,illustration3 ,copyright1 ,ewing ,galloway ,the drop forge4 ,a fourteen-ton hydraulic press is employed in forging an immense open hearth steel plate4 ,,popular ,,science ,,library ,,editor-,,in-,,chief ,,garrett ,p4 ,,serviss ,,authors ,,william ,j4 ,,miller ,,hippolyte ,,gruener ,a4 ,,russell ,,bond ,d4 ,w4 ,,hering ,,loomis ,,havemeyer ,,ernest ,g4 ,,martin ,,arthur ,,selwyn-,,brown ,,robert ,,chenault ,,givler ,,ernest ,,ingersoll ,,wilfred ,,mason ,,barton ,,william ,b4 ,,scott ,,ernest ,j4 ,,streubel ,,norman ,,taylor ,,david ,,todd ,,charles ,,fitzhugh ,,talman ,,robin ,,beach ,,arranged ,,in ,,sixteen ,,volumes ,,with ,a ,,history ,,of ,,science1 ,,glossaries ,,and ,a ,,general ,,index ,,illustrated ,illustration3 ,,logo ,,volume ,,five ,p4 ,f4 ,,collier ,,son ,,company ,,new ,,york ,copyright #aibb ,,by ,p4 ,f4 ,,collier ,,son ,,company ,,manufactured ,,in ,u4 ,s4 ,a4 ,,mechanics ,,the ,,science ,,of ,,machinery ,,by ,a4 ,,russell ,,bond ,,formerly ,,managing ,,editor1 ,,scientific ,,american ,illustration ,p4 ,f4 ,,collier ,,son ,,company ,,new ,,york ,,preface ,,although strictly speaking the term 8,mechanics0 applies to that branch of ,physics that deals with the actions of forces on material bodies1 originally the word had a broader meaning embracing all machinery and mechanical inventions4 ,to-day popular usage is restoring to the term its original broad interpretation1 and it is in this popular but rather unorthodox sense that 8,mechanics0 has been chosen as the title of this book2 for although certain elementary principles of mechanics are described and explained1 the major portion of the book deals with machines and their evolution to their present stage of perfection4 ,machines are man's creation1 and yet in a sense the man of to-day is a machine product2 for modern civilization owes its material and in large measure its esthetic development to machinery4 ,the story of machinery1 from primitive man's first attempts to augment his physical powers with mechanical aids down to the present era of gigantic1 steel-muscled machinery and marvelously intricate mechanisms1 is the story of human progress4 ,it is this story that we have endeavored to tell in the following pages1 but the subject is too large to be covered in a single volume or even a dozen volumes4 ,under the circumstances we have been obliged to confine ourselves to a mere outline1 selecting certain avenues of progress more marked than others and presenting brief sketch maps of them4 ,we have aimed in this way to give a bird's-eye view of the whole story of human progress in things material4 ,the book has not been written for the mechanical engineer1 but for the layman who would learn of the mechanical contrivances that contribute to his material welfare2 hence technical terms have been avoided1 as far as possible1 and where unavoidable have been explained and defined4 ,a4 ,,russell ,,bond ,,contents ,,chapter ,,page ,i4 ,,tool-,,making ,,animals #i ,,ii4 ,,the ,,anatomy ,,of ,a ,,machine #bj ,,iii4 ,,machines ,,for ,,making ,,machines #db ,,iv4 ,,counting ,,seconds #eg ,v4 ,,putting ,,rivers ,,to ,,work #ge ,,vi4 ,,liquid ,,levers ,,and ,,gears #id ,,vii4 ,,air vs4 ,,water #aji ,,viii4 ,,air ,,springs ,,and ,,cushions #abf ,,ix4 ,,power ,,from ,,heat #aci ,x4 ,,burning ,,fuel ,,in ,,the ,,engine ,,cylinder #aee ,,xi4 ,,when ,,coal ,,and ,,oil ,,are ,,exhausted #aga ,,xii4 ,,invasion ,,of ,,the ,,sea #ahb ,,xiii4 ,,sliding1 ,,rolling1 ,,walking1 ,,and ,,creeping #bjc ,,xiv4 ,,invasion ,,of ,,the ,,sky #bai ,,xv4 ,,helping ,,the ,,farmer #bci ,,xvi4 ,,machining ,,the ,,earth #bea ,,xvii4 ,,from ,,fiber ,,to ,,fabric #bfh ,,xviii4 ,,the ,,making ,,of ,,paper #bhi ,,xix4 ,,typesetting ,,and ,,printing ,,machinery #cjj ,,xx4 ,,cast ,,iron1 ,,wrought ,,iron1 ,,and ,,steel #cad ,,xxi4 ,,animated ,,machinery #cbf ,,xxii4 ,,heat ,,vacuums #cde ,,xxiii4 ,,engines ,,of ,,destruction #cei ,,xxiv4 ,,summary ,,of ,,mechanical ,,progress #cgf ,,list ,,of ,,illustrations ,,the ,,drop ,,forge--,,forging ,a ,,steel ,,plate ,frontispiece ,,facing ,,page ,,raising ,,water ,,with ,a ,,chain ,,of ,,pots--,a ,,primitive ,,pump ,,used ,,in ,,egypt #cb ,,horse-,,operated ,,chain ,,pump ,,used ,,in ,,greece #cb ,,multiple ,,spindle ,,drill ,,in ,a ,,motor ,,car ,,factory #cc ,,bucket ,,of ,a ,,giant ,,dredge ,,with ,,its ,,jaws ,,wide ,,open #fd ,,gold ,,dredge ,,eating ,,its ,,way ,,through ,,river ,,sands #fe ,,suction ,,dredge ,,excavating ,a ,,channel ,,and ,,building ,,new ,,land #fe ,,air ,,lock ,,of ,a ,,pneumatic ,,caisson #if ,,subaqueous ,,tunnel ,,showing ,,the ,,shield ,,in ,,the ,,background #ig ,,wharf ,,protected ,,by ,a ,,pneumatic ,,breakwater #abh ,,sun-,,power ,,plant ,,in ,,egypt #abi ,,close-,,up ,,of ,,one ,,of ,,the ,,reflectors ,,of ,a ,,sun-,,power ,,plant #abi ,,giant ,,caproni ,,hydroaeroplane #afj ,,concrete ,,steamship 8,,faith0 #afa 8,,virginian10 ,,the ,,largest ,,locomotive ,,in ,,the ,,world #afa ,,loom ,,provided ,,with ,a ,,jacquard ,,attachment #bbd ,,battery ,,of ,,mule ,,spinning ,,frames #bbe ,,jacquard ,,attachment ,,for ,,loom #bbe ,,digging ,a ,,trench ,,with ,a ,,machine ,,of ,,the ,,chain ,,type #bef ,,multiple ,,plowing ,,on ,a ,,western ,,wheat ,,field #beg ,,sawing ,,logs ,,of ,,pulpwood ,,into #af-;,,inch ,,lengths #bhh ,,heater ,,in ,a ,,pulp ,,mill ,,where ,,the ,,wood ,,pulp ,,is ,,mixed ,,with ,,clay #bhh ,,modern ,,fourdrinier ,,paper-,,making ,,machines #bhi ,,molten ,,metal ,,from ,a ,,blast ,,furnace #cbj ,,bessemer ,,converter ,,blowing ,,air ,,through ,a ,,mass ,,of ,,molten ,,iron #cbj ,,steel ,,beam ,,passing ,,through ,,the ,,finishing ,,rolls #cba ,,compositor ,,at ,,work ,,on ,a ,,linotype ,,machine #ceb ,,the ,,optophone1 ,,which ,,enables ,,the ,,blind ,,to ,,read ,,print #cec ,,blind ,,man ,,reading ,,with ,,his ,,ears #cec ,,chapter ,i ,,tool-,,making ,,animals ,,when we review the marvelous achievements of modern civilization we are quite willing to agree with the ancient psalmist that man is 8little lower than the angels40 ,but at the other end of the scale our complacency is liable to receive a rude shock2 apparently the boundary between man and beast is not so very easy to draw4 ,we used to be told that one important superiority of mankind lies in the fact that he makes use of tools1 while the beast never uses any implement except those that nature has furnished him as part of his own organism4 ,but a gorilla will throw stones at his enemy2 and he knows how to brandish a club and use it with telling force4 ,some of the apes are known to use sticks to knock down fruit which is out of the reach of their hands1 and they will crack nuts with a stone4 ,clearly these animals are tool users4 ,a very intelligent orang-utan in the ,bronx ,zological ,garden1 ,new ,york1 after trying for days to wrench off a bracket from the wall of his cage eventually used the horizontal bar of his trapeze as a lever and with it pried the offending bracket from its fastenings4 ,here was real invention and the discovery of the principle of leverage4 ,the great black arara cockatoo of ,new ,guinea uses his beak as a saw to weaken the shells of hard nuts1 and to keep his bill from slipping off the smooth shell he is ingenious enough to wrap a leaf around the nut to hold it steady4 ,even in the insect world we find creatures resourceful enough to make use of tools4 ,prof4 ,franz ,doflein of the ,university of ,breslau tells of an interesting study of certain ants1 known as the ,oecophylla smaragdina1 who build their nests in bushes by fastening leaves together with fine threads4 ,but the ants that build the nests cannot spin these threads1 because they possess no spinning glands4 ,they must depend upon their larv for this product4 ,when a rent was made in one of these nests1 a band of the tiny creatures ranged themselves side by side along the torn edge of the leaf and reached across the gap until they could catch hold of the opposite edge with their mandibles4 ,then they drew back step by step1 with perfect teamwork1 until the two edges were brought together4 ,in the meantime1 other ants had rushed to the nursery and each one had picked up a larva1 not with the idea of bearing it off to safety1 but in order that the babies might spin the thread which the adult ants were unable to do4 ,the larv were carried to the breach in the nest and moved back and forth across the rent4 ,they were pressed first against one side of the tear and then the other and all the while were squeezed tightly1 evidently with the purpose of making them spin4 ,gradually a fine silky web was woven across the torn leaf and eventually the rent was completely patched4 ,unquestionably these little ants are tool-using animals1 because they make their larv serve as spinning spindles and also as weavers' shuttles4 ,however1 this can hardly be cited as a point in common with even the lowest type of man1 for the ants merely use the tools they find at their disposal4 ,they certainly cannot be credited with having produced or even improved the tool which they use1 whereas even in the most primitive of men we find that the tools used are not only carefully selected for the work to be performed1 but are actually1 shaped1 be it ever so crudely1 to suit the job4 ,clearly we must shift the boundary between man and beast1 distinguishing the former as the creature who artificially improves his tools4 ,but even here it is not absolutely certain that the boundary will stand4 ,wilhelm ,boelsche1 a well-known ,german writer on natural history1 calls attention to the 8blacksmith woodpecker0 which will thrust hard pine nuts into cracks in the trunk of a tree1 so that they are held as if in a vise1 enabling the bird to operate upon the seed more easily4 ,furthermore1 this woodpecker will actually make a hole in the tree to receive the nut if there is not a hole or crack handy1 so that evidently this animal does produce or artificially improve the tool that it uses4 ,there are a few such examples in nature1 just enough to cast a bit of uncertainty on the boundary we have set4 ,but although the actual line of demarcation may not be clear1 there is no question but that the lowest type of humanity now existent1 or of which we have any record1 is or was a tool maker4 ,chipped stones evidently fashioned by man for some useful purpose are found even in the remains of the ,middle ,tertiary ,epoch4 ,the spirit of inquiry1 of experiment1 of invention1 and the ambition to dominate over other members of the animal kingdom or over the obstacles imposed by nature1 are to be found more or less active among all peoples1 no matter how lowly a position they may occupy in the scale of civilization4 ,,war ,,as ,a ,,stimulus ,,of ,,invention ,the most primitive implements were probably developed for the purpose of war4 ,from the very earliest times1 down to the present day1 war has been a most potent stimulus of invention4 ,the first tools ever used were probably intended to enable the user to cope with dangerous enemies4 ,they marked the first stage in the conquest of brain over mere brawn4 ,the primitive weapons were used not only in fighting other men1 but in fighting off dangerous animals1 and then in hunting animals for food4 ,no doubt the first implement ever used was a club1 which gave a real advantage over the unarmed1 scratching1 tearing1 and biting enemy4 ,this was a lever which increased the reach of the fighter1 and also increased the power of his blow4 ,the heavier the club1 the more dangerous the weapon1 particularly when most of the weight was centered at the outer end of the stick4 ,but he was a real genius who first fastened a rock to the end of his club4 ,,the ,,art ,,of ,,breaking ,,stones ,then arose the art of breaking stones--breaking them skillfully1 so as to form a jagged cutting edge4 ,when man began to fashion tools of stone he left imperishable records of his craftsmanship which enable us to trace his progress in invention4 ,the first finished tool we find was the fist hatchet--a stone roughly chipped to form a cutting edge and of convenient shape for the grasp of the hand4 ,this primitive tool very slowly1 through a period covering thousands of years1 developed into all manner of cutting implements1 some with handles of wood and bone4 ,the ax head was followed by the spearhead and this finally by the arrowhead1 showing that man had at last found a mechanical substitute for his muscles to hurl projectiles farther and with greater accuracy than he could throw them by hand4 ,we marvel at the resourcefulness and skill of the primitive savage in working so difficult a material as stone4 ,it would baffle a modern mechanic to be required to shape a piece of flint into an arrowhead with no other tool than a piece of bone4 ,he is so accustomed to using tools which are harder than the material they are intended to shape that he cannot conceive of making any impression upon a piece of flint with a piece of bone1 to say nothing of a stick of hard wood1 and yet such tools were used away back in the ,stone ,age4 ,at first stones were roughly shaped by hammering them together4 ,then the artisans became more skilled4 ,they discovered that certain stones could be chipped more regularly and evenly1 and the art of flaking off chips of flint sprang up4 ,some specimens that belonged to ages long preceding that of recorded history are beautifully done4 ,the spearheads are symmetrically shaped like a long narrow leaf1 and the stone is evenly furrowed on both sides with a keen edge all around4 ,not only did primitive artisans shape the stone implements with hammer blows1 but they learned how to shape stone by pressure as well1 using a tool that was relatively soft4 ,it is not a very difficult matter to shape even so hard a substance as glass merely by pressure4 ,if a piece of glass is laid on a table with its edge slightly overhanging that of the table1 it is possible to chip off the overhanging edge by pressing a nail or even a hard stick of wood against this edge4 ,a small flake of glass is thus removed1 and1 by continuing the process1 arrowheads of any shape may be formed4 ,the tool is placed not against the upper surface of the glass1 but against the edge of the glass1 so that only the lower surface of it is split or flaked off4 ,then the glass is turned over and a chip is taken off the opposite face4 ,in the ,middle ,stone ,age we find the primitive craftsman equipped with a very complete assortment of stone tools4 ,he had hammers1 chisels1 scrapers1 drills1 and polishing tools4 ,he knew how to make useful household implements1 such as spoons and ladles1 out of bone4 ,he polished his work and ornamented the implements with carvings of animals4 ,ivory pins and needles show that he had begun to make himself clothing from the skins of animals and that he sewed them together with thongs or tendons4 ,in the ,late ,stone ,age he had learned how to make vessels of fire-baked clay4 ,his axes were ground to a sharp edge1 and he bored holes in the ax head to receive the ax handle4 ,the ,swiss lake dwellers built houses of wood and fitted them with all sorts of wooden furniture carved with stone tools4 ,among the remains of these interesting settlements may be found balls of clay which1 from the fact that one of them was discovered with a spool of flax still attached to it1 were evidently used as spinning 8whorls0 used for spinning flax into thread4 ,clothing of skins was giving way to or being supplemented with clothing of woven fabric4 ,,discovery ,,of ,,the ,,lever ,,and ,,the ,,wedge ,prior to the ,stone ,age the club was undoubtedly used1 in time of peace--if there ever was a time of peace in those days--to batter down trees1 to beat through entanglements and to dislodge great stones4 ,here the first idea of leverage was evidently employed4 ,the club with a rock tied to it1 particularly if the rock was shaped with a sharp edge1 made a better implement for hewing trees4 ,it is quite probable that soon after this stage of development had been reached1 some one discovered the use of the wedge1 particularly in splitting timber4 ,of course1 no one realized in those early days why it was that he could pry up a greater weight with a lever than he could lift directly by hand1 or why he could split open a log by driving wedges into it4 ,the art of mechanics was in existence long ages before science of mechanics began to be studied4 ,but it was not until men began to look into the why of things that rapid progress was made4 ,we can go on endlessly with our speculations on the evolution of tools and machinery up to the time when historians began to record the mechanical achievements of man4 ,unfortunately even after historians began to write they were so filled with admiration for the destructive work of man that they had no time to record his constructive work4 ,the warrior who spread havoc and terror received all the glory1 and his deeds were written on parchment1 inscribed in clay and carved in stone2 but the humble artisan was not worthy of mention4 ,even when the science of mechanics came to be studied1 it was shrouded in a veil of mystery1 and it was beneath the dignity of the man of science to impart his knowledge to the artisan4 ,there was a lack of cooperation between science and industry that has persisted to a certain extent even up to the present time4 ,some of the most ingenious inventions of the ancients were employed by a corrupt and crafty priesthood to produce apparently miraculous effects and hoodwink the general public2 and so1 in looking back to the early days of mechanics1 we are obliged to draw upon our imagination to trace its evolution1 supplementing this by a study of the tools of primitive people of more recent time4 ,practically every form of hand tool we now use must have been known to the ancient artisan4 ,,invention ,,of ,,the ,,wheel ,we are not going to attempt to write a history of the evolution of machinery1 but there is one invention whose origin is lost in the remote prehistoric ages which deserves more than passing attention4 ,it is a pity that we have no clue as to who invented the wheel or how this most important element that enters into the construction of nearly all machinery was evolved4 ,the invention called for a remarkable degree of originality4 ,there is nothing like a wheel in nature4 ,levers we have in our own physical frame4 ,but a wheel is something that is distinctly a human creation4 ,whoever invented it must have been a real genius1 a ,james ,watt or a ,thomas ,edison of his day4 ,certainly we owe more to the invention of the wheel than we do even to so revolutionary a machine as the steam engine1 or the flying machine4 ,how it was ever first conceived is a mystery4 ,maybe this primeval genius got his idea from seeing a stone rolling downhill1 or he may have seen a tumbling weed rolling along the ground before the wind4 ,it may be that the forerunner of the wheel was a roller shaped out of a log1 for certainly primitive civilization must have advanced enough to have known how to hew timber before it would have been capable of fashioning a wheel4 ,some observant man might have noticed that he could drag a heavy timber over a rolling log much more easily than he could along the bare ground1 and gradually the roller evolved into a wheel4 ,we can speculate upon the evolution of vehicles and transportation1 once the wheel was invented4 ,of course1 the first method of transporting loads was to carry them in the arms4 ,possibly loads were placed on skids and dragged along by one end4 ,away back in early times1 it was discovered that two persons could carry more than twice as much as one1 if the load were placed on a couple of poles4 ,there was no friction to contend with1 and not only was the load cut in two1 because each man bore half of it1 but the position of the load was such that it could be borne more easily4 ,after the wheel was discovered1 some one must have conceived of the idea of dispensing with an assistant by placing a wheel between the poles of the stretcher1 thus making a crude wheelbarrow4 ,it is more likely that two wheels were first used1 making a cart of the stretcher1 because the crude workmen of those days could hardly have produced anything but a very wobbly wheelbarrow4 ,at any rate1 the wheel1 or pair of wheels1 robbed one man of his job4 ,only one bearer was required where before two had been used4 ,labor costs were immediately reduced #ej per cent4 ,,displacing ,,men ,,with ,,machines ,in the very earliest days of invention machines began to displace men4 ,had there been unions in those days1 no doubt there would have been strenuous opposition to the introduction of this substitute for an honest worker4 ,but among the ancients1 even more than at the present time1 invention meant greater production rather than less work1 because the laborer of that time was not a hired man but a slave4 ,there was no object in cutting down labor when it cost practically nothing4 ,the only stimulus to invention was greater production4 ,the invention of the wheel meant the dawn of transportation1 which is the backbone of civilization1 and from it resulted no end of other inventions4 ,it made it possible for communities to come into closer touch with each other4 ,it meant circulation--an interchange of knowledge and of products4 ,food was transported from one locality to another1 enabling certain communities to dispense with agricultural work and specialize in certain lines of manufacture2 for they could barter their products for food raised by other communities4 ,there are some tribes to-day which are most backward because they are separated from other tribes by rivers1 while other tribes similarly placed owe their progress to the fact that they have developed sufficient skill to build crude bridges and thus gain access to the outside world4 ,,raising ,,water ,in ,egypt the wheel had a wonderful effect on agriculture4 ,in that dry land water is1 and always has been1 most precious4 ,no wonder the ,nile was venerated6 ,it meant life--life to crops1 and hence life to man4 ,how to raise water from this stream of life in time of drought was the great problem of the ,egyptian4 ,as slave labor was cheap1 it was customary to haul up the precious water1 a bucket at a time1 and pour it over the fields4 ,then some one discovered that this process could be simplified by using a shadoof or swape2 in other words1 a long pole fulcrumed near one end1 with a heavy rock for a counterbalance lashed to the shorter arm1 and a bucket tied by a long rope to the longer arm of the lever4 ,this primitive machine is still to be found in some rural districts4 ,with this contrivance1 a heavier load could be lifted than by hand1 because1 when raising the bucket1 the weight of the rock would assist in lifting the water4 ,after the swape came all manner of ingenious devices for lifting the water4 ,there were seesaw arrangements which would scoop up some of the water at each oscillation of the seesaw1 and in one ingenious contrivance there was a succession of seesaws by which the water was raised