy spots1 or over ground obstructed with boulders and tree-stumps4 ,but it is not always possible or practicable to build a road for the machines to travel upon1 and it is necessary to have some sort of self-propelled vehicle that can travel over all kinds of ground4 ,some time ago a ,british inventor developed a machine with large wheels on which were mounted the equivalent of feet4 ,as the wheels revolved1 these feet would be planted firmly on the ground1 one after the other1 and the machine would proceed step by step4 ,it could travel over comparatively rough ground1 and could actually walk up a flight of stairs4 ,we have a very curious walking-machine in this country4 ,it is a big dredge provided with two broad feet and a swivel chair4 ,the machine makes progress by alternately planting its feet on the ground1 lifting itself up1 chair and all1 pushing itself forward1 and sitting down again4 ,although many other types of walking-machines have been patented1 none of them has amounted to very much4 ,clearly1 nature hopelessly outclasses us in this form of propulsion4 ,years ago it occured to one ingenious man that if wheeled machines must have tracks or roads for their wheels to run on1 they might be allowed to lay their own tracks4 ,and so he arranged his track in the form of an endless chain of plates that ran around the wheels of his machine4 ,the wheels merely rolled on this chain1 and as they progressed1 new links of the track were laid down before them and the links they had passed over were picked up behind them4 ,a number of inventors worked on this idea1 but one man in particular1 ,benjamin ,holt1 of ,peoria1 ,illinois1 brought the invention to a high state of perfection4 ,he arranged a series of wheels along the chain track1 each carrying a share of the load of the machine1 and each mounted on springs so that it would yield to any unevenness of the ground1 just as a caterpillar conforms itself to the hills and dales of the surface it creeps over4 ,in fact1 the machine was called a caterpillar tractor because of its crawling locomotion4 ,but it was no worm of a machine4 ,in power it was a very elephant4 ,it could haul loads that would tax the strength of scores of horses4 ,stumps and boulders were no obstacles in its path4 ,even ditches could not bar its progress4 ,the machine would waddle down one bank and up the other without the slightest difficulty4 ,it was easily steered2 in fact1 it could turn around in its own length by traveling forward on one of its chains1 or traction-belts1 and backward on the other4 ,the machine was particularly adapted to travel on soft or plowed ground1 because the broad traction-belts gave it a very wide bearing and spread its weight over a large surface4 ,it was set to work on large farms1 hauling gangs of plows and cultivators4 ,little did ,mr4 ,holt think1 as he watched his powerful mechanical elephants at work on the vast ,western wheat-fields1 that they1 or rather their offspring1 would some day play a leading role in a war that would rack the whole world4 99 99 99 99 99 ,but we are getting ahead of our story4 ,to start at the very beginning1 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 enemy4 ,this was the start of the never-ending competition between arms and armor4 ,as the weapons of offense developed from stone to spear1 to arrow1 to arquebus1 the wooden plank developed into a shield of brass and then of steel2 and then1 since a separate shield became too bothersome to carry1 it was converted into armor that the warrior could wear and so have both hands free for battle4 ,for every improvement in arms there was a corresponding improvement in armor4 ,after gunpowder was invented1 the idea of armor for men began to wane1 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 wear4 ,the struggle between arms and armor was then confined to the big guns and the steel protection of forts and war-ships4 ,but not so long ago the machine-gun was invented1 and this introduced a new phase of warfare4 ,not more than one rifle-bullet in a thousand finds its mark on the battle-field4 ,the ,boers in the battle of ,colenso established a record with one hit in six hundred shots4 ,in the excitement of battle men are too nervous to take careful aim and they are apt to fire either too high or too low1 so that the mortality is not nearly so great as some would expect4 ,but with the machine-gun there is not this waste of ammunition1 because it fires a stream of bullets1 the effect of which can readily be determined by the man who operates the volley4 ,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 water4 ,it is no easy matter to score a hit with the stone2 but any one can train a garden hose on the can1 because he can see where the water is striking and move his hose accordingly until he covers the desired spot4 ,in the same way1 with the machine-gun1 it is much easier to train the stream of bullets upon the mark1 and1 having once found the mark1 to hold the aim4 ,that is one reason why the destruction of a machine-gun is so tremendous2 another1 of course1 being that it will discharge so many more shots per minute than the common rifle4 ,illustration3 7,c7 ,underwood ,underwood ,british ,tank ,climbing out of a ,trench at ,cambrai ,in the ,russo-,japanese ,war1 the ,russians played havoc with the attacking ,japanese at ,port ,arthur by using carefully concealed machine-guns1 and the ,german military attachs were quick to note the value of the machine-gun4 ,secretely they manufactured large numbers of machine-guns and established a special branch of service to handle the guns1 and they developed the science of using them with telling effect4 ,and so1 when the recent great war suddenly broke out1 they surprised the world with the countless number of machine-guns they possessed and the efficient use to which they put them4 ,thousands of ,british soldiers in the early days of the war fell victims to these death-dealing machines4 ,two or three men with a machine-gun could defy several companies of soldiers1 especially when the attackers had to cut their way through barbed wire entanglements4 ,it was clearly evident that something must be done to defend the men against the machine-gun2 for to charge against it meant1 simply1 wholesale slaughter4 ,illustration3 7,c7 ,underwood ,underwood ,even ,trees were no ,barrier to the ,british ,tank ,illustration3 ,press ,illustrating ,service ,the ,german ,tank was very heavy and cumbersome ,at first the only means of combating the machine-guns seemed to be to destroy them with shell-fire2 but they were carefully concealed1 and it was difficult to search them out4 ,only by long-continued bombardment was it possible to destroy them and tear away the barbed wire sufficiently to permit of a charge4 ,before an enemy position was stormed it was subjected to the fire of thousands of guns of all calibers for hours and even days4 ,but this resulted in notifying the enemy that a charge was ere long to be attempted at a certain place1 and he could assemble his reserves for a counter-attack4 ,furthermore1 the ,germans learned to conceal their machine-guns in dugouts twenty or thirty feet underground1 where they were safe from the fire of the big guns1 and then1 when the fire let up1 the weapons would be dragged up to the surface in time to mow down the approaching infantry4 ,it was very clear that something would have to be done to combat the machine-gun4 ,if the necessary armor was too heavy for the men to carry1 it must carry itself4 ,armored automobiles were of no service at all1 because they could not possibly travel over the shell-pitted ground of ,no ,man's ,land4 ,the ,russians tried a big steel shield mounted on wheels1 which a squad of soldiers would push ahead of them1 but their plan failed because the wheels would get stuck in shell-holes4 ,a one-man shield on wheels was tried by the ,british4 ,under its shelter a man could steal up to the barbed wire and cut it and even crawl up to a machine-gun emplacement and destroy it with a hand-grenade4 ,but this did not prove very successful1 either1 because the wheels did not take kindly to the rough ground of the battle-field4 99 99 99 99 99 ,and here is where we come back to ,mr4 ,holt's mechanical elephants4 ,just before the great war broke out1 ,belgium--poor unsuspecting ,belgium--was holding an agricultural exhibit4 ,an ,american tractor was on exhibition4 ,it was the one developed by ,mr4 ,holt1 and its remarkable performances gained for it a reputation that spread far and wide4 ,colonel ,e4 ,d4 ,swinton of the ,british ,army heard of the peculiar machine1 and immediately realized the advantages of an armored tractor for battle over torn ground4 ,but in the first few months of the war that ensued1 this idea was forgotten1 until the effectiveness of the machine-gun and the necessity for overcoming it recalled the matter to his mind4 ,at his suggestion a caterpillar tractor was procured1 and the military engineers set themselves to the task of designing an armored body to ride on the caterpillar-tractor belts4 ,of course the machine had to be entirely re-designed4 ,the tractor was built for hauling loads1 and not to climb out of deep shell-holes2 but by running the traction-belts over the entire body of the car1 and running the forward part of the tractor up at a sharp angle the engineers overcame that difficulty4 ,in war1 absolute secrecy is essential to the success of any invention1 and the ,british engineers were determined to let no inkling of the new armored automobiles reach the enemy4 ,different parts of the machines were made in different factories1 so that no one would have an idea of what the whole would look like4 ,at first the new machine was known as a land-cruiser or land-ship2 but it was feared that this very name would give a clue to spies1 and so any descriptive name was forbidden4 ,many of the parts consisted of rolled steel plates which might readily be used in building up vessels to hold water or gasolene2 and to give the impression that such vessels were being constructed the name tank was adopted4 ,the necessity of guarding even the name of the machines was shown later1 when rumors leaked out that the tanks were being built to carry water over the desert regions of ,mesopotamia and ,egypt4 ,another curious rumor was that the machines were snow-plows for use in ,russia4 ,to give some semblance of truth to this story1 the parts were carefully labeled1 ,for ,petrograd4 ,probably never was a military secret so well guarded as this one1 and when1 on ,september #ae1 #aiaf1 the waddling steel tractors loomed up out of the morning mists1 the ,german fighters were taken completely by surprise4 ,two days before1 their airmen had noticed some peculiar machines which they supposed were armored automobiles4 ,they had no idea1 however1 that such formidable monsters were about to descend upon them4 ,the tanks proceeded leisurely over the shell-torn regions of ,no ,man's ,land1 wallowing down into shell-holes and clambering up out of them with perfect ease4 ,they straddled the trenches and paused to pour down them streams of machine-gun bullets4 ,wire entanglements were nothing to them2 under their weight steel wire snapped like thread4 ,the big brutes marched up and down the lines of wire1 treading them down into the ground and clearing the way for the infantry4 ,even trees were no barrier to these tanks4 ,of course they did not attack large ones1 but the smallish trees were simply broken down before their onslaughts4 ,as for concrete emplacements for machine-guns1 the tanks merely rode over them and crushed them4 ,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 stone4 ,there was no stopping these monsters1 and the ,germans fled in consternation before them4 ,there were two sizes of tanks4 ,the larger ones aimed to destroy the machine-gun emplacements1 and they were fitted up with guns for firing a shell4 ,the smaller tanks1 armed with machine-guns1 devoted themselves to fighting the infantry4 ,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 ripe4 ,but the tanks also furnished an indirect protection for the troops4 ,it was not necessary for the men to conceal themselves behind the big tractors4 ,naturally1 every ,hun who stood his ground and fought1 directed all his fire upon the tanks1 leaving the ,british infantry free to charge virtually unmolested4 ,the success of the tank was most pronounced4 ,in the meantime the ,french had been informed of the plans of their allies1 and they set to work on a different design of tractor4 ,it was not until six months later that their machines saw service4 ,the ,french design differed from the ,british mainly in having the tractor belt confined to the wheels instead of running over the entire body of the tank4 ,it was more blunt than the ,british and was provided at the forward end with a steel cutting-edge1 which adapted it to break its way through wire entanglements4 ,at each end there are two upward-turning skids which helped the tank to lift itself out of a hole4 ,the larger machines carried a regular #ge-millimeter 7#c-;inch7 field-gun1 which is a very formidable weapon4 ,they carried a crew of one officer and seven men4 ,life in a tank is far from pleasant4 ,the heat and the noise of machinery and guns are terrific4 ,naturally1 ventilation is poor and the fumes and gases that accumulate are most annoying1 to say the least4 ,sometimes the men were overcome by them4 ,but war is war1 and such discomforts had to be endured4 ,but the tank possessed one serious defect which the ,germans were not slow to discover4 ,its armor was proof against machine-gun fire1 but it could not ward off the shells of field-guns1 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 target4 ,and so the ,germans ordered up their guns to the front lines1 where they could score direct hits4 ,only light guns were used for this purpose1 especially those whose rifling was worn down by long service1 because long range was not necessary for tank fighting4 ,illustration3 7,c7 ,underwood ,underwood ,the ,speedy ,british ,whippet ,tank that can travel at a speed of twelve miles per hour ,illustration3 7,c7 ,underwood ,underwood ,the ,french ,high-,speed ,baby ,tank ,when the ,germans began their final great drive1 it was rumored that they had built some monster tanks that were far more formidable than anything the ,allies had produced4 ,unlike the ,british1 they used the tanks not to lead the army but to follow and destroy small nests of ,french and ,british that were left behind4 ,when the ,french finally did capture one of the ,german tanks1 which had fallen into a quarry1 it proved to be a poor imitation4 ,it was an ugly-looking affair1 very heavy and cumbersome4 ,owing to the scarcity of materials for producing high-grade armor1 it had to make up in thickness of plating what it lacked in quality of steel4 ,the tank was intended to carry a crew of eighteen men and it fairly bristled with guns1 but it could not manoeuver as well as the ,british tank2 for when some weeks later a fleet of ,german tanks encountered a fleet of heavy ,british tanks1 the ,hun machines were completely routed4 ,illustration3 ,courtesy of ,automotive ,industries ,section through our ,mark ,,viii ,tank showing the layout of the interior with the locations of the most important parts in the fighting compartment in the engine room ,it was then that the ,british sprang another surprise upon the ,germans4 ,after the big fellows had done their work1 a lot of baby tanks appeared on the scene and chased the ,german infantry4 ,these little tanks could travel at a speed of twelve miles an hour1 which is about as fast as an ordinary man can run4 ,whippets1 the ,british called them1 because they were like the speedy little dogs of that name4 ,they carried but two men1 one to guide the tank and the other to operate the machine-gun4 ,the ,french1 too1 built a light mosquito tank1 which was even smaller than the ,british tank1 and fully as fast4 ,it was with these machines1 which could dart about quickly on the battle-field and dodge the shell of the field-guns1 and which were immune to the fire of the machine-gun1 that the ,allies were able to make progress against the ,germans4 ,when the ,germans retired1 they left behind them nests of machine-guns to cover the withdrawal of their armies4 ,these gunners were ordered to fight to the very end4 ,they looked for no mercy and expected no help4 ,had it not been for the light tanks1 it would have been well nigh impossible to overcome these determined bodies of men without frightful losses4 ,since ,america invented the machine-gun and also barbed wire1 and since ,america furnished the inspiration for the tank with which to trample down the wire entanglements and stamp out the machine-guns1 naturally people expected our army to come out with something better than anything produced by our allies4 ,we did turn out a number of heavy machines patterned after the original ,british tank1 with armor that could stand up against heavy fire1 and we also produced a small and very speedy tank similar to the ,french baby tank1 but before we could put these into service the war ended4 ,the tanks we did use so effectively at ,st4-,mihiel and in the ,argonne ,forest were supplied by the ,french4 ,,chapter ,,vii ,,the ,,war ,,in ,,the ,,air ,we ,americans are a peace-loving people1 which is the very reason why we went into the war4 ,we had to help down the power that was disturbing the peace of the world4 ,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 while4 ,eleven years before ,germany undertook to conquer ,europe two young ,americans made the greatest conquest that the world has ever seen4 ,the ,wright brothers sailed up into the heavens and gained the mastery of the air4 ,they offered their conquest to the ,united ,states2 but while we accepted their offering with enthusiasm at first1 we did not know what to do with the new realm after we got it4 ,there seemed to be no particular use in flying4 ,it was just a bit too risky to be pleasant sport1 and about all we could see in it was an exhibition for the circus or the county fair4 ,not so in ,europe1 however4 ,flying meant something over there--there where the frontiers have ever bristled with big guns and strong fortifications1 and where huge military forces have slept on their arms1 never knowing what dreadful war the morning would bring forth4 ,the war-lovers hailed the airplane as a new instrument with which to terrorize their neighbors2 the peace-lovers saw in it another menace to their homes2 it gave them a new frontier to defend4 ,and so the military powers of ,europe took up the airplane seriously and earnestly and developed it4 ,at first military authorities had rated the airplane chiefly as a flying scout4 ,some bomb-dropping experiments had been made with it1 but it proved very difficult to land the bombs near the target1 and1 besides1 machines of those days were not built to carry very heavy loads1 so that it did not seem especially profitable to attack the enemy from the skies4 ,as for actual battles up among the clouds1 they were dreamed of only by the writers of fiction4 ,but wild dreams became stern realities in the mighty struggle between the great powers of the world4 ,,eyes ,,in ,,the ,,sky ,as a scouting-machine the airplane did prove to be far superior to mounted patrols which used to perform scout-work4 ,in fact1 it changed completely the character of modern warfare4 ,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 doing4 ,he could see whether large forces of men were collecting for an attack4 ,he could watch the course of supply-trains1 and judge of their size4 ,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 acquire4 ,surprise attacks were impossible1 with eyes in the sky4 ,the aviator could help his own batteries by signaling to them where to send their shell1 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 target4 ,the ,french sprang a surprise on the ,germans by actually attacking the infantry from the sky4 ,the idea of attack from overhead was so novel that armies did not realize the danger of exposing themselves behind the battle-front4 ,long convoys of trucks and masses of infantry moved freely over the roads behind the lines and they were taken by surprise when the ,french began dropping steel darts upon them4 ,these were about the size of a pencil1 with pointed end and fluted tail1 so that they would travel through the air like an arrow4 ,the darts were dropped by the hundred wherever the airmen saw a large group of the enemy1 and they struck with sufficient velocity to pierce a man from head to foot4 ,but steel darts were not used very long4 ,the enemy took to cover and then the only way to attack him was to drop explosives which would blow up his shelter4 ,at the outset1 air scouts were more afraid of the enemy on the ground than in the sky4 ,the ,germans had anti-aircraft guns that were fired with accuracy and accounted for many ,allied planes4 ,in those days1 airplanes flew at comparatively low altitudes and they were well within the reach of the enemy's guns4 ,but it was not long before the airplanes began to fight one another4 ,each side was very much annoyed 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-guns4 ,two months after the war started the first airplane was sent crashing to earth after a battle in the sky4 ,the fight took place five thousand feet above the earth1 between a ,french and a ,german machine4 ,the ,german pilot was killed and the plane fell behind the ,french lines1 carrying with it a ,prussian nobleman who died before he could be pulled out of the wreckage4 ,the war had been carried into the skies4 ,but if scouts were to fight one another1 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--scouting1 artillery-spotting1 battling1 and bombing4 ,each called for special training and its own type of machine4 ,as air fighting grew more specialized these classes were further subdivided1 but we need not go into such refinements4 ,,air ,,scouts ,,and ,,their ,,dangers ,the scouting-airplane usually carried two men1 one to drive the machine and the other to make observations4 ,the observer had to carry a camera1 to take photographs of what lay below1 and he was usually equipped with a wireless outfit1 with which he could send important information back to his own base4 ,the camera was sometimes fitted with a stock like that of a gun1 so that it could be aimed from the shoulder4 ,some small cameras were shaped so that they could be held in the hand like a pistol and aimed over the side of the fuselage1 or body1 of the airplane2 but the best work was done with large cameras fitted with telescopic lenses1 or telephoto lenses1 as they are called4 ,some of these were built into the airplane1 with the lens opening down through the bottom of the fuselage4 ,illustration3 7,c7 ,underwood ,underwood ,a ,handley-,page ,bombing ,plane with ,one of its ,wings ,folded ,back ,the scouting-airplane carried a machine-gun1 not for attack1 but for defense4 ,it had to be a quick climber and a good dodger1 so that it could escape from an attacking plane4 ,usually it did not have to go very far into the enemy country1 and it was provided with a large wing-spread1 so that if anything happened to the engine1 it could volplane1 or glide back1 to its own lines4 ,as the scouting-planes were large1 they offered a big target to anti-aircraft guns1 and so the work of the air scout was to swoop down upon the enemy1 when1 of course1 the machine would be traveling at high velocity1 because it would have all the speed of falling added to that which its own propeller gave it4 ,illustration3 ,how an object dropped from the ,woolworth ,building would increase its speed in falling ,it was really a very difficult matter to hit a rapidly moving airplane2 and even if it were hit1 there were few spots in which it could be mortally wounded4 ,hundreds of shots could go through the wings of an airplane without impairing its flying in the least4 ,the engine1 too1 could be pretty well peppered with ordinary bullets without being disabled4 ,as for the men in the machine1 they furnished small targets1 and even they could be hit in many places without being put entirely out of business4 ,and so the dangers of air scouting were not so great as might at first be supposed4 ,one of the most vulnerable spots in the airplane was the gasolene-tank4 ,if that were punctured so that the fuel would run out1 the airplane would have to come to the ground4 ,worse still1 the gasolene might take fire and there was nothing the aviator dreaded more than fire4 ,there were occasions in which he had to choose between leaping to earth and burning to death1 and the former was usually preferred as a quicker and less painful death4 ,in some of the later machines the gasolene-tank could be pitched overboard if it took fire1 by the throwing of a lever1 and then the aviator could glide to earth in safety4 ,,the ,,self-,,healing ,,gasolene-,,tank ,one of the contributions which we made to military aronautics was a gasolene-tank that was puncture-proof4 ,it was made of soft rubber with a thin lining of copper4 ,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 through1 because the rubber has closed in and healed the wound4 ,such was the rubber used in the gasolene-tank4 ,it could be peppered with bullets and yet would not leak a drop of gasolene1 unless the bullet chanced to plow along the edge of the tank and open a long gash4 ,the ,germans used four different kinds of cartridges in their aircraft guns4 ,the first carried the ordinary bullet1 a second type had for its bullet a shell of ,german silver filled with a phosphor compound4 ,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 aim4 ,at night the bright spot of light made by the burning compound would serve the same purpose4 ,such a bullet1 if it hit an ordinary gasolene-tank1 would set fire to its contents4 ,the bullet would plow through the tank and out at the opposite side and there1 at its point of exit1 is where the gasolene would be set on fire4 ,such incendiary bullets were repeatedly fired into or through the rubber tanks and the hole would close behind the bullet1 preventing the contents from taking fire4 ,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 bullet which was intended to pierce armor or penetrate into vital parts of an airplane engine4 ,machines with which artillery-spotting was done were usually manned by a pilot and an observer1 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 machine4 ,these machines were usually of the pusher type1 so that the observer could have an unobstructed view4 ,they did not have to be fast machines4 ,it was really better for them to move slowly4 ,had it been possible for them to stop altogether and hover over the spot that was being shelled1 it would have been a distinct advantage4 ,that would have given the observer a chance to note with better accuracy the fall of the shell4 ,like the scout1 the spotter had to be a fast climber1 so that it could get out of the range of enemy guns and run away from attacking planes4 ,,giants ,,of ,,the ,,sky ,the largest war-planes were the bomb-dropping machines4 ,they had to be capable of carrying heavy loads of explosives4 ,they were usually slow machines1 speed being sacrificed in carrying-capacity4 ,the ,germans paid a great deal of attention to big bomb-dropping machines1 particularly after their ,zeppelins proved a failure4 ,their huge ,gothas were built to make night raids on undefended cities4 ,the ,italians and the ,british retaliated with machines that were even larger4 ,at first the ,french were inclined to let giant planes alone4 ,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 inflicted4 ,later they built some giant machines1 although not so large as those of the ,italians and the ,british4 ,the large triplane ,capronis built by the ,italians held a crew of three men4 ,they were armed with three guns and carried #bgej pounds of explosives4 ,that made a useful load of #djjj pounds4 ,the machine was driven by three engines with a total of #ijj horse-power4 ,the big ,british plane was the ,handley-,page1 which had a wing-spread of #abe feet and could carry a useful load of three tons4 ,these enormous machines conducted their raids at night because they were comparatively slow and could not defend themselves against speedy battle-planes4 ,the big ,italian machines used search-light bombs to help them locate important points on the ground beneath4 ,these were brilliant magnesium torches suspended from parachutes so that they would fall slowly and give a broad illumination1 while the airplane itself was shielded from the light by the parachute4 ,but these giants were not the only bombing-machines4 ,there were smaller machines that operated over the enemy's battle-line and dropped bombs on any suspicious object behind the enemy lines4 ,these machines had to be convoyed by fast battle-planes which fought off hostile airmen4 ,,how ,,fast ,,is ,a ,,hundred ,,and ,,fifty ,,miles ,,per ,,hour8 ,in naval warfare the battle-ship is the biggest and heaviest ship of the fleet1 but in the air the battle-planes are the lightest and the smallest of the lot4 ,they are one-man machines1 as a rule1 little fellows1 but enormously speedy4 ,speed is such an important factor in arial warfare that there was a continuous struggle between the opposing forces to produce the faster machine4 ,airplanes were constantly growing speedier1 until a speed of #aej miles per hour was not an uncommon rate of travel4 ,it is hard to imagine such a speed as that1 but we may gain some idea if we consider a falling object4 ,the observation platform of the ,woolworth ,building1 in ,new ,york1 is about #gej feet above the ground4 ,if you should drop an object from this platform you would start it on a journey that would grow increasingly speedy1 particularly as it neared the ground4 ,by the time it had dropped from the sixtieth story to the fifty-ninth it would have attained a speed of nearly #bj miles per hour4 7,we are not making any allowances for the resistance of the air and what it would do to check the speed47 ,as it passed the fiftieth story it would be traveling as fast as an express-train1 or #fj miles per hour4 ,it would finally reach the ground with a speed equal to that of a fast battle-plane--#aej miles per hour4 ,the battle-plane was usually fitted with a single machine-gun that was fixed to the airplane1 so that it was brought to bear on the target by aiming the entire machine4 ,in this the plane was something like a submarine1 which must point its bow at its intended victim in order to aim its torpedo4 ,the operator of the battle-plane simply drove his machine at the enemy and touched a button