to a considerable height1 whence it poured down into ditches that irrigated the fields4 ,then some one invented a water wheel or a great wheel1 fitted with buckets1 which was turned by human or ox power1 and which poured a steady stream of water into the irrigating ditches4 ,but the greatest invention was that of the engineer who actually made the river turn the wheel4 ,it was probably on the ,nile that the noria1 as this machine was called1 was first put into service4 ,the wheel was provided with paddles1 so that the current made it revolve1 and the water spilled out of the buckets into a trough as they were turned over by the wheel4 ,we can imagine the triumph of the ancient inventor who developed that machine4 ,true1 the river might arise in its wrath now and then and wreck the machine1 but in wrecking the wheel it had to flood the land1 which1 after all1 was exactly what was aimed at4 ,the anger of the river was short-lived2 it soon quieted down and went on placidly turning the wheel which robbed it of the precious water4 ,it was a great event in the history of engineering4 ,the ,nile had been harnessed4 ,one of the great powers of nature had been set to work4 ,,chapter ,,ii ,,the ,,anatomy ,,of ,a ,,machine ,,every animal is a complex machine1 provided with its own motive power and a brain for directing the operation of its own mechanical elements4 ,not satisfied with the mechanism that nature has put into the human machine1 man has reached for other elements and devised mechanisms of his own in order to supplement the human machine and increase its efficiency4 ,at first1 as we have seen1 these elements were hand tools of the crudest sort2 but they were gradually improved and then they were combined into what we term machines4 ,in developing these machines1 he naturally took his own system as a pattern and was guided to a large extent by an examination of his own physical structure4 ,we see this very clearly in the names of the different parts of machinery1 which are taken from the names of similar parts in the human frame4 ,almost every member of the body is used in mechanical terminology4 ,for instance1 we have the 8head0 and the 8foot10 the 8arms0 and the 8legs10 the 8fingers0 and the 8ankles10 8elbows10 8shoulders10 8trunk10 8hips10 and various parts of the face1 such as the 8eyes10 8ears10 8nose10 8mouth10 8teeth10 8lips10 and even the 8gums10 to indicate parts of machinery which have some remote resemblance to these features4 ,before we can understand machinery we must have some general knowledge of the elements of which it is composed4 ,probably most of the readers of this book already possess a fair knowledge of machine elements and mechanical movements and they can well afford to skip this chapter4 ,however1 for the benefit of the uninitiated1 we must put a machine on the operating table1 dissect it1 and explain its anatomical structure4 ,we cannot attempt a very detailed study1 but will confine ourselves to the most important elements4 ,every machine is made up of movable parts and fixed parts1 the latter serving to guide or constrain the motion of the former2 for no combination of elements will constitute a machine unless the parts are constrained to move in certain predetermined directions4 ,,the ,,lever ,among the moving elements the first to be considered is the lever1 which really forms a broad classification comprising many elements that will hardly be recognized as levers at first blush4 ,levers in some form are to be found in practically every machine4 ,a wheel1 a gear1 and a pulley are really levers in disguise1 as will be explained presently4 ,of course everyone knows that a simple lever consists of a rigid bar that swings on a fulcrum4 ,the fulcrum may be a knife edge1 a shaft passing through the bar or any element on which the bar can be swung or oscillated4 ,the purpose of the lever is to give a certain advantage in the application of a force to a load4 ,this may be a change of speed and distance of travel1 and hence of power1 or merely a change of direction4 ,illustration3 ,,fig4 #a4--,,three ,,orders ,,of ,,simple ,,levers ,there are three types or orders of levers produced by varying the relative positions of the points where the fulcrum1 the force or effort1 and the weight or load are applied4 ,these are shown in ,figure #a4 ,in the lever of the first order the fulcrum is placed between the effort and the weight2 in the lever of the second order the weight is applied between the fulcrum and the effort2 and in the lever of the third order the effort is applied between the fulcrum and the weight4 ,in each case that part of the lever which extends from the fulcrum to the point where the effort is applied is called the effort arm1 and that which extends from the fulcrum to the point where the weight is supported is the weight arm4 ,the weight that can be lifted with a given effort depends upon the ratio of the effort arm to the weight arm4 ,if the two arms are of equal length1 the effort is equal to the weight1 but twice the weight can be lifted with the same effort if the effort arm is twice as long as the weight arm4 ,you can lift a ton with an effort of only #ajj pounds if your effort arm is twenty times as long as your weight arm but the end of your effort arm would have to move twenty inches to raise the ton weight one inch4 ,we are assuming in all these cases that the lever itself has no weight and that there is no friction at the fulcrum4 ,of course levers are not used merely for the purpose of lifting weight1 but to overcome any resistance or merely to apply pressure upon an object4 ,in almost every household we may find examples of the three orders of levers4 ,a pair of shears1 for instance1 is composed of two levers of the first order1 swinging on a common fulcrum4 ,the effort is applied at the handles1 and the weight or load is the material that is cut by the blades or1 speaking more technically1 the handles are the effort arms and the blades are the weight arms4 ,a material that is too tough to be cut at the tip ends of the blades may be easily cut if we move it in near the fulcrum or pin that hinges the blades together2 for by doing this we shorten the weight arms1 because the weight arm is measured not to the end of the blade1 but to the point where it is cutting into the material4 ,to cut very tough material1 such as heavy tin or sheet steel1 we use long-handled short-bladed shears4 ,the cutting pressure depends upon the ratio of the effort arm to the weight arm4 ,if the effort arms are twice as long as the weight arms1 the cutting pressure is twice as great as that applied at the handles4 ,a nutcracker consists of a pair of levers of the second order4 ,the fulcrum is at one end and the effort or pressure is applied at the opposite end of the levers or handles1 while the equivalent of the weight 7in this case the nut7 is placed between the effort and the fulcrum4 ,again the effort arm is measured from the fulcrum or hinge pin of the tool to the point where the hand pressure is applied1 and the weight arm is measured from the fulcrum to the nut4 ,the effort arm may be four or five times as long as the weight arm1 so that the pressure exerted on the nut is four or five times as great as that exerted by the hand on the ends of the handles4 ,illustration3 ,,fig4 #b4--;,,an ,,angular ,,or ,,bell-,,crank ,,lever ,in the case of a pair of sugar tongs we have another tool something like the nutcracker in construction1 but here the weight1 i4e41 the lump of sugar1 is seized by the ends of the tongs while the hand pressure is applied somewhere between the fulcrum and the weight4 ,hence we have here a lever or pair of levers of the third order4 ,the effort arm of a pair of tongs is always shorter than the weight arm and the pressure on the sugar lump is always less than that exerted on the tongs by the hand4 ,evidently the most powerful tool of the three is the nutcracker1 because the effort arms extend over the full length of the tool and are always longer than the weight arms4 ,a lever need not consist of a straight bar2 the effort arm may form an angle with the weight arm1 forming what is known as an angular or bell-crank lever 7,figure #b74 ,when a common claw hammer is used to pull out a nail1 the claws that slip under the head of the nail form the weight arm and the hammer handle the effort arm4 ,a horizontal pull on the handle produces a vertical lift on the nail4 ,sometimes two or more levers are interconnected1 as in ,figure #c1 the effort arm of one being linked to the weight arm of the other4 ,this serves to increase the lifting force at the weight and at the same time keep the mechanism within compact limits4 ,such compounding can go on indefinitely and is subject to all sorts of variations4 ,illustration3 ,,fig4 #c4--;,,compound ,,leverage ,one thing we must not forget1 and it is a matter that is commonly overlooked by perpetual motion cranks1 namely1 that while a pound of pressure on the effort arm may be made to lift two1 four1 or a hundred times as many pounds on the weight arm by varying the relative length of these arms1 it has to move two1 four1 or a hundred times as far as the weight arm1 so that the work done on one side of the fulcrum is always exactly equal to that done on the other side4 ,,continuous ,,revolving ,,leverage ,illustration3 ,,fig4 #d4--,,primitive ,,gear ,,wheels--,,two ,,coacting ,,groups ,,of ,,levers ,if we take a number of levers radiating from a common fulcrum like the spokes of a carriage wheel1 we have a primitive gear wheel4 ,two such groups of levers may be mounted on parallel shafts so that when one is turned its spokes will successively engage the spokes of the other group and make the latter turn 7see ,figure #d74 ,each spoke is first an effort arm on one side of the wheel and then a weight arm as it turns around to the other side of the wheel1 and as the effort arms and weight arms are of the same length there is no multiplication of power4 ,a pound on one side of the wheel cannot lift more than a pound on the other4 ,the driven wheel receives the same power as the driving wheel except for such loss as may be due to friction at the bearings or where the spokes contact4 ,the only advantage of such a pair of gears is that the direction of rotation of the driven wheel is the reverse of that of the driving wheel4 ,if the spokes of one wheel are longer than those of the other1 we have at once a variation in the rate of rotation proportional to the relative diameters of the two wheels4 ,in ,figure #e1 for instance1 the diameter of the driving wheel ,a is twice the diameter of the driven gear ,b1 and so1 for each revolution of ,a1 ,b must make two revolutions1 i4e41 the driver must make two revolutions for each revolution of the driven wheel4 ,in other words1 the speed of revolution is doubled4 ,however1 if we make ,b the driver the speed of the driven wheel ,a will be half of that of wheel ,b4 ,illustration3 ,,fig4 #e4--;,,coacting ,,levers ,,of ,,unequal ,,length ,in primitive machines spoke gears were seldom mounted on parallel shafts because of the difficulty of keeping the spokes in alignment4 ,instead1 one shaft was mounted at right angles to the other so that one set of spokes would cross the other 7,figure #f71 thus producing the equivalent of a bevel gear4 ,this was of advantage in changing the plane of rotation4 ,a later development was the barrel or lantern gear1 which permitted transfer of power without changing the plane of rotation4 ,a cylindrical bundle of rods constituted one of the wheels 7as shown in ,figure #g74 ,instead of being crudely formed of spokes1 the other wheel sometimes consisted of a disk with pins radiating from its rim4 ,such gears in far more refined form are still used in modern clocks and watches4 ,a still further development for transmitting motion to a plane at right angles to that of the driving shaft is shown in ,figure #h4 ,here we have a crown gear in which the pins instead of radiating from the periphery of the disk project from the side face of the gear4 ,illustration3 ,,fig4 #f4--,,primitive ,,equivalent ,,of ,,the ,,bevel ,,gear ,illustration3 ,,fig4 #g4--,,primitive ,,lantern ,,gear ,turning back to our first spoked wheels1 it is very evident that we may put a rim over the spokes or even fill in between the spokes and convert the wheels into solid disks that are in frictional engagement with each other without getting away from the fact that we are dealing with levers4 ,each wheel1 then1 consists of a continuous revolving lever4 ,friction gears are used quite commonly in machinery when it is desirable to have the wheels slip if subjected to excessive strain4 ,,toothed ,,gears ,by forming teeth on one gear to mesh between similar teeth on the other1 we convert the friction gears into a pair of spur gears 7,figure #i74 ,we need not go into the intricacies of the form of gear teeth4 ,they are designed to be in continuous rolling contact while they are in mesh4 ,the novice is apt to call all spur gears 8cogwheels0 and gear-teeth 8cogs40 ,mechanics1 however1 recognize a difference between cog wheels and spur wheels4 ,in the former1 the teeth1 or cogs1 are not cast upon or cut out of the wheel body1 but are separate pieces fitted to the wheel4 ,such wheels are found in old water mills4 ,they consist of wooden wheels with iron or steel teeth mortised in the wooden rim of the wheel4 ,in general it is safer to speak of spur gears because there are few cogwheels now in use4 ,illustration3 ,,fig4 #h4--;,,crown ,,and ,,lantern ,,gear ,when a small gear engages a large one1 the former is commonly known as a pinion4 ,illustration3 ,,fig4 #i4--,,spur ,,and ,,pinion ,,gear ,illustration3 ,,fig4 #aj4--;,,bevel ,,friction ,,gears ,if two friction wheels are to turn at right angles one to the other1 they must have conical bearing surfaces1 as in ,figure #aj4 ,the angle between the shafts of the two gears and the relative size of the gears may be changed as desired1 provided each cone surface has its apex at the intersection of the two shafts or axes4 ,it is easy to understand how such conical friction gears may be converted into toothed bevel gears 7,figure #aa71 by forming teeth on the conical surfaces1 and it will be evident that the teeth must taper toward the apex of the two cones4 ,two bevel gears of equal diameter1 and with shafts set at right angles one to the other1 are known as miter gears4 ,illustration3 ,,fig4 #aa4--,,toothed ,,bevel ,,gears ,so far we have not shown any combination of gearing that will multiply power4 ,in ,figure #e1 the driver ,a is twice the diameter of the driven wheel ,b1 and the latter makes two revolutions for one of ,a1 but the speed at the periphery of the two wheels is the same4 ,a pull of one pound at the point a produces a pressure of one pound at b1 and this in turn produces a lift of one pound at c because the levers in each wheel are perfectly balanced1 that is1 each lever has equal effort and weight arms4 ,the way to obtain an increase of power and of peripheral speed is to fasten two wheels of unequal diameters together on the same center and apply the effort to one of the wheels 7as in ,figure #ab7 and the weight to the other wheel4 ,this gives us what is technically known as a wheel and axle4 ,the dotted lines show that we have here a lever of the first order which can be used to multiply power in the same way that a bar lever does4 ,if one wheel is twice the diameter of the other then a pound of effort will lift two pounds of weight4 ,illustration3 ,,fig4 #ab4--,,wheel ,,and ,,axle ,,or ,,revolving ,,lever ,,of ,,first ,,order ,illustration3 ,,fig4 #ac4--,,revolving ,,levers ,,of ,,the #b;,d ,,and #c;,d ,,order ,figure #ac shows how the effort and weight can be shifted about in such fashion as to give us a lever of the second and one of the third order4 ,the power may be enormously increased and the speed of the final wheel greatly reduced by setting up a train of gears in which the effort is received by the larger one of each couple and is delivered by the smaller one4 ,in ,figure #ad the smaller wheels are half the diameter of the larger ones4 ,a pound of pressure at ,a will amount to #b at ,b1 #d at ,c1 #h at ,d1 #af at ,e1 and #cb at ,f4 ,on the other hand1 point ,a will have to move through #cb inches to make the point ,f move an inch4 ,illustration3 ,,raising ,,water ,,with ,a ,,chain ,,of ,,pots ,a primitive pump still used in ,egypt ,illustration3 ,a ,,horse-,,operated ,,chain-,,pump ,,used ,,in ,,greece ,illustration3 ,,multiple ,,spindle ,,drill ,,in ,,motor ,,car ,,factory ,illustration3 ,,fig4 #ad4--;,a ,,train ,,of ,,spur ,,gears ,illustration3 ,,fig4 #ae4--,,pulleys ,,of ,,the #a,,st1 #b;,d1 ,,and #c;,d ,,orders ,illustration3 ,,fig4 #af4--,,typical ,,arrangement ,,of ,,block ,,and ,,tackle ,a pulley is merely a modification of the wheel4 ,figure #ae shows how it may be arranged to correspond to the three orders of simple levers4 ,if the pulley axis is fixed1 as in the first order1 the effort and weight arms are equal and hence balanced4 ,in the second order the wheel is bodily movable1 hence one pound will raise two pounds of weight because the power arm is twice as long as the weight arm1 while in the third order it takes two pounds of lift to raise one pound of weight4 ,there is no end of possible combinations of pulleys which will multiply power in the same way that bar levers do when compounded4 ,a common arrangement of block and tackle is given in ,figure #af4 ,there is a four-sheave pulley block above and a three-sheave block below1 but in order to trace the rope clearly the pulley wheels or sheaves are represented as of different diameters4 ,the arrangement consists of a series of levers of the first order in the upper pulley block coupled to a series of levers of the second order in the lower block4 ,to find the weight that a given power will lift1 multiply the effort by the number of strands of rope that are supporting the weight4 ,in this case there are seven such strands1 not counting the strand ,e1 to which the effort or pull is applied4 ,this means that a pull of a hundred pounds at ,e will lift #gjj pounds at ,w4 ,of course a pull of seven feet at ,e will raise the weight only one foot4 ,illustration3 ,,fig4 #ag4--;,,inclined ,,plane ,,with ,,effort ,,parallel ,,to ,,the ,,inclined ,,face ,,the ,,inclined ,,plane ,,and ,,its ,,family ,the inclined plane constitutes a second broad classification of machine elements4 ,the wedge1 the screw1 the cam1 and the eccentric1 all belong to the family of the inclined plane4 ,illustration3 ,,fig4 #ah4--;,,inclined ,,plane ,,with ,,effort ,,parallel ,,to ,,the ,,base ,a simple form of inclined plane is pictured in ,figure #ag1 which shows a weight ,w being rolled up an incline4 ,the effort required to carry it to the top of the incline depends1 of course1 upon the steepness of the incline4 ,the drawing shows a rise of #c feet on a slope #e feet long1 and the weight of the wheel is1 say #bj pounds4 ,to find the effort required1 the weight is multiplied by the rise 7#bj #c #fj7 and divided by the length of the slope 7#fj_/e #ab7 and we find that it takes only #ab pounds to roll the #bj-pound wheel to the top of the incline4 ,this holds true when the pull is parallel to the inclined face4 ,if the pull is parallel to the base of the incline1 as in ,figure #ah1 we must divide by the length of the base instead of the length of the incline 7#fj_/d #ae7 and we find that it takes #ae pounds of effort to pull the weight up the incline4 ,if the pull is exerted at an angle both to the base and the inclined face1 we have a problem that is slightly more complicated and we need not go into it here because it involves a bit of trigonometry4 ,in all cases1 however1 it may be noted that the amount of rope that is taken in1 in hauling the weight up the incline1 bears a definite relation to the amount of effort required to raise the weight4 ,in ,figure #ag1 #e feet of rope must be pulled in1 in order to raise the weight #c feet1 so that of #bj or #ab pounds is all that is required to pull up the weight1 while in ,figure #ah1 #d feet of rope is hauled in for a lift of #c feet1 so that of #bj or #ae pounds is required to pull up the weight4 ,in this respect the inclined plane is exactly like the lever or the pulley1 for the effort multiplied by the distance through which it is exerted is always exactly equal to the weight multiplied by the distance through which it moves4 ,thus in ,figure #ag1 the effort #ab pounds multiplied by the distance #e the weight #bj pounds times the distance #c1 and in ,figure #ah1 effort #ae x distance #d weight #bj x distance #c4 ,of course1 we are ignoring the weight of the rope and the friction which1 in actual practice1 are important factors to be reckoned with4 ,illustration3 ,,fig4 #ai4--;,,endless ,,screw ,,or ,,worm ,,gear ,so far we have considered a fixed inclined plane1 but when the inclined plane is moved between the weight and a fixed base it is known as a wedge1 and in this case1 too1 the effort required to move the wedge multiplied by the distance the wedge moves is equal to the weight multiplied by the distance it is lifted4 ,the commonest form of inclined plane is the screw which is merely an inclined plane bent around a cylinder4 ,a screw engaging a toothed wheel1 as in ,figure #ai1 gives a combination known as an 8endless screw10 or1 more commonly1 as a worm gear4 ,the screw or worm is always the driver1 and as it must make a complete turn to move the gear through a space of one tooth1 the power of this combination is very great4 ,it is practically impossible to turn the worm by using the gear wheel as a driver because the friction developed at the point where the worm and gear contact is very great4 ,for this reason worm gearing is used in the steering gear of automobiles4 ,the shaft of the steering wheel is fitted with a worm which meshes with a worm gear on the parts connected with the wheels4 ,it is very easy to turn the wheels by operating the steering wheel1 but if the wheels strike a rut or a stone they are not deflected from their course1 because the worm makes it impossible for them to turn the steering wheel4 ,illustration3 ,,fig4 #bj4--;,,helical ,,or ,,spiral ,,gears ,the spiral gear shown in ,figure #bj is a cross between a worm gear and spur gear4 ,the teeth are spirals set at an angle of #de degrees to the axis of the wheel4 ,in this case either gear can be used to drive the other1 and the advantage of such a pair is that power is transmitted from one shaft to another in a different plane and at right angles to the first4 ,illustration3 ,,fig4 #ba4--;,,drum ,,cam ,illustration3 ,,fig4 #bb4--,,profile ,,or ,,disk ,,cam ,cams are usually irregular revolving inclined planes4 ,figure #ba1 shows a cylinder or drum cam4 ,a groove is cut in the cylindrical wall of the cam and an arm or lever is provided with a roller which rolls in the groove4 ,when the cam is revolved the lever is constrained to follow all the twists and turns of the groove4 ,a different form of cam is