on his steering-lever to start his machine-gun going4 ,,shooting ,,through ,,the ,,propeller ,now1 the fleetest machines and the most easily manoeuvered are those of the tractor type1 that is1 the ones which have the propeller in front2 but having the propeller in front is a handicap for a single-seater machine1 for the gun has to be fired through the propeller and the bullets are sure to hit the propeller-blades4 ,nevertheless the ,french did fire right through the propeller1 regardless of whether or not the blades were hit2 but at the point where they came in line with the fire of the gun they were armored with steel1 so that there was no danger of their being cut by the bullets4 ,it was calculated that not more than one bullet in eighteen would strike the propeller-blade and be deflected from its course1 which was a very trifling loss2 nevertheless1 it was a loss1 and on this account a mechanism was devised which would time the operations of the machine-gun so that the shots would come only when the propeller-blades were clear of the line of fire4 ,illustration3 ,machine-,gun mounted to ,fire over the ,blades of the ,propeller ,illustration3 ,courtesy of ,scientific ,american ,mechanism for ,firing ,between the ,blades of the ,propeller ,the cam ,b on the propeller shaft lifts the rod ,c1 rocking the angle lever ,d which moves the rod ,e and operates the firing-piece ,f4 ,firing may be stopped by means of lever ,h and ,bowden wire ,g4 ,i is the ejection-tube for empty cartridges4 ,illustration3 ,it would take a ,hundred ,horses to ,supply the ,power for a ,small ,airplane ,a cam placed on the propeller-shaft worked the trigger of the machine-gun4 ,this did not slow up the fire of the machine-gun4 ,quite the contrary4 ,we are apt to think of the fire of the machine-guns as very rapid1 but they usually fire only about five hundred rounds per minute1 while an airplane propeller will make something like twelve hundred revolutions per minute4 ,and so the mechanism was arranged to pull the trigger only once for every two revolutions of the propeller4 ,,fighting ,,among ,,the ,,clouds ,there was no service of the war that began to compare with that of the sky fighter4 ,he had to climb to enormous heights4 ,air battles took place at elevations of twenty thousand feet4 ,the higher the battle-plane could climb1 the better1 because the man above had a tremendous advantage4 ,clouds were both a haven and a menace to him4 ,at any moment an enemy plane might burst out of the clouds upon him4 ,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 position4 ,if he were getting the worst of it1 he might feign death and let his machine go tumbling and fluttering down for a thousand feet or so1 only to recover his equilibrium suddenly and dart away when the enemy was thrown off his guard4 ,he might escape into some friendly cloud1 but he dared not hide in it very long1 lest he get lost4 ,it is a peculiar sensation that comes over an aviator when he is flying through a thick mass of clouds4 ,he is cut off from the rest of the world4 ,he can hear nothing but the terrific roar of his own motor and the hurricane rush of the wind against his ears4 ,he can see nothing but the bluish fog of the clouds4 ,he begins to lose all sense of direction4 ,his compass appears to swing violently to and fro1 when really it is his machine that is zig-zagging under his unsteady guidance4 ,the more he tries to steady it1 the worse becomes the swing of the compass4 ,as he turns he banks his machine automatically1 just as a bicyclist does when rounding a corner4 ,he does this unconsciously1 and he may get to spinning round and round1 with his machine standing on its side4 ,in some cases aviators actually emerged from the clouds with their machines upside down4 ,to be sure1 this was not an alarming position for an experienced aviator2 at the same time1 it was not altogether a safe one4 ,a machine was sometimes broken by its operator's effort to right it suddenly4 ,and so while the clouds made handy shelters1 they were not always safe harbors4 ,to the battle-plane fell the task of clearing the air of the enemy4 ,if the enemy's battle-planes were disposed of1 his bombing-planes1 his spotters1 and his scouts could not operate1 and he would be blind4 ,and so each side tried to beat out the other with speedier1 more powerful1 and more numerous battle-planes4 ,fast double-seaters were built with guns mounted so that they could turn in any direction4 ,,the ,,flying ,,tank ,the ,germans actually built an armored battle-plane known as the flying tank4 ,it was a two-seater intended mainly for attacking infantry and was provided with two machine-guns that pointed down through the floor of the fuselage4 ,a third gun mounted on a revolving wooden ring could be used to fight off hostile planes4 ,the bottom and sides of the fuselage or body of the airplane from the gunner's cockpit forward were sheathed with plates of steel armor4 ,the machine was a rather cumbersome craft and did not prove very successful4 ,a flying tank was brought down within the ,american lines just before the signing of the armistice4 ,,america',s ,,help ,our own contribution to the war in the air was considerable1 but we had hardly started before the armistice brought the fighting to an end4 ,before we entered the war we did not give the airplane any very serious consideration4 ,to be sure1 we built a large number of airplanes for the ,british1 but they were not good enough to be sent to the front2 they were used merely as practice planes in the ,british training-schools4 ,we knew that we were hopelessly outclassed1 but we did not care very much4 ,then we stepped into the conflict4 ,what can we do to help8 we asked our allies1 and their answer gave us a shock4 ,airplanes6 they cried4 ,build us airplanes--thousands of them--so that we can drive the enemy out of the air and blind his armies6 ,it took us a while to recover from our surprise1 and then we realized why we had been asked to build airplanes4 ,the reputation of the ,united ,states as a manufacturer of machinery had spread throughout the world4 ,we ,americans love to take hold of a machine and turn it out in big quantities4 ,our allies were sure that we could turn out first-class airplanes1 and many of them1 if we tried4 ,congress made an appropriation of six hundred and forty million dollars for aronautics1 and then things began to hum4 ,a ,,birthday ,,present ,,to ,,the ,,nation ,the heart of an airplane is its engine4 ,we know a great deal about gasolene-engines1 especially automobile engines2 but an airplane engine is a very different thing4 ,it must be tremendously powerful1 and at the same time extremely light4 ,every ounce of unnecessary weight must be shaved off4 ,it must be built with the precision of a watch2 its vital parts must be true to a ten-thousandth part of an inch4 ,it takes a very powerful horse to develop one horse-power for a considerable length of time4 ,it would take a hundred horses to supply the power for even a small airplane1 and they would weigh a hundred and twenty thousand pounds4 ,an airplane motor of the same power would weigh less than three hundred pounds1 which is a quarter of the weight of a single horse4 ,it was this powerful1 yet most delicate1 machine that we were called upon to turn out by the thousand4 ,there was no time to waste2 a motor must be designed that could be built in the ,american way1 without any tinkering or fussy hand-work4 ,two of our best engineers met in a hotel in ,washington on ,june #c1 #aiag1 and worked for five days without once leaving their rooms4 ,they had before them all the airplane knowledge of our allies4 ,american engine-builders offered up their trade secrets4 ,everything was done to make this motor worthy of ,america's reputation4 ,there was a race to have the motor finished by the ,fourth of ,july4 ,sure enough1 on ,independence ,day the finished motor was there in ,washington--the ,liberty motor1 a birthday present to the nation4 ,of course that did not mean that we were ready at once to turn out ,liberty motors by the thousand4 ,the engine had to undergo many tests and a large number of alterations before it was perfectly satisfactory and then special machinery had to be constructed before it could be manufactured in quantity4 ,it was ,thanksgiving ,day before the first manufactured ,liberty was turned out and even after that change upon change was made in this little detail and that4 ,it was not until a year after we went to war that the engine began to be turned out in quantity4 ,there was nothing startlingly new about the engine4 ,it was a composite of a number of other engines1 but it was designed to be turned out in enormous quantities1 and it was remarkably efficient4 ,it weighed only #hbe pounds and it developed over #dbj horse-power4 ,some machines went up as high as #dhe horse-power4 ,an airplane engine weighing less than #b pounds per horse-power is wonderfully efficient4 ,of course the ,liberty was too heavy for a light battle-plane 7a heavy machine1 no matter how powerful1 cannot make sharp turns71 but it was excellent for other types of airplanes and large orders for ,liberty engines were made by our allies4 ,of course we made other engines as well1 and the planes to carry them4 ,we built large ,caproni and ,handley-,page machines1 and we were developing some remarkably swift and powerful planes of our own when the ,germans thought it about time to stop fighting4 ,,flying ,,boats ,so far we have said nothing about the seaplanes which were used in large numbers to watch for submarines4 ,these were big flying boats in which speed was not a very important matter4 ,one of the really big machines we developed1 but which was not finished until after the war1 was a giant with a #aaj-;foot span and a body or hull #ej feet long4 ,during the war seaplanes carried wireless telephone apparatus with which they could call to destroyers and submarine-chasers when they spotted a submarine4 ,they also carried bombs which they could drop on ,u-boats1 and even heavy guns with which they could fire shell4 ,a still later development are the giant planes of the ,n4 ,c4 type with a wing-spread of #abf feet and driven by four ,liberty motors4 ,they carry a useful load of four and a half tons4 ,illustration3 7,c7 ,underwood ,underwood ,the ,flying-tank--an ,armored ,german ,airplane designed for firing on troops on the march ,early in the war1 large guns were mounted on airplanes1 but the shock of the recoil proved too much for the airplane to stand4 ,however1 an ,american inventor produced a gun which had no recoil4 ,this he accomplished by using a double-end gun1 which was fired from the middle4 ,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 end4 ,the sand spread out and did no damage at a short distance from the gun1 but care had to be taken not to come too close4 ,these non-recoil guns were made in different sizes1 to fire #a-a_/b-;inch to #c-;inch shell4 ,,the ,,automatic ,,seaplane ,another interesting development was the target airplane used for the training of arial gunners4 ,this was a small seaplane with a span of only #ah-a_/b feet1 driven by a #ab-;horse-power motor1 the whole machine weighing but #age pounds4 ,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 out1 when it would drop down into the sea4 ,it afforded a real target for gunners in practice machines4 ,illustration3 7,c7 ,underwood ,underwood ,an ,n-,c 7,navy-,curtiss7 ,seaplane of the type that made the first flight across the ,atlantic ,early in the war an ,american inventor proposed that seaplanes be provided with torpedoes which they could launch at an enemy ship4 ,the seaplane would swoop down out of the sky to within a short distance of the ship1 drop its projectile1 and fly off again1 and the torpedo would continue on its course until it blew up the vessel4 ,it was urged that a fleet of such seaplanes protected by a convoy of fast battle-planes could invade the enemy harbors and destroys its powerful fleet4 ,it seemed like a rather wild idea1 but the ,british actually built such torpedo-planes and tested them4 ,however1 the ,german fleet surrendered before it was necessary to blow it up in such fashion4 ,,airplanes ,,after ,,the ,,war ,with the war ended1 all the ,allied powers have large numbers of airplanes on their hands and also large numbers of trained aviators4 ,undoubtedly airplanes will continue to fill the skies in ,europe and we shall see more and more of them in this country4 ,even during the war they were used for other purposes than fighting4 ,there were ambulances on wings--machines with the top of the fuselage removable so that a patient on a stretcher could be placed inside4 ,a ,french machine was furnished with a complete hospital equipment for emergency treatment and even for performing an operation in case of necessity4 ,the flying hospital could carry the patient back to the field or base hospital after treatment4 ,mail-carrying airplanes are already an old story4 ,in ,europe the big bombing-machines are being used for passenger service between cities4 ,there is an air line between ,paris and ,london4 ,the airplanes carry from a dozen to as many as fifty passengers on a single trip4 ,in some cities here1 as well as abroad1 the police are being trained to fly1 so that they can police the heavens when the public takes to wings4 ,evidently the flying-era is here4 ,,chapter ,,viii ,,ships ,,that ,,sail ,,the ,,skies ,shortly after the ,civil ,war broke out1 ,thaddeus ,s4 ,c4 ,lowe1 an enthusiastic ,american aronaut1 conceived the idea of sending up scout balloons to reconnoiter the position of the enemy4 ,these balloons were to be connected by telegraph wires with the ground1 so that they could direct the artillery fire4 ,the idea was so novel to the military authorities of that day that it was not received with favor4 ,balloons were looked upon as freak inventions1 entirely impracticable for the stern realities of war2 and as for telegraphing from a balloon1 no one had ever done that before4 ,illustration3 7,c7 ,underwood ,underwood ,a big ,german ,zeppelin that was forced to come down on ,french soil ,but this enthusiast was not to be daunted1 and he made a direct appeal to ,president ,lincoln1 offering to prove the practicability of this means of scouting4 ,so he took his balloon to ,washington and made an ascent from the grounds of the ,smithsonian ,institution1 while the ,president came out on the lawn south of the ,white ,house to watch the demonstration4 ,in order to test him1 ,mr4 ,lincoln took off his hat1 waved his handkerchief1 and made other signals4 ,lowe observed each act through his field-glasses and reported it to the ,president by telegraph4 ,mr4 ,lincoln was so impressed by the demonstration that he ordered the army to use the observation balloon1 and so with some reluctance the gas-bag was introduced into military service1 ,professor ,lowe being made chief aronautic engineer4 ,under ,lowe's direction the observation balloons played an important part in the operations of the ,union ,army4 ,illustration3 ,courtesy of ,scientific ,american ,observation ,car lowered from a ,zeppelin sailing above the clouds ,on one occasion a young ,german military attach begged the privilege of making an ascent in the balloon4 ,permission was given and when the ,german officer returned to earth he was wildly enthusiastic in praise of this arial observation post4 ,he had had a splendid view of the enemy and could watch operations through his field-glasses which were of utmost importance4 ,realizing the military value of the aircraft1 he returned to ,germany and urged military authorities to provide themselves with captive balloons4 ,this young officer was ,count ,ferdinand von ,zeppelin1 who was destined later to become the most famous aronautic 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 ,england4 ,he also lived to see the virtual failure of this type of war-machine in the recent great conflict1 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 ,march1 #aiag4 ,however1 he was spared the humiliation of seeing a fleet of ,zeppelins lose their way in a fog and fall into ,france1 one of them being captured before it could be destroyed1 so that all its secrets of construction were learned by the ,french4 ,,the ,,weight ,,of ,,hydrogen ,before we describe the ,zeppelin airships and the means by which they were eventually overcome1 we must know something about the principles of balloons4 ,every one knows that balloons are kept up in the air by means of a very light gas1 but somehow the general public fails to understand why the gas should hold it up4 ,some people have a notion that there is something mysterious about hydrogen gas which makes it resist the pull of gravity1 and that the more hydrogen you crowd into the balloon the more weight it will lift4 ,but hydrogen has weight and feels the pull of gravity just as air does1 or water1 or lead4 ,the only reason the balloon rises is because it weighs less than the air it displaces4 ,it is hard to think of air as having weight1 but if we weigh air1 hydrogen1 coal-gas1 or any other gas1 in a vacuum1 it will tip the scales just as a solid would4 ,a thousand cubic feet of air weighs #hj pounds4 ,in other words1 the air in a room ten feet square with a ceiling ten feet high1 weighs just about #hj pounds4 ,the same amount of coal-gas weighed in a vacuum would register only #dj pounds2 while an equal volume of hydrogen would weigh only #e-a_/b pounds4 ,but when we speak of volumes of gas we must remember that gas1 unlike a liquid or a solid1 can be compressed or expanded to almost any dimensions4 ,for instance1 we could easily fill our room with a ton of air if the walls would stand the pressure2 or we could pump out the air1 until there were but a few ounces of air left4 ,but in one case the air would be so highly compressed that it would exert a pressure of about #cge pounds on every square inch of the wall of the room1 while in the other case its pressure would be almost infinitesimal4 ,but #hj pounds of air in a room of a thousand cubic feet would exert the same pressure as the atmosphere1 or #ae pounds on every square inch4 ,and when we say that a thousand cubic feet of hydrogen weighs only a little over #e pounds1 we are talking about hydrogen at the same pressure as the atmosphere4 ,since the hydrogen is sixteen times lighter than air1 naturally it will float in the air1 just as a piece of wood will float in water because it is lighter than the same volume of water4 ,if we surrounded the thousand cubic feet of hydrogen with a bag so that the gas will not diffuse into the air and mix with it1 we shall have a balloon which would float in air provided the bag and the hydrogen it contains do not weigh more than eighty pounds4 ,as we rise from the surface of the earth1 the air becomes less and less dense1 or1 in other words1 it becomes lighter1 and the balloon will keep on rising through the atmosphere until it reaches a point at which its weight1 gas-bag and all1 is exactly the same as that of an equal volume of air4 ,but there are many conditions that affect the height to which the balloon will ascend4 ,the higher we rise1 the colder it is apt to become1 and cold has a tendency to compress the hydrogen1 collapsing the balloon and making it relatively heavier4 ,when the sun beats upon a balloon1 it heats the hydrogen1 expanding it and making it relatively lighter1 and if there is no room for this expansion to take place in the bag1 the bag will burst4 ,for this reason1 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 air4 ,although a round balloon carries no engine and no propeller1 it can be guided through the air to some degree4 ,when an aronaut wishes to go in any particular direction1 he sends up his balloon by throwing out ballast or lowers it by letting out a certain amount of gas1 until he reaches a level at which he finds a breeze blowing in the desired direction4 ,such was the airship of ,civil ,war times1 but for military purposes it was not advisable to use free balloons1 because of the difficulty of controlling them4 ,they were too liable to fall into the hands of the enemy4 ,all that was needed was a high observation post from which the enemy could be watched1 and from which observations could be reported by telegraph4 ,the balloon was not looked upon as a fighting-machine4 ,,zeppelin',s ,,failures ,,and ,,successes ,but ,count ,zeppelin was a man of vision4 ,he dreamed of a real ship of the air--a machine that would sail wherever the helmsman chose1 regardless of wind and weather4 ,many years elapsed before he actually began to work out his dreams1 and then he met with failure after failure4 ,he believed in big machines and the loss of one of his airships meant the waste of a large sum of money1 but he persisted1 even though he spent all his fortune1 and had to go heavily in debt4 ,every one thought him a crank until he built his third airship and proved its worth by making a trip of #bgj miles4 ,at once the ,german ,government was interested and saw wonderful military possibilities in the new craft4 ,the ,zeppelin was purchased by the government and money was given the inventor to further his experiments4 ,that was not the end of his failures4 ,before the war broke out1 thirteen ,zeppelins had been destroyed by one accident or another4 ,evidently the building of ,zeppelin airships was not a paying undertaking1 although they were used to carry passengers on short arial voyages4 ,but the government made up money losses and ,zeppelin went on developing his airships4 ,of course1 he was not the only one to build airships1 nor even the first to build a dirigible4 ,the ,french built some large dirigibles1 but they failed to see any great military advantage in ships that could sail through the air1 particularly after the airplane was invented1 and so it happened that when the war started the ,french were devoting virtually all their energies to the construction of speedy1 powerful airplanes4 ,as for the ,british1 they did not pay much attention to airships4 ,the idea that their isles might be attacked from the sky seemed an exceedingly remote possibility4 ,,rigid1 ,,semi-,,rigid1 ,,and ,,flexible ,,balloons ,count ,zeppelin always held that the dirigible balloons must be rigid1 so that they could be driven through the air readily and would hold their shape despite variations in the pressure of the hydrogen4 ,the ,french1 on the other hand1 used a semi-rigid airship2 that is1 one in which a flexible balloon is attached to a rigid keel or body4 ,the ,british clung to the idea of an entirely flexible balloon and they suspended their car from the gas-bag without any rigid framework to hold the gas-bag in shape4 ,in every case1 the balloons were kept taut or distended by means of air-bags or ballonets4 ,these air-bags were placed inside the gas-bags and as the hydrogen expanded it would force the air out through valves1 but the hydrogen itself would not escape4 ,when the hydrogen contracted1 the air-bags were pumped full of air so as to maintain the balloon in its fully distended condition4 ,additional supplies of compressed hydrogen were kept in metal tanks4 ,illustration3 7,c7 ,underwood ,underwood ,giant ,british ,dirigible built along the lines of a ,zeppelin ,illustration3 7,c7 ,underwood ,underwood ,one of the engine cars or power eggs of a ,british ,dirigible ,in the ,zeppelin balloon1 however1 the gas was contained in separate bags which were placed in a framework of aluminum covered over with fabric4 ,count ,zeppelin did not believe in placing all his eggs in one basket4 ,if one of these balloons burst or was injured in any way1 there was enough buoyancy in the rest of the gas-bags to hold up the airship4 ,as the ,zeppelins were enormous structures1 the framework had to be made strong and light1 and it was built up of a latticework of aluminum alloy4 ,aluminum itself was not strong enough for the purpose1 but a mixture of aluminum and zinc and later another alloy known as duralumin1 consisting of aluminum with three per cent of copper and one per cent of nickel1 provided a very rigid framework that was exceedingly light4 ,duralumin is four or five times as strong as aluminum and yet weighs but little more4 ,illustration3 ,photograph by ,international ,film ,service ,crew of the ,c-#e 7,american ,coastal ,dirigible7 starting for ,newfoundland to make a ,transatlantic ,flight ,the body of the ,zeppelin is not a perfect circle in section1 but is made up in the form of a polygon with sixteen sides1 and the largest of the ,zeppelins used during the war contained sixteen compartments1 in each of which was placed a large hydrogen gas-bag4 ,a super-,zeppelin1 as the latest type is called1 was about seventy-five feet in diameter and seven hundred and sixty feet long1 or almost as long as three ,new ,york street blocks4 ,in its gas-bags it carried two million cubic feet of hydrogen and although the whole machine with its fuel1 stores1 and passengers weighed close to fifty tons1 it was so much lighter than the air it displaced that it had a reserve buoyancy of over ten tons4 ,,keeping ,,engines ,,clear ,,of ,,the ,,inflammable ,,hydrogen ,as hydrogen is a very inflammable gas1 it is extremely dangerous to have an internal-combustion engine operating very near the gas-bags4 ,in the super-,zeppelins the engines were placed in four cars suspended from the balloon4 ,there was one of these cars forward1 and one at the stern1 while near the center were two cars side by side4 ,in the rear car there were two engines1 either of which could be used to drive the propeller4 ,by means of large steering rudders and horizontal rudders1 the machine could be forced to dive or rise or turn in either direction laterally4 ,the pilot of the ,zeppelin had an elaborate operating-compartment from which he could control the rudders1 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 dirigible4 ,there were nineteen men in the crew of the ,zeppelin--two in the operating-compartment1 and two in each of the cars containing engines1 except for the one at the stern in which there were three men4 ,the other men were placed in what was known as the cat walk or passageway running inside the framework under the gas-bags4 ,these men were given various tasks and were supposed to get as much sleep as they could1 so as to be ready to replace the other men at need4 ,the engine cars at each side of the balloon were known as power eggs because of their general egg shape4 ,at the center of the ,zeppelin the bombs were stored1 and there were electro-magnetic releasing-devices operated from the pilot's room by which the pilot could drop the bombs whenever he chose4 ,the ,zeppelin also carried machine-guns to fight off airplanes4 ,gasolene was stored in tanks which were placed in various parts of the machine1 any one of which could feed one or all of the engines1 and they were so arranged that they could be thrown overboard when the gasolene was used up1 so as to lighten the load of the ,zeppelin4 ,water ballast was used instead of sand1 and alcohol was mixed with the water to keep it from freezing4 ,the machine which came down in ,french territory and was captured before it could be destroyed by the pilot1 found itself unable to rise because in the intense cold of the upper air the water ballast had frozen1 and it could not be let out to lighten the load of the ,zeppelin4 ,illustration3 ,photograph from ,kadel ,herbert ,the ,curious ,tail of a ,kite ,balloon ,illustration3 ,british ,official ,photograph from ,kadel ,herbert ,observers in the ,basket of an ,observation-,balloon ,,the ,,zeppelin',s ,,tiny ,,antagonists ,the one thing above all others that the ,zeppelin commander feared was the attack of airplanes4 ,in the early stages of the war1 it was considered unsafe for airplanes to fly by night because of the difficulty of making a landing in the dark4 ,later this difficulty was overcome by the use of search-lights at the landing-fields4 ,the airplane would signal its desire to land and the search-lights would point out the proper landing-field for it4 ,so that after the first few months of the war ,zeppelins were subjected to the danger of airplane attack4 ,of course1 on a dark night it was very difficult for an airplane to locate a ,zeppelin1 because the huge machine could not be seen and the throb of its engines was drowned out by the engines of the airplane itself4 ,nevertheless1 ,zeppelins were occasionally located and destroyed by airplanes4 ,illustration3 ,photograph by ,kadel ,herbert ,enormous ,range-finders mounted on a ,gun ,turret of an ,american ,warship ,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 destruction of the giant of the air4 ,and so the machine-guns carried by airplanes were provided with explosive1 flaming bullets4 ,a burst of flame within the gas-bag would not set the gas on fire1 because there would be no air inside to feed the fire1 but surrounding the gas-bag there was always a certain leakage of hydrogen which would mix with the air in the compartment and this would produce an explosive mixture which needed but the touch of fire to set it off4 ,the ,zeppelin was provided with a ventilating-system to carry off these explosive gases1 but they could never be disposed of very effectively1 and1 as a consequence1 a number of ,zeppelins were destroyed by the tiny antagonists that were sent up by the ,british and the ,french4 ,to fight off these assailants the ,germans provided their ,zeppelins with guns which would fire shrapnel shell4 ,it is difficult for a ,zeppelin to use machine-guns against an airplane because the latter would merely climb above the ,zeppelin and would be shielded by the balloon itself4 ,and so the ,germans put a gun emplacement on top of the balloon both forward and aft4 ,there was a deck extending along the top of the balloon which was reached by a ladder running up through the center of the airship4 ,but it was impossible to ward off the fleet little antagonists1 once the dirigible was discovered4 ,true1 a ,zeppelin could make as much as seventy miles per hour1 but the fastest airplanes could travel twice as fast as that4 ,,suspending ,,an ,,observer ,,below ,,the ,,zeppelin ,one ingenious scheme that was tried was to suspend an observation car under the ,zeppelin4 ,the car was about fourteen feet long and five feet in diameter1 fitted with a tail to keep it headed in the direction it was towed4 ,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 below4 ,the car with its observer could be lowered a few thousand feet below the ,zeppelin1 so that the observer could watch proceedings below1 while the airship remained hidden among the clouds4 ,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 ship4 ,but despite everything that could be done1 the ,zeppelin eventually proved a failure as a war-vessel because it was so very costly to construct and operate and could so easily be destroyed1 and the ,germans began to build huge airplanes with which bombing-raids could be continued4 ,strange to say1 however1 although the ,germans were ready to admit the failure of their big airship1 when the war stopped the ,allies were actually building machines patterned after the ,zeppelin1 but even larger1 and expected to use them for bombing-excursions over ,germany4 ,this astonishing turn of the tables was due to the fact that ,america had made a contribution to aronautics that solved the one chief drawback of the ,zeppelin4 ,a ,,balloon ,,gas ,,that ,,will ,,not ,,burn ,when we entered the war against ,germany1 our allies placed before us all their problems and among them was this one of the highly inflammable airship4 ,could we not furnish a substitute for hydrogen that would not burn8 ,it was suggested to us that helium would do if we could produce that gas cheaply and in sufficient quantity4 ,now1 helium has a history of its own that is exceedingly interesting4 ,every now and then the moon bobs its head into our light and we have a solar eclipse4 ,but our satellite is not big enough to cut off all the light of the big luminary and the fiery atmosphere of the sun shows us a brilliant halo all around the black disk of the moon4 ,long ago1 astronomers analyzed this flaming atmosphere with the spectroscope1 and by the different bands of light that appeared they were able to determine what gases were present in the sun's atmosphere4 ,but there was one band of bright yellow which they could not identify4 ,evidently this was produced by a gas unknown on earth1 and they called it helium or sun gas4 ,for a quarter of a century this sun gas remained a mystery2 then one day1 in #ahie1 ,sir ,william ,ramsay discovered the same band of light when studying the spectrum of the mineral cleveite4 ,the fact that astronomers had been able to single out an element on the sun ninety million miles away before our chemists could find it right here on earth1 produced a mild sensation1 but the general public attached no special importance to the gas itself4 ,it proved to be a very light substance1 next to hydrogen the lightest of gases1 and for years it resisted all attempts at liquefaction4 ,only when ,onnes1 the ,dutch scientist1 succeeded in getting it down to a temperature of #dej degrees below zero1 ,fahrenheit1 did the gas yield to the chill and condense into a liquid4 ,the gas would not burn2 it would not combine with any other elements1 and apparently it had no use on earth1 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 ,hun4 ,because the gas had no commercial value1 there was only a small amount of helium to be found in the whole world4 ,not a single laboratory in the ,united ,states had more than five cubic feet of it and its price ranged from #a1ejj to #f1jjj per cubic foot4 ,at the lowest price it would cost #c1jjj1jjj1jjj to provide gas enough for one airship of ,zeppelin dimensions and it seemed absurd even to think of a helium airship4 ,,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 ,oklahoma1 ,texas1 and ,kansas1 and ,sir ,william ,ramsey suggested that our chemists might study some method of getting helium from this source4 ,the only way of separating it out was to liquefy the gases by subjecting them to extreme cold4 ,all gases turn to liquid if they are cooled sufficiently1 and then further cold will freeze them solid4 ,but helium can stand more cold than any other and this fact gave the clue to its recovery from natural gas4 ,the latter was frozen and one after another the different elements condensed into liquid1 until finally only helium was left4 ,this sounds simple1 but it is a difficult matter to get such low temperature as that on a large scale and do it economically4 ,to be of any real service in aronautics helium would have to be reduced in cost from fifteen hundred dollars to less than ten cents per cubic foot4 ,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 foot1 with the prospect of reducing its cost still further4 ,a large plant for recovering helium was being built4 ,the plant will have been completed before this book is published1 and it will be turning out helium for peaceful instead of military airships4 ,the reduction in the cost of helium is really one of the most important developments of this war4 ,by removing the fire risk from airships we can safely use these craft for arial cruises or for quick long-distance travel over land and sea4 ,for1 even in time of peace1 sailing under millions of cubic feet of hydrogen is a serious matter4 ,although no incendiary bullets are to be feared1 there is always the danger of setting fire to the gas within the exhaust of the engines4 ,engines have had to be hung in cars well below the balloon proper4 ,but with helium in the gas-bags the engines can be placed inside the balloon envelop and the propellers can operate on the center line of the car4 ,in the case of one ,zeppelin1 the hydrogen was set on fire by an electric spark produced by friction on the fabric of one of the gas-bags1 and so even with the engine exhausts properly screened there is danger4 ,the helium airship1 however1 would be perfectly safe from fire and passengers could smoke on deck or in their cabins within the balloon itself without any more fear of fire than they would have on shipboard4 ,wonderful possibilities have been opened by the production of helium on a large and economical scale1 and the airship seems destined to play an important part in transportation very soon4 ,as this book is going to press1 we learn of enormous dirigibles about to be built in ,england for passenger service1 which will have half again as great a lifting-power as the largest ,zeppelins4 ,the final chapter of the story of dirigibles is yet to be written1 but in concluding this chapter it is interesting to note that the world's greatest aronautic expert got his first inspiration from ,america and finally that ,america has now furnished the one element which was lacking to make the dirigible balloon a real success4 ,,chapter ,,ix ,,getting ,,the ,,range ,every person with a good pair of eyes in his head is a range-finder4 ,he may not know it1 but he is1 just the same1 and the way to prove it is to try a little range-finding on a small scale4 ,use the top of a table for your field of operations1 and pick out some spot within easy reach of your hand for the target whose range you wish to find4 ,the target may be a penny or a small circle drawn on a piece of white paper4 ,take a pencil in your hand and imagine it is a shell which you are going to land on the target4 ,it is not quite fair to have a bird's-eye view of the field1 so get down on your knees and bring your eyes within a few inches of the top of the table4 ,now close one eye and making your hand describe an arc through the air1 like the arc that a shell would describe1 see how nearly you can bring the pencil-point down on the center of the target4 ,do it slowly1 so that your eye may guide the hand throughout its course4 ,you will be surprised to find out how far you come short1 or overreach the mark4 ,you will have actually to grope for the target4 ,if by any chance you should score a hit on the first try1 you may be sure that it is an accident4 ,have a friend move the target around to a different position1 and try again4 ,evidently1 with one eye you are not a good range-finder2 but now use two eyes and you will score a hit every time4 ,not only can you land the pencil on the penny1 but you will be able to bring it down on the very center of the target4 ,the explanation of this is that when you bring your eyes to bear upon any object that is near by1 they have to be turned in slightly1 so that both of them shall be aimed directly at that object4 ,the nearer the object1 the more they are turned in1 and the farther the object1 the more nearly parallel are the eyes4 ,long experience has taught you to gage the distance of an object by the feel of the eyes--that is1 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 object4 ,you do not know what the distance is in feet or inches1 but you can tell when the pencil-point has moved out until it is at the same focus as the target4 ,the experiment can be tried on a larger scale with the end of a fishing-rod1 but here you will probably have to use a larger target4 ,however1 there is a limit to which you can gage the range4 ,at a distance of1 say1 fifteen or twenty feet1 a variation of a few inches beyond or this side of the target makes scarcely any change in the focus of the eyes4 ,that is because the eyes are so close together4 ,if they were farther apart1 they could tell the range at much greater distances4 ,,spreading ,,the ,,eyes ,,far ,,apart ,now the ordinary range-finder1 used in the army and in the navy1 is an arrangement for spreading the eyes apart to a considerable distance4 ,of course the eyes are not actually spread1 but their vision is4 ,the range-finder is really a double telescope4 ,the barrel is not pointed at an object1 but it is held at right angles to it4 ,you look into the instrument at the middle of the barrel and out of it at the two ends4 ,a system of mirrors or prisms makes this possible4 ,the range-finder may be a yard or more in length1 which is equivalent to spreading your eyes a yard or more apart4 ,now1 the prisms or object-glasses at the ends of the tube are adjustable1 so that they will turn in until they focus directly on the target whose range you wish to find1 and the angle through which these glasses are turned gives a measure of the distance of the target4 ,the whole thing is calculated out so that the distance in feet1 yards1 or meters1 or whatever the measure may be1 is registered on a scale in the range-finder4 ,ordinarily only one eye is used to look through the range-finder1 because the system of mirrors is set to divide the sight of that one eye and make it serve the purposes of two4 ,that leaves the other eye free to read the scale1 which comes automatically into view as the range-finder is adjusted for the different ranges4 ,on the battle-ships enormous range-finders are used4 ,some of them are twenty feet long4 ,with the eyes spread as far apart as that and with a microscope to read the scale1 you can imagine how accurately the range can be found1 even when the target is miles away4 ,but on land such big range-finders cannot conveniently be used2 they are too bulky4 ,when it is necessary to get the range of a very distant object1 two observers are used who are stationed several hundred yards apart4 ,these observers have telescopes which they bear upon the object1 and the angle through which they have to turn the telescope is reported by telephone to the battery1 where1 by a rapid calculation1 it is possible to estimate the exact position of the target4 ,then the gun is moved up or down1 to the right or to the left1 according to the calculation4 ,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 target4 ,sometimes they are placed on top of telegraph poles or hidden up a tall tree1 or in a church steeple4 ,,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 through4 ,but the great ,european conflict brought out wonderful improvements in all branches of fighting2 and range-finding was absolutely revolutionized1 because shelling was done at greater ranges than ever before1 but chiefly because the war was carried up into the sky4 ,a bird's-eye observation is much more accurate than any that can be obtained from the ground4 ,even before this war1 some observations were taken by sending a man up in a kite1 particularly a kite towed from a ship1 and even as far back as the ,civil ,war captive balloons were used to raise an observer to a good height above the ground4 ,they were the ordinary round balloons1 but the observation balloon of to-day is a very different-looking object4 ,it is a sausage-shaped gas-bag that is held on a slant to the wind like a kite1 so that the wind helps to hold it up4 ,to keep it head-on to the wind1 there is a big air-bag that curls around the lower end of the sausage4 ,this acts like a rudder1 and steadies the balloon4 ,some balloons have a tail consisting of a series of cone-shaped cups strung on a cable4 ,a kite balloon will ride steadily in a wind that would dash a common round balloon in all directions4 ,observers in these kite balloons are provided with telephone instruments by which they can communicate instantly with the battery whose fire they are directing4 ,but a kite balloon is a helpless object2 it cannot fight the enemy4 ,the hydrogen gas that holds it up will burn furiously if set on fire4 ,in the war an enemy airplane had merely to drop a bomb upon it or fire an incendiary bullet into it1 and the balloon would go up in smoke4 ,nothing could save it1 once it took fire1 and all the observers could do was to jump for their lives as soon as they saw the enemy close by4 ,they always had parachutes strapped to them1 so they could leap without an instant's delay in case of sudden danger4 ,at the very first approach of an enemy airplane1 the kite balloon had to be hauled down or it would surely be destroyed1 and so kite balloons were not very dependable observation stations for the side which did not control the air4 ,as stated in the preceding chapter1 just before the fighting came to an end1 our army was preparing to use balloons that were not afraid of flaming bullets1 because they were to be filled with a gas that would not burn4 ,,making ,,maps ,,with ,a ,,camera ,because airplanes filled the sky with eyes1 everything that the army did near the front had to be carefully hidden from the winged scouts4 ,batteries were concealed in the woods1 or under canopies where the woods were shot to pieces1 or they were placed in dugouts so that they could not be located4 ,such targets could seldom be found with a kite balloon4 ,it was the task of airplane observers to search out these hidden batteries4 ,the eye alone was not depended upon to find them4 ,large cameras were used with telescopic lenses which would bring the surface of the earth near while the airplane flew at a safe height4 ,these were often motion-picture cameras which would automatically make an exposure every second1 or every few seconds4 ,illustration3 7,c7 ,underwood ,underwood ,british ,anti-aircraft ,section getting the ,range of an ,enemy ,aviator ,when the machine returned from a photographing-expedition1 the films were developed and printed1 and then pieced together to form a photographic map4 ,the map was scrutinized very carefully for any evidence of a hidden battery or for any suspicious enemy object4 ,as the enemy was always careful to disguise its work1 the camera had to be fitted with color-screens which would enable it to pick out details that would not be evident to the eye4 ,as new photographic maps were made from day to day1 they were carefully compared one with the other so that it might be seen if there was the slightest change in them which would indicate some enemy activity4 ,as soon as a suspicious spot was discovered1 its position was noted on a large-scale military map and the guns were trained upon it4 ,illustration3 7,c7 ,kadel ,herbert ,a ,british ,aviator making ,observations over the ,german ,lines ,,correcting ,,the ,,aim ,it is one thing to know where the target is and another to get the shell to drop upon it4 ,in the firing of a shell a distance of ten or twenty miles1 the slightest variation in the gun will make a difference of many yards in the point where the shell lands4 ,not only that1 but the direction of the wind and the density of the air have a part to play in the journey of the shell4 ,if the shell traveled through a vacuum1 it would be a much simpler matter to score a hit by the map alone4 ,but even then there would be some differences1 because a gun has to be warmed up before it will fire according to calculation4 ,that is why it is necessary to have observers1 or spotters as they are called1 to see where the shell actually do land and tell the gun-pointers whether to elevate or depress the gun1 and how much to traverse it--that is1 move it sideways4 ,this would not be a very difficult matter if there were only one gun firing1 but when a large number of guns are being used1 as was almost invariably the case in the war1 the spotter had to know which shell belonged to the gun he was directing4 ,one of the most important inventions of the war was the wireless telephone1 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 difficulty1 from a distance of ten miles2 and in some cases he could reach a range of fifty miles4 ,with the wireless telephone1 the observer could communicate instantly with the gun-pointer1 and tell him when to fire4 ,usually thirty seconds were allowed after the signal sent by the observer before the gun was fired1 and on the instant of firing1 a signal was sent to the man in the airplane to be on the lookout for the shell4 ,knowing the position of the target1 the gun-pointer would know how long it would take the shell to travel through the air1 and he would keep the man in the airplane posted1 warning him at ten seconds1 five seconds1 and so forth1 before the shell was due to land4 ,in order to keep the eyes fresh for observation and not to have them distracted by other sights1 the observer usually gazed into space until just before the instant the shell was to land4 ,then he would look for the column of smoke produced by the explosion of the shell and report back to the battery how far wide of the mark the shell had landed4 ,a number of shell would be fired at regular intervals1 say four or five per minute1 so that the observer would know which shell belonged to the gun in question4 ,there are different kinds of shell4 ,some will explode on the instant of contact with the earth4 ,these are meant to spread destruction over the surface4 ,there are other shell which will explode a little more slowly and these penetrate the ground to some extent before going off2 while a third type has a delayed action and is intended to be buried deep in the ground before exploding1 so as to destroy dugouts and underground positions4 ,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 sky4 ,the instantaneous shell1 however1 produces a broad burst of smoke which can be spotted much more readily1 and this enables the man in the airplane to determine the position of the shell with greater accuracy4 ,for this reason1 instantaneous shell were usually used for spotting-purposes1 and after the gun had found its target1 other shell were used suited to the character of the work that was to be done4 ,,miniature ,,battle-,,fields ,observation of shell-fire from an airplane called for a great deal of experience1 and our spotters were given training on a miniature scale before they undertook to do spotting from the air4 ,a scaffolding was erected in the training-quarters over a large picture of a typical bit of enemy territory4 ,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 map1 and they were connected by telephone or telegraph with men below who represented the batteries4 ,the instructor would flash a little electric light here and there on the miniature battle-field1 and the observers had to locate these flashes and tell instantly how far they were from certain targets4 ,this taught them to be keen and quick and to judge distance accurately4 ,airplane observing was difficult and dangerous1 and often impossible4 ,on cloudy days the observer might be unable to fly at a safe height without being lost in the clouds4 ,then dependence had to be placed upon observers stationed at vantage-points near the enemy1 or in kite balloons4 ,,spotting ,,by ,,sound ,when there is no way of seeing the work of a gun1 it is still possible to correct the aim1 because the shell can be made to do its own spotting4 ,every time a shell lands1 it immediately announces the fact with a loud report4 ,that report is really a message which the shell sends out in all directions with a speed of nearly #hjj miles per hour--#a1adb feet per second1 to be exact4 ,this sound-message is picked up by a recorder at several different receiving-stations4 ,of course it reaches the nearest station a fraction of a second before it arrives at the next nearest one4 ,the distance of each station from the target is known by careful measurement on the map1 and the time it takes for sound to travel from the target to each station is accurately worked out4 ,if the sound arrives at each station on schedule time1 the shell has scored a hit2 but if it reaches one station a trifle ahead of time and lags behind at another1 that is evidence 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 mark4 ,in this way it was possible to come within fifty or even twenty-five yards of the target4 ,this sound-method was also used to locate an enemy battery4 ,it was often well nigh impossible to locate a battery in any other way4 ,with the use of smokeless powder1 there is nothing to betray the position of the gun1 except the flash at the instant of discharge1 and even the flash was hidden by screens from the view of an airplane4 ,aside from this1 when an airplane came near enough actually to see one of these guns1 the gun would stop firing until the airplane had been driven off4 ,but a big gun has a big voice1 and it is impossible to silence it4 ,often a gun whose position has remained a secret for a long time was discovered because the gun itself peached4 ,the main trouble with sound-spotting was that there were usually so many shell and guns going off at the same time that it was difficult if not impossible to distinguish one from another4 ,sometimes the voice of a hidden gun was purposely drowned by the noise of a lot of other guns4 ,after all1 the main responsibility for good shooting had to fall on observers who could actually see the target1 and when we think of the splendid work of our soldiers in the war1 we must not forget to give full credit to the tireless men whose duty it was to watch1 to the men on wings who dared the fierce battle-planes of the enemy1 to the men afloat high in the sky who must leap at a moment's notice from under a blazing mass of hydrogen1 and finally to the men who crept out to perilous vantage-points at risk of instant death1 in order to make the fire of their batteries tell4 ,,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-making4 ,before the war1 an aviator when on the wing was both deaf and dumb4 ,he could communicate with other airplanes or with the ground only by signal or1 for short distances1 by radiotelegraphy1 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 engine4 ,now the range of his voice has been so extended that he can chat with fellow aviators miles away4 ,this remarkable achievement and many others in the field of radio-communication hinge upon a delicate electrical device invented by ,deforest in #aijf and known as the audion4 ,for years this instrument was used by radiotelegraphers without a real appreciation of its marvelous possibilities1 and1 as a matter of fact1 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 ,telephone ,system4 ,,the ,,audion ,although the audion is familiar to all amateur radio-operators1 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 telegraphy4 ,the audion is a small glass bulb from which the air is exhausted to a high degree of vacuum4 ,the bulb contains three elements4 ,one is a tiny filament which is heated to incandescence by a battery1 so that it emits negatively charged electrons4 ,the filament is at one side of the bulb and at the opposite side there is a metal plate4 ,when the plate and the filament are connected with opposite poles of a battery1 there is a flow of current between them1 but because only negative electrons are emitted by the filament1 the current will flow only in one direction--that is1 from the plate to the filament4 ,if the audion be placed in the circuit of an alternating-current generator1 it will let through only the current running in one direction4 ,thus it will rectify the current or convert alternating current into direct current4 ,but the most important part of the audion1 the part for which ,deforest is responsible1 is the third element1 which is a grid or flat coil of platinum wire placed between the filament and the plate4 ,this grid furnishes a very delicate control of the strength of the electric current between plate and filament4 ,the slightest change in electric power in the grid will produce large changes of power in the current flowing through the audion4 ,this makes it possible to magnify or amplify very feeble electric waves1 and the extent to which the amplifying can be carried is virtually limitless1 because a series of audions can be used1 the current passing through the first being connected with the grid of the next1 and so on4 ,,talking ,,from ,,new ,,york ,,to ,,san ,,francisco ,there is a limit to which telephone conversations can be carried on over a wire1 unless there is some way of adding fresh energy along the line4 ,for years all sorts of experiments were tried with mechanical devices which would receive a telephone message and send it on with a fresh relay of current4 ,but these devices distorted the message so that it was unintelligible4 ,the range of wire telephony was greatly increased by the use of certain coils invented by ,pupin1 which were placed in the line at intervals2 but still there was a limit to which conversation could be carried on by wire and it looked as if it would never be possible to telephone from one end of this big country of ours to the other4 ,but the audion supplied a wonderfully efficient relay and one day we awoke to hear ,san ,francisco calling1 ,hello1 to ,new ,york4 ,used as a relay1 the improved audion made it possible to pick up very faint wireless-telegraph messages and in that way increased the range of radio outfits4 ,messages could be received from great distances without any extensive or elaborate arials1 and the audion could be used at the sending-station to magnify the signals transmitted and send them forth with far greater power4 ,having improved the audion and used it successfully for long-distance telephone conversation over wires1 the telephone company began to experiment with wireless telephony4 ,they believed that it might be possible to use radiotelephony in places where wires could not be laid4 ,for instance1 it might be possible to talk across the ,atlantic4 ,but before we go farther1 just a word of explanation concerning radiotelegraphy and radiotelephony for the benefit of those who have not even an elementary knowledge of the subject4 ,,simple ,,explanation ,,of ,,radiotelegraphy ,suppose we should set up two stakes in a pond of water1 at some distance from each other1 and around each we set a ring-shaped cork float4 ,if we should move one of these floats up and down on its stake1 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 hand4 ,in wireless telegraphy the two stakes are represented by antenn or arials and the cork floats are electric charges which are sent oscillating up and down the antenn4 ,the oscillations produced at one arial will set up electro-magnetic waves which will spread out in all directions in the ether until they reach a receiving-arial1 and there they will produce electric oscillations similar to the ones at the transmitting-antenna4 ,telegraph signals are sent by the breaking up of the oscillations at the transmitting-station into long and short trains of oscillations corresponding to the dots and dashes of ordinary wire telegraphy4 ,in other words1 while the sending-key is held down for a dash1 there will be a long series of oscillations in the antenna1 and for the dot a short series1 and these short and long trains of waves will spread out to the receiving-arial where they will reproduce the same series of oscillations4 ,but only a small part of the energy will act on the receiving-arial because the waves like those on the pond spread in all directions and grow rapidly weaker4 ,hence the advantage of an extremely delicate instrument like the audion to amplify the signals received4 ,the oscillations used in wireless telegraphy these days are very rapid1 usually entirely too rapid1 to affect an ordinary telephone receiver1 and if they did they would produce a note of such high pitch that it could not be heard4 ,so it is customary to interrupt the oscillations1 breaking them up into short trains of waves1 and these successive trains produce a note of low enough pitch to be heard in the telephone receiver4 ,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 waves4 ,now in radiotelephony it is not necessary to break up the oscillations1 but they are allowed to run continuously at very high speed and act as carriers for other waves produced by speaking into the transmitter2 that is1 a single speech-wave would be made up of a large number of smaller waves4 ,to make wireless telephony a success it was necessary to find some way of making perfectly uniform carrier-waves1 and then of loading on them waves of speech4 ,of course1 the latter are not sound-waves1 because they are not waves of air1 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 same way that it is affected by the electric waves which are sent over telephone wires4 ,the telephone engineers found that the audion could be used to regulate the carrier-waves and also to superpose the speech-waves upon them1 and at the receiving-station the audion was used to pick up these waves1 no matter how feeble they might be1 and amplify them so that they could be heard in a telephone receiver4 ,,talking ,,without ,,wires ,attempts at long-distance talking without wires were made from ,montauk ,point1 on the tip of ,long ,island1 to ,wilmington1 ,delaware1 and they were successful4 ,this was in #aiae4 ,the apparatus was still further improved and then the experiment was tried of talking from the big ,arlington station near ,washington to ,darien1 on the ,isthmus of ,panama4 ,this was a distance of twenty-one hundred miles1 and speech was actually transmitted through space over that great distance4 ,that having proved successful1 the next attempt was to talk from ,arlington to ,mare ,island and ,san ,diego1 on the ,pacific ,coast1 a distance of over twenty-five hundred miles4 ,this proved a success1 too1 and it was found possible even to talk as far as ,honolulu4 ,illustration3 7,c7 ,g4 ,v4 ,buck ,radio ,head-gear of an ,airman ,illustration3 7,c7 ,g4 ,v4 ,buck ,carrying on ,conversation by ,radio with an ,aviator ,miles ,away ,the engineers now felt confident that they could talk across the ,atlantic to ,europe1 and so in ,october of #aiae arrangements were made to conduct experiments between ,arlington and the ,eiffel ,tower in ,paris4 ,although the war was at its height1 and the ,french were straining every effort to hold back the ,germans at that time1 and although there were constant demands for the use of radiotelegraphy1 the ,french showed such an appreciation of science that they were willing to lend their aid to these experiments4 ,the ,eiffel ,tower could be used only for short periods of time1 and there was much interference from other high-powered stations4 ,nevertheless1 the experiment proved perfectly successful1 and conversation was carried on between our capital and that of ,france1 a distance of thirty-six hundred miles4 ,at the same time1 an operator in ,honolulu1 forty-five hundred miles away1 heard the messages1 and so the voice at ,arlington carried virtually one third of the way around the globe4 ,after that achievement1 there was a lull in the wireless-telephone experiments because of the war4 ,but there soon came an opportunity to make very practical use of all the experimental work4 ,as soon as there seemed to be a possibility that we might be drawn into the war1 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 stations4 ,of course all vessels are equipped with wireless-telegraph apparatus1 but there is a decided advantage in having the captain of one ship talk directly with the captain of another ship1 or take his orders from headquarters1 with an ordinary telephone receiver and transmitter4 ,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 miles4 ,the apparatus was so improved that nine conversations could be carried on at the same time without any interference of one by the others4 ,illustration3 7,c7 ,american ,institute of ,electrical ,engineers ,long ,distance ,radio ,apparatus at the ,arlington 7,va47 ,station1 with enlarged view of the ,type of ,vacuum ,tube used ,when it became certain that we should have to enter the war1 there came a call for radiotelephone apparatus for submarine-chasers1 and work was started on small1 compact outfits for these little vessels4 ,,radiotelephones ,,for ,,airplanes ,then there was a demand for radiotelephone apparatus to be used on airplanes4 ,this was a much more complicated matter and called for a great deal of study4 ,the way in which problem after problem arose and was solved makes an exceedingly interesting narrative4 ,it seemed almost absurd to think that a delicate radiotelegraph apparatus could be made to work in the terrific noise and jarring of an airplane4 ,the first task was to make the apparatus noise-proof4 ,a special sound-proof room was constructed in which a noise was produced exactly imitating that of the engine exhaust of an airplane engine4 ,in this room1 various helmets were tried in order to see whether they would be proof against the noise1 and finally a very suitable helmet was designed1 in which the telephone receiver and transmitter were installed4 ,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 miles4 ,the antenna of the airplane consisted of a wire with a weight on the lower end1 which hung down about one hundred yards from the body of the machine4 ,but a trailing antenna was a nuisance in airplane manoeuvers1 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 airplane4 ,it had to fit very tightly around the ears and the mouth1 and as the airplane went to high altitudes where the air-pressure was much lower than at the ground level1 painful pressures were produced in the ears which were most annoying4 ,aside from that1 in actual warfare airplanes have to operate at extreme heights1 where the air is so rare that oxygen must be supplied to the aviators1 and it was difficult to provide this supply of oxygen with the radio helmet tightly strapped to the head of the operator4 ,but after considerable experiment1 this difficulty was overcome and also that of the varying pressures on the ears4 ,another great difficulty was to obtain a steady supply of power on the airplane to operate the transmitting-apparatus4 ,it has been the practice to supply current on airplanes for wireless-telegraph apparatus by means of a small electric generator which is revolved by a little propeller4 ,the propeller in turn is revolved by the rush of air as it is carried along by the plane4 ,but the speed of the airplane varies considerably4 ,at times1 it may be traveling at only forty miles per hour1 and at other times as high as one hundred and sixty miles per hour1 so that the little generator is subjected to great variations of speed and consequent variations of voltage4 ,this made it impossible to produce the steady oscillations that are required in wireless telephony4 ,after considerable experiment1 a generator was produced with two windings1 one of which operated through a vacuum tube1 somewhat like an audion1 and to resist the increase of voltage produced by the other winding4 ,then another trouble developed4 ,the sparks produced by the magneto in the airplane motor set up electro-magnetic waves which seriously affected the receiving-instrument4 ,there was no way of getting rid of the magneto1 but the wires leading from it to the engine were incased in metal tubes which were grounded at frequent intervals1 and in that way the trouble was overcome to a large extent4 ,the magnetos themselves were also incased in such a way that electro-magnetic waves would not be radiated from them4 ,instead of using trailing wires which were liable to become entangled in the propeller1 the antenna was extended from the upper plane to the tail of the machine1 and later it was found that by using two short trailing antenn one from each tip of the wings1 the very best results could be obtained4 ,still another development was to embed the antenna wires in the wings of the plane4 ,it was considered necessary1 if the apparatus was to be practicable1 to be able to use it over a distance of two thousand yards1 but in experiments conducted in ,october1 #aiag1 a couple of airplanes were able to talk to each other when twenty-three miles apart1 and conversations were carried on with the ground from a distance of forty-five miles4 ,the conditions under which these distances were attained were unusual1 and a distance of three miles was accepted as a standard for communication between airplanes4 ,the apparatus weighed only fifty-eight pounds and it was connected with both the pilot and the observer so that they could carry on conversations with each other and could both hear the conversation with other airplanes or the ground4 ,as a matter of fact1 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 favorable1 and they can receive messages from the ground over almost any distance4 ,a similar apparatus was constructed for submarine-chasers with a standard range of conversation of over five miles4 ,apparatus was manufactured in large quantities in this country and all our submarine-chasers were equipped with it1 as well as a great many of our airplanes and seaplanes1 and we furnished radio-apparatus sets to our allies which proved of immense value in the war4 ,this was particularly so in the case of submarine detection1 when it was possible for a seaplane or a balloon to report its findings at once to submarine-chasers and destroyers1 and to guide them in pursuit of submarines4 ,the improved audion holds out a wonderful future for radiotelephony4 ,for receiving1 at least1 no elaborate arial will be needed1 and with a small loop of wire1 an audion or two1 and simple tuning-apparatus any one can hear the radio gossip of the whole world4 ,,telegraphing ,,twelve ,,hundred ,,words ,,per ,,minute ,some remarkable advances were made in telegraphy also4 ,during the war and since1 messages have been sent direct from ,washington to all parts of the world4 ,in the telegraph room operators are connected by wire with the different radio stations along the coast and they can control the radio transmitters1 sending their messages without any repeating at the radio stations4 ,long messages are copied off on a machine something like a type-writer1 which1 however1 does not make type impressions1 but cuts perforations in a long sheet of paper4 ,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 minute4 ,at the receiving-station1 the message is received photographically on a strip of paper4 ,the receiving-instrument has a fine quartz thread in it1 which carries a tiny mirror4 ,a beam of light is reflected from the mirror upon the strip of sensitized paper4 ,the radio waves twist the quartz thread ever so slightly1 which makes the beam of light play back and forth1 but of course the motion is greatly magnified4 ,in this way a perfect record is made of the message in dots and dashes1 which are translated into the corresponding letters of the alphabet4 ,,detecting ,,radio ,,spies ,there is another radio invention which we contributed during the war1 that proved of utmost service in thwarting ,german spies and which is going to prove equally valuable in time of peace4 ,although a war invention1 its peacetime service will be to save lives4 ,it is a very simple matter to rig up a wireless-telegraph system that will send messages to a considerable distance1 and simpler still to rig up a receiving-set4 ,european governments have always discouraged amateur radiotelegraphy1 but in this country restrictions used to be so slight that almost any one could set up and use a radio set1 both for receiving and for transmitting4 ,when we entered the war we were glad that amateurs had been encouraged to play with wireless1 because we had hundreds of good radio operators ready to work the sets which the army and the navy needed4 ,but this was a disadvantage1 too4 ,many operators were either ,germans or pro-,germans and were only too willing to use their radio experience in the interest of our enemies4 ,it was a simple matter to obtain the necessary apparatus1 because there was plenty of it to be had everywhere4 ,they could send orders to fellow workers and receive messages from them1 or they could listen to dispatches sent out by the government and glean information of great military and naval importance4 ,the apparatus could easily be concealed3 a wire hung inside a chimney1 a water-pipe1 even a brass bedstead could be used for the receiving-arial4 ,it was highly important that these concealed stations be located1 but how were they to be discovered8 ,,the ,,wireless ,,compass ,this problem was solved very nicely4 ,the audion had made it possible to receive radio signals on a very small arial4 ,in place of the ordinary stationary arial a frame five feet square was set up so that it could be turned to any point of the compass4 ,a few turns of copper-bronze wire were wound round it4 ,this was called the wireless compass4 ,it was set up on the roof of the radio station and concealed within a cupola4 ,the shaft on which it was mounted extended down into the operating-room and carried a wheel by which it could be turned4 ,on the shaft was a circular band of aluminum engraved with the #cfj degrees of the circle1 and a couple of fixed pointers indicated true north and south4 ,now when a signal was received by the arial1 if it struck the frame edgewise the radio waves would reach one side before they would the other4 ,taking a single wave1 as shown by the drawing1 ,fig4 #aa1 we see that while the crest of the wave is sweeping over one side of the frame1 the trough of the wave is passing the other side4 ,two currents are set up in the radio compass1 one in the wires at the near side of the compass1 and another in the wires at the far side of the compass4 ,as these currents are of the same direction1 they oppose each other and tend to kill each other off1 but one of the currents is stronger than the other because the crest of the wave is sweeping over that side1 while the trough of the wave is passing over the other4 ,the length of the wave may be anything1 but always one side will be stronger than the other1 and a current equal in strength to the difference between the two currents goes down into the operating-room and affects the receiver4 ,now when the compass is set at right angles to the oncoming wave1 both sides are affected simultaneously and with the same strength1 so that they kill each other off completely1 and no current goes down to the receiver4 ,thus the strength of the signal received can be varied from a maximum1 when the compass is parallel to the oncoming waves1 to zero1 when it is at right angles to them4 ,illustration3 ,courtesy of the ,scientific ,american ,,fig4 #aa4 ,the radio compass turned parallel to an oncoming electro-magnetic wave ,to find out where a sending-station is1 the compass is turned until the loudest sound is heard in the receiver and then the compass dial shows from what direction the signals are coming4 ,at the same time1 another line on the signals will be found by a second station with another compass4 ,these directions are traced on a map2 and where they meet1 the sending-station must be located4 ,with this apparatus it was possible to locate the direction of the station within a degree4 ,after the station had been located as closely as possible in this way1 a motor-truck was sent out in which there was a concealed radio compass4 ,the truck would patrol the region located by the fixed compasses1 and with it the position of the concealed station could be determined with perfect accuracy4 ,the building would be raided and its occupants jailed and the radio equipment confiscated4 ,even receiving-sets were discovered with the portable compass1 but to find them was a far more difficult task4 ,for the receiving of messages from distant points without a conspicuous arial 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 compass4 ,,piloting ,,ships ,,into ,,port ,and now for the peace-time application of all this4 ,if the compass could be used to find those who tried to hide1 why could it not also be used to find those who wished to be found8 ,every now and then a ship runs upon the rocks because it has lost its bearings in the fog4 ,but there will be no excuse for such accidents now4 ,a number of radio-compass stations have been located around the entrance and approach to ,new ,york ,harbor4 ,similar stations have been1 or soon will be1 established at other ports4 ,as soon as a ship arrives within fifty or a hundred miles of port she is required to call for her bearings4 ,the operator of the control station instructs the ship to send her call letters for thirty seconds1 and at the same time notifies each compass station to get a bearing on the ship4 ,this each does1 reporting back to the control station4 ,the bearings are plotted on a chart and inside of two minutes from the time the ship gives her call letters1 her bearing is flashed to her by radio from the control station4 ,illustration3 ,courtesy of the ,scientific ,american ,,fig4 #ab4 ,approaches to ,new ,york ,harbor showing location of three radio compass stations and how position of a ship sending signals from ,a may be determined ,the chart on which the plotting is done is covered with a sheet of glass4 ,holes are pierced through the glass at the location of each compass station4 ,see ,fig4 #ab4 ,on the chart1 around each station1 there is a dial marked off in the #cfj degrees of the circle4 ,a thread passes through the chart and the hole in the glass at each station4 ,these threads are attached to weights under the chart4 ,when a compass station reports a bearing1 the thread of that station is pulled out and extended across the corresponding degree on the dial4 ,the same is done as each station reports and where the threads cross1 the ship must be located4 ,not only can the direction-finder be used to pilot a ship into a harbor1 but it will also serve to prevent collisions at sea1 because a ship equipped with a radio compass can tell whether another ship is coming directly toward her4 ,and so as one of the happy outcomes of the dreadful war1 we have an apparatus that will rob sea-fogs of their terrors to navigation4 ,,chapter ,,xi ,,warriors ,,of ,,the ,,paint-,,brush ,when the great ,european war broke out1 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 world4 ,but who ever imagined that geologists would be called in to choose the best places for boring mines under the enemy3 that meteorologists would be summoned to forecast the weather and determine the best time to launch an offensive2 that psycologists would be employed to pick out the men with the best nerves to man the machine-guns and pilot the battle-planes8 ,certainly no one guessed that artists and the makers of stage scenery would play an important part in the conflict4 ,but the airplane filled the sky with eyes that at first made it impossible for an army to conceal its plans from the enemy4 ,and then there were eyes that swam in the sea--cruel eyes that belonged to deadly submarine monsters1 eyes that could see without being seen1 eyes that could pop up out of the water at unexpected moments1 eyes that directed deadly missiles at inoffensive merchantmen4 ,they were cowardly eyes1 too1 which gave the ship no opportunity to strike back at the unseen enemy4 ,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 eyes4 ,it was a game of hide-and-seek in which the pursuer and not the pursued was hidden4 ,something had to be done to conceal the pursued as well1 but in the open sea there was nothing to hide behind4 ,,hiding ,,in ,,plain ,,sight ,there is such a thing as hiding in plain sight4 ,you can look right at a tree-toad without seeing him1 because his colors blend perfectly with the tree to which he is clinging4 ,you can watch a green leaf curl up and shrivel without realizing that the curled edge is really a caterpillar1 cunningly veined and colored to look just like a dying leaf2 and out in the woods a speckled bird or striped animal will escape observation just because it matches the spotted light that comes through the underbrush4 ,nature is constantly protecting its helpless animals with colored coats that blend with the surroundings4 ,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 distance4 ,actually the paint made them more conspicuous2 but1 then1 concealment did not count for very much before the present war4 ,it was the eyes of the submarines that brought a hurry call for the artists1 and up to them was put the problem of hiding ships in plain sight4 ,a new name was coined for these warriors of the paint-brush3 camoufleurs they were called1 and their work was known as camouflage4 ,,matching ,,the ,,sky ,of course1 no paint will make a ship absolutely invisible at a short distance1 but a large vessel may be made to disappear completely from view at a distance of six or seven miles if it is properly painted4 ,to be invisible1 a ship must reflect as much light and the same shade of light as do its surroundings4 ,if it is seen against the background of the sea1 it must be of a bluish or a greenish tint1 but a submarine lies so low in the water that any object seen at a distance is silhouetted against the sky1 and so the ship must have a coat of paint that will reflect the same colors as does the sky4 ,now1 the sky may be of almost any color of the rainbow1 depending upon the position of the sun and the amount of vapor or dust in the air4 ,fortunately in the ,north ,sea and the waters about the ,british ,isles1 where most of the submarine attacks took place1 the weather is hazy most of the time1 and the ship had to be painted of such a color that it would reflect the same light as that reflected by a hazy sky4 ,with a background of haze and more or less haze between the ship and the periscope of the ,u-boat1 it was not a very difficult matter to paint a ship so that it would be invisible six or seven miles away4 ,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 ,mediterranean4 ,illustration3 7,c7 ,international ,film ,a ,giant ,gun ,concealed ,among ,trees ,behind the ,french ,lines ,in this way1 the artists made it possible for ships to sail in safety much nearer the pursuer who was trying to find them1 and by just so much they reduced his powers of destruction4 ,but still the odds were too heavy against the merchantman4 ,something must be done for him when he found himself within the seven-mile danger-zone4 ,here again the artists came to the rescue4 ,illustration3 7,c7 ,committee on ,public ,information ,observing the ,enemy from a ,papier-,mch ,replica of a ,dead ,horse ,before merchant ships were armed1 a submarine would not waste a torpedo on them1 but would pound them into submission with shell4 ,even after ships were provided with guns1 submarines mounted heavier guns and unless a ship was speedy enough to show a clean pair of heels1 the pursuing ,u-boat would stand off out of range of the ship's guns and pour a deadly fire into it4 ,but the ships1 too1 mounted larger guns and the submarines had to fall back upon their torpedoes4 ,,getting ,,the ,,range ,,for ,,the ,,torpedo ,in order to fire its torpedo with any certainty1 the ,u-boat had to get within a thousand yards of its victim4 ,a torpedo travels at from thirty to forty miles per hour4 ,it takes time for it to reach its target and a target which is moving at1 say1 fifteen knots1 will travel five hundred yards while a thirty-knot torpedo is making one hundred yards4 ,and so before the ,u-boat commander could discharge his torpedo1 he had to know how fast the ship was traveling and how far away it was from him4 ,he could not come to the surface and make deliberate observations1 but had to stay under cover1 not daring even to keep his eye out of water1 for fear that the long wake of foam trailing behind the periscope would give him away4 ,all he could do1 then1 was to throw his periscope up for a momentary glimpse and make his calculations very quickly2 then he could move to the position he figured that he should occupy and shoot up his periscope for another glimpse to check up his calculations4 ,on the glass of this periscope1 there were a number of graduations running vertically and horizontally4 ,if he knew his victim and happened to know the height of its smoke-stacks or the length of the boat1 he noted how many graduations they covered1 and then by a set formula he could tell how far he was from the boat4 ,at the same time he had to work out its rate of travel and note carefully the course it was holding before he could figure where his torpedo must be aimed4 ,there was always more or less uncertainty about such observations1 because they had to be taken hastily1 and the camoufleurs were not slow to take advantage of this weakness4 ,they increased the enemy's confusion by painting high bow-waves which made the ship look as if it were traveling at high speed4 ,they painted the bow to look like the stern1 and the stern to look like the bow1 and the stacks were painted so that they appeared to slant in the opposite direction1 so that it would look as if the vessel were headed the other way4 ,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 about1 and so destroyers were painted on the sides of ships as scarecrows to frighten off the enemy4 ,,making ,,straight ,,lines ,,look ,,crooked ,we say that seeing is believing1 but it is not very hard to deceive the eye4 ,the lines in ,fig4 #ac look absolutely parallel1 and they are2 but cross-hatch the spaces between them1 with the hatching reversed in alternate spaces1 as in ,fig4 #ad1 and they no longer look straight4 ,take the letters on the left1 ,fig4 #ae4 ,they look all higgledy-piggledy1 but they are really straight and parallel1 as one can prove by laying a straight-edge against them1 or by drawing a straight line through each letter1 as shown at the right1 ,fig4 #af4 ,such illusions were used on ships4 ,stripes were painted on the hull that tapered slightly1 from bow to stern1 so that the vessel appeared to be headed off at an angle1 when it was really broadside to the watcher at the other end of the periscope4 ,illustration3 ,,fig4 #ac4 ,parallel lines that look straight ,illustration3 ,,fig4 #ad4 ,parallel lines that do not look straight ,illustration3 ,courtesy of the ,submarine ,defense ,association ,,fig4 #ae4 ,letters that look all higgledy-piggledy1 but are really straight ,there are color illusions1 too1 that were tried4 ,if you draw a red chalk-mark and a blue one on a perfectly clean blackboard1 the red line will seem to stand out and the blue one to sink into the black surface of the board1 because your eye has to focus differently for the two colors1 and a very dazzling effect can be had with alternating squares of blue and red4 ,other colors give even more dazzling effects1 and some of them1 when viewed at a distance1 will blend into the very shade of gray that will make a boat invisible at six miles4 ,when ,u-boat commanders took observations on a ship painted with a dazzle camouflage1 they saw a shimmering image which it was hard for them to measure on the fine graduations of their periscopes4 ,some ships were painted with heavy blotches of black and white1 and the enemy making a hasty observation would be apt to focus his attention on the dark masses and overlook the white parts4 ,so he was likely to make a mistake in estimating the height of the smoke-stack or in measuring the apparent length of a vessel4 ,a ,,joke ,,on ,,the ,,photographer ,early in the submarine campaign one of our boats was given a coat of camouflage1 and when the vessel sailed from its pier in the ,north ,river1 ,new ,york1 the owners sent a photographer two or three piers down the river to photograph the ship as she went by4 ,he took the picture1 but when the negative was developed1 much to his astonishment he found that the boat was not all on the plate4 ,in the finder of his camera1 he had mistaken a heavy band of black paint for the stern of the ship1 quite overlooking the real stern1 which was painted a grayish white4 ,the artist had fooled the photographer and at a distance of not more than two or three hundred yards6 ,,seeing ,,beyond ,,the ,,horizon ,the periscope of a submarine that is running awash can be raised about fifteen feet above the water1 which means that the horizon as viewed from that elevation is about six miles away1 and if you draw a circle with a six-mile radius on the map of the ,atlantic1 you will find that it is a mere speck in the ocean2 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 water4 ,the smoke-stacks of some vessels rise a hundred feet above the water-line1 and the masts reach up to much greater altitudes4 ,aside from this1 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 away4 ,when this was realized1 efforts were made to cut down the superstructure of a ship as much as possible4 ,some vessels had their stacks cut down almost to the deck-line1 and air-pumps were installed to furnish the draft necessary to keep their furnaces going4 ,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 notice1 to carry the arials of the wireless system4 ,over the ship from stem to stern was stretched1 a cable1 familiarly known as a clothes-line1 upon which were laid strips of canvas that completely covered the superstructure of the ship4 ,these boats lay so low that they could not be seen at any great distance1 and it was difficult for the ,u-boats to find them4 ,they were slow boats2 too slow to run away from a modern submarine1 but because of their lowly structure1 they managed to elude the ,german ,u-boats4 ,when they were seen1 the ,u-boat commanders were afraid of them4 ,they were suspicious of anything that looked out of the ordinary1 and preferred to let the clothes-line ships go4 ,illustration3 7,c7 ,committee on ,public ,information ,from ,western ,newspaper ,union ,camouflaged ,headquarters of the ,american #bfth ,division in ,france ,,the ,,british ,,mystery ,,ships ,the ,germans had some very unhealthy experiences with the ,q-boats or mystery ships of the ,british4 ,these were vessels rigged up much like ordinary tramp steamers1 but they were loaded with wood1 so that they would not sink1 and their hatches were arranged to fall open at the touch of a button1 exposing powerful guns4 ,they also were equipped with torpedo-tubes1 so that they could give the ,u-boat a dose of its own medicine4 ,these ships would travel along the lanes frequented by submarines1 and invite attack4 ,they would limp along as if they had been injured by a storm or a ,u-boat attack1 and looked like easy prey4 ,when a submarine did attack them1 they would send out frantic calls for help1 and they had so-called panic parties which took to the boats4 ,meantime1 a picked crew remained aboard1 carefully concealed from view1 and the captain kept his eye upon the enemy through a periscope disguised as a small ventilator1 waiting for the ,u-boat to come within range of certain destruction4 ,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 ship4 ,at the proper moment1 up would go the white ensign--the ,british man-of-war flag--the batteries would be unmasked1 and a hail of shell would break loose over the ,hun4 ,many a ,german submarine was accounted for by such traps4 ,illustration3 7,c7 ,underwood ,underwood ,a ,camouflaged ,ship in the ,hudson ,river on ,victory ,day ,submarines themselves used all sorts of camouflage4 ,they were frequently equipped with sails which they would raise to disguise themselves as peaceful sloops1 and in this way they were able to steal up on a victim without discovery4 ,sometimes they would seize a ship and hide behind it in order to get near their prey4 ,,camouflage ,,on ,,land ,but the call for the wielders of the paintbrush came not only from the sea4 ,their services were needed fully as much on land1 and the making of land camouflage was far more interesting because it was more varied and more successful4 ,besides1 it called for more than mere paint2 all sorts of tricks with canvas1 grass1 and branches were used4 ,of course1 the soldiers were garbed in dust-colored clothing and shiny armor was discarded4 ,the helmets they wore were covered with a material that cast no gleam of light4 ,in every respect1 they tried to make themselves of the same shade as their surroundings4 ,like the ,indians1 they painted their faces4 ,this was done when they made their raids at night4 ,they painted their faces black so that they would not show the faintest reflection of light4 ,a ,,paper ,,horse ,the most interesting camouflage work was done for the benefit of snipers or for observers at listening-posts close to the enemy trenches4 ,it was very important to spy on the enemy and discover his plans1 and so men were sent out as near his lines as possible1 to listen to the conversation and to note any signs of unusual activity which would be likely to precede a raid4 ,these men were supplied with telephone wires which they