shown in ,figure #bb4 ,it is formed with an irregular periphery against which the roller is pressed by a spring4 ,as the cam wheel revolves1 the roller and the arm to which it is attached must move in and out over all the hills and valleys of the periphery4 ,the cam is one of the most useful elements in modern machinery1 for it provides a very simple means of producing the most complicated and irregular motions4 ,illustration3 ,,fig4 #bc4--;,,eccentric ,,by ,,which ,,rotary ,,motion ,,is ,,converted ,,into ,,rectilinear ,,motion ,we cannot attempt to describe all the different types of cams1 but reference should be made to the eccentric1 which is a form of cam commonly used to operate the valves of a steam engine4 ,the cam in this case is a perfectly circular disk1 but the shaft that turns it does not lie at the center of the disk1 consequently an object bearing against the periphery must move toward and away from the center as the disk revolves4 ,instead of using a spring-pressed roller to bear against one side of the disk1 the whole disk is encircled with a ring of steel known as an eccentric strap4 ,this strap is bolted to a valve rod and as the eccentric revolves the strap makes the valve rod move back and forth4 7,see ,figure #bc47 ,a description of all the various combinations of gearing1 link motions1 ratchets1 escapements1 clutches1 and miscellaneous movements would easily fill the rest of this book1 and we must therefore content ourselves with this very brief survey of a few of the more important elements employed in the construction of modern machinery4 ,,chapter ,,iii ,,machines ,,for ,,making ,,machines ,,while we may glory in the wonderful mechanical progress of to-day1 we must not overlook the marvelous skill of the ancient artisan nor forget that it is to his inventive genius that we are indebted for practically every hand tool we possess4 ,only a few special tools owe their origin to the modern inventor4 ,all the rest date back beyond the twilight of history4 ,we have merely improved upon these tools by slight changes of design or the employment of better materials in their construction4 ,as users of these tools we cannot begin to compare with the skilled workman of ancient days4 ,our progress is shown not in the development of skill1 but in the loss of it4 ,we have taken the tool out of the human hand and put it into an inanimate machine4 ,it is only very recently that the tool was delivered to the machine and that act marked the dawn of the present remarkable mechanical era4 ,machines for making machines date back to the time of the early ,egyptians4 ,they had their pole lathes and bow drills1 but these machines only partially relieved the workman of his labors1 and the quality of the work still depended upon a degree of skill that was acquired only through years of patient apprenticeship4 ,the pole lathe1 by the way1 consisted merely of a pair of centers between which the work was mounted1 a pole attached to the ceiling and a strap or rope passed around the work and fastened at one end to a pole and at the other to a pedal resting against the floor4 7,see ,figure #bd47 ,when the pedal was depressed1 the strap was pulled down and the work was revolved4 ,on releasing the pedal1 the spring of the pole pulled the strap up and reversed the rotation of the work4 ,thus by alternately depressing and releasing the pedal1 the work was intermittently revolved against a chisel which was rested on a block and guided by the workman4 ,small work could be turned out on such a lathe with considerable precision1 but when it came to large parts1 particularly parts of steel1 the workman was easily tired by the effort of operating the pedal and was apt to be irregular in the guiding of the tool4 ,illustration3 ,,fig4 #bd4--,,primitive ,,pole ,,lathe ,up to the middle of the eighteenth century practically no advance had been made over the ancient lathe of the ,egyptians1 and when1 #aej years ago1 the steam engine was invented the task of building the engine seemed almost insuperable4 ,james ,watt was a maker of mathematical instruments1 a man of great skill and precision as a craftsman1 but he dealt with parts of small dimensions4 ,when he conceived of his steam engine1 he mentally pictured the various parts as turned out with all the accuracy and finish that was possible in the diminutive members of a scientific instrument4 ,to him it seemed perfectly feasible to turn a cylinder which would be practically perfect in contour1 and to fit it with a piston around which no steam could leak4 ,with the lathe then in existence such a fit was easily possible on small work4 ,but when he undertook to have the cylinder of his engine bored1 he discovered that there was no machine that could begin to do the work properly4 ,in fact1 when ,smeaton1 who was a prominent engineer of that time1 investigated ,watt's steam engine1 he declared that it was such a complicated piece of work that neither tools nor workmen existed that could build it4 ,in ,watt's first engine1 the cylinder was only six inches in diameter and two feet long1 and a special type of boring machine was devised to bore the forged cylinders4 ,but the boring was so irregular that when the piston was inserted and the steam was turned on1 nothing would stop the flow of steam that leaked around the piston4 ,in vain did ,james ,watt use cork1 oiled rags1 tow1 paper1 and even old hats to stop the leakage4 ,however1 the boring machine was improved and later a cylinder1 eighteen inches in diameter1 was bored with such accuracy that the large diameter exceeded the small diameter in the worst place by only of an inch4 ,this ,watt considered a very good bit of turning4 ,to-day cylinders of that size that vary from true by half the thickness of the paper that this is printed on would be thrown out as defective4 ,it was in #agfi that ,watt invented the steam engine1 but that great event did not mark the dawn of the present era of machinery4 ,for a quarter of a century thereafter there was little progress in the development of machine tools4 ,a boring machine was built that did fair work4 ,there were a few sawmills in which wind power was employed to drive the saw4 ,but lathes were still driven by foot power and the cutting tool was still held and guided by hand4 ,,maudsley',s 8,,go-,,cart0 ,the real father of the present era was a very clever ,british mechanical engineer1 ,henry ,maudsley1 who undertook to eliminate the uncertainties of the human hand by clamping the cutting tool of the lathe in a rest and arranging the rest to slide along the length of the lathe or transversely toward or away from the center4 ,these two motions made it possible to accomplish all that the workman could accomplish by hand and at the same time the tool was held so firmly that accuracy and precision of turning was assured4 ,furthermore1 he provided this slide rest with a nut that engaged a screw driven through suitable gearing by the lathe spindle4 ,then1 as the work revolved1 the slide rest was compelled to move along the bed of the lathe at a uniform rate4 ,by varying the gearing1 the speed of the slide rest and the tool it carried could be varied at will1 thus making it possible to cut screw threads of any pitch desired with a degree of accuracy unattainable by hand4 ,remarkable as was this improvement1 it met with the usual opposition that every real advance in machinery received in those days4 ,people referred to the slide rest as ,maudsley's 8go-cart10 but it proved such an important element of the lathe and so very valuable that before long it was universally adopted4 ,from that time on the skill of the workman began to lose its importance4 ,the man began to give way to the machine4 ,precision was possible in large as well as small work4 ,the human element was also dispensed with in the driving of the lathe4 ,the foot pedal was superseded by the steam engine1 and the machine came to be known as the engine lathe4 ,there are many ways of working metals now in common use4 ,metals may be cast in a molten state1 or they may be pressed and molded into shape in a cold state1 or they may be hammered either cold or hot1 but in nearly all cases in which metal is removed in order to form a piece of work1 the chisel is used as a cutting instrument4 ,this is perfectly apparent in lathes and planers1 but not quite so apparent in sawing1 drilling1 filing1 and grinding4 ,a drill is merely a spiral chisel which revolves upon its own center4 ,a saw is a gang of tiny chisels1 and a file consists of still smaller chisels which are broader than those of the saw4 ,in grinding we have rough surfaces in which particles of emery or carborundum act as tiny chisels4 ,the shears1 the punch1 and the cutting torch are practically the only exceptions to the rule that metals are always cut by chisels1 and even the shears may be conceived as consisting of a pair of broad coacting chisels1 while it takes little imagination to see a form of chisel in the punch4 ,the cutting torch is1 of course1 in no sense a chisel4 ,in the cutting of metals the work may move against a fixed tool or the tool may move against a fixed piece of work4 ,in a lathe1 it is the work that revolves or rotates against the tool4 ,in the drill and the milling machine the tool revolves against the work4 ,in the planer1 the tool is fixed and the work slides against it4 ,the shaper reverses the operation2 the work is fixed and the tool moves in a rectilinear direction4 ,up to the nineteenth century practically the only machines for cutting metals were the lathe and a crude form of boring machine4 ,the machinists of that day had not reached the stage where they were able to produce anything but round work on a machine4 ,the planer had not been born4 ,it was for this reason that ,watt had a great deal of difficulty in getting rectilinear motion for the piston of his engine4 ,he had to invent a complicated system of links and levers in order to obtain a practically parallel motion to guide his piston in and out of the cylinder4 ,when the planer was invented and it was possible to produce straight surfaces with a considerable degree of accuracy1 all of ,watt's ingenious parallel motions1 went into the discard and the cross-head and guides took their place4 ,it was not until long after the planer had been invented that ,eli ,whitney1 the ,american genius of cotton-gin fame1 conceived the milling machine4 ,he reversed the operation of the lathe by placing the cutting tool on the revolving spindle and sliding the work against it4 ,milling cutters consist of wheels formed with a number of cutting edges or chisels which are arranged either on the periphery of the wheel or on the face of the wheel4 ,following the milling machine1 came the grinder1 in which a revolving wheel of an abrasive material served to wear away the surface of a piece of work1 and with this form of machine steels of great hardness could be finished with accuracy and a high polish4 ,,the ,,interchangeable ,,system ,the most notable advance in machine work came early in the nineteenth century1 when what was known as the 8,american ,system0 of manufacture1 or the interchangeable system1 was introduced4 ,as long as mechanics were obliged to perform their operations largely by hand1 it was impossible to attain great accuracy4 ,each workman put his own individuality into the work4 ,as a consequence1 no two pieces were of exactly the same size or shape4 ,this was true even with the early power-driven machine tools4 ,the parts might be very close to the same size1 but careful measurements showed that they varied by a minute fraction of an inch4 ,hence1 when a machine was assembled the unyielding metal parts had to be filed and trimmed and hammered to fit them together4 ,if any accident occurred to a machine1 the damaged part could not be replaced by another taken from stock4 ,the entire machine had to go back to the shop where an experienced mechanic would make a new part to replace the damaged one4 ,in those days a machine was not manufactured but was built as an individual mechanism1 just as a house or a boat is built to-day4 ,with the advent of accurate machine tools came the idea of standardizing the parts so that hundreds and thousands of pieces could be made of exactly the same dimensions1 and in assembling a machine the parts could be picked at random from the stock and put together without the use of special tools and without requiring any special fitting4 ,this was of special importance in the tools of warfare1 because armies need quantity production1 i4 e41 rifles1 cannon1 etc4 ,more machines of the same kind were required for an army than for any other organization or line of work4 ,at the close of the ,napoleonic ,war the ,british ,government had #bjj1jjj parts of muskets either partly finished or waiting repairs4 ,their muskets were made after the old system4 ,each one was built separately with its parts individually fitted together1 so that whenever any part was injured1 the musket had to be laid aside and sent back to the workshop for repairs4 ,long before that time1 the idea of making standard guns had been hit upon in ,france4 ,thomas ,jefferson1 while ,minister to ,france1 in #aghe1 wrote of the ,french system which was then being developed by a mechanic named ,le ,blanc4 ,he was building a musket in which the parts were of standard pattern1 and which could be assembled by taking pieces haphazard as they came to hand and putting them together without special fitting4 ,thomas ,jefferson called the attention of the ,american ,government to this system and showed that it was possible to produce muskets cheaper by that method of manufacture4 ,however1 our ,government at that time failed to avail itself of the opportunity of utilizing this system of manufacture4 ,later on1 the idea was taken up in this country by ,eli ,whitney and by ,simeon ,north4 ,when ,whitney attempted to introduce the system1 he was laughed at by ,french and ,english ordnance officials1 and even our own ,government officials were skeptical1 particularly when they found that it required so much preparation in the way of machinery and designing of parts before a single musket was completed4 ,it seemed like a waste of money to invest in so much preparation4 ,but ,whitney was soon able to silence all his critics by taking to ,washington ten pieces of each part of a musket and then selecting at hazard from each pile of pieces the requisite parts and putting together ten muskets4 ,it was not long before the foreign governments saw the importance of this method of manufacture4 ,great ,britain later adopted it in the making of her own rifles and called the process the 8,american ,system40 ,but it was not only in the field of rifles that interchangeable manufacture made itself felt4 ,the ,new ,england clock industry provides an interesting illustration4 ,at first the clocks were made of wood1 but early in the nineteenth century1 a clock maker1 ,chauncey ,jerome by name1 designed a brass clock in which the parts were made on the interchangeable system4 ,instead of building each clock as a separate piece of work1 clocks were turned out by the thousands1 and at an extremely low price4 ,soon he had flooded this country with his clocks and began to look around for other markets4 ,machinery had been used by other clock makers in producing wooden clocks1 and movements which had cost #ej each in #ahdj had been reduced to #e4 ,but ,chauncey ,jerome's clock was made of brass and by means of the interchangeable system of manufacture he could produce it for less than #ej cents4 ,the clock was such a success in this country that ,jerome decided to try it abroad4 ,consequently he made arrangements with an agent in ,england and shipped over a large consignment4 ,the ,british ,government was astonished at the low price of the clock and was convinced that it had been undervalued4 ,at that time1 they had a simple and ingenious method of punishing a consigner who undervalued the goods he wished to introduce into the country4 ,this consisted in promptly appropriating the property at the price given in the invoice4 ,in due course of time1 much to ,jerome's astonishment1 he received a letter from the ,british ,government stating that his clocks had been confiscated1 and with the letter came a check paying for them at the invoice price4 ,jerome was not in the least dejected by the rebuke2 on the contrary1 he was rather elated1 for1 as far as he could figure it out1 he had a spot-cash buyer for his goods and no selling expenses4 ,he did not mind at all letting the ,british ,government have the clocks at the invoice price4 ,so he decided to try again with a larger shipment4 ,to his great delight this shipment met the same fate as the first1 and in due course another good ,british check arrived4 ,thus encouraged1 ,jerome sent over a third and still larger shipment1 but by that time ,johnny ,bull began to suspect that the ,yankee clock maker was getting the best of the bargain and1 finally convinced that clocks really could be produced with profit at the low invoice price1 he permitted them to enter his country4 ,with this striking example1 the fame of the ,yankee system of manufacture spread over the world4 ,in order to have two parts alike1 they must be placed under a machine in exactly the same way4 ,in other words1 they must be set in 8jigs0 or frames which are fitted into the machine in such a way that the tools will approach the work from exactly the same angle or penetrate the work to exactly the same depth in ten1 or a hundred1 or a thousand1 or a million pieces1 as the case may be4 ,making jigs and dies consumes a great deal of time in preparation work1 but once the preparation stage has been passed1 articles are produced with wonderful rapidity and very little waste of time4 ,formerly it was necessary to determine the location of each hole in a casting separately and spend precious time in adjusting the work to the proper position under the tool4 ,if the hole was to be threaded1 it had to pass through several separate operations4 ,,the ,,turret ,,lathe ,after the slide rest invented by ,maudsley1 the next great improvement on the lathe was a turret head or a sort of turntable which carried a number of tools4 ,the tools are arranged to come automatically into play one after the other4 ,one tool1 for instance1 may cut a groove in the work1 another finish the face of the work1 another bore a hole in the piece and another tap the hole4 ,in many cases1 several of these operations are performed simultaneously4 ,the head of the lathe is provided with a hollow spindle so that the work is automatically fed to the tools through this spindle1 and as soon as one piece is finished1 it is automatically cut off and the jaws of the clutch which holds the work1 or stock as it is called1 open automatically so that a new length may slide forward and be operated upon by the tools4 ,the machine requires no attention once the tools have been set up to the proper angle1 except that it must be kept supplied with bars of stock as they are consumed1 and with a copious flow of lubricant on the tools4 ,one operator can therefore take charge of a number of automatic lathes4 ,all he does is to feed them2 they do the rest4 ,the modern drill has also gone through a great many developments in order to speed up the work that it performs4 ,when a casting is to have forty or fifty holes drilled and tapped in it1 instead of following the old method of drilling each hole separately1 a lot of separate drilling spindles are used1 each fitted with a drill1 and these are brought simultaneously into play4 ,as many as fifty or sixty holes may be drilled at a single operation1 and after the holes have been drilled1 the drilling spindles move to one side to make way for the taps1 which thread such of the holes as are to receive screws4 ,by first setting the spindles in the proper position and then using jigs to locate the work properly under them1 the assurance is had that every one of the scores of holes drilled will be accurately spaced apart and the spacing in every casting will be identical4 ,the multiple tool system is also used in milling machines in which a number of milling cutters either of the face or the end type come into play simultaneously upon a piece of work set in a suitable jig1 and cut the piece with absolute precision1 so that all castings will have faces accurately spaced apart and cut to exactly the same level4 ,it is by such methods as these that we are able to produce such large quantities of machinery at remarkably low cost4 ,one of the most notable examples of such work was the development of the ,liberty engine during the ,world ,war4 ,this engine did not differ in principle from others built in ,europe or in this country1 but its design was carefully adapted to permit of interchangeable manufacture4 ,no careful finish was used except where indispensable4 ,special jigs1 tools1 and fixtures were prepared4 ,ingenious wrinkles of ,american manufacture were introduced4 ,all this consumed time1 and great was the irritation of the general public4 ,under ordinary conditions1 it would have taken years to have developed the ,liberty engine to the manufacturing stage1 but under the urgent stress of war1 the whole work of design and preparation for manufacture was crowded into a few short months1 and then ,liberty engines began to be manufactured on a stupendous scale4 ,,cutting ,,with ,,red-,,hot ,,tools ,one of the most remarkable advances in machine tools was due to the studies of ,fred ,w4 ,taylor4 ,he entered a large steel plant in #ahhj and was immediately struck with the enormous waste of effort on the part of the men in the plant4 ,there was at that time considerable dissatisfaction among the workmen1 and when ,taylor endeavored to speed up work he was faced by the incontrovertible argument that he had no idea how much work a certain machine ought to turn out4 ,there was nothing for him to do but either back down or study machine tools and discover their maximum capacity4 ,this led him to investigate the matter of cutting speeds4 ,for years he spent all of his spare time studying this subject1 timing machines and experimenting with different types of cutting tools4 ,he estimated that in the twenty-six years of his investigation he converted #hjj1jjj pounds of steel into chips4 ,what he wished to discover was the best depth of cut1 the best speed of cutting1 and the best speed at which the tool should be fed into the work4 ,he soon discovered that1 contrary to prevailing opinion1 the round-nosed tool was better than the diamond-pointed tool1 that the coarse slow-cutting speed was better than a fine cut at high speed4 ,he discovered that the best method of lubricating the tools was to keep them bathed in a heavy stream of water1 supersaturated with carbonate of soda1 so as to prevent the metal from rusting4 ,the best tool steel of that day was known as a self-hardening steel4 ,manufacturers of the cutting steels had warned ,taylor that he must not use water on these tools4 ,taylor1 