dragged over ,no ,man's ,land1 and by which they could communicate their discoveries to headquarters4 ,some very ingenious listening-posts were established4 ,in one case a papier-mch duplicate of a dead horse was made1 which was an exact facsimile of an animal that had been shot and lay between the two lines4 ,one night1 the carcass of the horse was removed and the papier-mch replica took its place4 ,in the latter a man was stationed with telephone connection back to his own lines4 ,here he had an excellent chance to watch the enemy4 ,on another occasion a standing tree1 whose branches had been shot away1 was carefully photographed and an exact copy of it made1 but with a chamber inside in which an observer could be concealed4 ,one night while the noise of the workmen was drowned by heavy cannonading1 this tree was removed and its facsimile was set up instead1 and it remained for many a day before the enemy discovered that it was a fake tree-trunk4 ,it provided a tall observation post from which an observer could direct the fire of his own artillery4 ,,fooling ,,the ,,watchers ,,in ,,the ,,sky ,in the early stages of the war1 it seemed impossible to hide anything from the ,germans4 ,they had eyes everywhere and were able to anticipate everything the ,allies did4 ,but the spies that infested the sky were the worst handicap4 ,even when the ,allies gained control of the air1 the control was more or less nominal because every now and then an enemy observer would slip over or under the patrolling aroplanes and make photographs of the ,allies' lines4 ,the photographs were carefully compared with others previously taken1 that the slightest change in detail might be discovered4 ,airplane observers not only would be ready to drop bombs on any suspicious object or upon masses of troops moving along the roads1 but would telephone back to their artillery to direct its fire upon these targets4 ,of course1 the enemy knew where the roads were located and a careful watch was kept of them4 ,the ,french did not try to hide the roads1 but they concealed the traffic on the roads by hanging rows of curtains over them4 ,as these curtains hung vertically and were spaced apart1 one would suppose that they would furnish little concealment1 but they prevented an observer in an aroplane from looking down the length of a road4 ,all the road he could see was that which lay directly under his machine1 because there he could look between the curtains2 if he looked obliquely at the road1 the curtains would appear to overlap one another and would conceal operations going on under them4 ,in one case1 the ,germans completely covered a sunken road with canvas painted to represent a road surface4 ,under this canvas canopy1 troops were moved to an important strategic point without the slightest indication of such a movement4 ,,hiding ,,big ,,guns ,nature's tricks of camouflage were freely used in the hiding of the implements of war on land4 ,our big guns were concealed by being painted with leopard spots and tiger stripes1 the color and nature of the camouflage depending upon the station they were to occupy4 ,in many cases1 they were covered with branches of trees or with rope netting overspread with leaves4 ,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 gun4 ,,roads ,,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 arial observers4 ,even foot-paths leading to it had to be concealed4 ,plans were carefully made to cover up all traces of the work before the work was begun4 ,where it was impossible to conceal the paths1 they were purposely made to lead well beyond the point where the emplacement was building1 and1 still further to deceive the enemy1 a show of work was sometimes undertaken at the end of the path4 ,wherever the sod had to be upturned1 it was covered over with green canvas4 ,the earth that was removed 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 apparent to an observer in an aroplane4 ,if no shell-hole were handy1 the excavated material had to be hauled for miles before a safe dumping-ground could be found4 ,as far as possible everything was sunk below the earth level4 ,big pits were dug in which the mortars were placed1 or if a shell-hole were empty1 this was used instead4 ,,shadowless ,,buildings ,any projection above the ground was apt to cast a shadow which would show up on the observer's photographs4 ,this was a difficulty that was experienced in building the hangars for airplanes4 ,the roofs of these sheds were painted green so as to match the sod around them1 but as they projected above their surroundings1 they cast shadows which made them clearly evident to the enemy4 ,this was overcome by the building of shadowless hangars2 that is1 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 low4 ,in some cases1 aroplanes were housed in underground hangars1 the approach to which was concealed by a canvas covering4 ,as for the machines themselves1 they scorned the use of camouflage4 ,paint was little protection to them4 ,some attempt was made to use transparent wings of cellon1 a material similar to celluloid1 but this did not prove a success4 ,,the ,,photographic ,,eye ,although camoufleurs made perfect imitations of natural objects and surroundings1 they were greatly concerned to find that the flying observers could see through their disguises4 ,to the naked eye the landscape would not show the slightest trace of any suspicions object1 but by the use of a color-screen to cut out certain rays of light1 a big difference would be shown between the real colors of nature and the artist's copies of them4 ,for instance1 if a roof painted to look like green grass were viewed through a red color-screen1 it would look brown2 while the real grass1 which apparently was of exactly the same shade as the roof1 would look red4 ,it had not been realized by the artists who had never studied the composition of light1 that there is a great deal of red in the green light reflected by grass1 and that if they were to duplicate this shade of green1 they must put a certain amount of red paint in their imitation grass roofs4 ,air scouts did not depend upon their eyes alone1 but used cameras so that they could study their photographs at their leisure and by fitting the cameras with different color-screens1 they could analyze the camouflage and undo the patient work of the artist4 ,a ,,call ,,for ,,the ,,physicist ,to meet this situation1 another man was summoned to help--the physicist1 who looks upon color merely as waves of ether2 who can pick a ray of light to pieces just as a chemist can analyze a lump of sugar4 ,under his expert guidance1 colors of nature were imitated so that they would defy detection4 ,aside from this1 the physicist helped to solve the tricks of the enemy's camoufleurs4 ,but the physicist had barely rolled up his sleeves and got into the fray when the armistice was signed which put an end to the shams as well as to the realities of the great war4 ,while the work of camouflage was not completed1 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 light1 and although their trade was a trade of deception and shams1 there was no sham about the service they rendered4 ,,making ,,ships ,,visible ,while in war safety lies in invisibility1 in peace the reverse is true4 ,now that the war is over1 it may seem that the work of the camoufleurs can find no useful application2 but it was impossible to learn how to make objects invisible without also learning how to make them conspicuously visible4 ,as a consequence1 we know now how to paint a ship so that it will show up more clearly in foggy weather1 thereby reducing the danger of collision4 ,we know1 too1 how to paint light-ships1 buoys1 etc41 so that they will be much more conspicuous and better guides to mariners1 and how to color railroad signals and road signs so that they will be more easily seen by locomotive engineers and automobile drivers4 ,,chapter ,,xii ,,submarines ,it was an ,american invention that dragged ,america into the war--an ,american invention in the hands of barbarians and put to unspeakably barbarous use4 ,after seeing how the ,huns used the submarine we are not so sure that we can take much pride in its invention4 ,but if any blame attaches to us for developing the submarine1 we made amends by the way in which we fought the ,german ,u-boat and put an end to ,german frightfulness on the sea4 ,of course1 the credit for ,germany's defeat is not for a moment claimed by ,americans alone1 but it must be admitted that we played an important part in overcoming the menace of the ,u-boat4 ,there is no question that the submarine was an ,american invention4 ,to be sure1 we can look into ancient books and find suggestions for navigating under the surface of the sea1 but the first man who did actually build a successful submarine was ,david ,bushnell1 back in the ,revolutionary ,war4 ,after him came ,robert ,fulton1 who carried the invention farther4 ,he built and operated a submarine for the ,french ,government1 and1 in more recent years1 the submarine became a practical vessel of war in the hands of ,john ,p4 ,holland and ,simon ,lake1 both ,americans4 ,however1 we are not interested1 just now1 in the history of the submarine1 but rather in the development of this craft during the recent war4 ,with ,great ,britain as an enemy1 ,germany knew that she was hopelessly outclassed on the sea2 but while ,britannia ruled the waves1 she did not rule the depths of the sea1 and so ,germany decided to claim this realm for her own4 ,little attention did she pay to surface vessels4 ,except in the ,dogger ,bank engagement and the ,battle of ,jutland1 the ,german first-class vessels did not venture out upon the open sea1 and even the lighter craft merely made occasional raids under cover of fog or darkness1 only to cut and run as soon as the ,british vessels appeared4 ,the submarine boat1 or unterseeboot as the ,germans called it1 was virtually the only boat that dared go out into the high seas2 consequently1 the ,germans specialized upon that type of craft and under their close attention it grew into a highly perfected war-vessel4 ,but the ,germans were not the only ones to develop the submarine1 as we shall see4 ,,construction ,,of ,,the ,u-,,boats ,when the great war broke out1 the ,german ,u-boat was a comparatively small craft1 less than #aej feet long1 with its main hull only #ab feet in diameter4 ,it could make a speed of #ab knots on the surface and only #i when submerged4 ,but as the war progressed1 it grew larger and larger1 until it attained a length of over #cjj feet and its speed was increased to #ab knots when submerged and #ah knots on the surface4 ,figs4 #af to #ah show the construction of one of the early ,u-boats4 ,the later boats were built after the same general plan1 but on a bigger scale4 ,illustration3 ,courtesy of the ,scientific ,american ,,fig4 #af4 ,sectional view of one of the earlier ,german ,u-,boats ,illustration3 ,courtesy of the ,scientific ,american ,,fig4 #ag4 ,sectional plan view of a ,german ,u-,boat of the type used at the beginning of the war ,it is not always safe to judge a thing by its name2 to do so is apt to lead to sad mistakes4 ,one would naturally suppose1 from its name1 that a submarine is a boat that lives under water1 like a fish4 ,but it is not a fish2 it is an air-breathing animal that prefers to stay on the surface1 only occasionally diving under to hide from danger or to steal upon its prey4 ,during the war1 the ,german ,u-boats did not average three hours per day under the surface6 ,because they were intended to run on the surface they had to be built in the form of a surface vessel1 so as to throw off the waves and keep from rolling and pitching too much in a seaway4 ,but they also had to be built to withstand the crushing weight of deep water1 and as a cylinder is much stronger than a structure of ordinary boat shape1 the main hull was made circular in section and of heavy plating1 strongly framed1 while around this was an outer hull of boat shape1 as shown in ,fig4 #ah4 ,,putting ,,holes ,,in ,a ,,tank ,,to ,,keep ,,it ,,full ,the space between the inner and outer hulls was used for water ballast and for reservoirs of oil to drive the engines2 and1 strange as it may seem1 the oil-tanks were always kept full by means of holes in the bottom of them4 ,as the oil was consumed by the engines1 water would flow into the reservoir to take its place1 and the oil1 being lighter than water1 would float on top4 ,the false hull was of light metal1 because as it was open to the sea1 the pressure on the inside was always the same as that on the outside4 ,the reservoirs of oil and the water-ballast tanks protected the inner hull of the vessel from accidental damage and from hostile shell and bombs4 ,there were water-ballast tanks inside the inner hull as well1 as shown in the cross-sectional view1 ,fig4 #ah4 ,the water in the ballast-tanks was blown out by compressed 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 tanks4 ,illustration3 ,courtesy of the ,scientific ,american ,,fig4 #ah4 ,transverse section through conning-tower1 showing the interior 7circular7 pressure-resisting hull and the lighter exterior hull1 which is open to the sea ,a heavy lead keel was attached to the bottom of the boat1 to keep it from rolling too much4 ,in case of accident1 if there were no other way of bringing the boat to the surface1 this keel could be cast loose4 ,at the forward end1 where the torpedo-tubes were located1 there was a torpedo-trimming tank4 ,torpedoes are heavy missiles and every time one was discharged the boat was lightened1 and the balance of the submarine was upset4 ,to make up for the loss of weight1 water had to be let into the torpedo-trimming tank4 ,a submarine cannot float under-water without swimming2 in other words1 it must keep its propellers going to avoid either sinking to the bottom of the sea or bobbing up to the surface4 ,to be sure1 it can make itself heavier or lighter by letting water into or blowing water out of its ballast-tanks1 but it is impossible to regulate the water ballast so delicately that the submarine will float submerged2 and should the boat sink to a depth of two hundred feet or so1 the weight of water above it would be sufficient to crush the hull1 so it is a case of sink or swim4 ,usually enough ballast is taken on to make the submarine only a little lighter than the water it displaces2 and then to remain under1 the vessel must keep moving1 with its horizontal rudders tilted to hold it down4 ,the horizontal rudders or hydroplanes of the ,u-boat are shown in ,fig4 #ag1 both at the bow and at the stern4 ,the main hull of the vessel was literally filled with machinery4 ,in the after part of the boat were the ,diesel oil-engines with which the ,u-boat was propelled when on the surface4 ,there were two engines1 each driving a propeller-shaft4 ,it was impossible to use the engines when the vessel was submerged1 not because of the gases they produced--these could easily have been carried out of the boat--but because every internal-combustion engine consumes enormous quantities of air4 ,in a few minutes the engines would devour all the air in the hull of the submarine and would then die of suffocation4 ,and so the engines were used only when the submarine was running awash or on the surface1 and then the air consumed by them would rush down the hatchway like a hurricane to supply their mighty lungs4 ,,engines ,,that ,,burn ,,heavy ,,oil ,the oil-engines were strictly a ,german invention4 ,in the earlier days of the submarine gasolene-engines were used1 but despite every precaution1 gasolene vapors occasionally would leak out of the reservoirs and accumulate in pockets or along the floors of the hull1 and it needed but a spark to produce an explosion that would blow up the submarine4 ,but ,rudolph ,diesel1 a ,german1 invented an engine which would burn heavy oils4 ,illustration3 7,c7 ,underwood ,underwood ,complex ,mass of ,wheels and ,dials inside a ,german ,submarine ,in the ,diesel engine there are no spark-plugs and no magneto3 the engine fires itself without electrical help4 ,air is let into the cylinder at ordinary atmospheric pressure1 or fifteen pounds per square inch4 ,but it is compressed by the upward stroke of the piston to about five hundred pounds per square inch4 ,when air is compressed it develops heat and the sudden high compression to over thirty times its normal pressure raises the temperature to something like #ajjj degrees ,fahrenheit4 ,just as this temperature is reached1 a jet of oil is blown into the cylinder by air under still higher pressure4 ,immediately the spray of oil bursts into flame and the hot gases of combustion drive the piston down4 ,because of the intense heat almost any oil1 from light gasolene to heavy1 almost tarlike oils1 can be used4 ,as heavy oils do not throw off any explosive vapors unless they are heated1 they make a very safe fuel for submarines4 ,illustration3 ,photograph by ,international ,film ,service ,surrendered ,german ,submarines1 showing the ,net ,cutters at the ,bow ,to drive the ,u-boat when no air was to be had for the engines1 electric motors were used4 ,there was one on each propeller-shaft and the shafts could be disconnected from the oil-engines when the motors were driving4 ,the motors got their power from storage batteries in the stern of the submarine and under the floors forward4 ,the motors when coupled to and driven by the engines generated current which was stored in the storage batteries4 ,the submarine could not run on indefinitely underwater4 ,when its batteries were exhausted it would have to come to the surface and run its engines to store up a fresh charge of electricity4 ,the electric motors gave the boat a speed of about nine knots4 ,in addition to the main engines and motors1 there was a mass of auxiliary machinery4 ,there were pumps for compressing air to blow the ballast-tanks and to discharge the torpedoes4 ,there was a special mechanism for operating the rudder and hydroplanes1 and all sorts of valves1 indicators1 speaking-tubes1 signal lines1 etc4 ,the tiny hull was simply crammed with mechanism of all kinds and particularly in the early boats there was little room for the accommodation of the officers and crew4 ,the officers' quarters were located amidships1 and forward there were the folding berths of the crews4 ,in the later boats more space was given the men4 ,the large ,u-boats carried a crew of forty and as the hazards of submarine warfare increased1 more attention had to be paid to the men4 ,,fat ,,men ,,not ,,wanted ,oddly enough1 small1 slender men were preferred for submarine duty1 not because of lack of space1 but because it was apt to be very cold in a submarine1 particularly in the winter-time4 ,the water cooled off the boat when the submarine was traveling submerged1 and the motors gave off little heat2 while when the vessel was running on the surface the rush of wind to supply the engines kept the thermometer low4 ,this meant that the men had to pile on much clothing to keep warm1 which made them very bulky4 ,the hatchway was none too large and a fat man1 were he bundled up with enough clothing to keep him warm1 would have a hard time squeezing through4 ,in the center of the vessel was the main hatchway1 leading up to the conning-tower1 which was large enough to hold from three to five men4 ,this was the navigating-room when the vessel was running submerged1 and above it was the navigating-bridge1 used when the submarine was on the surface4 ,in the conning-tower there was a gyroscopic compass2 a magnetic compass would not work at all inside the steel hull of the ,u-boat4 ,and here were the periscopes or eyes of the submarine1 rising from fifteen to twenty feet above the roof of the conning-tower4 ,there were usually two periscopes4 ,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 surface1 to give a longer range of vision4 ,,the ,,blindness ,,of ,,the ,,submarine ,now1 a submarine cannot see anything underwater4 ,the commander cannot even see the bow of his boat from the conning-tower1 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-gage4 ,it was always an anxious moment for the ,u-boat commander1 when he was coming up1 until his periscope broke out of the water and he could get his bearings2 and even that was attended with danger1 for his periscope might be seen4 ,of course a periscope is a very insignificant object on the broad sea1 but when a submarine is moving its periscope is followed by a wake which is very conspicuous1 and so the ,u-boat ran a chance of being discovered and destroyed before it could dive again to a safe depth4 ,later1 telescoping periscopes were used1 which could be raised by means of a hand-lever4 ,the submarine would run along just under the surface and every now and then it would suddenly raise its periscope for an observation and drop it down again under cover if there was danger nigh4 ,this was much simpler and quicker than having a six-or eight-hundred-ton boat come up to the surface and dive to safety4 ,he might even collide with a vessel floating on the surface1 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 propellers4 ,in the bow were the torpedo-tubes and the magazine of torpedoes4 ,at first there were only two torpedo-tubes1 but later the number was increased to four4 ,these were kept constantly loaded1 so that the projectiles could be launched in rapid succession1 if necessary1 without a pause for the insertion of a fresh torpedo4 ,in some submarines tubes were provided in the stern also so that the boat could discharge a torpedo at its enemy while running away from him4 ,each tube was closed at the outer end by a cap and at the inside end by a breech-block4 ,the tube was blown clear of water by means of compressed air1 and of course the outer cap was closed when the breech was open to let in a torpedo4 ,then the breech was closed1 the cap opened1 and the torpedo was discharged from the tube by a blast of air4 ,,the ,,torpedo ,a torpedo is really a motor-boat1 a wonderfully constructed boat1 fitted with an engine of its own that is driven by compressed air and which drives the torpedo through the water at about forty miles per hour4 ,the motor-boat is shaped like a cigar and that used by the ,germans was about fifteen feet long and fourteen inches in diameter4 ,we used much larger torpedoes1 some of them being twenty-two feet long4 ,ours have a large compressed-air reservoir and will travel for miles2 but the ,germans used their torpedoes at short ranges of a thousand yards and under1 cutting down the air-reservoir as much as possible and loading the torpedo with an extra large explosive charge4 ,we found in the ,diesel engine that when air is highly compressed it becomes very hot4 ,when compressed air is expanded1 the reverse takes place1 the air becomes very cold4 ,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 frost4 ,and so an alcohol flame is used to heat the air4 ,the air-motor is started automatically by release of a trigger as the torpedo is blown out of the torpedo-tube4 ,by means of gearing1 the motor drives two propellers4 ,these run in opposite directions1 so as to balance each other and prevent any tendency for the torpedo to swerve from its course4 ,the torpedo is steered by a rudder which is controlled by a gyroscope1 and it is kept at the proper depth under water by diving-rudders which are controlled by a very sensitive valve worked by the weight of the water above it4 ,the deeper the water1 the greater the weight or pressure2 and the valve is so arranged that1 should the torpedo run too far under1 the pressure will cause the diving-rudders to tilt until the torpedo comes up again2 then if the torpedo rises too high1 the valve will feel the reduction of pressure and turn the rudders in the other direction4 ,the business end of a torpedo is a war-head packed with about four hundred pounds of ,,tnt4 ,at the nose of the torpedo is a firing-pin1 with which the war-head is exploded4 ,ordinarily1 the firing-pin does not project from the torpedo1 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 course4 ,this draws out the firing-pin and gets everything ready for the ,,tnt to explode as soon as the firing-pin is struck4 ,but the firing-pin is not the only means of exploding the torpedo4 ,inside there is a very delicate mechanism that will set off the charge at the least provocation4 ,in one type of torpedo a steel ball is provided which rests in a shallow depression and the slightest shock1 the sudden stopping or even a sudden swerve of the torpedo1 would dislodge the ball and set off the charge4 ,hence various schemes1 proposed by inventors1 for deflecting a torpedo without touching the firing-pin1 would have been of no value at all4 ,,guns ,,on ,,submarines ,as torpedoes are expensive things1 the ,u-boats were supplied with other means of destroying their victims4 ,the ,germans sprang a surprise by mounting guns on the decks of their submarines4 ,at first these were arranged to be lowered into a hatch when the boat was running submerged1 but later they were permanently mounted on the decks so that they would be ready for instant use4 ,they were heavily coated with grease and the bore was swabbed out immediately when the boat came to the surface1 so that there was no danger of serious rust and corrosion4 ,the #c-;inch gun of the early months of the war soon gave way to heavier pieces and the latest ,u-boats were supplied with guns of almost #f-;inch caliber and there was a gun on the after deck as well as forward4 ,the ,u-boats depended upon radiotelegraphy to get their orders and although they did not have a very wide sending-range1 they could receive messages from the powerful ,german station near ,berlin4 ,the masts which carried the radio arials could be folded down into pockets in the deck4 ,from stem to stern over the entire boat a cable was stretched which was intended to permit the ,u-boat to slide under nets protecting harbor entrances1 and in later boats there were keen-toothed knives at the bow which would cut through a steel net4 ,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 sea4 ,america1 ,great ,britain1 ,france1 and ,italy made good use of submarines1 operating them against enemy vessels1 blockading enemy ports1 and actually fighting enemy submarines4 ,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 ,germans4 ,for instance1 they developed a submarine which is virtually a submersible destroyer4 ,it is #cdj feet long and it can make a speed of #bd knots on the surface4 ,the most remarkable part of this boat is that its engines are driven by steam4 ,its boilers are fired with oil fuel4 ,there are two smoke-stacks which fold down when it submerges4 ,of course when running under-water the vessel is driven by electricity and it makes a speed of #aj knots4 ,it carries three #d-;inch guns1 two forward and one aft1 and its displacement submerged is #bgjj tons as against #hjj tons for the largest ,german submarines4 ,a ,,submarine ,,that ,,mounts ,a ,,twelve-,,inch ,,gun ,still more remarkable is the big super-submarine designed by the ,british to bombard the forts of the ,dardanelles1 but unfortunately it was built too late to be used there4 ,this submarine carries a gun big enough for a battle-ship4 ,it is of #ab-;inch caliber and weighs #ej tons4 ,of course a big gun like that could not be fired athwart the submarine4 ,it might bowl the little vessel over1 even though it was a #agjj-ton submarine4 ,the gun is mounted to fire fore and aft1 with a deviation of only a few degrees to one side or the other1 so that the shock of the recoil is taken by the length instead of the beam of the submarine4 ,it fires a shell weighing #fbj pounds and a full charge is not used1 so that the extreme range is only about #ae1jjj yards4 ,this submarine monitor would have been a very difficult target for the ,turkish gunners to hit4 ,when the war came to an end and the ,german submarines surrendered to the ,entente ,allies at ,harwich1 there was considerable public curiosity as to whether or not an examination of the ,u-boats would disclose any wonderful secrets4 ,but they contained nothing that the ,allies did not already know1 and one ,british officer stated that the plans of the ,german submarines had often fallen into their hands long before a ,u-boat of the same type was captured6 ,,chapter ,,xiii ,,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 fear4 ,he was out to murder1 not to fight4 ,his prey was always out in the open1 while he could kill without exposing more than his eye above water4 ,not even a sporting chance was allowed his victims1 particularly when he chose unarmed merchantmen for his targets4 ,he could come up boldly to the surface and shell a ship into submission4 ,this was cheaper than torpedoing the vessel1 because torpedoes are expensive4 ,if the ship were speedy it might run away2 or if the ,u-boat came up too close to its intended prey1 the latter might run it down4 ,that happened occasionally and it was the only danger that the ,herr ,kommandant had to fear4 ,if a destroyer suddenly appeared1 the ,u-boat could dive into the shelter of the sea4 ,if the water were not too deep1 it could lie on the bottom for two or more days if need be4 ,there was plenty of air in the hull to sustain life for many hours1 and then the compressed air used for blowing the ballast-tanks could be drawn upon4 ,in the ,u-boat there were potash cartridges to take up the carbon-dioxide1 and tanks of pure oxygen to revitalize the air4 ,if the submarine were damaged1 it was not necessary for it to come to the surface to effect repairs4 ,there were air-locks through which a diver could be let out of the boat4 ,he was fitted with oxygen and potash cartridges1 so that he did not need to be connected by an air-hose with the boat1 but could walk around it freely to mend injured rudders or to clear the propeller of entanglements4 ,even the small submarines of those early days were capable of taking long voyages4 ,setting his course at a comfortable pace of #aj knots1 the ,u-boat commander could count on enough fuel to carry him #afjj miles1 and if need be he could slow down to #h knots and by using certain of his water-ballast tanks for additional oil-reservoirs1 extend his cruising-radius to nearly #cjjj miles4 ,the big #hjj-ton ,u-boats that were built later had a radius of #ejjj miles at an #h-knot speed4 ,and so when the ,british closed the ,english ,channel with nets and mines1 ,herr ,kommandant was not at all perturbed2 he could sail around the ,british ,isles if he chose and make war upon transatlantic shipping4 ,when harbors were walled off with nets1 he could remain outside and sink vessels that were leaving or entering them4 ,,submarine-,,chasers ,a