however1 was not satisfied to take the word of others1 but proceeded to investigate the matter himself1 and discovered that he could safely increase the cutting speed of his tools #cc per cent by the use of a heavy stream of water for lubricating purposes4 ,this led ,taylor and his associate1 ,maunsel ,white1 to investigate the different kinds of tool steels1 and eventually they evolved a chrome tungsten tool which could do from two to four times the work of other tools4 ,later vanadium was added to the alloy1 further improving the tool4 ,at the ,exposition in ,paris1 in #aijj1 foreign manufacturers were astonished to find enormous lathes operating at high speed with the cutting tools taking such heavy cuts and feeding so fast that the nose of the tool was actually heated to a dull red heat1 and yet it kept its cutting edge perfectly4 ,this was a revelation to tool makers abroad1 and it led immediately to the adoption of ,american high-speed cutting tools4 ,the development of the automobile1 which began to take on serious proportions at about that time1 is responsible above all other machines for improvements in ,american machine tools1 and for the extension of the ,american system of interchangeable manufacture4 ,when automobiles came to be made on the interchangeable system and in enormous quantities so that the cost was reduced to within the limits of the average man's pocketbook1 they began to make mechanics of men who before that had never used a tool2 and this new and widespread interest in machinery stimulated the production of better and more efficient tools4 ,hence the progress of machine tools in the past few years has been simply phenomenal4 ,,chapter ,,iv ,,counting ,,seconds ,,you ,,can measure civilization by its timepieces4 ,the higher the civilization of a community the more it appreciates the value of time and the more minutely does it measure the passage of time4 ,the savage divides his day into but two periods3 the period of light and that of darkness2 the early ,romans divided their day into eight watches1 four watches of daylight and four of night1 but the higher and more complex civilization became1 the smaller became the subdivisions of time4 ,people began to feel the need of carrying the time with them1 and about #aejj ,a4 ,d4 watches came into use1 but it was not until #affe that watches began to be equipped with minute hands1 and it was almost exactly a century later that they were equipped with a second hand4 ,to-day time means so much to us that we will fight our way into a subway express1 instead of riding more comfortably in a local train1 merely for the sake of saving five minutes4 ,the tiny second hands of our watches divide the day into eighty-six thousand four hundred parts1 and in some operations we measure time intervals down to the thousandth part of a second4 ,only among the most highly civilized nations are timepieces carried by the common people4 ,it used to be that time was made for slaves1 but now time has made slaves of us4 ,shift the hands of the clock and the whole nation is forced to change its habits4 ,time-measuring mechanism is given early prominence in this book because clocks were among the earliest machines invented1 and they furnish an example of the wonderful ingenuity of inventors before the dawn of the modern era of machinery4 ,naturally this chapter must be largely historical4 ,the first thought of measuring time came from the ancient astronomers and astrologers1 who1 in watching the motions of heavenly bodies1 the sun by day and the moon by day and night1 found it necessary to keep a record of these motions and sought about for some mechanical means of doing so4 ,the studies of the old astrologers were closely associated with religion1 and as a consequence the most advanced intellects were centered upon astronomical matters and incidentally upon horology4 ,fortunately the design and construction of mechanisms for measuring time were not considered beneath the dignity of the scientists of those early days4 ,mathematicians felt free to record their investigations in this branch of mechanics1 and as a consequence of the early cooperation of science and mechanics in this field much real progress was made1 and the development of timepieces was more rapid than that of any other machine4 ,,telling ,,time ,,with ,a ,,leaky ,,bucket ,the ancient ,egyptians early felt the need of a better clock than the sundial1 because it operated only on cloudless days and was absolutely worthless to tell off the hours of darkness4 ,realizing that time is a measure of motion1 they sought for some slowly moving body whose motion could be used to measure time1 and naturally they turned to water4 ,the earliest form of clock consisted merely of a leaking bucket4 ,either the bucket was filled with water which was allowed to escape through a very tiny orifice1 or else the heavily loaded bucket was placed in water and the water was allowed to leak into the bucket until it sank4 ,the period it took for a bucket to run dry or for a bucket to fill and sink indicated a lapse of an hour or some other standard of time4 ,the idea of subdividing this period was a later development4 ,as the water leaked out of a bucket1 the water level descended1 but unfortunately not at a uniform rate4 ,the weight of water in a full bucket made the drops come faster than when the bucket was nearly empty4 ,consequently the time graduations on the side of the bucket had to be set farther apart at the top of the bucket than at the bottom4 ,various ingenious schemes were devised for maintaining a uniform discharge4 ,in one type of water clock or clepsydra a conical bucket was used so that there would be a constant relation between the head of water and the volume in the bucket and the time graduations could be spaced uniformly4 ,,the ,,remarkable ,,water ,,clock ,,of ,,ctesibius ,the most remarkable clepsydr were those invented by an old ,alexandrian mathematician1 ,ctesibius1 who lived about #bej years before ,christ4 ,ctesibius introduced the siphon principle into his clocks1 and also employed gear wheels and even a cord and pulley4 ,furthermore1 he was the first man to employ jeweled bearings in a timepiece4 ,the use of jewels in timepieces was reinvented in #agjd ,a4 ,d4 ,however1 ,ctesibius used his jewels in a very different way from that in which they are used now1 as will be described below4 ,illustration3 ,,fig4 #be4--,,the ,,jeweled ,,water ,,clock ,,built ,,by ,,ctesibius ,,about #bej ,b4 ,c4 ,figure #be illustrates the most interesting clock he built and it was arranged to run year in and year out4 ,the clock had a cylindrical face mounted on a hollow pedestal in which the mechanism was concealed4 ,the column was divided off into twenty-four hours and a pointer that rose vertically marked off the lapse of time4 ,but here he was faced with a serious complication4 ,hours in those days varied with the time of the year4 ,a day from sunrise to sunset consisted of twelve hours4 ,in summer1 when the days were long1 the hours were long1 and in the short days of winter the hours were correspondingly shortened4 ,to be sure1 the variations in the length of the day are not so great in ,egypt as they are in our latitude1 because it is nearer to the equator2 nevertheless there is a difference which the precise old mathematician had to take into account4 ,in order to provide for variations in the hours1 ,ctesibius ran the lines spirally around the column and arranged his cylindrical clockface to turn slightly each day1 so that in the winter months the clock hand or pointer moved over that part of the face where the daylight hour lines were closer together and the hours of night were farther apart1 while in summer1 the reverse would obtain4 ,at the bottom of the column were two little cherubs4 ,the cherub on the left was a sad little fellow who was constantly weeping4 ,tears trickled from his eyes and dropped into a basin4 ,the tears passed into the hollow pedestal of the clock and gradually filled a cylinder formed in the base of the clock4 ,a piston in this cylinder supported the other cherub4 ,as the water gradually filled the cylinder this cherub was slowly raised and a wand he held in his hand pointed off the hours on the clockface4 ,when the twenty-fourth hour was reached1 a siphon came into play1 which suddenly emptied the cylinder1 permitting the pointer to drop4 ,the siphon discharged its water into a small water wheel1 which1 by means of the system of gears1 turned the column slightly to bring the hour lines in proper positions for measuring the time intervals of the next day4 ,the column made one complete turn in #cfe days4 ,the jeweled bearings1 referred to above1 were placed in the eyes of the weeping boy1 so that the holes that pierced them would not be enlarged by the constant wear of the water and thereby increase the rate of flow4 ,,timing ,,ancient ,,orators ,we have dwelt at considerable length upon this old clock of the pre-,christian era to show the ingenuity of inventors of that day1 and also the careful study that was made of time by ancient mathematicians and astronomers4 ,of course water clocks were used before the time of ,ctesibius4 ,in fact1 we read of them in the comedies of ,aristophanes1 written #djj ,b4 ,c4 ,water clocks were used to limit the long speeches of orators at court1 and in one place we find ,demosthenes accusing a man of 8talking in my water10 while at another time1 when he was interrupted1 he called to the officer to stop the water1 showing that he valued every moment of time allotted to him for his speech4 ,in #hjg ,charlemagne was presented with a clock by the ,king of ,persia4 ,this consisted of an elaborate mechanism in which were all manner of wheels1 and the clock would actually strike the hours4 ,the driving power1 however1 was water4 ,but there were serious disadvantages in the use of water for the measurement of time4 ,no great accuracy was ever obtainable with it1 owing to the fact that its volume varied considerably with the temperature1 and also with the dryness or moisture in the surrounding atmosphere4 ,the idea of using a weight instead of water is claimed to have originated as far back as #iij ,a4 ,d4 ,the next important advance in the motive power of clocks was in #aejj1 when ,peter ,hele of ,nuremberg invented the mainspring4 ,that was long before the pendulum made its appearance4 ,the clock mechanism was slowed down and kept under control by what was known as a balance lever4 7,see ,figure #bf47 ,this was a horizontal lever mounted to oscillate in a horizontal plane4 ,the lever was fitted with sliding weights1 so that it could be carefully adjusted4 ,the last wheel of the train of gears was provided with escapement teeth1 somewhat similar to those used on our clocks and watches1 but which would alternately move the lever this way and that4 ,the inertia of the lever with the heavy weights on it was sufficient to prevent the mechanism from racing1 and by this means1 the motion was governed and slowed down1 so that it measured time with a fair degree of accuracy4 ,,discovery ,,of ,,the ,,pendulum ,illustration3 ,,fig4 #bf4--,,the ,,balance ,,lever1 ,,predecessor ,,of ,,the ,,pendulum ,the pendulum had an interesting origin4 ,galileo1 while a student in ,pisa in #aeha1 was attending a service in the cathedral one day when his attention was drawn to the swinging of a large hanging lamp4 ,one of the attendants had drawn the lamp toward him1 so that he could reach it more readily to light it4 ,when he let go the lamp began to swing slowly back and forth1 and the observant young student noticed that although the oscillations gradually slowed down the period of oscillation was constant4 ,he had no watch with which to measure the length of the period1 but being a medical student he knew that he had a fair timepiece in his own heartbeats1 and so by counting his pulse he proved that it took the lamp just as long to complete each oscillation when it swept through a long arc as when it died down to but a few inches4 ,he made note of this peculiar action and began experimenting with pendulums of different lengths4 ,then it occurred to him that if he could time the pendulum with his pulse he could time his pulse with a pendulum4 ,so he devised a pendulum whose length could be adjusted until its oscillation would coincide with the throb of a patient's pulse1 and then the length of the pendulum would give him the rate of the pulse beat4 ,the invention was seized upon by the medical profession of that day1 and the pulsilogia1 as it was called1 became an indispensable instrument for physicians4 ,illustration3 ,,bucket ,,of ,a ,,giant ,,dredge ,,with ,,its ,,jaws ,,spread ,,wide ,,open ,illustration3 ,,gold ,,dredger ,,eating ,,its ,,way ,,through ,,river ,,sands ,illustration3 ,a ,,suction ,,dredge ,,excavating ,a ,,channel ,,and ,,building ,,new ,,land ,the idea of using the pendulum to control the action of the clock also occurred to ,galileo1 and in later years1 after he had lost his sight1 he passed the idea down to his son1 ,vincent4 ,however1 it is generally conceded that the credit for introducing the pendulum and doing away with the balance lever belongs to ,christian ,huygens1 the ,dutch mathematician1 whose first pendulum clock dates back to #afei4 ,about the same time ,dr4 ,robert ,hooke invented the balance spring which made it unnecessary to use the pendulum in portable timepieces4 ,prior to that watches were fitted with balance levers and they gave a great deal of trouble1 because the time varied with the position in which they were carried4 ,but the balance wheel overcame all these difficulties and made it possible for a person to carry an accurate timepiece in his vest pocket1 although the early watches were very bulky mechanisms4 ,,the ,,first ,,ship',s ,,chronometer ,the importance of having accurate timepieces aboard ship was felt as far back as the time of ,columbus4 ,when ships began to go out beyond the sight of land1 it was highly important that they be equipped with some means of locating their position at sea4 ,by noting the elevation of the sun at noon with a sextant it was possible to determine the latitude of the ship1 but there was no means of determining its longitude1 except by dead reckoning1 that is1 using a log to measure the speed of a ship1 and estimating its position by calculating the number of miles it had traveled since leaving port4 ,if ships could be provided with an accurate timepiece which would keep the same time as that of some fixed observatory1 it would be possible definitely to locate the position of the ship east or west by noting how fast or slow the sun was at noon on the particular day on which the observation was taken4 ,this use of the chronometer is common in these days1 but up to #aej years ago there was no timepiece sufficiently accurate to permit a navigator to tell with any certainty just where he was4 ,it was ,john ,harrison1 the son of a ,yorkshire carpenter1 who was the first to build a chronometer worthy of the name4 ,a prize of #aj1jjj pounds was offered by the ,british ,parliament for anyone who could invent and sell a chronometer which would enable a ship to take a voyage from ,england to any of the ,west ,indian islands and back and keep track of the longitude within one degree4 ,if this could be defined within two-thirds of a degree1 the prize would be #ae1jjj pounds4 ,harrison made a bid for this prize1 and after years of effort and patient labor1 he succeeded in being granted a trial4 ,his son1 ,william1 was sent on a ship to ,jamaica with the now celebrated chronometer1 which was mounted on a large cushion4 ,the instrument was constantly attended by the young man1 its position being adjusted from time to time to suit the 8lie0 of the ship4 ,when the ship was eighteen days out1 the vessel was estimated by dead reckoning to be #ac #ej west of ,portsmouth1 but the chronometer indicated the position as #ae #ai4 ,the timepiece was immediately condemned as worthless1 but ,william ,harrison had not lost faith in the instrument1 and insisted that if the ship continued on the same course1 a certain island1 if properly marked on the chart1 would be seen the following day4 ,true to the prediction1 the next morning at seven o'clock the island appeared4 ,by means of his chronometer ,william ,harrison was able to predict the appearance of the other islands1 and at the end of the voyage1 which occupied sixty-one days1 the chronometer was only nine seconds slow4 ,when he returned to ,portsmouth1 after an absence of five months1 the error of the chronometer was only one minute and five seconds1 giving an error in distance of only eighteen miles1 whereas thirty miles was the margin of error allowed by the prize conditions4 ,such accuracy seemed so incredible that the chronometer had to be tested on a second voyage1 during which it was kept under lock and key and when ,william ,harrison had to wind the instrument he was obliged to do so in the presence of two witnesses1 lest he move the hand of the chronometer surreptitiously4 ,at the end of the second voyage there was no further doubt that ,harrison was fully entitled to the prize4 ,chronometers soon came to be used extensively1 until now they are one of the most perfect of machines made by man1 and operate with an accuracy that is almost incredible4 ,usually a ship is provided with several chronometers1 so that one may be used as a check upon another4 ,they are mounted in ball sockets and gimbal joints1 so that they are not affected by the roll of the ship1 but always lie in a horizontal position4 ,,marvelous ,,precision ,,of ,,modern ,,watches ,while we may well marvel at the precision of the chronometer1 it is equally marvelous1 if not more so1 that we may equip ourselves for a few dollars with a timepiece which is so wonderfully accurate as to vary little more than a second per day4 ,if one took the pains to regulate his watch carefully1 any of the better makes could be adjusted to such accuracy4 ,there is nothing very mysterious about the mechanism of a watch4 ,it consists merely of a train of gears which slow down the motions of the mainspring to a convenient speed2 and these gears moreover keep the proper relation between the hour and minute and second hands4 ,but when we reflect that a small watch possesses a tiny second hand which travels something like ten miles in a year1 and that if carefully regulated it will not vary from that of another watch in the whole journey by more than six or eight inches at the most1 we certainly have a reason to marvel4 ,there are #hf1djj seconds in a day1 and a watch is usually arranged to make five beats per second or #dcb1jjj per day4 ,the interval between beats must be adjusted with such minuteness that one beat must not differ from another by #a_/hfjjj part of a second1 else the watch will register more than a second fast or slow at the end of a day4 ,and yet watches capable of such precision are being turned out daily by the thousands4 ,of course1 such perfection would be absolutely impossible without the use of extremely accurate machine tools4 ,it would have been impossible as long as we had to depend upon a watchmaker to make a watch by hand4 ,,the ,,pacemaker ,,of ,a ,,watch ,if we look at the works of a clock the most conspicuous feature is the rapidly oscillating balance wheel which1 by the way1 is the most important part of the watch1 for it governs the release of the power stored up in the spring4 ,it controls the escapement which brings the whole mechanism of the clock to a standstill five times each second--in fact it is the pacemaker of the watch1 for it gives the watch a step-by-step movement and fixes the rate at which the steps are taken4 ,illustration3 ,,fig4 #bg4--;,,escapement ,,of ,a ,,watch ,the last wheel of the watch train is what is known as an escape wheel4 ,it is formed with teeth of an odd shape1 such as shown at ,a in ,figure #bg4 ,these teeth are engaged by a pair of pallets ,b and ,c1 carried by a three-armed lever ,d4 ,the pallets are usually bits of sapphire or similar hard stone to prevent wear4 ,the third of the lever is slotted at its extremity to engage a sapphire pin ,e1 carried by a disk ,f1 which is mounted on the staff of the balance wheel4 ,the escape wheel ,a revolves in the direction of the arrow1 being impelled by the mainspring acting through the train of gears4 ,one of the teeth of this wheel engages the pallet ,b1 causing the lever ,d to swing on its axis and push the sapphire pin ,e toward the left1 thereby giving the disk ,f an impulse in the same direction4 ,here a delicate coil spring1 known as the hairspring1 comes into play4 ,without the hairspring the parts would stand still1 the escape wheel being blocked by the pallet ,b4 ,the hairspring is attached at one end to the shaft or staff of the disk ,f and the other to the frame of the watch4 ,it tries to hold the disk ,f in a fixed position1 but is disturbed by the action of the escape wheel and is constantly oscillating the disk in its effort to bring it back to its normal position4 ,when the disk swings over to the left the pallet ,b is clear of the teeth of the escape wheel4 ,this releases the escape wheel and it springs forward in the direction of the arrow1 but before it can move through an interval of one tooth it is arrested by the second pallet ,c1 which has been projected into its path by the swing of the lever ,d4 ,the lever swings back until the pallet ,c clears the escape wheel and the pallet ,b engages the next tooth4 ,and so the action continues1 the lever swinging back and forth and at each complete oscillation releasing one tooth of the escape wheel4 ,the hairspring takes up the shock of this intermittent motion and a balance wheel carried by the staff to which ,f is fastened steadies the oscillatory motion of the lever ,d4 ,a watch is full of microscopic parts4 ,in a small timepiece there are machine-made screws so small that without the aid of a magnifying glass one cannot see the screw threads cut upon them4 ,but the most marvelous part of the whole watch is the delicate hairspring and the means of adjusting its tension and compensating for its expansion and contraction with changes of temperature4 ,,inanimate ,,matter ,,in ,,continual ,,motion ,when working with minute intervals of time many factors must be considered which are not even thought of in machines of grosser proportions4 ,it never occurs to the man in the street that not only the animate world but the inanimate as well is in ceaseless and variable motion4 ,if our eyes were capable of taking in minute microscopic details1 we should see that everything is expanding or contracting1 swelling or shriveling1 twisting and warping in response to the atmospheric changes4 ,our steel bridges and skyscrapers are in constant motion2 solid concrete dams must be provided with expansion joints2 the ,washington ,monument goes through a diurnal gyration in response to the sun's rays4 ,of course all this motion is almost immeasurably small4 ,a bar of steel a mile long will expand of an inch for every increase of a degree ,fahrenheit in temperature4 ,the expansion of a hairspring1 which may be nine or ten inches long1 is infinitesimally small and yet this must be considered by the watchmaker4 ,we must remember that the escapement mechanism divides the day into #dcb1jjj parts1 each of which contains some minute error1 for absolute perfection is impossible1 and if we add up all these #dcb1jjj errors they must not foot up to more than a second per day4 ,if the hairspring expands ever so slightly its power is weakened1 but this loss of power is compensated by an ingenious form of balance wheel4 ,the rim is in two parts1 half of it being attached to one spoke of the wheel and the other half to the other1 as shown in ,figure #bh4 ,each half rim is formed of two strips of metal1 an inner strip of steel1 and an outer strip of brass fused together4 ,brass expands and contracts almost twice as much as steel1 and hence when there is a rise of temperature the rim sections tend to curl in1 bringing their center of gravity nearer the center of the wheel and making less of a load for the weakened hairspring to move1 while on the other hand1 when the spring is contracted by cold1 the rims spread out slightly1 giving it a greater load to oscillate4 ,the weight of the balance wheel is thus automatically adjusted against variations in power of the spring4 ,illustration3 ,,fig4 #bh4--,,the ,,self-,,correcting ,,balance ,,wheel ,,of ,a ,,watch ,aside from this automatic variable adjustment1 the balance wheel must have a primary permanent adjustment4 ,the rim of the wheel is loaded by means of small screws4 ,screws placed near the free ends of the rim sections will have a greater inward or outward play as the rim contracts and expands1 and by their locations in different positions on the rims the balance wheel may be adjusted with great accuracy to compensate for temperature variation in the hairspring4 ,,the ,,pendulum ,,escapement ,illustration3 ,,fig4 #bi4--,,pendulum ,,escapement ,in the case of clocks such delicacy of adjustment is hardly necessary4 ,pendulum clocks1 if they are to run accurately1 must have their pendulums automatically adjustable for variations in temperature1 because the longer the pendulum the more slowly it oscillates4 ,many years ago a grid type of pendulum was invented in which various alloys were used1 which reacted one against the other and preserved the center of gravity always at the same distance from the center of oscillation4 ,the action of a pendulum movement is similar to that of a balance-wheel movement described above4 ,the pendulum operates a pallet lever similar to that shown in ,figure #bi4 ,the teeth of an escape wheel1 which are commonly somewhat different from those of the watch movement1 strike the pallets of the pallet lever1 and the escape wheel is intermittently stopped and permitted to proceed4 ,the pressure of the escapement teeth against the pallets is just enough to keep the pendulum swinging and the speed of the clock is regulated by lengthening or shortening the pendulum4 ,we have added little to clock or watch movements in recent years4 ,about the only conspicuous modern invention is the torsion pendulum4 ,the pendulum in this case is a heavy horizontal disk suspended by a wire1 and the disk rotates first in one direction and then in the other1 twisting and untwisting the wire4 ,the advantage of this pendulum is that the oscillations are very slow1 and hence it is possible to keep the clock going for a year at a single winding4 ,the electric regulation of clocks is another important improvement4 ,a clock need not be a very perfect timepiece1 but if provided with an electric regulator its hands are brought up to the correct time every hour in response to an impulse sent from an accurate master clock which in turn has its time corrected daily from the ,national ,observatory in ,washington4 ,,chapter ,v ,,putting ,,rivers ,,to ,,work ,,flowing water exerts a strange fascination upon mankind1 even to the present day4 ,tourists travel hundreds of miles to view the glorious spectacle of a riotous tumbling cataract4 ,is it strange1 then1 that in the olden times1 when the world was peopled with gods and genii and strange spirits1 the ancients looked upon ceaselessly flowing rivers as the symbol of life8 ,it was most natural for them to covet the endless power of a river and eventually1 despite their superstitions1 to try to utilize some of its energy4 ,it may be that sailboats antedate the first water wheel1 but it seems much more probable that flowing water was the first inanimate power harnessed by man4 ,windmills were certainly a later development4 ,they possessed the advantage that they could be located anywhere while the water mill had of necessity to be built along the bank of a stream4 ,however1 the power of the wind is so unreliable and fluctuates so widely that it was little used1 except in flat countries1 where there was little if any available water power4 ,water power predominated until the steam engine was introduced1 when it had to give way to an even more reliable power and one which could be located at any place to which fuel could be transported4 ,now1 however1 we are going back to our first power1 seeking it out in the most inaccessible mountainous regions1 because we have discovered the means of taking the power it yields and transmitting it hundreds of miles1 over hills and plains to the point where we can put it to useful service4 ,hydroelectric power has very aptly been termed 8white coal40 ,the first prime motor was the current wheel1 that is1 a wheel fitted with paddles1 which was journaled over a stream with the paddles projecting into the water4 ,this was a very inefficient machine2 it converted very little of the energy of a stream into useful mechanical power4 ,the idea of damming the stream and letting the waters flow over the dam through a raceway upon a water wheel was a much later development4 ,,water ,,wheels ,three types of water wheel which were in universal use before the advent of the steam engine were the undershot wheel1 the overshot wheel1 and the breast wheel 7,figure #cj74 ,in the undershot wheel the water stored back of a dam is let out near the bottom of the dam and strikes the under side of the wheel1 so that the top of the wheel turns toward the dam4 ,in the overshot wheel1 the water flows over the wheel striking the paddles or buckets on top and on the forward side1 so that the wheel turns forward4 ,in the breast wheel1 the water strikes the paddles half way up the wheel on the rear side and drives the wheel in the same direction as that of the undershot wheel4 ,when we speak of water power we are apt to think of the water as actually furnishing the energy4 ,as a matter of fact1 it is not water but gravity that drives the wheel1 the water being merely the medium that gravity acts upon4 ,by having the water drop from a great height1 its velocity is greatly increased and the power it imparts to the wheel is much higher4 ,in mountainous regions it is easy to obtain a high head of water and thus generate a great deal of power from a relatively small stream4 ,however1 the ancient type of wheel with its paddles or buckets has now practically passed out of existence1 being superseded by the ,pelton wheel for high heads and the turbine for low heads of water4 ,illustration3 ,,fig4 #cj4--,,undershot1 ,,overshot1 ,,and ,,breast ,,wheels ,,invention ,,of ,,the ,,pelton ,,wheel ,illustration3 ,,fig4 #ca4--,,sectional ,,view ,,of ,a ,,pair ,,of ,,pelton ,,wheel ,,buckets ,,showing ,,how ,,the ,,water ,,jet ,,is ,,divided ,,and ,,follows ,,the ,,contour ,,of ,,the ,,buckets ,in ,california1 a number of years ago1 they made use of what was known as the hurdy-gurdy wheel4 ,this consisted of an ordinary wheel with bucket-shaped paddles against which was directed a stream of water at high velocity through a nozzle4 ,there was a carpenter1 named ,l4 ,a4 ,pelton1 who used to make a business of building and repairing such wheels and the flumes that carried the water to them4 ,although uneducated1 he was possessed of considerable native ingenuity and was a very observant man4 ,one day1 when he was called in to repair a wheel1 he noticed that one of the buckets which had been misplaced received the water from the nozzle without any splashing4 ,the water struck the edge of the bucket with practically no shock1 whereas the other buckets produced a great deal of splashing4 ,pelton had enough knowledge of the principles of mechanics to realize that a splash means a waste of energy1 and that here was a bucket which1 although out of plumb and apparently defective1 was really more efficient than any of the others in the wheel4 ,it occurred to him then that instead of having the jet of water strike the middle of the buckets it ought to strike the edge1 so that all its power would be absorbed without any wasteful splashing4 ,he might have displaced the jet laterally so as to accomplish this result1 but he realized that that would have produced a considerable side thrust on the wheel1 which1 of course1 would have been objectionable1 and so he hit upon the plan of using double buckets and letting the stream of water strike the pair of buckets along their dividing line4 7,see ,figure #ca47 ,this would split the stream in two and let each half strike the slanting face of the bucket1 and follow the surface around in the same way that it did on the single misplaced bucket1 but the reaction or side thrust on one bucket would be counteracted by that on the other4 ,this idea proved successful and out of it has grown the ,pelton wheel which is now universally used in all power plants employing high heads of water4 ,a #d1jjj-;,,foot ,,head ,,of ,,water ,a notable illustration of such a plant is the great installation at ,big ,creek1 ,cal4 ,big ,creek1 despite its name1 used to be a small stream flowing down the mountains into a canyon4 ,one would hardly suppose that it was capable of yielding much power1 but it had its source high up in the ,sierras and was fed mainly by melting snows4 ,in the springtime1 it swelled to a good-sized torrent4 ,by building three dams near the top of the mountain1 a lake was formed in which the water of the melting snow was impounded1 so that a steady stream of water could be supplied the year round for power purposes4 ,but even so1 the stream hardly amounts to very much if we consider only the quantity of water that passes through it4 ,the particular advantage of this installation is the fact that in a distance of six miles from the dam the creek falls #d1jjj feet4 ,an inhabitant of the ,eastern ,states who is unused to mountain heights may gain some conception of the meaning of this elevation by gazing up to the pinnacle of the ,woolworth ,tower1 which rises #gie feet above street level1 then mentally multiplying its altitude by five4 ,evidently even a small stream of water dropping from such an elevation would develop an enormous amount of power4 ,in fact1 it was considered inexpedient to use the entire fall at a single drop and so it was divided into two stages4 ,the water is carried through a tunnel three-quarters of a mile long and then through a flow pipe along the face of the mountain to a point where it may drop #b1jjj feet to the first power plant4 ,after passing through this plant the water is discharged into the creek and is then diverted into a second tunnel four miles long and a series of steel conduits to a point from which it may drop #b1jjj feet more to the second power plant4 ,in each power house there are two electric generators1 each fitted with a pair of ,pelton wheels4 ,these wheels are a little less than eight feet in diameter and each one develops #bc1jjj horsepower4 ,the water is directed into the buckets of the ,pelton wheel in a stream six inches in diameter1 and it issues from the nozzle with a velocity of #cjj feet per second or about #baj miles per hour4 ,a jet of water is almost like a solid bar of wood4 ,in fact1 it is impossible to chop through it with an ax4 ,the water would swing the ax out of one's hand before it got part way through the jet4 ,traveling at such a high speed the friction is so great that it would tear the skin off one's hands1 if it did not actually tear the hand off the arm1 and yet it strikes the buckets of the wheels with no shock at all1 for the first part of the bucket it touches is nearly parallel to the jet1 and as the water sweeps around the curved face of the bucket it loses practically all of its pressure and velocity and falls into the tail race4 ,the electric power generated by the two plants is stepped up to #aej1jjj volts and sent out over transmission lines to points of service4 ,the street cars of ,los ,angeles are connected by a #bdj-mile electric harness to the hydraulic horses of ,big ,creek4 ,powerful as this stream is1 a still higher head is used in ,switzerland1 at ,lake ,fully1 where there is a drop of over a mile in a distance of #b4h miles4 ,the water is carried by a short tunnel through the mountain1 and then makes a drop of over #e1jjj feet to the power plant1 where it strikes the ,pelton wheels at a velocity of #djj miles per hour1 or about seven times the speed of a fast express train4 ,,harnessing ,,the ,,mississippi ,in contrast to such high heads1 we have the low-head power plants which are employed where a large volume of water is available4 ,the most notable installation of this type1 and the largest in the world1 is that at ,keokuk1 ,iowa1 where a dam has been thrown across the ,mississippi ,river4 ,for many years it was thought impossible to make any use of the vast volume of water that flows through this great river4 ,but above ,keokuk there used to be a rapid extending back about twelve miles4 ,by building a dam across the river just below the rapid it was possible to obtain a working head of about thirty-two feet1 and with the enormous volume of water available this provided sufficient energy to make the development worth while4 ,in marked contrast to the installation at ,big ,creek1 it is volume rather than velocity that is employed1 and hence turbines rather than ,pelton wheels are used4 ,more water goes through a single turbine than is used in the whole of the city of ,new ,york with all its elaborate aqueduct system4 ,enormous turbines are used1 fifteen feet in diameter1 and when the installation is complete there will be thirty units1 each yielding #aj1jjj horsepower1 or a total of #cjj1jjj horsepower4 ,a turbine1 it may be explained1 differs from the ordinary water wheel in the fact that the water runs through the wheel instead of around it 7,figure #cb74 ,the water may enter at the center and then flow out at the periphery1 or it may enter at the periphery and then be discharged from the center of the wheel1 or it may run axially through the wheel4 ,in a ,pelton wheel there is a single jet which strikes but one pair of buckets at a time1 but in a turbine there are many jets distributed all around the circumference of the wheel4 ,the water is divided into a series of jets by being forced through a stationary set of curved vanes4 ,the blades of the rotor or revolving part of the turbine are oppositely curved4 ,if the rotor were immovable the jets would have to change their direction in passing through the rotor1 but as the rotor is free to turn1 the jets react against these blades and set the wheel to revolving4 ,the turbine may be designed to run either on a horizontal axis or on a vertical one4 ,illustration3 ,,fig4 #cb4--,,turbine ,,wheels2 ,,inflow ,,type ,,shown ,,on ,,the ,,left ,,and ,,outflow ,,type ,,on ,,the ,,right ,the turbines used at the ,keokuk plant are of the inflow type4 ,the rotor is mounted on a vertical shaft in a scroll-shaped concrete chamber1 something like a snail shell4 ,water pouring into this chamber is thus given a swirling motion in the direction of rotation of the wheel4 ,as it flows into the wheel it passes first through a ring of fixed vanes1 which divide it into the jets4 ,the highest velocity of a wheel is naturally at the periphery and the advantage of an inflowing turbine such as this is that the water is traveling at its highest velocity when it strikes the periphery of the rotor4 ,as it loses its velocity it flows in toward the slower-moving portions of the rotor4 ,finally it reaches the center1 after giving up practically all its energy1 and falls into the tail pool through a draft tube at the center of the rotor4 ,the scroll chambers at ,keokuk are thirty-nine feet in diameter and the draft tubes are eighteen feet in diameter4 ,water enters the scroll chambers with a velocity of fourteen feet per second and comes out of the draft tubes into the tail pool with its velocity cut down to but four feet per second4 ,compare this with the velocity of the water jets at ,big ,creek6 ,the current generated at ,keokuk goes to ,st4 ,louis and surrounding towns and serves a population of #a1abj1jjj4 ,now that we have learned how to transmit electrical power without serious loss over enormous distances1 it is only a question of time before all the water power in the world is harnessed and put to the service of man4 ,the power costs nothing after once the plant has been built2 the only expense is that of maintaining the machinery and keeping it in repair4 ,it is estimated that there is some #bjj1jjj1jjj horsepower available in this country1 but this includes all flowing water1 much of which it would be impracticable1 if not almost impossible1 to utilize4 ,however1 there is about #fj1jjj1jjj horsepower commercially available1 according to the figures of the ,u4 ,s4 ,geological ,survey1 of which we have developed so far only #f1jjj1jjj horsepower4 ,the ancients used flowing streams not so much for power purposes as to lift water to a higher level so that it would flow into their irrigating ditches4 ,nowadays1 electricity1 steam1 or air is used for elevating water1 but we have a very ingenious machine which makes the stream lift a part of itself4 ,this machine is very different in principle from the old ,egyptian noria4 ,it depends upon the kinetic energy of water in motion4 ,you cannot push a nail into a piece of wood with a hammer but you can easily drive it in by striking it with the hammer4 ,as the hammer is swung it acquires what we term kinetic energy or energy of motion4 ,,setting ,,kitchen ,,faucets ,,to ,,work ,it is not generally realized that water in motion also acquires kinetic energy4 ,whenever a faucet is turned off very quickly1 there is a hammering sound which is due to the fact that the moving water in the water pipe is brought to an abrupt stop4 ,this puts a severe strain on the piping4 ,a great deal of trouble was experienced from this source in the early days of plumbing4 ,at a hospital in ,bristol1 ,england1 there was a lead pipe leading from a cistern in one of the upper stories to the kitchen4 ,every time the faucets were turned off abruptly the momentum of the water caused the lead pipe to expand1 and every now and then the pipe was burst4 ,in order to relieve the situation1 a plumber connected a pipe to the faucet and carried it up the side of the building to the level of the cistern4 ,his idea was that whenever the water was turned off suddenly it would have a vent leading up to the level of the water reservoir4 ,much to his surprise1 the water issued from the pipe in a jet of considerable height4 ,to prevent the escape of the water1 he extended the pipe considerably1 and still a jet of water would issue from it4 ,eventually the relief pipe was carried up twice the height of the cistern and even then the water would squirt out occasionally when the faucets in the kitchen were turned off very suddenly4 ,then the idea was conceived of placing a reservoir on one of the upper floors of the hospital and letting the jet of water fill this reservoir4 ,every time the faucet was operated in the kitchen a certain amount of water flowed into the new cistern1 and in this way it was kept supplied with enough water to furnish that which was required for the upper floors of the hospital4 ,illustration3 ,,fig4 #cc4--,,sectional ,,view ,,of ,a ,,water ,,ram ,it is on this principle that the hydraulic ram operates4 ,water from a stream is made to flow down a pipe1 and as it gains velocity a check valve suddenly stops the flow which produces enough pressure to force open a valve in an air chamber and let some of the water enter the chamber4 ,as soon as the pressure is relieved the check valve opens and the valve into the chamber closes automatically until a moment later the stream of water has gained sufficient velocity to repeat the performance4 ,thus an intermittent jet of water is forced into the air chamber and thence through a pipe to a reservoir4 ,the height to which the water will rise depends entirely upon the velocity of the water flowing through the system4 ,the air chamber is necessary to cushion the action of the hydraulic ram and provide a fairly steady pressure upon the water that flows up through the vent pipe4 ,the check valve is entirely automatic4 ,it is held open against the pressure of the water by a spring or a weight1 but when the water is in motion is dragged shut1 only to spring open again when the pressure is reduced by the escape of the water into the air chamber4 ,illustration3 ,,fig4 #cd4--,,the ,,gyrating ,,water ,,meter ,there is a very ingenious water-driven motor which is employed merely to record the amount of water flowing through it4 ,this is the ,thomson water meter which is illustrated in ,figure #cd4 ,it consists of a circular chamber with inwardly dished or conical top and bottom walls4 ,in the chamber is a flat disk with a ball and socket bearing4 ,at one side there is a vertical diaphragm in the chamber which passes through a slot in the disk4 ,this prevents the disk from revolving1 but it is free to oscillate4 ,it has a motion similar to the gyrations of a top when it is beginning to lose speed and die down1 except that the disk does not revolve4 ,when the disk is in contact with the bottom wall of the chamber on one side it contacts with the top wall on the other so that the chamber is virtually divided into two compartments by the disk1 but by gyrating the disk these compartments are made to revolve4 ,water enters at one side and discharges at the other side of the vertical diaphragm4 ,now1 if the disk is in the position shown in ,figure #cd1 the water1 on entering1 bears upon the upper face of the inclined disk and wedges its way between the disk and the upper wall of the chamber1 making the disk oscillate on its ball center4 ,as the edge of the disk rises across the face of inlet port the water entering the chamber bears against the under side of the disk1 continuing the gyratory motion4 ,the water cut off on the upper side of the disk is carried around to the outlet and discharges1 while a fresh supply flows in on the other side of the vertical partition and at the next half turn the water in the lower compartment discharges at the outlet side of the partition1 