real menace came when the ,u-boat commander popped his periscope out of the sea and saw several little motor-boats bearing down upon him4 ,they seemed harmless enough1 but a moment's inspection showed them to be armed with guns fully as powerful as those he carried4 ,it was useless to discharge a torpedo at so speedy and small a foe4 ,a torpedo has to have a fairly deep covering of water1 else its course will be disturbed by surface waves2 and the submarine-chasers drew so little water that a torpedo would pass harmlessly under them4 ,it was useless for the ,u-boat commander to come up and fight them with his guns4 ,they would have been upon him before he could do that1 and their speed and diminutive size made them very difficult targets to hit4 ,besides1 he dared not risk a duel of shell1 for he knew that if the precious inner hull of his boat were punctured1 he could not seek refuge under water2 and if he could not hide1 he was lost4 ,the little armed mosquito craft swarmed about the harbor entrances1 ready to dash at any submarine that showed itself4 ,they could travel twice as fast as the submarine when it was submerged and half again as fast as when it was running on the surface4 ,submarines had to take to cover when these chasers were about4 ,herr ,kommandant did not even dare to take a look around through his periscope1 because the streak of foam that trailed in its wake would betray him and immediately the speedy motor-boats would take up the chase2 and they had a disagreeable way of dropping bombs which1 even if they did not sink the submarine1 might produce such a concussion as to spring its seams4 ,his foes had discovered one of his most serious defects4 ,he was blind under-water and they were making the most of this handicap4 ,illustration3 7,c7 ,underwood ,underwood ,forward ,end of a ,u-boat4 ,note the ,four ,torpedo ,tubes ,behind the ,officer ,groping along under-water by dead-reckoning was not any too safe a procedure near land1 because he was liable at any moment to crash into an uncharted rock or maybe into the wreck of some submarine victim4 ,he could not correct his bearings without coming to the surface1 and1 in the black depths of the sea1 a slight miscalculation might send him to his doom4 ,as was explained in the previous chapter1 he had to keep moving1 because he could not remain suspended under water4 ,illustration3 7,c7 ,press ,illustrating ,service ,a ,depth-bomb ,mortar and a ,set of ,ash ,cans at the ,stern of an ,american ,destroyer ,he was more helpless than a ship sailing in the densest of fogs4 ,a ship can stop and listen to sound-signals1 or even to the beating of the surf on the shore1 or it can take soundings to locate its position2 and yet it is no uncommon occurrence for a ship to run ashore in a fog4 ,how much easier it is for a submarine to lose its bearings when obliged to travel by dead-reckoning1 particularly in the disconcerting excitement of the chase6 ,to avoid the danger of collision with surface vessels1 the commander chose to run at a depth of sixty-five feet4 ,that was the upper limit of his safety-zone4 ,a depth of over two hundred feet was his lower limit1 because1 as stated before1 the water-pressure at that depth would crush in his hull or at least start its seams4 ,if the bottom were smooth and sandy1 and not too deep1 he could settle gently upon it and wait for darkness1 to make his escape4 ,but while he lay on a sandy bottom1 he was still in danger4 ,trawlers were sweeping the bottom with nets4 ,he might be discovered2 and then if he did not come up and surrender1 a bomb would let in the sea upon him4 ,a ,,hint ,,from ,,nature ,while he could not see under water1 his adversaries could4 ,they had taken a hint from nature4 ,the fish-hawk has no difficulty in spying his submarine prey4 ,flying high above the water1 he can see his victims at a considerable depth1 and wait his chance to pounce upon an unwary fish that comes too near the surface4 ,it is said that the ,british trained sea-gulls to hunt submarines4 ,sea-gulls will follow a ship far out to sea for the sake of feeding on refuse that is thrown overboard4 ,british submarines encouraged the birds to follow them1 by throwing out bait whenever they came to the surface4 ,of course the birds could see the submarine even when it was submerged1 and if they pursued it1 they were always rewarded with plenty of food4 ,the gulls drew no fine distinction between ,hun and ,briton1 and so it came that ,herr ,kommandant often groped his way along in the dark sea1 totally oblivious of the fact that he was attended by an escort of feathered folk who kept the ,british chasers informed of his presence4 ,in this connection it is interesting to note that the ,british trained sea lions to hunt submarines4 ,the animals were taught at first to swim to a friendly submarine1 locating it by the sound of its propellers4 ,they were always rewarded with fish4 ,these sea lions were muzzled so that they could not go fishing on their own account4 ,then they learned to locate enemy submarines and pointed them out by swimming directly toward them and diving down to them4 ,but there were human eyes1 as well1 that spied upon the ,u-boat4 ,fast seaplanes patrolled the waters1 searching constantly for any trace of submarine4 ,its form could be vaguely outlined to a depth of from fifty to seventy-five feet1 unless the sea were choppy1 and once it was discovered1 chasers or trawlers were signaled to destroy it with bombs or to entangle it in nets4 ,often a submarine would be discovered by a leak in its oil-tank which would leave a tell-tale trail4 ,sometimes when the ,u-boat itself could not be discerned1 there would be slight shimmer1 such as may be seen above a hot stove1 caused by refraction of light in its wake4 ,this was easily recognized by trained observers4 ,illustration3 7,c7 ,press ,illustrating ,service ,a ,depth-bomb ,mortar in ,action and a ,depth-bomb snapped as it is being hurled through the air ,even better arial patrols were the small dirigibles known as ,blimps4 ,they are a cross between a balloon and an airplane1 for they have the body and the power-plant of an airplane1 but the planes are replaced by a gas-bag4 ,blimps could cruise leisurely and search the sea thoroughly4 ,they could stop and hover directly over a submarine and drop explosives upon it with great accuracy4 ,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 overhead4 ,this made it imperative to leave the shallower waters near shore and push out into the deep sea1 where the small chasers could not pursue him4 ,but he could not shake off his pursuers4 ,stream-trawlers are built to ride the heaviest gales and they took up the chase out into the ocean4 ,illustration3 ,courtesy of ,scientific ,american ,airplane ,stunning a ,u-boat with a ,depth-bomb ,there was a decided advantage for the ,u-boat in moving out to sea4 ,it had a wider field of activity and could more easily escape from its pursuers4 ,but on the other hand1 its prey also had an advantage4 ,out in the open ocean they were not obliged to follow the usual ship lanes and it was more difficult for a submarine to intercept them4 ,there it took more ,u-boats to blockade a given area4 ,a ,,game ,,of ,,hide-,,and-,,seek ,then1 it ceased to be quite so one-sided a game when merchantmen began to carry guns4 ,that made it necessary for the submarine commander to creep up on his victims stealthily1 and depend upon his torpedoes4 ,he had to get within a thousand yards of the ship and preferably within five hundred yards1 in order to be sure of hitting it4 ,if the ship could travel faster than he could1 he had to do this without betraying his presence4 ,but ship-captains soon learned that their safety lay in zig-zagging4 ,when ,herr ,kommandant reached the point from which he had planned to attack1 he would raise his telescopic periscope out of the water1 expecting to see his victim within good torpedo range1 only to find it sailing safely on another tack4 ,again1 he would have to take observations and make another try1 probably with no better luck4 ,it was a game of hide-and-seek in which the merchant ship had a good chance of making its escape1 particularly when blotches of camouflage paint made it difficult for him to get the range1 as described in ,chapter ,,xi4 ,illustration3 ,courtesy of the ,submarine ,defense ,association ,,fig4 #ai4 ,how a ship hid behind smoke produced on its own stern1 with different directions of wind ,slower ships could be attacked without all this manoeuvering1 provided the submarine's guns outranged those of the ship4 ,and so ,u-boats were provided with larger and larger guns1 which made it possible for them to stand off and pound the merchantmen while out of reach of the vessel's guns4 ,but ships found a way of hiding on the surface of the sea4 ,a vessel would spout forth volumes of dense black smoke which would obliterate it from view4 7,see ,fig4 #ai47 ,if the wind was quartering1 the ship would change its course and dodge behind the sheltering pall of smoke4 ,not only was the smoke produced on the vessel itself1 but smoke-boxes were cast overboard to form a screen behind the vessel4 ,these smoke-boxes contained a mixture of coal-tar and phosphorus and other chemicals which would produce incomplete combustion4 ,they were ignited by the rubbing of a phosphorus compound on a priming-composition1 and then cast adrift to pour out dense volumes of heavy smoke4 7,see ,fig4 #bj47 ,behind this screen1 the ship could dodge and zig-zag and if her speed were greater than that of the submarine1 her chances of escape were very good4 ,illustration3 ,courtesy of the ,submarine ,defense ,association ,,fig4 #bj4 ,how a ship hid behind a screen of smoke produced by throwing smoke-boxes overboard ,another annoyance that ,herr ,kommandant experienced was1 when he lifted his periscopic eye above water1 to find it so smeared with a sticky substance that he could not see4 ,his foes had strewn the water with tar-oil that had spread in a thin film over a surface miles in extent4 ,this blinded him at first1 but before long he was equipped with a jet for washing off the periscope glass and that little annoyance was overcome4 ,but the craft most dreaded by the ,u-boat commander were the destroyers4 ,these light1 high-powered1 heavily armed vessels could travel twice as fast as he could on the surface and three times as fast as he could submerged4 ,shells were invented which would not ricochet from the surface of the sea1 but would plow right through the water1 where they struck and hit the submarine below water-level4 ,,death-,,dealing ,,ash ,,cans ,however1 it was not shell-fire that he dreaded1 but the big ash cans loaded with ,,tnt which were timed to explode far under water1 and which would crush his boat or start its seams4 ,it was not necessary for these bombs to hit the ,u-boat4 ,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 explosion4 ,within limits1 the deeper the explosion the wider would its destructive area be4 ,the timing-mechanism of some depth bombs consisted merely of a float on the end of a cord4 ,when the bomb was thrown overboard this float remained on the surface until the cord was pulled out to its full length1 when there would be a yank on the firing-trigger and the charge would explode4 ,in other depth bombs there was a valve operated by the pressure of the water4 ,when the bomb sank to the depth for which the valve was set1 the pressure of the water would force the valve in1 exploding a cartridge which set off the charge4 ,so powerful were these depth bombs that the destroyer had to travel at high speed to get out of range of the explosion4 ,depth bombs were rolled off the stern of the destroyer and also thrown out from the sides of the vessel by means of mortars4 ,some of the mortars were ,y-shaped and held a depth bomb in each arm of the ,y4 ,when a blank #c-;inch shell was exploded at the base of the gun1 both bombs would be hurled from the ship1 one to port and the other to starboard4 ,in this way the destroyer could drop the bombs in a pattern of wide area4 ,herr ,kommandant gained a wholesome respect for these terriers of the sea4 ,it was suicide to show himself anywhere near a destroyer4 ,in a moment the speedy boat would be upon him1 sowing depth bombs along his course4 ,his chances of escaping through this hail of high explosives were remote indeed4 ,the ships that he was most eager to destroy were either too speedy for him to catch1 unless they happened to come his way1 or else they were herded in large convoys protected by these dreaded destroyers4 ,the convoy proved a most baffling problem for ,herr ,kommandant4 ,he dared not attack the convoy by daylight4 ,in a fog he might take a chance at picking off one of the ships1 but even that was very risky4 ,he could trail the convoy until dusk and then under cover of darkness draw near enough to discharge a torpedo1 but in the daytime he must keep his distance because there were eyes in the sky watching for him4 ,at the van and rear of the convoy there were kite balloons high in the sky1 with observers constantly watching for periscopes1 and for ,u-boats that might be lurking under the surface4 ,as the destroyers gained in experience1 the difficulties of the ,u-boat attack grew greater and its work grew more and more perilous4 ,the crew grumbled and grew mutinous4 ,the morale of the men was shaken4 ,we can imagine the horror of plunging hurriedly into the depths of the sea1 and rushing along blindly under the surface1 dodging this way and that1 while terrific explosions of depth bombs stagger the submarine and threaten to crush it1 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 water4 ,the tables were turned4 ,now1 if never before1 ,herr ,kommandant1 the hunter1 knew what it felt like to be hunted4 ,illustration3 7,c7 ,underwood ,underwood ,the ,false ,hatch of a ,mystery ,ship and-- ,illustration3 ,the same ,hatch opened to disclose the #c-;,inch ,gun and ,crew ,it takes an exceptional man to go through such a harrowing experience with unshattered nerves4 ,on at least one occasion1 a submarine that was being depth-bombed came suddenly to the surface4 ,the hatch flew open and the crew rushed out1 holding up their hands and crying1 ,kamerad4 ,the ,u-boat was uninjured1 but the shock of a depth bomb explosion had put the electric-lighting system out of commission1 and the crew1 unnerved by the explosion and terrified by the darkness1 had overpowered their officers and brought the boat to the surface4 ,illustration3 ,a ,french ,hydrophone ,installation with which the presence of ,submarines was detected ,,eyes ,,in ,,the ,,sea ,there were other craft that ,herr ,kommandant had to look out for4 ,his were not the only submarines in the sea4 ,his foes also were possessed of submarines4 ,they could not see under water any better than he could1 but they could fight on the surface as well as he1 and they could creep up on him even as he crept up on his prey4 ,as a ,french submarine commander puts it3 ,the ,u-boats used to enjoy the advantage of remaining themselves invisible while all the surface and arial craft which were sent in pursuit of them were boldly outlined against the sky and visible to them4 ,this is one of the reasons we used submarines to ambush ,u-boats4 ,submarines were also used to accompany the convoys1 so that the ,u-boat commander had to watch not only for the eyes of the ship's lookouts and the eyes in the kite balloons1 but also for the periscope eyes that swam in the sea4 ,,trailing ,u-,,boats ,,by ,,sound ,the troubles of the submarine-commander were multiplying4 ,all over the world inventors were plotting his destruction4 ,as long as we depended upon our eyes to ferret him out1 the sea was a safe refuge1 provided he dived deep enough1 but when we began to use our ears as well1 he found himself in a very serious predicament4 ,although light is badly broken up in its passage through water1 sound-waves will travel through water much better than in air4 ,the first listening-devices used were crude affairs and did not amount to much1 particularly when the ,u-boats muffled their motors and engines so that they were virtually noiseless4 ,but the ,french invented a very sensitive sound-detector4 ,it consisted of a lot of tiny diaphragms set in a big hemisphere4 ,there were two of these hemispheres1 one at each side of the boat4 ,when sound-waves struck these hemispheres1 the diaphragms would respond4 ,at the focus of each hemisphere there was a megaphone receiver2 one of these carried the sound to the operator's right ear and the other to his left4 ,he would turn a megaphone around until he found the diaphragm that produced the loudest sound4 ,this gave him the direction of the sound-wave4 ,then the boat would be steered in that direction4 ,he knew that it was aimed properly when the sound coming to his right ear was just as loud as that which came into his left ear4 ,a still better hydrophone was developed by a group of ,american inventors4 ,the details of this cannot yet be disclosed1 but we know that it was adopted at once by our allies4 ,a very sensitive receiver was used which could detect a ,u-boat miles away and determine its direction accurately4 ,under ideal conditions the range of the device was from fifteen to twenty-five miles1 but the average was from three to eight miles4 ,if two or more boats fitted with sound-detectors were used1 they could determine the position of the ,u-boat perfectly4 ,one drawback was that the vessel would have to stop so that the noise of its own engines would not disturb the listener1 but this was largely overcome by trailing the detector a hundred feet or more from the stem of the ship4 ,the sounds were then brought in by an electric cable to the listener in the ship4 ,these sound-detectors were placed on ,allied submarines as well as surface vessels and they were actually tried out on balloons and dirigibles1 so that they could follow a ,u-boat after it had submerged too deeply to be followed by sight4 ,illustration3 ,courtesy of the ,scientific ,american ,,fig4 #ba4 ,chart of an actual pursuit of a ,u-boat which ended in the destruction of the submarine ,illustration3 ,section of a captured ,mine-laying ,u-boat1 showing how the mines were laid ,many ,u-boats were chased to their doom by the aid of the ,american hydrophone4 ,fig4 #ba illustrates a very dramatic chase4 ,the full line shows the course of the ,u-boat as plotted out by hydrophones and the broken line the course of the submarine-chasers4 ,the dots represent patterns of depth bombs dropped upon the ,u-boat4 ,try as he would1 the ,herr ,kommandant could not shake off his pursuers4 ,at one time1 as the listeners stopped to take observations1 they heard hammering in the ,u-boat as if repairs were being made4 ,the motors of the submarine would start and stop1 showing clearly that it was disabled4 ,more depth bombs were dropped and then there was perfect silence1 which was soon broken by twenty-five revolver-shots4 ,evidently the crew1 unable to come to the surface1 had given up in despair and committed suicide4 ,illustration3 7,c7 ,underwood ,underwood ,a ,paravane hauled up with a ,shark caught in its jaws ,the ,adriatic ,sea was an ideal place for the use of the hydrophone4 ,the water there is so deep that submarines dared not rest on the bottom1 but had to keep moving1 and so they could easily be followed4 ,across the sea1 at the heel of the boot of ,italy1 a barrage of boats was established4 ,u-boats would come down to this barrage at night and1 when within two or three miles of the boats1 dive and pass under them4 ,but when hydrophones were used that game proved very hazardous4 ,our listeners would hear them coming when they were miles away4 ,then they would hear them shift from oil-to electric-drive and plunge under the surface4 ,darkness was no protection to the ,u-boats4 ,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 bottom4 ,on one occasion after an attack it was evident that the submarine had been seriously injured4 ,its motors were operating1 but something must have gone wrong with its steering-gear1 or its ballast-chambers may have been flooded1 because it kept going down and soon the listeners heard a crunching noise as it was crushed by the tremendous pressure of the water4 ,and so ,u-boat warfare grew more and more terrible for ,herr ,kommandant4 ,the depths of the sea were growing even more dangerous than the surface4 ,on every hand he was losing out4 ,he had tried to master the sea without mastering the surface of the sea4 ,but he can never really master who dares not fight out in the open4 ,for a time1 the ,german did prevail1 but his adversaries were quick to see his deficiencies and1 by playing upon these1 to rob the terror of the sea of his powers4 ,and as ,herr ,kommandant looks back at the time when he stepped into the lime-light as the most brutal destroyer the world has ever seen1 he cannot take much satisfaction in reflecting that the sum total of his efforts was to spread hatred of ,germany throughout the world1 to summon into the conflict a great nation whose armies turned the tide of victory against his soldiers1 and finally to subject his navy1 second only to that of ,great ,britain1 to the most humiliating surrender the world has ever seen4 ,,chapter ,,xiv ,,devil',s ,,eggs ,in modern warfare a duel between fixed forts and floating forts is almost certain to end in a draw4 ,because the former are fixed they make good targets1 while the war-ship1 being able to move about1 can dodge the shell that are fired against it4 ,on the other hand1 a fort on land can stand a great deal of pounding and each of its guns must be put out of action individually1 before it is subdued1 while the fort that is afloat runs the risk of being sunk with a few well-directed shots4 ,but fortifications alone will not protect a harbor from a determined enemy4 ,they cannot prevent hostile ships from creeping by them under cover of darkness or a heavy fog4 ,to prevent this1 the harbor must be mined1 and this must be done in such a way that friendly shipping can be piloted through the mine-field1 while hostile craft will be sure to strike the mines and be destroyed4 ,the mines may be arranged to be fired by electricity from shore stations1 in which case they are anchored at such a depth that ships can sail over them without touching them4 ,if a hostile vessel tried to dash into the harbor1 the touch of a button on shore would sink it when it passed over one of the mines4 ,but the success of electrically fired mines would depend upon the seeing4 ,in a heavy fog they would prove no protection4 ,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 particular mines it was at the moment passing4 ,no friendly vessel would undertake to enter the harbor in a fog or after dark and the operator would not hesitate to blow up the invader even if he could not see him4 ,however1 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 slightest touch of a ship's hull--and leave tortuous passages through the fields for friendly shipping4 ,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 then4 ,the mines are1 therefore1 made so that they can be taken up by friendly mine-sweepers who know just how to handle them1 and planted elsewhere4 ,these are defensive mines1 but there are other mines that are not intended to be moved4 ,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 with4 ,,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 depth4 ,submerged mines are more dangerous to the enemy because they cannot be seen and avoided4 ,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 them4 ,as the sea bottom may be very irregular1 it is impossible to tell how long the anchor cable should be without sounding the depth of the water at every point at which a mine is planted4 ,but the automatic anchor takes care of this4 ,very ingeniously it does its own sounding and holds the mine down to the depth for which it is set4 ,the mine cable is wound up on a reel in the anchor and the mine is held fast to the anchor by a latch4 ,the anchor is of box-shape or cylindrical form1 with perforations in it4 ,at first it sinks comparatively slowly1 but as it fills with water it goes down faster4 ,attached to the anchor is a plummet or weight1 connected by a cord to the latch4 ,the length of this cord determines the depth at which the mine will float4 ,illustration3 ,courtesy of the ,scientific ,american ,,fig4 #bb4 ,how the mine automatically adjusts itself to various depths of water ,the operation of the mine is shown in ,fig4 #bb4 ,when it is thrown overboard 7#a7 it immediately turns over so that the buoyant mine ,a floats on the surface 7#b74 ,while the anchor is slowly filling and sinking1 the plummet ,b runs out 7#c74 ,if the mines are to float at a depth of1 say1 ten feet1 this cord must be ten feet long4 ,as soon as it runs out to its full length 7#d7 it springs a latch1 ,c1 releasing the mine ,a4 ,then the mine cable ,d pays out1 as the anchor ,e sinks1 until the plummet ,b strikes bottom 7#e74 ,as soon as the plummet cord slackens a spring-pressed pawl is released and locks the mine-cable reel1 so that as the anchor continues to sink it draws the mine down with it1 until it touches bottom 7#f71 and as the anchor was ten feet from the bottom when the plummet touched bottom and locked the reel1 the mine must necessarily be dragged down to a depth of ten feet below the surface4 ,the mine itself1 or the devil's egg as it is called1 is usually a big buoyant sphere of metal filled with ,,tnt or some other powerful explosive2 and projecting from it are a number of very fragile prongs which if broken or even cracked will set off the mine4 ,there is a safety-lever or pin that makes the mine harmless when it is being handled1 and this must be withdrawn just before the mine is to be launched4 ,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 out4 ,when the plungers are broken1 water enters and1 coming in contact with certain chemicals1 produces enough heat to set off a cartridge which fires the mine4 ,,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 raising the mines or destroying them4 ,if they were of the offensive type1 it was much better to destroy them4 ,but occasionally1 when conditions permitted1 mine-sweepers undertook to raise the mines and reclaim them for future use against the enemy4 ,the work of seizing a mine and making it fast to the hoisting-cable of the mine-sweeper was usually done from a small rowboat4 ,raising the first mine was always the most perilous undertaking1 because no one knew just what type of mine it was and how to handle it with safety1 or whether there was any way in which it could be made harmless4 ,there were some mines1 for instance1 that contained within them a small vial partly filled with sulphuric acid4 ,the mine carried no prongs1 but if it were tilted more than twenty degrees the acid would spill out and blow up the mine4 ,such a mine would be exceedingly difficult if not impossible to handle from a boat that was rocked about by the waves4 ,after the first mine of the field was raised and its safety-mechanism studied1 the task of raising the rest was not so dangerous4 ,a water telescope was used to locate the mine and to aid in hooking the hoisting-cable into the shackle on the mine4 ,the hook was screwed to the end of a pole and after the mine was hooked1 the pole was unscrewed and the cable hauled in1 bringing up the devil's egg bristling with death4 ,care had to be taken to keep the bobbing boat from touching the delicate prongs until the safety-device could be set4 ,however1 this painstaking and careful method of raising mines was not often employed4 ,shallow-draft mine-sweepers would run over the mine-field1 dragging a cable between them4 ,the cable would be kept down by means of hydrovanes or water kites deep enough to foul the anchor cables of the mines4 ,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 under4 ,the action is just the reverse of a kite1 which is set to nose up into the wind and carry the kite up when it is dragged through the air4 ,by means of the cable the anchor chain of the mine was caught and then the mine with its anchor was dragged up4 ,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 cable4 ,,floating ,,mines ,when ,england entered the war she mined her harbors because1 although she had the mastery of the sea1 she had to guard against raids of enemy ships carried out in foggy and dark weather4 ,but the mines were no protection against submarines4 ,they would creep along the bottom under the mines4 ,then cable nets were stretched across the harbor channels to bar the submarines1 but the ,u-boats were fitted with cutters which would tear through the nets1 and it became necessary to use mines set at lower depths so that the submarines could not pass under them2 and nets were furnished with bombs which would explode when fouled by submarines4 ,in fact1 mines were set adrift with nets stretched between them1 to trap submarines4 ,floating mines were also used by the ,germans for the destruction of surface vessels and these were usually set adrift in pairs1 with a long cable connecting them1 so that if a vessel ran into the cable the mines would be dragged in against its hull and blow it up4 ,the laws of war require that floating mines be of such a design that they will become inoperative in a few hours2 otherwise they might drift about for weeks or months or years and be a constant menace to shipping4 ,sometimes anchored mines break away from their moorings and are carried around by ocean currents or are blown about by the winds4 ,a year after the ,russo-,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 planted4 ,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 vessels2 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 rust4 ,illustration3 ,courtesy of the ,scientific ,american ,,fig4 #bc4 ,ocean currents of the ,north ,atlantic showing the probable path of drifting mines ,the chart on the next page shows the course of ocean currents in the ,north ,atlantic as plotted out by the ,prince of ,monaco1 from which it may be seen that ,german mines will probably make a complete circuit of the ,north ,atlantic1 drifting down the western coast of ,europe1 across the ,atlantic1 around the ,azores1 and into the ,gulf ,stream1 which will carry them back to the ,north ,sea1 only to start all over4 7,see ,fig4 #bc47 ,some of them will run up into the ,arctic ,ocean1 where they will be blown up by striking icebergs and many will be trapped in the mass of floating seaweed in the ,sargasso ,sea4 ,but many years will pass before all danger of mines will be removed4 ,in the meantime1 the war has left a tremendous amount of work to be done in raising anchored