while the compartment is filling on the other side of the partition4 ,a measured amount of water flows through the chamber at each gyratory oscillation of the disk4 ,a train of gearing is driven by the gyrating disk which operates a set of dial pointers and a measure of the amount of water passing through the meter is indicated4 ,,digging ,,with ,,water ,,jets ,we have referred to the enormous velocity of the jets used to drive ,pelton wheels4 ,where high heads of water are obtainable water jets are used very effectively for excavating purposes1 particularly in mining plants for washing down gold-bearing gravel banks4 ,if water is not found near such banks expensive canals1 flumes1 and pipe lines are constructed and even tunnels are bored to bring the water to the point where it can be utilized4 ,some of the giant nozzles spout streams from #b to #h inches in diameter with a pressure of from #ej to #bjj pounds per square inch4 ,the powerful streams tear into the gravel banks1 washing them away into sluices in which riffle boxes are placed to catch the precious metal4 ,the back pressure of these nozzles is very heavy and the larger ones have to be provided with strong anchorages4 ,water in motion resists any change of direction and long levers have to be provided to permit the miners to guide the nozzles4 ,the hydraulic jet is also used for general excavating wherever water power is available4 ,sometimes it is employed under water when clearing a channel to level down piles of stones that are too large to be picked up by a suction dredge4 ,hollow iron piles are driven into a sandy bottom by means of hydraulic jets4 ,no hammer is needed4 ,water is pumped into the pile and on issuing from the bottom of the pile it carries sand with it1 making a hole into which the pile sinks4 ,wooden piles are driven in the same way by loosely attaching a water pipe to them so that the pipe may be withdrawn when the pile has been driven far enough4 ,the pile is grooved at the lower end so that the pipe outlet may be centered at the bottom of the pile4 ,,compressing ,,air ,,with ,,water ,illustration3 ,,fig4 #ce4--;,,how ,,the ,,vena ,,contracta ,,raises ,,water ,a very ingenious apparatus for compressing air was invented in the earliest years of the iron age to furnish a continuous blast of air for the ,catalan forges4 ,this compressor1 known as a 8trompe10 can hardly be termed a machine because it contains no moving parts except water1 which is the motive power1 and the air which it traps and compresses4 ,to understand its operation we must look into a peculiar property of water flowing out of a reservoir into a pipe or nozzle4 ,there is a converging motion that tends to contract the jet of water just after it leaves the pipe4 ,this is known as the vena contracta4 ,it produces a partial vacuum in the pipe4 ,if air ports are opened into the pipe at this point1 air will be sucked in to fill the vacuum and will be carried out of the pipe by the friction of the water4 ,in ,figure #ce a pipe is shown running from the vena contracta to a water tank below4 ,the rise of water in this pipe indicates the degree of vacuum produced by the jet4 ,illustration3 ,,fig4 #cf4--,,the 8,,trompe0 ,,by ,,which ,,compressed ,,air ,,was ,,furnished ,,for ,,catalan ,,forges ,this principle is used in the hydraulic-air compressor or 8trompe0 as it is called4 ,water flows out of one reservoir through a pipe into another reservoir lower down4 7,see ,figure #cf47 ,air enters the pipe through ports at the point where the vein of water contracts and is carried down into the second reservoir4 ,this reservoir is sealed so that the air is trapped in it4 ,the water passes out through a pipe which is carried high enough to keep a certain pressure of air in the reservoir and prevent it from blowing out4 ,illustration3 ,,fig4 #cg4--;,,diagrammatic ,,section ,,of ,a ,,large ,,hydraulic ,,air ,,compressor ,,in ,,michigan ,there is a compressor of this type1 constructed on an enormous scale1 in the northern part of ,michigan4 ,a sketch of the compressor is given in ,figure #cg4 ,the air reservoir in this case is a huge underground rock-walled chamber nearly #cej feet below the surface1 #h feet wide1 #bf feet high1 and about #bhj feet long4 ,there are three intake pipes1 #e feet in diameter1 each filled with an annular funnel-shaped head1 which sucks air into the water and carries it down into the chamber4 ,at the bottom of each intake pipe there is a concrete block with a conical top projecting up into the pipe4 ,the column of water flowing down the pipe is spread out into an annular stream by the conical block and the bubbles of air escape into the chamber4 ,the water outlet of the chamber is an inclined shaft which leads up about #bgj feet to the surface of the ground where it discharges into the tail race4 ,the water is forced up this inclined shaft by the pressure of the air trapped in the chamber4 ,the mouth of the shaft is1 of course1 below the level of the water in the chamber so that there is no chance for the air to escape unless the pressure becomes excessively high1 when it will force the water level below the mouth of the shaft and blow out4 ,the discharge sometimes forms a geyser #gjj feet high4 ,the air will continue to blow until the pressure is reduced enough for the water level to rise and cut off access of the air to the mouth of the shaft4 ,under normal conditions there is a fall of #cdc feet from the water level at the top of the intake pipe to the water level in the chamber1 and a vertical rise of #bga feet from the water level in the chamber to the tail-water level4 ,the difference1 or #gb feet1 represents the working head4 ,with all three intakes operating1 a total of #e1jjj horsepower is developed4 ,each intake delivers #aa1icj cubic feet of air per minute at a pressure of #abh pounds4 ,air enters the intake heads through tubes inch in diameter and there are #a1hjj of them to each head4 ,the air is employed to operate machinery and tools in an adjacent mine4 ,one advantage of this type of air compressor is that it cools the air while compressing it4 ,this was hardly an advantage in the ,catalan forges1 but when the air is used to drive machinery it is important that it be precooled4 ,when air is compressed by mechanical means a great deal of heat is generated and the machines must be water jacketed to extract this heat1 but in the hydraulic compressor the air bubbles are compressed as they pass down with the water to the reservoir and the water absorbs the heat1 delivering cool compressed air at the bottom of the intake pipe4 ,,chapter ,,vi ,,liquid ,,levers ,,and ,,gears ,,many an inventor has strayed off into the delusive pursuit of perpetual motion because he did not know that the pressure in a body of water at any given point is equal in all directions1 upward1 downward1 or laterally4 ,a cubic foot of water weighs #fb pounds4 ,take a hollow column with an internal cross-sectional area of one square foot and if it be filled with water to a depth of ten feet there will be a weight of #fbe pounds of water in the column and hence a pressure of #fbe on the bottom of the tube or #d4cd pounds on every square inch of the bottom4 ,but the water presses on the sides of the tube as well and the amount of this pressure depends upon the depth or 8head0 of water and not upon the quantity of water4 ,at the bottom of the tube the pressure on the side walls is #fbe pounds per square foot or #d4cd pounds per square inch2 at a depth of one foot the pressure on the side walls is #fb4e pounds per square foot or 4#dcd pound per square inch2 at a depth of two feet it will be 4#hfd pound per square inch1 etc4 ,the pressure on each square inch depends not upon the mass of the water but upon its depth4 ,if the column of water had a cross-sectional area of a mile or a thousand miles1 the pressure at a depth of one foot would always be 4#dcd pound per square inch4 7,of course there are slight variations from this figure due to salt or other substances dissolved in water or to changes in density produced by variations of temperature1 but we need not consider such minute differences here47 ,that is why a dam which is strong enough to hold back the waters of a pond will be just as able to hold back the waters of the whole ocean if it be placed in a sheltered bay where ocean waves cannot tear it to pieces4 ,the ocean1 despite its enormous mass1 can exert no more pressure per foot of depth than the water in a cistern4 ,,why ,a ,,ship ,,floats ,it is because the pressure of water at a given depth is exerted upward1 as well as laterally and downward1 that a ship floats4 ,it is the upward pressure of the water that holds up the boat4 ,when an object is placed in a reservoir of water it sinks into zones of increasing pressure until it finally reaches a depth at which the pressure on the bottom of the object balances the weight of the body4 ,if the body is entirely submerged before reaching such a point1 it will continue to sink to the bottom of the reservoir because water will flow over the top of the object and keep adding downward pressure to offset the increasing upward pressure4 ,the amount of water in the reservoir makes no difference4 ,a battleship will float just as high in a flooded dry dock as it will in the open ocean4 ,if the dry dock were so narrow as to leave a clearance of but a few inches of water around the ship1 the latter would still float even though the ship weighed considerably more than the water in the dock4 ,there is a big difference1 then1 between the weight of water and the pressure it exerts4 ,in ,figure #ch we have an ,l-shaped receptacle with the lower arm of the ,l terminating in a chamber ,a4 ,the top wall ,b of this chamber measures ten square inches4 ,the tube ,c has a cross sectional area of one square inch4 ,if tube ,c is filled to a height of twelve inches above wall ,b we shall have an upward pressure of #j4dcd pound on every square inch of wall ,b1 or a total of #d4cd pounds4 ,if by means of a plunger ,d we add a hundred pounds of pressure to the column of water in tube ,c1 we shall be adding a thousand pounds to the pressure on the wall ,b4 ,the side walls and bottom of the chamber ,a will also be subjected to a pressure of #a1jjj pounds per inch plus the pressure due to the depth or head of water4 ,illustration3 ,,fig4 #ch4--;,,diagram ,,illustrating ,,hydrostatic ,,pressure ,illustration3 ,,the ,,air-,,lock ,,of ,a ,,pneumatic ,,caisson ,illustration3 ,,subaqueous ,,tunnel1 ,,showing ,,the ,,shield ,,in ,,the ,,background ,illustration3 ,,fig4 #ci4--,,principle ,,of ,,the ,,hydraulic ,,press ,here1 then1 we have a convenient means of multiplying force or effort and it is a means that is used very largely in certain classes of machinery4 ,figure #ci is a diagrammatic representation of a hydraulic press4 ,it consists of a cylinder ,a in which is fitted a ram ,b4 ,an ,l-shaped tube ,c connects with the cylinder and is fitted with a plunger ,d4 ,the cylinder and tube are filled with water and then when the plunger is depressed the ram ,b has to rise1 ,if the area of the plunger is one square inch and that of the ram thirty square inches1 a #ajj pounds pressure on the plunger will exert #c1jjj pounds of lift on the ram4 ,,hydraulic ,,leverage ,however1 we must remember that in mechanics1 as in all walks of life1 we cannot get 8something for nothing40 ,if we multiply the pressure or force1 we must pay for it in some way1 otherwise we should be getting more work out of the press than we put in it1 which is what the perpetual motion crank is ever trying to do4 ,as the cross-sectional area of the plunger ,d is only #a_/cjth of that of the ram1 the plunger must descend thirty inches to raise the ram one inch4 ,we need not consider the difference in the head of water because it would not amount to more than a few ounces at most1 nor need we consider frictional losses4 ,the case is parallel to that of the lever4 ,in fact1 we may consider the hydraulic press as a fluid lever with the water in tube ,c as the effort arm and that in cylinder ,a as the weight arm4 ,the two arms are here so proportioned that the power arm must move thirty times as far as the weight arm4 ,the work put into the press is exactly balanced by that we get out of it4 ,an effort of #ajj pounds exerted through a distance of thirty inches is exactly balanced by the moving of #c1jjj pounds through a distance of one inch4 ,it is a decided disadvantage to have to move the plunger so far and in actual commercial practice hand-operated hydraulic presses are not worked in that way4 ,a pump is used to force water into the cylinder so that a great many short strokes may be taken in place of one long one1 and the pump handle provides an added leverage1 enabling a man with little effort to exert an enormous lift4 ,the water enters the ram cylinder through a valve1 and the pressure is maintained on the ram until relieved by the opening of an outlet port4 ,,maudsley',s ,,leather ,,collar ,all this seems very simple and one would suppose that the inventor of the hydraulic press must have been exceptionally free from the troubles and trials that beset most inventors4 ,however1 there is a vast difference between a laboratory apparatus and a commercial machine4 ,when1 towards the close of the eighteenth century1 ,joseph ,bramah1 the eminent ,british tool builder1 invented the hydraulic press1 he experienced all sorts of difficulty in holding the water in the ram cylinder4 ,of course1 the ram has to slide freely into and out of the cylinder1 but how could he prevent the water from leaking out past the ram8 ,he resorted to all the plumbing expedients of the day4 ,he used a stuffing box and gland1 but when this was packed tight enough to hold the water in1 it gripped the ram so tightly that the latter would not move down into the cylinder on the return stroke4 ,bramah had in his employ a very clever young mechanic named ,henry ,maudsley1 who later became famous as an inventor and designer of machine tools4 ,we read of him in ,chapter ,,iii4 ,maudsley attacked the baffling problem of the hydraulic press and provided a solution that survives to this day4 ,in place of the stuffing box which is a means of jamming a mass of cotton waste about the collar1 he provided a cupped leather collar4 ,when the pressure was applied it expanded the collar and made it bear tightly against the ram1 but on relieving the hydraulic pressure the pressure of the cup leather was also reduced automatically4 ,there are many machines analogous to the hydraulic press in principle4 ,they do not use water in every case for the fluid lever4 ,where the fluid is used over and over again oil is frequently employed4 ,the compactness of this form of lever makes it most useful wherever an operation calls for the overcoming of a very heavy load or resistance through a relatively short distance4 ,for instance1 there are machines for bending pipe1 for curving railroad rails1 for punching holes in metal1 for pulling wheels off their shafts1 for jacking up heavy weights1 for baling cotton1 paper1 and other materials1 all of which operate on the same principle as the hydraulic press4 ,water pressure is supplied sometimes by a hand pump1 sometimes by a power-driven pump1 and sometimes it is taken from a reservoir in which compressed air imparts the requisite pressure to the water4 ,,blasting ,,with ,,water ,a novel use of water pressure has been developed in ,england4 ,in certain mines it is dangerous to use dynamite for blasting purposes owing to the presence of explosive gases1 and successful experiments have been made with hydraulic cartridges4 ,this consists of a cylinder of steel fitted with a series of little plungers arranged in a row in the cylindrical wall of the cartridge4 ,as in powder blasting1 a series of holes are drilled in the face of the rock and the cartridges with the plungers retracted are fitted into the holes4 ,then the cartridges are connected to a high-pressure water supply4 ,the water forces the plungers out1 exerting enough pressure to burst the rock4 ,not only is this system perfectly safe1 but it is economical1 because the gallery does not have to be cleared of workmen before every blast4 ,there is more certainty in the use of water cartridges1 and the danger1 common where dynamite is used1 of having the rock drill or pick strike and explode a stick of dynamite which failed to go off with the rest of the charge in a previous blast is avoided4 ,hydraulic pressure is also used in jacks for lifting heavy weights4 ,the principle of the hydraulic jack is the same as that of the hydraulic press4 ,,raising ,a ,,bridge ,,span ,,with ,,water ,an interesting illustration of the use of these liquid levers was afforded in the construction of the ,quebec ,bridge4 ,this huge bridge1 it will be recalled1 consists of two cantilevers which stretch out from opposite shores of the ,st4 ,lawrence ,river and support between them a center span #fdj feet long and weighing #e1djj tons4 ,the span was built on barges1 towed down to position between the cantilever arms and then lifted up #aej feet to the floor level of the bridge4 ,eight #a1jjj-ton hydraulic lifting jacks were used1 two at each corner of the span4 ,they were ideally suited to this kind of work4 ,the bridge span had to be lifted with utmost care and the motion had to be simultaneous on all four corners4 ,if one corner were raised faster than another the span would be twisted and subjected to serious strains4 ,in the first attempt the fastening gave way at one corner and the span crumpled up and plunged down into the river4 ,but a year later at the second attempt the span was hoisted successfully to position4 ,the jacks had a lift of two feet1 and1 counting the time required to secure the huge plate chains by which the span was suspended1 move the jacks down and give them a fresh hold1 it took fourteen minutes to complete each two-foot lift4 ,the work was done only during the daylight hours and on the third day the span was finally brought into position and made fast to the cantilever arms by means of twelve-inch pins driven home at each corner4 ,hydraulic power is used very largely in the operation of cranes4 ,as the plunger or ram has a very limited range of motion some means of multiplying distance of travel is required4 ,one simple scheme is to use a set of pulley wheels or sheaves attached to the cylinder and another set to the ram and pass the hoisting chain around them4 ,if we refer back to ,figure #af1 on page #cd1 we shall see that seven feet of rope must be pulled in at ,e in order to raise the lower pulley block one foot4 ,it is very evident that the process can be reversed4 ,power might be applied to spread the two-pulley blocks apart when a movement of one foot would produce a travel of seven feet at ,e4 ,that is what is done on the hydraulic crane4 ,the ram is lifted1 spreading the pulley blocks apart and thus multiplying the motion of the lifting cable to any extent1 depending upon the number of sheaves1 so that a travel of but a few feet will result in lifting a load forty or fifty feet4 ,,hydraulic ,,elevators ,the same principle is used in hydraulic elevators4 ,the hydraulic cylinder lies horizontally on the basement floor and by means of pulley gearing a short motion of the plunger is sufficient to raise the car several stories4 ,in a more modern type of elevator the plunger acts directly on the car4 ,the plunger is long enough to reach to the top story of the building which means that it must sink far into the ground in order to let the car down to the first story or basement4 ,a steel pipe is sunk into the ground and serves as the cylinder and in this the long plunger operates4 ,in one of ,new ,york's tall buildings the cars are lifted to a height of #bhb feet4 ,the plungers are #f inches in diameter and they travel at a speed of over #djj feet per minute4 ,the car which1 when loaded1 weighs #a1fag pounds1 is supported on the top of the plunger4 ,however1 counterweights are provided which balance the weight of the car1 so that practically the only weight lifted by the plunger is that of the passengers4 ,the advantage of this type of elevator is that it reduces the danger of accident4 ,the motion of the car is steady and easily controlled4 ,the car cannot move down above a given speed and the only possible danger is that the plunger might break4 ,however1 a shaft of steel #f inches in diameter1 even if hollow1 is hardly likely to give way even under the most extraordinary loads to which it might be subjected in elevator service4 ,,lift ,,locks ,,for ,,canals ,there is another type of elevator that completely dwarfs anything used in office buildings4 ,on some canals where it is necessary to make a sudden change of level of considerable extent1 instead of using a flight of locks1 a hydraulic elevator is employed to lift or lower not only the vessel but the water it is floated in4 ,there are two huge tanks which ply between the upper and lower levels of the canal4 ,these are so connected that as one rises the other descends4 ,the tanks are big enough to take in the largest vessels that are likely to use the canal4 ,they are fitted with water-tight gates at each end1 and after a vessel has entered one of them1 say at the lower level1 the gate behind it is closed4 ,then hydraulic mechanism is operated to lift the tank1 and when the top is reached the other gate is opened and the vessel sails out into the upper level4 ,it seems like a tremendous undertaking to lift a heavy ship1 but the two tanks balance each other and the only work that has to be done is to overcome the friction and inertia4 ,no matter how heavy a vessel may be1 it will not disturb the balance between the two tanks4 ,nor is it necessary to have a ship in each tank1 for the same depth of water is maintained in the two tanks1 and when a ship enters the weight of the tank is not increased1 for the ship displaces its own weight of water4 ,,hydraulic ,,variable ,,speed ,,gear ,water is frequently used to take the place of toothed gearing for the transmission of power1 particularly where it is desirable to vary speed4 ,one of the disadvantages of toothed gearing is that a change of speed can only be made by shifting gears4 ,the speed cannot be varied gradually but is changed by abrupt steps4 ,the guns of a battleship must be kept trained on the target1 while the ship rolls in the waves under them1 so as to be ready for a broadside at any instant4 ,a telescope is secured to the barrel of the gun and a man known as a 8pointer0 tries to keep the cross-hairs of a telescope on the target by constantly elevating or depressing the gun4 ,the speed of the elevating machinery must be constantly changing2 now running at high speed1 the next instant barely moving1 and the next moment reversing4 ,to produce these variations a hydraulic variable speed gear is used4 ,the construction is somewhat complicated1 but the general principle of operation is simple4 ,in a common pump water is lifted by operating a plunger in and out