mines and destroying them4 ,,egg-,,laying ,,submarines ,early in the war the ,british were astonished to find enemy mine-fields in their own waters1 far from any ,german ports4 ,they could not have been planted by surface mine-layers1 unless these had managed to creep up disguised as peaceful trawlers4 ,this seemed hardly likely1 because these fields appeared in places that were well guarded4 ,then it was discovered that ,german ,u-boats were doing this work4 ,special mine-laying ,u-boats had been built and one of them was captured with its cargo of devil's eggs4 ,a sectional view of the mine-laying ,u-boat is shown opposite page #bgb4 ,in the after part of the boat were mine-chutes in each of which three mines were stored4 ,a mine-laying submarine would carry about a score of mines4 ,these could be released one at a time4 ,the mine with its anchor would drop to the bottom4 ,as soon as it struck1 anchor-arms would be tripped and spread out to catch in the sand or mud1 while the mine cable would be released and the mine would rise as far as the cable would allow it4 ,the ,u-boat commander would have to know the depth of water in which the mines were to be laid and adjust the cables to this depth in advance4 ,this could not be done while the ,u-boat was submerged4 ,with the mines all set for the depth at a certain spot1 the ,u-boat commander had to find that very spot to lay his eggs1 otherwise they would either lie too deep to do any harm to shipping1 or else they would reach up to the surface1 where they might be discovered by the ,allied patrols4 ,as he had to do his navigating blindly1 by dead-reckoning1 it was very difficult for him to locate his mine-fields properly4 ,but the ,germans did not have a monopoly on submarine mine-laying4 ,the ,british also laid mines by submarine within ,german harbors and channels1 right under the guns of ,heligoland1 and many a ,u-boat was destroyed by such mines within its home waters4 ,illustration3 7,c7 ,press ,illustrating ,service ,a ,dutch ,mine-sweeper engaged in clearing the ,north ,sea of ,german ,mines ,,paravanes ,on the other hand1 the ,allies had a way of sailing right through fields of enemy mines with little danger4 ,our ships were equipped with paravanes which are something like the water kites used by mine-sweepers1 and they are still used in the waters of the war zone4 ,paravanes are steel floats with torpedo-shaped bodies and a horizontal plane near the forward end4 ,at the tail of the paravane1 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 it1 and at the desired depth below the surface4 ,two paravanes are used1 one at each side of the ship1 and the towing-cables lead from the bow of the vessel4 ,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 encountered4 ,the mine cable slides along the paravane cable and in this way is carried clear of the ship's hull4 ,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 surface4 ,the mine is then exploded by rifle or machine-gun fire4 ,illustration3 ,courtesy of ,scientific ,american ,hooking ,up ,enemy ,anchored ,mines ,in some forms of paravane there is a hinged jaw which is operated from the ship to shear the cable4 ,the jaw is repeatedly opened and closed by a line that runs to a winch on the ship4 ,this winch winds up the line until it is taut and then the line is permitted to slip1 letting the jaw open1 only to close again as the winch keeps on turning and winding up the line4 ,guarded by steel sharks on each side1 their jaws constantly working1 a ship can plow right through a field of anchored mines with little danger4 ,to be sure1 the bow might chance to hit a mine1 when1 of course1 there would be an explosion2 but the ship could stand damage here better than anywhere else and unless the bow actually hit the mine1 one or other of the paravanes would take care of it and keep it from being dragged in against the hull of the vessel4 ,,penning ,,in ,,the ,u-,,boats ,according to ,german testimony1 mines were responsible for the failure of the ,u-boat4 ,however1 it was not merely the scattered mine-fields sown in ,german waters that brought the ,u-boat to terms1 but an enormous mine-field stretching across the ,north ,sea from the ,orkney ,islands to the coast of ,norway4 ,early in the war1 ,u-boats had been prevented from entering the ,english ,channel by nets and mines stretched across the ,straits of ,dover4 ,as the submarine menace grew1 it was urged that a similar net be stretched across the ,north ,sea to pen the ,u-boats in4 ,but it seemed like a stupendous task4 ,the distance across at the narrowest point is nearly two hundred and fifty miles4 ,it would not have been necessary to have the net come to the surface4 ,it could just as well have been anchored so that its upper edge would be covered with thirty feet of water4 ,surface vessels could then have sailed over it without trouble and submarines could not have passed over it without showing themselves to patrolling destroyers4 ,it would not have been necessary to carry the net to the bottom of the sea4 ,a belt of netting a hundred and fifty feet wide would have made an effective bar to the passage of ,u-boats4 ,as ,u-boats might cut their way through the net1 it was proposed to mount bombs or mines on them which would explode on contact and destroy any submarine that tried to pass4 ,however1 laying a net two hundred feet long even when it is laid in sections1 is no small job1 but when the net is loaded with contact mines1 the difficulty of the work may be well imagined4 ,and yet had it been thought that the net would be a success it would have been laid anyhow1 but it was argued that seaweed would clog the meshes of the net and ocean currents would tear gaps in it4 ,even if it had not been torn away1 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 surface4 ,a ,,wall ,,of ,,mines ,when ,america entered the war1 we were very insistent that something must be done to block the ,north ,sea1 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 under4 ,this would do away with all the drawbacks of a net4 ,ocean currents and masses of seaweed could not affect individual mines as they would a net4 ,furthermore1 an ,american inventor had devised a new type of mine which was peculiarly adapted to the proposed mine barrage4 ,it had a firing-mechanism that was very sensitive and the mine had twice the reach of any other4 ,at length the ,british mine-laying forces were prevailed upon to join with us in laying this enormous mine4 ,it was one of the biggest and most successful undertakings of the war4 ,it was to be two hundred and thirty miles long and twelve miles wide on the average1 reaching from the rocky shores of the ,orkney ,islands to ,norway4 ,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 nation1 so that the ,u-boats might have had a clear passage around the end of the barrage4 ,but as it was also against the law for the ,u-boats to sail through neutral waters1 ,norway laid a mine-field off its coast to enforce neutrality1 and this was to join with that which the ,british and we were to lay4 ,most of the mine-laying was to be done by the ,united ,states and we were to furnish the mines4 ,the order to proceed with the work was given in ,october1 #aiag1 and it was a big order4 ,a hundred thousand mines were to be made and to preserve secrecy1 as well as to hurry the work as much as possible1 it was divided among five hundred contractors and subcontractors4 ,the parts were put together in one plant and then sent to another1 where each mine was filled with three hundred pounds of molten ,,tnt4 ,to carry them across the ocean small steamers were used1 so that if one should be blown up by a submarine the loss of mines would not be very great4 ,there were twenty-four of these steamers1 each carrying from twelve hundred to eighteen hundred mines and only one of them was destroyed by a submarine4 ,the steamers delivered their loads on the west coast of ,scotland and the mines were taken across to the east coast by rail and motor canal-boats4 ,here the mines were finally assembled1 ready for planting4 ,seventy thousand mines were planted1 four fifths of them by ,american mine-layers and the rest by the ,british4 ,,mine ,,railroads ,,on ,,ships ,to handle the mines the ships were specially fitted with miniature railroads for transporting the mines to the launching-point1 so that they could be dropped at regular intervals without interruption4 ,each anchor mine was provided with flanged wheels that ran on rails4 ,the mines were carried on three decks and each deck was covered with a network of rails1 switches1 and turn-tables1 while elevators were provided to carry the mines from one deck to another4 ,the mines1 like miniature railroad cars1 were coupled up in trains of thirty or forty and as each mine weighed fourteen hundred pounds1 steam winches had to be used to haul them4 ,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 time4 ,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 sea4 ,the mines were dropped every three hundred feet in lines five hundred feet apart1 as it was unsafe for the mine-layers to steam any closer to one another than that4 ,the mines were of the type shown in ,fig4 #bb and automatically adjusted themselves to various depths4 ,the depth of the water ran down to twelve hundred feet near the ,norwegian coast4 ,never before had mines been planted at anywhere near that depth4 ,it was dangerous work1 because the enemy knew where the mines were being planted1 as neutral shipping had to be warned months in advance4 ,the mine-layers were in constant danger of submarine attack1 although they were convoyed by destroyers to take care of the ,u-boats4 ,there was even danger of a surface attack and so battle-cruisers were assigned the job of guarding the mine-layers4 ,the mine-layers steamed in line abreast1 and had one of them been blown up1 the shock would probably have been enough to blow up the others as well4 ,enemy mines were sown in the path of the mine-layers1 so the latter had to be preceded by mine-sweepers4 ,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 chance4 ,but despite all risks the work was carried through4 ,the barrier was not an impassable one4 ,with the mines three hundred feet apart1 a submarine might get through1 even though the field was twenty-five miles broad1 but the hazards were serious4 ,before the first lines of mines had been extended half-way across1 its value was demonstrated by the destruction of several ,u-boats1 and as the safety-lane was narrowed down the losses increased4 ,it is said that altogether twenty-three ,german submarines met their doom in the great mine barrage4 ,u-boat commanders balked at running through it1 and ,u-boat warfare virtually came to a standstill4 ,according to ,captain ,bartenbach1 commander of submarine bases in ,flanders1 three ,u-boats were sunk by anchored mines for every one that was destroyed by a depth bomb4 ,,chapter ,,xv ,,surface ,,boats ,the war on the submarine was fought mainly from the surface of the sea and from the air above the sea1 and naturally it resulted in many interesting naval developments4 ,as described in ,chapter ,,xiii1 the first offensive measure against the ,u-boat was the building of swarms of speedy motor-boats which drove the invaders away from harbors and into the open sea4 ,to follow the ,u-boats out into rough water larger submarine-chasers were built1 but even they could not cope with the enemy far from the harbors4 ,,motor ,,torpedo-,,boats ,the ,italians made excellent use of speedy motor-boats in the protected waters of the ,adriatic ,sea4 ,one type of motor-boat was equipped with two torpedo-tubes in the bow4 ,small #ad-;inch torpedoes were used1 but as each torpedo carried two hundred pounds of high explosive1 the motor-boat was a formidable vessel if it crept in close enough to discharge one of these missiles at its foe4 ,on one occasion1 a patrol of these little boats sighted a couple of ,austrian dreadnoughts headed down the coast1 surrounded by a screen of ten destroyers4 ,favored by the mist1 two of the motor-boats crept through the screen of destroyers1 and torpedoed the battle-ships4 ,then they made good their escape4 ,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-boat4 ,,the ,,sea ,,tank ,the ,italians showed a great deal of naval initiative4 ,they were forever trying to trap the ,austrian fleet or to invade its harbors4 ,like all other naval powers1 the ,austrians protected their harbors with nets and mines4 ,it was impossible for submarines to make an entrance and the ports were too well fortified to permit an open attack on the surface4 ,nevertheless1 the ,italians did break through the harbor defenses on one or two occasions and sank ,austrian war-vessels4 ,again it was with a small boat that they did the trick4 ,the nets which the ,austrians stretched across their harbor entrance were supported on wooden booms or logs which served as floats4 ,these booms offered an effective bar to small boats which might attempt to enter the harbor under cover of darkness4 ,but the ,italians found a way to overcome this obstruction4 ,they built a flat-bottomed motor-boat which drew very little water4 ,running under the boat were two endless chains1 like the treads of a tank4 ,in fact1 the boat came to be known as a sea tank4 ,the chains were motor-driven and had spiked sprockets1 so that when a boom was encountered they would bite into the wood and pull the boat up over the log1 or maybe they would drag the log down under the boat4 ,at any rate1 with this arrangement it was not very difficult to pass the boom and enter the harbor4 ,at the rear the chains were carried back far enough to prevent the propeller from striking when the boat had passed over the log4 ,illustration3 ,courtesy of ,scientific ,american ,an ,italian ,sea-tank climbing over a ,harbor ,boom ,illustration3 7,c7 ,underwood ,underwood ,deck of a ,british ,aircraft ,mothership or ,hush ship ,,the ,,awkward ,,eagles ,a curious boat that we undertook to furnish during the war was a cross between a destroyer and a submarine-chaser4 ,after the submarine had been driven out to sea its greatest foe was undoubtedly the destroyer1 and frantic efforts were made to turn out as many destroyers as possible4 ,but it takes time to build destroyers and so a new type of boat was designed1 to be turned out quickly in large numbers4 ,a hundred and ten ,eagles 7as these boats are called7 were ordered1 but the armistice was signed before any of them were put into service2 and it is just as well that such was the case1 for in their construction everything was sacrificed to speed of production4 ,as a consequence they are very ugly boats1 with none of the fine lines of a destroyer1 and they roll badly1 even when the sea is comparatively peaceful4 ,they are five-hundred-ton boats designed to make eighteen knots1 which would not have been fast enough to cope with ,u-boats1 because the latter could make as high a speed as that themselves1 when traveling on the surface1 and the two #d-;inch guns of the ,eagles would have been far outranged by the #e4i-;inch guns of the larger ,u-boats4 ,,seaplane ,,towing-,,barges ,when the war on the ,u-boat was carried up into the sky1 many new naval problems cropped up1 particularly when ,german submarines chose to work far out at sea4 ,big seaplanes were used1 but they consumed a great deal of fuel in flying out and back1 cutting down by just so much their flying-radius at the scene of activities4 ,a special towing-barge was used4 ,these barges had trimming-tanks aft1 which could be flooded so that the stern of the barge would submerge4 ,a cradle was mounted to run on a pair of rails on the barge4 ,the body of the seaplane was lashed to this cradle and then drawn up on the barge by means of a windlass4 ,this done1 the water was blown out of the trimming-tanks by means of compressed air and the barge was brought up to an even keel4 ,the barge with its load was now ready to be towed by a destroyer or other fast boat to the scene of operations4 ,there water was again let into the trimming-tanks and the seaplane was let back into the water4 ,from the water the seaplane arose into the air in the usual way4 ,unfortunately1 when the sea is at all rough it is exceedingly difficult for a seaplane to take wing1 particularly a large seaplane4 ,a better starting-platform than the sea had to be furnished4 ,at first some seaplanes were furnished with wheels1 so that they could be launched from platforms on large ships2 and then1 to increase the flying-radius1 seaplanes were discarded in favor of airplanes4 ,once these machines were launched1 there was no way for them to get back to the ship4 ,they had to get back to land before their fuel was exhausted4 ,on the large war-vessels a starting-platform was built on a pair of long guns4 ,then the war-ship would head into the wind and the combined 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 guns4 ,but as long as aviators had no haven until they got back to land1 there were many casualties4 ,eager to continue their patrol as long as possible1 they would sometimes linger too long before heading for home and then they would not have enough fuel left to reach land4 ,many an aviator was lost in this way1 and finally mother-ships for airplanes had to be built4 ,illustration3 ,courtesy of ,scientific ,american ,electrically ,propelled ,boat or ,surface ,torpedo1 ,attacking a ,warship1 under ,guidance of an ,airplane ,scout ,,the ,,hush ,,ships ,the ,british ,navy had constructed a number of very fast cruisers to deal with any raiders the ,germans might send out4 ,these cruisers were light vessels capable of such high speeds that they could even overtake a destroyer4 ,they were #hdj feet long and their turbines developed #ij1jjj horse-power4 ,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 allowed to be published4 ,because of this secrecy the boats were popularly known as hush ships4 ,they were not armored2 it was not necessary to load them down with armor plate1 because their protection lay in speed and they were designed to fight at very long range4 ,in fact1 they were to carry guns that would outrange those of the most powerful dreadnoughts4 ,our largest naval guns are of #af-;inch caliber1 but the hush ships were each to carry two #ah-;inch guns4 ,the guns were monsters weighing #aej tons each and they fired a shell #ah inches in diameter and #g feet long to a distance of #cj miles when elevated to an angle of #de degrees4 ,the weight of the shell was #cfjj pounds and it carried #ejj pounds of high explosive or more than is carried in the largest torpedoes4 ,at the #cb-mile range the shell would pass through #ab inches of face-hardened armor and at half that range it would pass through armor #ah inches thick1 and there is no armor afloat any heavier than this4 ,illustration3 ,courtesy of ,scientific ,american ,hauling a ,seaplane up on a ,barge so that it may be ,towed at ,high ,speed by a ,destroyer ,,mother-,,boats ,,for ,,airplanes ,armed with such powerful guns as these1 the hush ships would have been very formidable indeed2 but when the guns were mounted on one of the cruisers1 the ,furious1 they were found too powerful for the vessel4 ,it was evident that the monsters would very seriously rack their own ship4 ,so the guns were taken off the cruiser and it was turned into a mother-ship for airplanes4 ,a broad1 unobstructed deck was built on the ship which provided a runway from which airplanes could be launched1 and this runway was actually broad enough to permit airplanes to land upon it4 ,under the runway were the hangars in which the airplanes were housed4 ,other hush ships were also converted into airplane mother-boats and there were special boats built for this very purpose1 although they were not able to make the speed of the hush ships4 ,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-deck1 #ccj feet long4 ,,torpedo-,,proof ,,monsters ,as for the #ah-;inch guns1 they were put to another use4 ,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 ,germans4 ,the ships that were built to meet this demand were known as monitors1 because like the famous monitor of our ,civil ,war they carried a single turret4 ,these monitors were very broad for their length and were very slow4 ,at best they could make only seven knots and in heavy weather they could not make more than two or three knots4 ,to be made proof against torpedoes these 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 feet4 ,the blisters were subdivided into compartments1 so that if a torpedo struck the ship it would explode against a blister at a considerable distance from the real hull of the ship and the force of the explosion would be expended in the compartments4 ,the blisters were the salvation of the monitors4 ,often were the boats struck by torpedoes without being sunk4 ,unfortunately1 this form of protection could not be applied to ordinary vessels1 because it would have interfered seriously with navigation4 ,the blisters made the monitors very difficult to steer and hampered the progress of a ship1 particularly in a seaway4 ,with ships such as these the ,british bombarded ,zeebrugge from a distance of twenty to twenty-five miles4 ,of course1 the range had to be plotted out mathematically1 as the target was far beyond the horizon of the ship1 and the firing had to be directed by spotters in airplanes4 ,at first guns from antiquated battle-ships were used in the monitors2 then larger guns were used1 until finally two of the monitors inherited the #ah-;inch guns of the ,furious4 ,a single gun was mounted on the after deck of each vessel and the gun was arranged to fire only on the starboard side4 ,no heavily armored turret was provided1 but merely a light housing to shelter the gun4 ,,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 ,germans4 ,because of the shallow water it was seldom possible for a submarine to creep up on them4 ,a ,u-boat required at least thirty-five feet of water for complete submergence and it did not dare to attack in the open4 ,this led the ,germans to launch a motor-boat loaded with high explosive1 which was steered from shore4 ,the motor-boat carried a reel of wire which connected it with an operator on shore4 ,there was no pilot in the boat1 but the helm was controlled electrically by the man at the shore station4 ,as it was difficult for the helmsman to see just what his boat was doing1 or just how to steer it when it was several miles off1 an airplane flew high above it and directed the helmsman1 by radiotelegraphy1 how to steer his boat4 ,of course1 radiotelegraphy might have been used to operate the steering-mechanism of the boat1 but there was the danger that the radio operators of the ,british might send out disturbing waves that would upset the control of the motor-boat1 and so direct wire transmission was used instead4 ,fortunately1 when the ,germans tried this form of attack1 an alert ,british lookout discovered the tiny motor-boat4 ,the alarm was given and a lucky shot blew up the boat with its charge before it came near the ,british vessel4 ,,chapter ,,xvi ,,reclaiming ,,the ,,victims ,,of ,,the ,,submarine ,nearly fifteen million tons of shipping lie at the bottom of the sea1 sunk by ,german ,u-boats1 and the value of these ships with their cargo is estimated at over seven billion dollars4 ,in one year1 #aiag1 the loss was nearly a million dollars a day4 ,of course these wrecks would not be worth anything like that now1 if they were raised and floated4 ,much of the cargo would be so damaged by its long immersion in salt water that it would be absolutely valueless1 but there are many kinds of merchandise that are not injured in the least by water4 ,every ship carries a certain amount of gold and silver2 and then the ship's hull itself is well worth salving1 provided it was not too badly damaged by the torpedo that sank it4 ,altogether1 there is plenty of rich treasure in the sea awaiting the salvor who is bold enough to go after it4 ,to be sure1 not all of the ,u-boat's victims were sunk in deep water4 ,many torpedoed vessels were beached or succeeded in reaching shallow water before they foundered4 ,some were sunk in harbors while they lay at anchor1 before the precaution was taken of protecting the harbors with nets4 ,the ,allies did not wait for the war to end before trying to refloat these vessels4 ,in fact1 during the war several hundred ships were raised and put back into service4 ,a special form of patch was invented to close holes torn by torpedoes4 ,electric pumps were built which would work under water and these were lowered into the holds of ships to pump them out4 ,the salvors were provided with special gas-masks to protect them from poisonous fumes of decayed matter in the wrecks4 ,our own navy has played an important part in salvage4 ,shortly after we entered the war1 all the wrecking-equipment in this country was commandeered by the government and we sent over to the other side experienced ,american salvors1 provided with complete equipment of apparatus and machinery4 ,the majority of wrecks1 however1 are found in the open sea1 where it would have been foolish to attempt any salvage-operations because of the menace of submarine attack4 ,on at least one occasion a salvage vessel1 while attempting to raise the victims of a submarine1 fell1 itself1 a prey to a ,hun torpedo4 ,now that this menace has been removed1 such vessels as lie in comparatively shallow water1 and in positions not subject to sudden tempests1 can be raised by the ordinary methods2 or if it is impracticable to raise them1 much of their cargo can be reclaimed4 ,however1 most of the torpedoed ships lie at such depths that their salvage would ordinarily be despaired of4 ,,in ,,the ,,depths ,,of ,,the ,,sea ,it will be interesting to look into conditions that exist in deep water4 ,somehow the notion has gone forth that a ship will not surely sink to the very bottom of the deep sea1 but on reaching a certain level will find the water so dense that even solid iron will float1 as if in a sea of mercury1 and that here the ship will be maintained in suspension1 to be carried hither and yon by every chance current4 ,indeed1 it makes a rather fantastic picture to think of these lost ships drifting in endless procession1 far down beneath the cold green waves1 and destined to roam forever like doomed spirits in a circle of ,dante's ,inferno4 ,but the laws of physics shatter any such illusion and bid us paint a very different picture4 ,liquids are almost incompressible4 ,the difference in density between the water at the surface of the sea and that at a depth of a mile is almost insignificant4 ,as a matter of fact1 at that depth the water would support only about half a pound more per cubic foot than at the surface4 ,the pressure1 however1 would be enormous4 ,take the ,titanic1 for instance1 which lies on the bed of the ocean in water two miles deep4 ,it must endure a pressure of about two long tons on every square inch of its surface4 ,long before the vessel reached the bottom her hull must have been crushed in4 ,every stick of wood1 every compressible part of her structure and of her cargo1 must have been staved in or flattened4 ,as a ship sinks it is not the water but the ship that grows progressively denser4 ,the ,titanic must have actually gained in weight as she went down1 and so she must have gathered speed as she sank4 ,we may be certain1 therefore1 that every victim of ,germany's ruthless ,u-boats that sank in deep water lies prone upon the floor of the sea4 ,it matters not how or where it was sunk1 whether it was staggered by the unexpected blow of the torpedo and then plunged headlong into the depths of the sea1 or whether it lingered1 mortally wounded1 on the surface1 quietly settling down until the waves closed over it4 ,theoretically1 of course1 a perfect balance might be reached which would keep a submerged vessel in suspension1 but practically such a condition is next to impossible4 ,once a ship has started down1 she will keep on until she reaches the very bottom1 whether it be ten fathoms or ten hundred4 ,a ,,submarine ,,graveyard ,instead of the line of wandering specters1 then1 we must conjure up a different picture1 equally weird--an under-world shrouded in darkness2 for little light penetrates the deep sea4 ,here in the cold blackness1 on the bed of the ocean1 the wrecks of vessels that once sailed proudly overhead lie still and deathly silent--some keeled over on their sides1 some turned turtle1 and most of them probably on even keel4 ,here and there may be one with its nose buried deep in the mud2 and in the shallower waters we may come across one pinned down by the stern1 but with its head buoyed by a pocket of air1 straining upward and swaying slightly with every gentle movement of the sea1 as if still alive4 ,this submarine graveyard offers wonderful opportunities for the engineer1 because the raising of wrecked vessels is really a branch of engineering4 ,it is a very special branch1 to be sure1 and one that has not begun to receive the highly concentrated study that have such other branches as tunneling1 bridge-construction1 etc4 ,nevertheless it is engineering1 and it has been said of the engineer that his abilities are limited only by the funds at his disposal4 ,now he has a chance to show what he can do1 for there are hundreds of vessels to be salved where before there was but one4 ,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 heretofore4 ,special apparatus that could not be built economically for a single wreck may be constructed with profit if a number of vessels demanding similar treatment are to be salved4 ,the principal fields of ,german activities were the ,mediterranean ,sea and the waters surrounding the ,british ,isles4 ,although the submarine zone covered some very deep water1 where the sounding-lead runs down two miles without touching bottom1 obviously more havoc could be wrought near ports where vessels were obliged to follow a prescribed course1 and so most of the ,u-boat victims were stricken when almost in sight of land4 ,in fact1 as was pointed out in a previous chapter1 it was not until efficient patrol measures made it uncomfortable for the submarines that they pushed out into the open ocean to pursue their nefarious work4 ,the ,lusitania went down only eight miles from ,old ,head of ,kinsale1 in fifty fathoms of water4 ,if we draw a line from ,fastnet ,rock to the ,scilly ,islands and from there to the westernmost extremity of ,france1 we enclose an area in which the ,german submarines were particularly active4 ,the soundings here run up to about sixty fathoms in some places1 but the prevailing depth is less than fifty fathoms4 ,in the ,north ,sea1 too1 except for a comparatively narrow lane along the ,norwegian coast--which1 by the way1 marked the safety lane of the ,german blockade zone--the chart shows fifty fathoms or under4 ,if our salvors could reach down as far as that1 most of the submarine victims could be reclaimed4 ,but fifty fathoms means #cjj feet1 which is a formidable depth for salvage work4 ,only one vessel has ever been brought up from such a depth and that was a small craft1 one of our submarines1 the ,f-#d1 which sank off the coast of ,hawaii four years ago4 ,,different ,,ways ,,of ,,salving ,a ,,wreck ,there are four well-known methods of raising a vessel that is completely submerged4 ,of course1 if the ship is not completely submerged1 the holes in her hull may be patched up1 and then when her hull is pumped out1 the sea itself will raise the ship1 unless it be deeply embedded in sand or mud4 ,if the vessel is completely submerged1 the same process may be resorted to1 but first the sides of the hull must be extended to the surface to keep the water from flowing in as fast as it is pumped out4 ,it is not usual to build up the entire length of the ship4 ,if the deck is in good condition1 it may suffice to construct coffer-dams or walls around several of the hatches4 ,but building up the sides of a ship1 or constructing coffer-dams on the ship's deck is a difficult task1 at best1 because it must be done under water by divers4 ,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 water4 ,her decks were submerged to a depth of forty feet4 ,it is doubtful that this salvage work could be duplicated by any other people of the world4 ,the wonderful patriotism and loyalty of the ,japanese race were called forth4 ,it is no small task to build a large coffer-dam strong enough to withstand the weight of forty feet of water1 or a pressure of a ton and a quarter per square foot1 even when the work is done on the surface4 ,perfect discipline and organized effort of the highest sort were required4 ,labor is cheap in ,japan and there was no dearth of men for the work4 ,over one hundred divers were employed4 ,in addition to the coffer-dam construction much repair work was necessary4 ,marvelous acts of devotion and heroism were performed4 ,it is rumored that in some places it was necessary for divers to close themselves in1 cut their air supply-pipes and seal themselves off from the slightest chance of escape2 and that there were men who actually volunteered to sacrifice their lives in this way for their beloved country and its young navy4 ,where1 indeed1 outside of the ,land of the ,rising ,sun could we find such patriotic devotion6 ,a second salvage method consists in building a coffer-dam not on the ship but around it1 and then pumping this out so as to expose the ship as in a dry-dock4 ,such was the plan followed out in recovering the ,maine4 ,obviously1 it is a very expensive method and is used only in exceptional cases1 such as this1 in which it was necessary to make a post-mortem examination to determine what caused the destruction of the vessel4 ,neither of these methods of salvage will serve for raising a ship sunk in deep water4 ,,raising ,a ,,ship ,,on ,,air ,a salvage system that has come into prominence within recent years consists in pumping air into the vessel to drive the water out1 thus making the boat light enough to float4 ,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 wreck1 and when the hole that sank the vessel is in or near the bottom1 so as to allow enough airspace above it to lift the boat4 ,the work of the diver in this case consists of closing hatches and bulkhead doors1 repairing holes in the upper part of the hull1 and generally strengthening the deck4 ,it must be remembered that a deck is built to take the strain of heavy weights bearing down upon it4 ,it is not built to be pushed up from beneath1 so that frequently this method of salving is rendered impracticable because the deck itself cannot stand the strain4 ,illustration3 ,climbing into an ,armored ,diving ,suit ,illustration3 ,lowering an ,armored ,diver into the ,water ,a more common salvage method consists in passing cables or chains under the wreck and attaching them to large floats or pontoons4 ,the slack in the chains is taken up when the tide is low1 so that on the turn of the tide the wreck will be lifted off the bottom4 ,the partially raised wreck is then towed into shallower water1 until it grounds4 ,at the next low tide1 the slack of the chains is again taken in1 and at flood-tide the wreck is towed nearer land4 ,the work proceeds step by step1 until the vessel is moved inshore far enough to bring its decks awash2 when it may be patched up and pumped out4 ,where the rise of the tide is not sufficient to be of much assistance1 hydraulic jacks or other lifting-apparatus are used4 ,illustration3 ,a ,diver's ,sea ,sled ready to be towed along the bed of the sea ,illustration3 ,the ,sea ,sled on ,land showing the forward horizontal and after vertical rudders ,,salving ,,the ,u4 ,s4 ,,submarine ,f-#d ,if the salvor could always be assured of clear weather1 his troubles would be reduced a hundredfold1 but at best it takes a long time to perform any work dependent upon divers1 and the chances are very good when they are operating in an unsheltered spot1 that a storm may come up at any time and undo the result of weeks and months of labor4 ,this is what happened when the submarine ,f-#d was salved4 ,after a month of trying effort the submarine was caught in slings hung from barges1 lifted two hundred and twenty-five feet1 and dragged within a short distance of the channel entrance of the harbor1 where the water was but fifty feet deep4 ,but just then a violent storm arose1 which made the barges surge back and forth and plunge so violently that the forward sling cut into the plating of the submarine and crushed it4 ,the wreck had to be lowered to the bottom and the barges cut free to save them from being smashed4 ,at the next attempt to raise the ,f-#d pontoons were again used1 but instead of being arranged to float on the surface1 they were hauled down to the wreck and made fast directly to the hull of the submarine4 ,then when the water was forced out of the pontoons with compressed air1 they came up to the surface1 bringing the submarine with them4 ,in this way all danger of damage due to sudden storms was avoided because water under the surface is not disturbed by storms overhead2 and when the wreck was floated1 the pontoons and submarine formed a compact unit4 ,while this method of salvage seems like a very logical one for work in the open sea1 one is apt to forget how large the pontoons must be to lift a vessel of any appreciable size4 ,not only must they support their own dead weight1 together with that of the sunken vessel1 but some allowance must usually be made for dragging the wreck out of the clutches of a sandy or muddy bottom4 ,imagine the work of building pontoons large enough to raise the ,lusitania4 ,they would have to have a combined displacement greater than that of the vessel itself1 and they would have to be so large that they would be very unwieldy things to handle in a seaway4 ,it is for this reason that submarine pontoons are not often used to take the entire weight of the vessel4 ,so far they have been employed mainly to salve small ships and then only to take a portion of the weight1 the principal work being done by large wrecking-cranes4 ,instead of horizontal pontoons it has been suggested that vertical pontoons be employed1 so as to provide a greater lifting-power without involving the use of enormous unwieldy units4 ,ships are not built so that they can be picked up by the ends4 ,such treatment would be liable to break their backs in the middle4 ,were they built more like a bridge truss1 the salvor's difficulties would be materially lessened4 ,it would be a much simpler matter to raise a vessel with pontoons were it so constructed that the chains of the pontoon could be attached to each end of the hull4 ,but because a ship is built to be supported by the water uniformly throughout its length1 the salvor must use a large number of chains1 properly spaced along the hull1 so as to distribute the load uniformly and see that too much weight does not fall on this or that pontoon4 ,the main problem1 however1 is to get hold of the wreck and this requires the services of divers1 so that if there were no other limiting factor1 the depth to which a diver may penetrate and perform his duties sets the mark beyond which salvage as now conducted is impossible4 ,illustration3 7,c7 ,international ,film ,service ,the ,diving ,sphere built for ,deep ,sea ,salvage ,operations ,a common diver's suit does not protect the diver from hydraulic pressure4 ,only a flexible suit and a thin layer of air separates him from the surrounding water4 ,this air must necessarily be of the same pressure as the surrounding water4 ,the air that is pumped down to the diver not only serves to supply his lungs1 but by entering his blood transmits its pressure to every part of his anatomy4 ,as long as the external pressure is equalized by a corresponding pressure within him1 the diver experiences no serious discomfort4 ,in fact1 when the pressure is not excessively high he finds it rather exhilarating to work under such conditions2 for1 with every breath1 he takes in an abnormal amount of oxygen4 ,when he returns to the surface he realizes that he has been working under forced draft4 ,he is very much exhausted and he is very hungry4 ,it takes a comparatively short time to build up the high internal pressure1 which the diver must have in order to withstand the pressure of the water outside1 but it is the decompression when he returns to the surface that is attended with great discomfort and positive danger4 ,if the decompression is not properly effected1 the diver will suffer agonies and even death from the so-called ,caisson ,disease4 ,illustration3 ,the ,pneumatic ,breakwater--,submerged ,air ,tubes protecting a ,california ,pier from ,ocean ,storms ,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 system1 and because of this knowledge divers have recently descended to depths undreamed of a few years ago4 ,when a diver breathes compressed air1 the oxygen is largely consumed and exhaled from the lungs in the form of carbon-dioxide1 but much of the nitrogen is dissolved in the blood and does not escape4 ,however1 like a bottle of soda-water1 the blood shows no sign of the presence of the gas as long as the pressure is maintained4 ,but on a sudden removal of the pressure1 the blood turns into a froth of nitrogen bubbles1 just as the soda-water froths when the stopper of the bottle is removed4 ,this froth interrupts the circulation4 ,the release of pressure is felt first in the arteries and large veins4 ,it takes some time to reach all the tiny veins1 and serious differences of pressure are apt to occur that often result in the rupture of blood-vessels4 ,the griping pains that accompany the ,caisson ,disease are excruciating4 ,the only cure is to restore the blood to its original pressure by placing the patient in a hospital lock1 or boiler-like affair1 where compressed air may be admitted2 and then to decompress the air very slowly4 ,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 bubbles1 and that is what is sought in decompressing a diver4 ,after careful research it has been found that the pressure may be cut down very quickly to half or even less of the original amount1 but then the diver must wait for the decompression to extend to the innermost recesses of his being and to all the tiny capillaries of his venous system4 ,in the salvage of the ,f-#d a diver went down #cjf feet1 and remained on the bottom half an hour4 ,the pressure upon him was #ace pounds per square inch1 or about #ade tons on the surface of his entire body4 ,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 #bae pounds to the square inch or only about #ej per cent more than the crushing pressure this diver had to endure4 ,it took the diver a very short time to go down4 ,on coming up he proceeded comparatively rapidly until he reached a depth of #ajj feet4 ,there he found the bottom rung of a rope ladder4 ,on it he was obliged to rest for several minutes before proceeding to the next rung4 ,the rungs of this ladder were #aj feet apart1 and on each rung the diver had to rest a certain length of time1 according to a schedule that had been carefully worked out4 ,at the top rung1 for instance1 only #aj feet from the surface1 he was obliged to wait forty minutes4 ,in all1 it took him an hour and forty-five minutes to come up to the surface4 ,the decompression was complete and he suffered no symptoms of the ,caisson ,disease4 ,but he was so exhausted from his efforts that he was unfit for work for several days4 ,yet the operations that he performed at the depth of #cjj feet would not have taken more than a few minutes on the surface4 ,a ,,submarine ,,rest-,,chamber ,the ,germans have paid a great deal of attention to deep-diving operations1 and no doubt while their ,u-boats were sinking merchant ships ,german salvors were anticipating rich harvests after hostilities ended4 ,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 place4 ,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 work4 ,entrance to the chamber is effected through a door in the floor4 ,the pressure of the air inside prevents the water from rising into the chamber and flooding it4 ,from this submarine base the divers may go out to the wreck1 either equipped with the ordinary air-tube helmets or with self-regenerating apparatus which makes them independent of an air-supply for a considerable period of time4 ,when the diver has worked for an hour or two1 or when he is tired1 he may return to this chamber1 remove his helmet1 eat a hearty meal1 take a nap if he needs it1 and then return to the salvage work without going through the exhausting operation of decompressing4 ,,cutting ,,metal ,,under ,,water ,,with ,a ,,torch ,the work of the diver usually consists of far more than merely passing lines under a sunken hull4 ,it is constantly necessary for him to cut away obstructing parts4 ,he must sometimes use blasting-power4 ,pneumatic cutting-tools frequently come into play1 but the ,germans have lately devised an oxy-hydrogen torch for underwater use1 with which the diver can cut metal by burning through it4 ,this is accomplished by using a cup-shaped nozzle through which a blast of air is projected under such pressure that it blows away the water over the part to be cut4 ,the oxygen and hydrogen jets are then ignited electrically1 and the work of cutting the metal proceeds in the hole in the water made by the air-blast4 ,a similar submarine torch has recently been developed by an ,american salvage company4 ,it was employed successfully in cutting drainage-holes in the bulkheads of the ,st4 ,paul1 which was raised in ,new ,york ,harbor in the summer of #aiah4 ,,exploring ,,the ,,sea ,,bottom ,,in ,a ,,diver',s ,,sled ,the diver's sled is still another interesting ,german invention4 ,it is a sled provided with vertical and horizontal rudders1 which is towed by means of a motor-boat at the surface4 ,the diver1 seated on the sled1 and provided with a self-contained diving-suit1 can direct the motor-boat by telephone and steer his sled up and down and wherever he chooses4 ,and so without any physical exertion1 he can explore the bottom of the sea and hunt for wrecks4 ,,armored ,,diving-,,suits ,from time to time attempts have been made to construct a diver's suit that will not yield to the pressure of the sea1 so that the diver will not be subjected to the weight of the water about him1 but can breathe air at ordinary atmospheric pressure4 ,curious armor of steel has been devised1 with articulated arms and legs1 in which the diver is completely encased4 ,with the ordinary rubber suit1 the diver usually has his hands bare1 because he is almost as dependent upon the sense of touch as a blind man4 ,but where the pressure mounts up to such a high degree that a metal suit must be used1 no part of the body may be exposed4 ,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 suit4 ,the best that can be done1 then1 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 it4 ,but if a diver feels helpless in the bag of a suit now commonly worn1 what would he do when encased in a steel boiler2 for that is virtually what the armored suit is6 ,a common mistake that inventors of armor units have made is to fail to consider the effects of the enormous hydraulic pressure on the joints of the suit4 ,in order to make them perfectly tight1 packings must be employed1 and these are liable to be so jammed by the hydraulic pressure that it is well nigh impossible to articulate the limbs4 ,again1 the construction of the suit should be such that when a limb is flexed it would not displace any more water than when in an extended position1 and vice versa4 ,a diver may find that he cannot bend his arm1 because in doing so he would expand the cubical content of his armor by a few cubic inches1 and to make room for this increment of volume it would be necessary for him to lift several hundred pounds of water4 ,the hydraulic pressure will reduce the steel suit to its smallest possible dimensions1 which may result either in doubling up the members or extending them rigidly4 ,but these difficulties are not insuperable4 ,there is no reason why a steel manikin cannot be constructed with a man inside to direct its movements4 ,,the ,,salvor',s ,,submarine ,other schemes have been devised to relieve the diver of abnormally high air-pressure4 ,one plan is to construct a large spherical working-chamber strong enough to withstand any hydraulic pressure that might be encountered4 ,this working-chamber is equipped with heavy glass ports through which the workers can observe their surroundings in the light of an electric search-light controlled from within the chamber4 ,the sphere is to be lowered to the wreck from a barge1 with which it will be in telephonic communication and from which it will be supplied with electric current to operate various electrically driven mechanisms4 ,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-chain4 ,this done1 the sphere would be moved to another position1 as directed by telephone and another chain made fast4 ,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 raised4 ,it is a pity that ship-builders have not had the forethought to provide substantial shackles at frequent intervals firmly secured to the framing4 ,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 divers4 ,one man proposes the use of a gigantic pair of ice-tongs2 and there have been no end of suggestions that lifting-magnets be employed1 but no one who has any idea of how large and how heavy such magnets must be would give these suggestions any serious consideration4 ,but1 after all1 the chief obstacle to salvage in the open sea is the danger of storms2 months of preparation and thousands of dollars' worth of equipment may be wiped out in a moment4 ,,fighting ,,the ,,waves ,,with ,,air ,however1 there has been another recent development which may have a very important bearing on this problem of deep-sea salvage work4 ,it has often been observed that a submerged reef1 twenty or thirty feet below the surface1 may act as a breakwater to stop the storming waves4 ,an inventor who studied this phenomenon arrived at the theory that the reefs set up eddies in the water which break up the rhythm of the waves and convert them into a smother of foam just above the reef4 ,thereupon he conceived the idea of performing the same work by means of compressed air4 ,he laid a pipe on the sea bottom1 forty or fifty feet below the surface1 and pumped air through it4 ,just as he had expected1 the line of air bubbles produced exactly the same effect as the submerged reef4 ,they set up a vertical current of water which broke up the waves as soon as they struck this barrier of air4 ,the pneumatic breakwater1 as it is called1 has been tried out on an exposed part of the ,california coast1 to protect a long pier used by an oil company4 ,it has proved so satisfactory that the same company has now constructed a second breakwater about another pier near by4 ,there is no reason why a breakwater of this sort should not be made about a wreck to protect the workers from storms4 ,where the water is very deep1 it would not be necessary to lay the compressed-air pipe on the bottom1 but it could be carried by buoys at a convenient depth4 ,summing up the situation1 then1 there are two serious bars to the successful salvage of ships sunk in the open sea--the wild fury of the waves on the surface2 and the silent1 remorseless pressure of the deep4 ,the former is the more to be feared2 and if the waves really can be calmed1 considerably more than half the problem is solved4 ,as for the pressure of the sea1 it can be overcome1 as we have seen1 either by the use of special submarine mechanisms1 or of man-operated manikins or even of unarmored divers4 ,we have reached a very interesting stage in the science of salvage1 with the promise of important developments4 ,fifty fathoms no longer seems a hopeless depth4 ,even in times of peace the sea exacts a dreadful toll of lives and property4 ,before the war the annual loss by shipwreck around the ,british ,isles alone was estimated at forty-five million dollars4 ,but the war1 although it was frightfully destructive to shipping1 may in the long run save more vessels than it sank2 for it has given us sound-detectors which should remove the danger of collisions in foggy weather1 and the wireless compass1 which should keep ships from running off the course and on the rocks4 ,and now1 if salvage engineering develops as it should1 the sea will be made to give up not only much of the wealth it swallowed during the war1 but also many of the rich cargoes of gold and silver it has been hoarding since the days of the ,spanish galleon4 ,,index ,air1 fighting waves1 #ccd raising ship1 on1 #cai war in1 #abc ,airplane1 ambulance1 #adf armored1 #aci artillery-spotting1 #aca camera1 #agc cartridges1 #aca classes of work1 #abg fighting among clouds1 #acg flying boats1 #add gasolene tank1 #acj giant1 #acb hospital1 #adf launching from ship1 #cjc ,liberty motor1 #adb scouting1 #abe scouts1 #abh speed of1 #acd spotting1 #agg training spotters1 #ahj wireless telephone1 #aid ,see also ,seaplane ,ambulance airplane1 #adf ,armored diving-suit1 #ccj ,arms and armor1 #aaa ,artillery1 hand1 #bc ,atmosphere1 shooting beyond1 #fd ,audion1 #ahe ,balloon1 ,blimp1 #bfj helium1 #afd historical1 #adh hydrogen1 #aej ,balloon1 kite1 #agd principles1 #aej record flight1 #fe ,barbed wire1 #ae cylinders1 #ag gate1 trench1 #i gates through1 #ae shelling1 #af ,barge for towing seaplanes1 #cjb ,barrage1 grenade1 #bg mine1 #bib ,battle-fields1 miniature1 #ahj ,blimp1 #bfj ,blisters on ships1 #cjg ,boats1 electric1 #cjh ,eagle1 #cja flying1 #add surface1 #bih ,bombs to destroy barbed wire1 #af ,breakwater1 pneumatic1 #cce ,browning1 ,john ,m41 #ef ,buildings1 shadowless1 #bbg ,caisson disease1 #cbe ,caliber1 #fh ,camera1 airplane1 #agc ,camouflage and camoufleurs1 #baa buildings1 #bbg grass1 #bbi horse1 #bbc land1 #bbb roads1 #bbe ,camouflage1 ships1 #baa ,cartridges1 aircraft guns1 #aca ,catapults1 #cf ,caterpillar tractor1 #aji ,caves1 #h ,coffer-dam1 salvage1 #cah ,color1 analyzing1 #bbi screens1 #bbi ,compass1 wireless1 #bja ,convoy1 #bfg ,countermines1 #ag ,deep sea1 conditions in1 #cab ,deep water diving1 #cbg ,depth bombs1 #bfe ,devil's eggs1 #bgf ,diesel engine1 #bdj ,direction-finder1 #bje ,dirigible1 see ,balloon ,disease1 caisson1 #cbe ,diver1 armored suit1 #ccj caisson disease1 #cbe rest chamber1 #cbh sled1 #ccj submarine torch1 #cbi suit1 #cbd ,diving1 deep1 #cbd record depth1 #cbg ,duck-boards1 #i ,dugouts1 #g ,dummy heads of papier mch1 #ac ,eagle boats1 #cja ,egg-laying submarines1 #bhg ,eggs1 ,devil's1 #bgf ,electric motor-boat1 #cjh ,engine1 ,diesel1 #bdj ,field-guns1 #ha ,fire broom1 #aje liquid1 #ajc ,forts1 machine-gun1 #eh ,fuse1 grenade1 #bh ,gas1 #he ,american1 #ajb ,gas attack1 boomerang1 #ib first1 #hi ,gas1 chlorine1 #hg diphosgene1 #if exterminating rats1 #id grenades1 #bf helium1 #afd hydrogen1 #aej lock1 #ig masks1 #ii mustard1 #ih phosgene1 #ic pouring like water1 #hf shell1 #ie sneezing1 #ih tear1 #ie vomiting1 #ih ,gasolene-tank1 airplane1 #acj ,gate1 barbed wire1 trench1 #i ,gates through barbed wire1 #ae ,gatling gun1 #dc ,geologists1 ,messines ,ridge1 #ai ,glass1 non-shattering1 #ajj ,grapnel shell1 #af ,graveyard1 submarine1 #cad ,grenade1 disk-shaped1 #cc fuse1 #bh gas1 #bf hair brush1 #cd history of1 #bc ,mills1 #bi parachute1 #ca range of1 #be rifle1 #bh throwing implement1 #bg ,grenade1 wind-vane safety device1 #cb ,gun1 aircraft1 #aca ,american1 #ej-mile1 #fc big1 hiding1 #bbf caliber1 #fh disappearing1 #gg double-end1 #ade #ah-;inch1 monitors1 #cjf elastic1 #gc field1 #ha #db-;centimeter1 #gi how made1 #gf #abj-mile1 #gj long range1 ,german1 #fb non-recoil1 #ade on submarine1 #bdi #af-;inch1 coast defense1 #gh ,skoda1 #ha spotting by sound1 #aha three-second life1 #gc #ab-;inch1 submarine1 #bea ways of increasing range1 #fg wire-wound1 #gf ,hand-grenade1 see ,grenade ,helium1 #afd ,hospital1 airplane1 #adg ,horizon1 seeing beyond1 #bai ,howitzer1 #gi ,hush ships1 #cjd ,hydroaroplanes1 see ,seaplanes ,hydrogen1 weight of1 #aej ,hydrophone1 #bgj ,illusions1 optical1 #bae ,kilometer1 length in miles1 #f ,kite balloons1 #agd ,kite1 water1 #bhc ,liberty motor1 #adb ,liquid-fire1 #ajc ,locomotives1 gasolene1 #aj ,lusitania1 #caf ,machine-gun1 #aab airplane1 #abg ,bent-,merci1 #eb ,browning1 #ec ,colt1 #dd forts1 #eh ,gatling1 #dc history1 #da ,hotchkiss1 #di ,lewis1 #ej ,maxim1 #db water-jacket1 #dg worth in rifles1 #eh ,machine-rifle1 #ee ,magnets1 lifting1 salvage1 #ccd ,maps1 making with camera1 #age ,marne1 first battle of1 #d ,messines ,ridge1 mine1 #ai ,metal-cutting under water1 #cbi ,microphone detectors1 mines1 #ah ,mine-field1 ,north ,sea1 #bij ,mine laying1 ,north ,sea1 #bib ,mine-laying submarine1 #bhg ,mine railroad1 #bid ,mine-sweeping1 #bha ,mines1 #bgf anchored1 #bgh and counter-mines1 #ag automatic sounding1 #bgh drift of1 #bhe electric1 #bgg floating1 #bhd ,messines ,ridge1 #ai ,mines1 paravanes1 #bhh ,monitors1 #cjf ,mortars1 #gi depth bomb1 #bff flying1 #bc ,mortars1 ,see also ,trench mortars ,mother-ships for airplanes1 #cje ,motor-boat1 electric1 #cjh sea ,tank1 #bii ,motor torpedo-boats1 #bih ,mystery ships1 #bbj ,net1 ,north ,sea1 #bij ,ocean currents1 #bhe ,optical illusions1 #bae ,oxy-hydrogen torch1 submarine1 #cbi ,paint in war1 #bji ,papier mch heads1 #ac ,papier mch horse1 #bbc ,parachute1 #age grenade1 #ca search-light shell1 #hd ,paravanes1 #bhh ,periscope1 submarine1 #bdd trench1 #aa ,pill-boxes1 #ei ,pneumatic breakwater1 #cce ,pontoons1 salvage1 #cbj ,propeller1 shooting through1 #acf ,radio1 see ,wireless ,railroad1 mine1 #bid ,railways1 trench1 #aj ,range-finder1 #agj ,range1 getting the1 #afi ,range of guns1 increasing1 #fg ,range1 torpedo1 #bac ,rats1 freeing trenches of1 #id ,rifle grenade1 #bh safety device1 #cb ,rifle1 machine1 #ee ,rifle stand1 fixed1 #ad ,roads1 camouflage1 #bbe ,salvage1 #caj diving1 #cbd ice-tongs1 #ccd lifting-magnets1 #ccd methods1 #cag pneumatic1 #cai pontoons1 #cbj shackles on ships1 #ccc submarine ,f-#d1 #cba submarine sphere1 #ccb ,scouts1 airplane1 #abh ,sea1 deep1 conditions1 #cab ,sea gulls finding submarines1 #beh ,sea lions locating submarines1 #bei ,sea tank1 #bii ,seaplane1 #adc automatic1 #ade submarine patrol1 #bei torpedo1 #ade towing-barges1 #cjb ,search-light shell1 #hd ,shackles1 salvage1 #ccc ,shadowless buildings1 #bbg ,shell1 gas1 #ie grapnel1 #af search-light1 #hd shrapnel1 #hc ,stokes mortar1 #ci ,shield on wheels1 #aad ,ships1 airplane1 #cjd ,ships1 blisters1 #cjg camouflage1 #baa clothes-line1 #bbj convoy1 #bfg hush1 #cjd making visible1 #bcj monitors1 #cjf mystery1 #bbj railroads on1 #bid sunk by submarines1 #caj ,ships1 see also ,salvage ,shrapnel shell1 #hc ,sled1 submarine1 #ccj ,smoke screen1 #bfb ,sniper1 locating1 #ac ,sniperscopes1 #ab ,sound1 detecting submarines1 #bfi ,sound detectors1 mines1 #ah ,sound1 spotting by1 #aha ,sphere1 salvor's submarine1 #ccb ,spotting by sound1 #aha ,spotting gun-fire1 #agg ,submarine1 blindness1 #bdd chasers1 #bee construction1 #bcd depth bombs1 #bfe egg-laying1 #bhg engines1 #bdf ,f-#d1 salving1 #cba getting best of1 #bec graveyard1 #cad guns on1 #bdi history1 #bcb hydrophone1 #bgj mine-field1 #bij mine-laying1 #bhg net1 #bij oil-tank1 #bcf periscope1 #bdd reclaiming victims of1 #caj rest chamber1 #cbh salvage vessel1 #ccb sea-gulls1 #beh sea-lions1 #bei seaplanes1 #bei ships sunk1 #caj sled1 #ccj steam-driven1 #bej torch1 #cbi torpedo1 #bdf #ab-;inch gun1 #bea vs4 submarine1 #bfi ,super-guns1 #fb ,tank1 #ajg ,american1 #abb flying1 #aci ,french1 #aai ,german1 #abj one-man1 #aad sea1 #bii small1 #aba ,telegraphy1 rapid1 #aii ,telephone1 ,new ,york to ,san ,francisco1 #ahf wireless1 #agh ,titanic1 #cad ,,tnt 7trinitrotoluol71 #ah ,torch1 submarine1 #cbi ,torpedo1 #bii boats1 motor1 #bih electrically steered1 #cjh construction1 #bdf getting range1 #bac proof ships1 #cjf seaplane1 #ade ,towing-barge1 seaplane1 #cjb ,trajectory1 #bb ,trench1 gas-lock1 #ig ,trench mortar1 #cf pneumatic1 #cg ,stokes1 #ch ,trench railways1 #aj ,trench warfare1 #d ,trenches1 #ba barbed wire gates1 #i duck-boards1 #i ,tunnels1 mines1 #ag to observation posts1 #ab ,u-boats1 see ,submarines ,villages1 underground1 #g ,walking-machine1 #ajh ,war1 paint1 #bji ,water kites1 #bhc ,waves1 fighting with air1 #ccd ,wireless compass1 #bja spy detector1 #bjj ,wireless telegraph1 rapid1 #aii ,wireless telegraphy explained1 #ahh ,wireless telephone1 #agh airplane1 #ahd ,wireless telephony across ,atlantic1 #aib ,woolworth ,building1 falling from1 #ace ,wrecks1 see ,salvage ,zeppelin and ,lowe's balloon1 #adi ,zeppelin balloon1 construction1 #aef ,zeppelin1 suspended observer1 #afb ,zeppelin's failures and successes1 #aed 99 99 99 99 99 99 ,transcribers' note3 ,punctuation and spelling were made consistent when a predominant preference was found in this book2 otherwise they were not changed4 ,simple typographical errors were corrected2 occasional unbalanced quotation marks retained4 ,ambiguous hyphens at the ends of lines were retained4 ,some illustrations have been slightly repositioned to improve their appearance in e,books4 ,page #gf3 eight tenths of an inch may be a misprint for eight ten-thousandths of an inch4 ,page #ajj3 inhaled air was misprinted as inhaled aid4 ,page #ajd3 would send the stream was misprinted as sent4 ,page #aac3 ,secretely was printed that way4 ,page #bji3 psycologists was printed that way4