of a cylinder4 ,it will be readily understood that the operation may be reversed1 and if power is applied to the water to force it through the pump1 it will make the plungers move in and out of the cylinder4 ,in the hydraulic variable speed gear the driving shaft is made to operate a set of little pumps which are connected to a second series of pumps that act upon the driven shaft4 ,instead of water oil is used1 and the oil pumped by the driving pumps is forced into the driven pumps4 ,the latter pumps are so connected to the driven shaft as to cause it to rotate4 ,but by a simple mechanical expedient the stroke of the driving pumps can be varied at will from maximum to zero1 and the motion of the pumps can also be reversed4 ,the variable amount of oil pumped into the driven pumps varies the speed of the driven shaft1 for if it takes two strokes of a driving pump to fill the cylinder of a driven pump the driven shaft will travel at only half the speed of the driving shaft4 ,in turbine-driven vessels some sort of gearing is required between the propeller and the turbine4 ,in order to operate at its best efficiency a turbine must run at very high speed1 but this speed is entirely too high for the propeller4 ,there is a limit to the rate at which a propeller may be driven4 ,if this limit is exceeded1 the propeller merely bores a hole in the water1 forming a vacuum which produces a drag on the ship4 ,it is customary to interpose some form of gearing between the propeller and the turbine shaft1 but because of the high speed and the vast amount of power to be transmitted it is a difficult matter to design gearing that will be reliable4 ,furthermore1 it is desirable to vary the speed of the vessel and even to reverse it without slowing down the turbine engine4 ,in some cases a specially designed system of toothed gearing has been employed1 in another the power of the turbine is converted into electricity and then reconverted into mechanical power by means of a motor on the propeller shaft4 ,this provides a very efficient transmission1 because the electricity can be very conveniently controlled to accelerate1 retard1 or reverse the speed of the propeller motor4 ,the same thing can also be done by using a hydraulic transmission gear4 ,this1 although quite different from the variable-speed gear1 yet operates on the same general principle4 ,the turbine drives a centrifugal pump and the water thus pumped is fed to a horizontal water turbine on the propeller shaft4 ,by an ingenious arrangement of turbine wheels the speed of the propeller shaft may be varied at will4 ,hydraulic machinery is notable for its reliability4 ,sometimes water or oil is used as a convenient means of transmitting pressure from one part of a machine to another4 ,if we take a tube filled with water and fit a plunger in each end1 then1 when one plunger is depressed or pushed in1 the other will be expressed or pushed out4 ,the pipe may be twisted around in any direction or be tied up in a double bowknot1 and yet pressure applied to one cylinder will immediately be felt by the other4 ,this method of transmission may do away with a vast number of gears or levers4 ,water is comparatively incompressible and hence not a very adaptable means of transmitting power1 but a certain amount of flexibility is secured in some systems by the use of what is termed an 8accumulator40 ,this consists of a large cylinder fitted with a plunger4 ,the plunger is heavily weighted and it maintains a constant pressure upon the column of water in the cylinder4 ,if1 for instance1 a hydraulic crane is being used and suddenly a larger quantity of water is required than would normally be delivered by a pump1 it is automatically supplied from the cylinder of the accumulator1 and at a constant pressure4 ,the accumulator is arranged to control the throttle valve of the steam pumping engine so that when the plunger of the accumulator reaches a predetermined height the stream is cut off and the engine stops pumping4 ,,transmitting ,,power ,,with ,,sound ,,waves ,during the war a new use of water for power transmission was discovered and it is now being developed for the operation of mining machinery4 ,the inventor of the new transmission is ,george ,constantinesco1 a ,rumanian engineer4 ,his first application of the invention was to a mechanism for synchronizing the firing of a machine gun with the rotation of an airplane propeller1 so that it was possible to fire through the propeller without danger of striking its blades4 ,there were several existing methods of gearing the propeller to the machine gun1 but ,constantinesco's system proved so much more reliable that it was adopted and widely used by the ,british in their battle planes4 ,instead of gears and levers1 the ,rumanian engineer used a column of water in a heavy steel tube to conduct impulses from the propeller to the machine gun4 ,the pulsations produced by the propeller were too rapid to cause an actual displacement of the whole column of water in the tube1 but a wave of pressure traveled through the water column at an enormously high velocity4 ,we are wont to think of liquids as incompressible1 but they are actually slightly compressible and highly elastic4 ,this is demonstrated by the submarine telephone or the submarine bell4 ,water1 we know1 is an excellent medium for the transmission of sound1 but sound1 we know1 is produced by a succession of pressure waves4 ,if water were absolutely incompressible1 it could not convey sound from one point to another4 ,when sound travels through a speaking tube the whole column of air does not move back and forth simultaneously1 but it is divided into a series of waves4 ,each particle of air has a local oscillatory motion which it communicates to its neighbor1 producing alternate compression and rarefication1 and it is this wave action that travels through the column4 ,the same is true of water1 except that the rate of travel of the pressure wave in water is much higher than in air1 namely #d1hjj feet per second4 ,it is this wave transmission that ,constantinesco employed and which he calls 8sonic0 wave transmission4 ,to-day sonic wave transmission is used to operate rock drills4 ,a wave generator is used1 which acts somewhat on the principle of a pump4 ,a pair of plungers are reciprocated at a rate of forty strokes per second by means of an electric or gasoline motor1 and they produce a train of pressure waves in a column of water4 ,the water is contained in a specially designed flexible steel piping which runs to the rock drill4 ,the pressure waves operate a plunger in the drill and the plunger carries the drill steel4 ,the latter pounds the rock under the wave impulses at the rate of forty strokes per second4 ,sonic wave transmission is analogous to alternating current transmission of electricity4 ,there are direct equivalents in the wave transmission1 of volts1 amperes1 frequency1 angle of phase1 induction1 inductance1 capacity1 resistance1 condensers1 transformers1 and single-phase or polyphase systems4 ,,chapter ,,vii ,,air ,,vs4 ,,water ,,the ,,steam engine had its origin in a kitchen2 the modern clock was first conceived in a cathedral2 our laws of motion were discovered under an apple tree1 but1 strangest of all1 pneumatic engineering had its beginning in a barber shop4 ,in each case it was an inquisitive boy who played the leading rle4 ,we do not hear much about the youthful father of pneumatic engineering1 possibly because he lived so very long ago1 but his story is fully as interesting as that of ,watt or ,galileo or ,newton4 ,young ,ctesibius dwelt in the city of ,alexandria1 ,egypt1 #bej years before the birth of ,christ4 ,his father kept a barber shop1 and the young lad used to watch his father practice his tonsorial art on the ,greek and ,egyptian dandies of the time4 ,no doubt ,ctesibius's father expected to make a first-rate barber of his son1 but history does not tell us much about his early life4 ,the barbers of those days had their mirrors as do the barbers of the present time4 ,but a mirror in those days was a treasured possession4 ,it consisted of a brightly polished plate of metal in which a person could see himself 8darkly0 or it might have been a plate of glass with a black backing4 ,these mirrors had to be carefully preserved from injury and from moisture1 and so1 instead of having them mounted on the wall as in a modern barber shop1 they were stowed carefully away and brought out only after the tonsorial artist had completed his operation and was ready to exhibit his finished product to the customer4 ,,the ,,boy ,,who ,,discovered ,,compressed ,,air ,now in the tonsorial parlors of ,ctesibius's father the precious mirror was suspended above the head of the customer and when the barber had finished the shave or haircut he pulled down the mirror and let the customer survey his remodeled countenance4 ,after the customer viewed himself to his heart's content he merely released the mirror and it was automatically drawn back into place by a counterweight that slid in a case fastened to the wall4 ,young ,ctesibius noticed that every time the mirror was released a curious whistling sound came from the case in which the counterweight moved4 ,no doubt this phenomenon had been recurring day after day for years1 but it excited no more curiosity than would a squeaky door1 until1 one day1 the barber's son happened to notice it4 ,immediately he was all curiosity4 ,no one knew anything about air in those days and the boy could get no satisfactory explanation of the phenomenon1 so he started an investigation of his own4 ,he found that the counterweight fitted very closely in its case and when it dropped it forced a stream of 8wind0 out of a crevice which produced a whistling sound4 ,that set ,master ,ctesibius to thinking4 ,he had discovered a method of harnessing the wind4 ,no more barber shop for him2 he was launched upon a career of scientific research and invention4 ,the first use he made of his discovery was to build a pipe organ which was driven by a water wheel and hence was known as a water organ4 ,but there were other and more lucrative fields for the newly discovered power4 ,being invisible1 compressed air proved a most valuable medium for performing seemingly miraculous tricks with which the corrupt priesthood of that time hoodwinked the public4 ,naturally such air-controlled apparatus was kept secret1 and we have only a meager record of a few of the ingenious devices used in the temples4 ,however1 ,ctesibius made many scientific discoveries and became the most famous mathematician and scientist of his age4 ,we have read in ,chapter ,,iv of his famous water clock adjusted to record hours of varying length according to the season4 ,while ,ctesibius is credited with being the first man to make scientific use of compressed air1 the use of free air or wind as a power far antedates him4 ,sailing vessels were probably in use long before windmills were invented4 ,as pointed out elsewhere1 windmills possessed an advantage over water wheels in that they could be placed anywhere1 instead of being confined to the banks of streams4 ,they were widely used for pumping water1 grinding grain1 and sawing wood until the steam engine arrived and displaced them4 ,although wind power is but little used to-day1 air is much more widely used in modern machinery than is generally realized4 ,a catalogue of the various devices in which it plays a prominent part is likely to prove astonishing4 ,for instance1 we employ it to bore through rock1 to stop the speeding express train1 and even to quell ocean billows4 ,being elastic and compressible1 it makes an ideal spring for the storage of power and a cushion for absorbing shocks4 ,it is also used to fight back water and permit men to work in the depths of the sea or in water-bearing sand and earth4 ,despite his extensive use of air ,ctesibius knew nothing of the atmospheric pressure4 ,it was not until the seventeenth century that atmospheric pressure was discovered and measured4 ,it was then learned that there is no such thing as suction4 ,,raising ,,water ,,with ,,atmospheric ,,pressure ,illustration3 ,,fig4 #dj4--,,sectional ,,view ,,of ,a ,,suction ,,pump ,a suction pump should be called an atmospheric pump4 ,the operation of such a pump is illustrated in ,figure #dj4 ,a piston ,a slides in a cylinder ,b4 ,there is an opening in the bottom of the cylinder which is normally closed by a clack valve ,c that opens upwardly4 ,there is a similar valve ,d in the piston ,a4 ,when the piston is pushed down it compresses the air in the cylinder1 closing the valve ,c while valve ,d opens1 permitting the air to escape4 ,then on the upward stroke the valve ,d closes and valve ,c opens permitting air to flow into the cylinder4 ,in this way the air in the pipe and cylinder are exhausted after a few strokes4 ,as the air is rarefied and the pressure is reduced above the column of water in the pipe the greater pressure of the water outside the pipe forces the column to rise until it eventually flows through the valve in the piston and out of the spout of the pump4 ,the maximum height to which water can be raised by a suction pump is thirty-four feet but in actual practice the lift seldom exceeds twenty-six to twenty-eight feet because the fit between the cylinder and piston is not perfect4 ,illustration3 ,,fig4 #da4--;,,conventionalized ,,sectional ,,view ,,of ,a ,,force ,,pump ,when water is raised to a greater height a force pump is used4 ,such a pump is shown in ,figure #da4 ,the pump cylinder ,a has two valves ,b and ,c4 ,the valve ,b opens upwardly and valve ,c opens downwardly4 ,the piston ,d is a solid member containing no valve4 ,when the piston rises the valve ,c closes and valve ,b opens1 letting water into the cylinder4 ,on the reverse stroke the valve ,b closes and the descending piston forces the water out through valve ,c into pipe ,e4 ,the height to which the water may be lifted depends upon the power applied to the piston and not upon atmospheric pressure4 ,in a fire pump two force pumps are used which alternately deliver water into an air chamber4 ,the air is compressed by the water that enters the chamber and exerts a steady pressure on the water1 forcing it out through the fire hose in a stream that is practically steady4 ,it is a decided disadvantage to install a force pump in a deep well because of the mechanical difficulty of operating the piston at a great depth4 ,often the suction and force pump principles are combined4 ,the force pump piston and cylinder are located twenty-six and twenty-eight feet above the level of the water in the well with a pipe leading down into the water4 ,the water is forced up into the cylinder by exhausting the air in the cylinder and pipe and then is forced out of the cylinder and up a pipe to the top of the well4 ,this also has its disadvantages4 ,in deep wells the pump piston must still be located and operated at considerable depth4 ,,the ,,air ,,lift ,a much more simple pump for deep wells is the air lift in which there are no valves and no piston4 ,the pump consists of two pipes that are let down into the water4 7,see ,figure #db47 ,the larger pipe is open at the top and bottom1 and the smaller pipe discharges air into the bottom of the larger one4 ,this air being directed upward has a lifting effect1 and mingling with the water in the pipe produces a sort of froth which is so much lighter than solid water that the atmospheric pressure on the water in the well is sufficient to raise the froth4 ,the water is thoroughly aerated and to a large extent purified by this system of pumping1 so that the air lift commends itself particularly for city waterworks4 ,sometimes a series of air lifts are used which lift water by successive stages to a greater height than would be possible with a single direct lift4 ,illustration3 ,,fig4 #db4--,,pumping ,,water ,,with ,,compressed ,,air ,,excavating ,,through ,,quicksand ,illustration3 ,,fig4 #dc4--,,sectional ,,view ,,of ,a ,,pneumatic ,,caisson ,centuries ago it was realized that it would be possible for men to descend into the open sea if they were protected by a bell-shaped chamber1 for the air trapped in the chamber would furnish them with oxygen requisite for breathing purposes1 and would prevent the water from drowning them out4 ,this same idea of a diving bell is used on land when sinking a shaft through quicksand or water-bearing strata4 ,a large box or caisson is used4 7,see ,figure #dc47 ,this box may be either cylindrical or rectangular1 and it is open at the top and bottom4 ,the lower edges of the box are shod with steel and form cutting edges that will sink into the soil that is being excavated4 ,at a height of about seven feet above the bottom of the box there is a transverse diaphragm known as the deck1 and the space below is known as the working chamber4 ,this deck is very strongly constructed1 as it has to support the weight of the concrete shaft that is built above it4 ,laborers1 commonly known as 8sand hogs10 enter the working chamber and dig out a shallow pit in the floor of clay or sand4 ,this pit is then extended to the cutting edges of the caisson4 ,the caisson thus undermined settles down into the excavation and another pit is started4 ,in this way1 step by step1 the caisson is sunk into the ground4 ,in order to overcome the friction of the caisson against the sides of the excavation and to insure its sinking1 it is heavily weighted4 ,when water-bearing sand is reached1 compressed air is admitted into the working chamber to force the water out4 ,when the air pressure is greater than the water pressure it drives the water out of the sand in the working chamber1 so that the men can work in perfectly dry ground1 even though the surrounding sand may be so saturated with water as to form a quicksand4 ,of course the farther the excavation proceeds below the water level the greater the air pressure required1 and the caisson would be blown up out of the ground by this air pressure or would float on the water were it not for the weights with which it is loaded4 ,when an open shaft is to be dug1 pig iron is loaded on the caisson to force it down1 but in most work the object is merely to sink a concrete column down to rock and so the caisson is filled with concrete above the deck4 ,sections are added to the caisson as it sinks into the ground1 and these sections are filled with concrete4 ,this method of building the column facilitates the work of laying the concrete1 and at the same time provides the weight necessary to overcome the buoyancy of the caisson and the skin friction on the side walls of the excavation4 ,after the caisson has been carried down to rock and a good seat has been blasted out of solid rock1 the working chamber is completely filled with concrete and the concrete shaft is thus anchored to the rock4 ,,the ,,air ,,lock ,access to the working chamber is had through a central shafting4 ,in order to hold the air pressure in the working chamber and yet provide for the entrance of men and materials1 an air lock is fitted to the upper end of the shafting4 ,this air lock1 as shown in ,figure #dc1 consists of a chamber formed with a trapdoor at the top and the bottom4 ,both doors open downwardly4 ,to enter the caisson1 the bottom door of the chamber must first be closed and means are provided for doing this from outside the air lock4 ,the compressed air in the chamber is then let out through a valve1 and when the pressure drops almost to normal the upper trapdoor falls open of its own weight1 giving access to the chamber4 ,after entering1 the upper door is closed while compressed air is admitted into the chamber2 the air pressure then serves to hold the upper trapdoor closed4 ,the bottom door1 in the meantime1 has been kept closed by the air pressure below1 which is greater than that above the door4 ,but after sufficient air has been introduced into the chamber to equalize the pressure on both sides of the lower trapdoor1 it falls open of its own weight4 ,the occupants of the chamber can then proceed down a ladder to the working chamber4 ,when leaving the caisson1 the action of the air lock is reversed4 ,the bottom door is pushed up and held closed for a moment while air is released from the chamber1 when the greater pressure beneath will hold the door closed1 and after the pressure within the air lock has been lowered practically to normal1 the upper door drops of its own weight1 permitting the occupants of the chamber to climb out4 ,the same process must be undergone by buckets loaded with sand or earth from the excavation and by empty buckets returning to the working chamber4 ,more time is required for a man to pass through an air lock than for a load of sand or any inanimate load4 ,in some of the larger caissons a separate small air lock is provided just for the use of the workmen4 ,in the air lock the pressure must be built up slowly so that it will permeate a man's whole system4 ,when we realize that the pressure that men have to support in caisson work may amount to from fifty to one hundred tons on the whole body1 it is difficult at first to understand why the body is not flattened out like a pancake4 ,it is only by permitting the system to absorb the pressure so that there is as much internal pressure as that outside that a man is able to enter a compressed air chamber without harmful results4 ,,the ,,caisson ,,disease ,compression is rather annoying to a man who has not experienced the sensation1 but the principal danger comes in decompression1 particularly after a person has been in the working chamber for a long time4 ,when breathing compressed air much larger volumes of oxygen are taken into the lungs at each breath than in the ordinary atmosphere1 and one feels decidedly exhilarated by this unusual supply of stimulating oxygen4 ,but with the oxygen large volumes of nitrogen are taken into the system as well4 ,the nitrogen permeates the blood while the oxygen is consumed and exhaled in the form of carbon dioxide4 ,the longer a man is exposed to the pressure the more nitrogen does he absorb4 ,when the pressure is released suddenly the nitrogen begins to froth1 just as a bottle of soda water does when the stopper is removed4 ,the nitrogen bubbles in the small veins stop the circulation and produce the dreaded 8caisson disease0 which makes itself felt in the form of severe cramps and excruciating pains4 ,not infrequently this disease ends in death4 ,by reducing the pressure gradually the nitrogen is enabled to pass off completely without bubbling or frothing1 just as it is possible to let out the gas from a soda bottle without frothing by permitting it to escape through a pin hole in the stopper4 ,the surest cure for a victim of the caisson disease is to put him immediately into what is known as a 8hospital tank0 and build up the pressure in the tank equal to that which he has just been subjected to in the caisson1 after which the air in the tank is let out so slowly that there is plenty of time for the nitrogen to pass off without forming bubbles4 ,a pressure of forty-five pounds per square inch above that of the atmosphere is considered a severe pressure for excavation work4 ,but work has been carried on in pressures up to fifty-two pounds1 corresponding to a depth of #abj feet below water level4 ,now that the cause of the caisson disease is understood formulas have been worked out to insure proper decompression4 ,on one occasion a diver descended #cjf feet into the ocean where the water pressure was #acc pounds on every square inch of his body4 ,this meant that the air which was pumped down to him had to be compressed to the same pressure4 ,the diver actually remained at the bottom only a very short time1 but it took two hours and three-quarters to bring him to the surface4 ,he came up half the distance very quickly and then had to rest on the bottom rung of a ,jacob's ladder4 ,the rungs on this ladder were ten feet apart and he was instructed to rest on each rung a certain specified time4 ,when he was ten feet below the surface he had to wait three-quarters of an hour for the last trace of nitrogen absorbed by his blood to pass off4 ,,boring ,,tunnels ,,through ,,river ,,beds ,it is comparatively simple to sink a vertical shaft into water-bearing soil1 but a horizontal shaft involves serious difficulties4 ,the action of a diving bell is easily illustrated by inverting a tumbler and pressing it down into a basin of water4 ,the air trapped in the tumbler will keep the upper part of the glass dry1 and by inserting a tube in the tumbler it is possible to fill the tumbler so full of compressed air as to drive out all the water4 ,this is virtually what is done in the caisson2 but when excavating a horizontal bore1 the caisson must be turned on its side4 ,turn the tumbler on its side and it is impossible to keep the water out of it1 no matter how much air we may blow into it4 ,the reason for this is that the pressure on the open end of the tumbler is not uniform4 ,at the bottom1 where the water is deeper1 it will be greater than at the top4 ,if air is pumped in to equalize the water pressure at the upper edge of the glass1 it will not prevent water from flowing in at the bottom2 and if it be equal to that at the bottom1 the water pressure at the top cannot hold the air in and keep it from pouring out4 ,illustration3 ,,fig4 #dd4--,,sectional ,,view ,,of ,a ,,tunnel ,,shield ,fortunately most of the soil through which a subaqueous tunnel is driven is not very fluid4 ,it is either sticky1 as in clay1 or sluggish enough to prevent the water from flowing in rapidly4 ,if there is enough cover of silt or earth above the tunnel bore1 it will help to hold the air in the tunnel4 ,when the bore comes very close to the surface of the bed of the stream that is being tunneled1 loads of clay are dumped along the line of the tunnel to provide the requisite cover4 ,in tunnel boring a shield is used which is the equivalent of the caisson in vertical boring4 ,the shield is a cylindrical box with a diaphragm across it corresponding to the deck of the caisson4 7,see ,figure #dd47 ,in front of the diaphragm there is a small working chamber which is protected above by an extension of the shield known as an apron4 ,in the diaphragm there are a number of doors at different levels1 which may be closed in case of danger4 ,if work is proceeding near the top of the shield1 the upper doors are opened and the pressure is regulated to equal the water pressure at that level4 ,if the work is carried on near the bottom of the shield1 the upper doors are closed and only the lower doors are open1 and the pressure is increased to equal the water pressure at that point4 ,sometimes the material is of such a nature that the men can safely pass out of the doors into the working chamber outside1 but more often it is possible to work only within a limited area immediately in front of the doors4 ,when the material is very soft it is often unnecessary to do any actual excavation by hand in front of the diaphragm4 ,the shield is merely pushed forward through the mud or silt and the doors are opened to let the material flow in through them4 ,workmen dig out this mud and it is hauled out of the tunnel4 ,whenever bowlders are encountered it is necessary for the men to work outside of the diaphragm to chip away the rocks with compressed-air drills1 or else bore them and blast them with small charges of dynamite4 ,in quicksand the material is so fluid that it is unsafe to open the ordinary doors of the caisson1 and they are then provided with shutters which are raised one at a time1 to permit of operating on a very small section of the head of the tunnel4 ,after enough material has been excavated from in front of the shield1 the latter is pushed forward and the excavating is renewed4 ,unlike caisson work1 the weight of the shield is of no assistance in making it penetrate the soil1 nor is it possible to move the entire lining of the tunnel with the shield4 ,the tunnel is lined with rings of cast iron which are bolted together1 the rings themselves being made up of heavily ribbed curved plates4 ,the shield is formed with a 8tail0 which fits over the end of the tunnel line like a cap4 ,when the shield is to be pushed forward1 a set of hydraulic jacks are fitted between the end of the tunnel lining and the diaphragm of the shield1 and by means of these the shield is given a shove forward far enough for a new section of the cast-iron lining to be added within the tail4 ,the tunnel-lining rings are usually sixteen inches wide so that it is customary to move the shield ahead sixteen inches at a time or just far enough for a new ring of lining to be installed4 ,of course1 the tunnel is fitted with air locks by which men can enter the working section without permitting the compressed air therein to escape1 and these locks are just like those used in sinking a caisson1 except that they are horizontal instead of vertical4 ,,quelling ,,ocean ,,billows ,,with ,,air ,air is also used in another and very novel way to battle against water4 ,in this case it is not quiet water pressure1 but the tremendous power of ocean storms that is combatted4 ,the influence of a shoal upon ocean waves has often been observed4 ,a sand barrier even when submerged to a depth of twenty or thirty feet will break the waves of a heavy storm and leave an area of comparatively quiet water behind it4 ,the reason for this is that the water in the waves does not travel with the waves1 but undergoes local oscillatory motion4 ,this motion is in the form of circular or elliptical currents which travel in a vertical plane4 ,when a sand bar is encountered it interferes with these local currents and breaks up the waves4 ,knowing this to be the case1 it occurred to ,mr4 ,philip ,brasher that some other means of disturbing the rhythmic movement of the water might be found1 and he determined to try the experiment of using compressed air for this purpose4 ,accordingly he laid a perforated pipe under water and connected it with an air compressor4 ,then when a storm arose air was pumped into the pipe and it rose in bubbles through the water4 ,the effect of this upward movement of air was instantly observable4 ,it upset the rhythmic water currents and the waves which struck this wall of air bubbles curled and broke as if they had encountered a shoal of sand4 ,several exposed piers on the ,pacific coast have had a pneumatic breakwater built around them so as to protect them or ships lying alongside from being pounded by the waves4 ,there is no expense attached to the breakwater except in time of storm when the air pumps must be kept going4 ,one important advantage of the breakwater is that it does not block navigation4 ,a ship can sail right over the wall of bubbles and find refuge behind it4 ,,chapter ,,viii ,,air ,,springs ,,and ,,cushions ,,unlike water1 air is a highly compressible1 elastic fluid1 and as such furnishes an excellent medium for the storage of energy4 ,it acts just like a clock spring into which energy may be introduced and stored by winding or compressing the spring4 ,the energy remains locked up in the spring and when the spring is released1 it gives back just as much energy as was put into it1 except for slight frictional and heat losses4 ,air is a much better spring than steel or any other metal because it never loses its elasticity from fatigue and because it has an enormous capacity for the storage of energy4 ,it possesses one serious drawback1 however4 ,much of the energy that is expended in compressing it is converted into heat4 ,if the air were to be used immediately and without transmitting it to a distance1 there would be no advantage in extracting the heat1 but heat cannot be stored in air for long and it would gradually escape from the storage reservoir or air receiver and from the pipes leading the air to the machines that it was to operate4 ,as the heat escaped it would lower the pressure of the air and hence much of the energy would be lost4 ,,heat ,,of ,,compression ,in ,chapter ,v we described a hydraulic system of compressing air and noted that one of the advantages of this system is that it delivers air cooled to the temperature of the water4 ,this1 of course1 does not mean that there is no loss due to heat4 ,the air bubbles as they are compressed are cooled by the water that compresses them2 in other words1 the heat of compression passes off into the water1 making the water warmer than it would otherwise be4 ,heat is not produced without expenditure of energy and a certain proportion of the water power is thus wasted4 ,in most cases air is compressed by steam or electrically driven compressors1 and in such machines the heat due to compression is a serious matter4 ,the air cylinders are water-jacketed to carry off the heat4 ,but air is a poor conductor2 it acquires heat faster than it can give it off to the water surrounding the cylinders4 ,in compound air compressors the air compressed in one cylinder is cooled before being passed on to the next cylinder1 where it is further compressed4 ,the heat loss in compressing air in a single stage up to #ajj pounds gauge pressure is about #cj per cent4 ,air that enters a compressor at the normal pressure of the atmosphere and with an initial temperature of #fj degrees ,f41 if not cooled will become heated to #dae pounds gauge pressure4 ,the higher the initial heat of the air1 the greater the rise of temperature4 ,if a volume of air be subjected to #bid pounds gauge pressure1 it will occupy about one-tenth of its former volume4 ,if the air was introduced into the compressor at zero1 it would acquire a temperature of about #fej degrees2 if introduced at #fj degrees1 it would show an increase of about #hjj degrees2 and1 if started at #ajj degrees1 it would show an increase of #ijj degrees in passing through the compressor4 ,this shows the advantage of compressing the air in stages and cooling the air between stages4 ,sometimes the heat developed is sufficient to produce a disastrous explosion4 ,air is noncombustible1 but the oils used to lubricate the compressor are vaporized by the heat and when mixed with air form a powerful explosive4 ,care has to be taken that none but high-grade oil with a high flash point be used in the compressor and that the temperature of compression does not rise to near the flash point lest the vaporized oil be ignited4 ,that fire can be produced by sudden compression of air has long been known in the ,philippine ,islands4 ,the natives use a small air tube with a close-fitting plunger4 ,combustible matter is placed in the bottom of the tube1 and on striking the plunger a sharp blow this is ignited4 ,when compressed air is used in an air motor it expands and in so doing absorbs heat4 ,the more rapidly it expands1 the more heat it absorbs4 ,this heat it extracts from the motor and from the atmosphere into which it escapes1 and it is a common occurrence to find a thick coating of frost around the exhaust port4 ,this is due to condensation of moisture in the atmosphere or in the compressed air itself1 which1 because of the rapid extraction of heat1 is converted into snow4 ,on cold days enough frost may be produced in the exhaust pipe to clog it and interrupt the operation of the motor1 and frost sometimes clogs the air lines leading to the motor4 ,illustration3 ,,wharf ,,on ,,the ,,pacific ,,coast ,,protected ,,by ,a ,,pneumatic ,,breakwater ,air issuing from the submerged perforated pipes breaks up the waves ,illustration3 ,,general ,,view ,,of ,a ,,sun ,,power ,,plant ,,in ,,egypt ,illustration3 ,,close-,,up ,,of ,,one ,,of ,,the ,,reflectors ,,showing ,,the ,,boiler ,the fact that compressed air on expanding is cooled1 makes it an ideal power for use in mining machinery4 ,steam is inconvenient because of the difficulty of transmitting it to the machines without loss of heat1 because it would heat the machines so that they cannot be handled readily and because the exhaust steam would fill the mine with an impenetrable fog2 electricity is dangerous in mines that are apt to contain explosive gases1 because the wires are liable to be broken and cause sparks by short circuiting1 and because sparks are likely to form between the brushes and commutators of the motors2 but compressed air has none of these objections1 and1 furthermore1 the discharge from the machines furnishes the operators with ample supplies of fresh cool air which drives out disagreeable and dangerous gases4 ,,air-,,driven ,,hammers ,the ordinary rock drill is really a pneumatic hammer4 ,the tool1 which is chisel-shaped1 is used as a hammer to pound a hole in the rock4 ,the tool is driven up and down or in and out by compressed air bearing alternately on opposite sides of a piston4 ,the elasticity of the compressed air acts as a cushion to relieve the machine from shock4 ,the drill is mounted upon a tripod in such a way that it may be operated in any direction4 ,the pneumatic riveter is another form of compressed-air hammer4 ,the machine is held in the hands1 and the tool1 which is rapidly reciprocated by air pressure1 pounds the red-hot shank of a rivet4 ,while this is being done an assistant holds a hammer against the head of the rivet4 ,however1 there is a type of riveter which has a ,u-shaped frame4 ,one arm of the frame carries the reciprocating tool while the other reaches around and bears against the head of the rivet4 ,all sorts of tools have been built in which a small air-driven motor furnishes the motive power4 ,there are hand drills in which the tool is revolved by a set of pistons1 shears for shearing sheep which operate somewhat on the principle of hair clippers1 and pneumatic chisels used for chipping stone4 ,pneumatic motors are widely used in operating cranes and air hoists4 ,they consist of a simple cylinder and piston1 and are used for short1 direct lifts of all sorts4 ,,stopping ,,trains ,,with ,,air ,air has played a most important part in transportation4 ,when the air brake was first introduced its purpose was to prevent collisions and provide greater safety of operation4 ,it was not generally realized that efficient air brakes are not only a safety precaution1 but a means of increasing schedule speeds4 ,the more quickly a train can stop1 the better speed it may make1 particularly on a schedule that calls for frequent stops4 ,in the first air brake invented by ,george ,westinghouse1 the locomotive was provided with a reservoir in which air was stored and compressed by means of a steam-operated air pump4 ,the cars were each provided with a cylinder and piston connected to the air reservoir through a valve conveniently located in the engineer's cab4 ,the piston of the air cylinder was connected with the air brakes so that whenever the engineer wished to stop his train he merely turned on the compressed air and all the brakes in the train were operated4 ,this was a great saving over the previous system of providing brakemen to operate hand brakes4 ,unfortunately1 the problem of stopping a train was not as simple as all this4 ,on a long train the cylinders near the engine were the first to receive pressure sufficient to operate the brakes1 and as a result1 the forward part of the train was retarded more than the rear part at the start of the brake operation1 and the train came to a stop with a series of jolts4 ,another serious disadvantage was the fact that an enormous reservoir was required to furnish all the air necessary for a long train4 ,but the most serious drawback was the fact that occasionally a train broke apart and then the engineer was powerless to control the brakes of the detached portion of the train4 ,if the accident occurred on a down grade1 there would result a collision between the cars running by their own momentum and gravity and those attached to the engine4 ,this led to the present system of reversing the process which consists in keeping air pressure constantly in the train pipe and setting the brakes by relieving the pressure in the train pipe4 ,each car is provided with its own cylinder which furnishes the necessary air for the operation of its brakes4 ,there is1 of course1 a main cylinder on the locomotive in which air is pumped at high pressure by a steam-operated pump4 ,when the pressure of the main reservoir falls below a predetermined amount1 the air pump starts operating automatically and continues until the requisite pressure is restored4 ,air from the reservoir is fed to the train pipe at a certain pressure and feeds the local reservoirs on the cars of the train4 ,at each car it passes through a very ingenious triple valve1 which consists of a cylinder with a double piston1 one operated by pressure in the train pipe1 and the other by pressure in the local cylinder4 ,the piston operated by the pressure of the train pipe is larger than the other and consequently the valve piston is normally pressed back1 uncovering a small port through which air from the train pipe feeds into the local reservoir4 ,in this way the air in each local reservoir is maintained at the same pressure as that of the train pipe4 ,whenever air is let out of the train pipe1 the piston is pushed out by the excess pressure on the local reservoir side and uncovers another port which permits air to flow from the local reservoir to the brake cylinder operating the brakes4 ,the advantage of this system is that each car is always supplied with sufficient power to act on the brakes immediately without having to draw its supply of air from the main reservoir4 ,in case the train breaks apart1 the air in the train pipe escapes and the brakes are set automatically4 ,there have been a number of improvements in air brakes aimed to make the operation of the brakes more uniform and to insure immediate action1 even on a very long train4 ,modern express trains weighing #ibj tons and traveling at a velocity of #fj miles per hour1 can be brought to a standstill in #hfj feet1 or practically their own length4 ,automatic arrangements are provided to insure the application of the brakes at graduated rate1 except1 of course1 when the emergency brakes are applied4 ,as the speed of the train slows down the pressure is gradually relieved1 otherwise the train would stop with a severe jolt4 ,the rate of applying the brakes so as to provide a smooth retardation depends in large measure upon the weight of the train4 ,on the ,new ,york subways1 it is interesting to note1 every passenger who boards a train has his weight recorded by the brake mechanism1 and allowance is automatically made for the inertia that his mass adds to the train when it is in motion4 ,the weight operates through a system of levers to control the amount of pressure that is applied to the brakes so that when the engineer operates the brake lever1 he does not have to consider whether the cars are light or jammed full of passengers2 the brake mechanism itself takes care of this4 ,,propelling ,,cars ,,with ,,air ,if air can be used to stop a train1 why cannot air be used to propel it8 ,this question occurred to many inventors and they answered it by building air-propelled cars and locomotives4 ,pneumatic cars were tried out on street railways1 but they have had to give way to electric cars which do not need to carry their power around with them1 but can draw it from a central power plant through a trolley wire4 ,in only a few situations1 such as in mines where electric sparking is feared1 are air-propelled cars and locomotives still used to any considerable extent4 ,however1 air plays another and highly important part in transportation and here it is employed not to deliver energy stored in it1 but to serve as a cushion4 ,without the soft1 flexible grip of the air-filled rubber tubes with which automobile wheels are shod1 high-speed motoring would be practically impossible4 ,there is nothing that can compare with air for absorbing shocks and unevennesses in the road4 ,whenever an obstruction is encountered1 not only is the shock absorbed by elasticity of the air1 but the impact is immediately distributed uniformly over the whole tire1 so that the strain on the tire is not localized and the life of the tire is correspondingly increased4 ,there have been many attempts to introduce substitutes for pneumatic tires1 such as combinations of metallic springs and straps1 but these have failed1 chiefly for the reason that they cannot distribute the shock as the pneumatic tire does4 ,consequently they are not only liable to damage1 but they do not absorb the obstructions as readily as the pneumatic tire does and the vehicle which they carry is subjected to heavy stresses and strains4 ,air as a cushion is used to prevent the rebound of the springs of an automobile and is also widely employed in machinery to absorb the momentum of moving parts or to slow the action of a spring4 ,in a door check1 for instance1 a powerful spring is provided which would slam the door shut were it not for the cushioning action of air4 ,a plunger is connected to the door and slides in a cylinder on the door frame4 ,the air compressed by the plunger can escape only very slowly through a small port4 ,,air ,,cushions ,,for ,,elevators ,air cushions are used in elevators to prevent too rapid a fall of the car in case of accident4 ,the lower part of the elevator shaft is completely inclosed and fitted with steel doors to form an air pocket4 ,the car fits the shaft closely enough to compress the air under it when it is moving downward4 ,at normal speeds1 this air escapes quite readily around the sides of the car and through cracks in the doors1 but when the speed is excessive the air cannot escape fast enough and sufficient pressure is built up to retard the car so that it will strike the bottom with a moderate impact not at all dangerous to the passengers4 ,in the ,woolworth ,building1 ,new ,york1 the highest elevator shafts are #fhj feet high and the air pockets are #acg feet deep--i4 e41 they reach up to the tenth story4 ,if the car broke away from its supports at the top of the shaft it would be traveling at the rate of #acb miles an hour when it struck the air pocket1 but before it reached the bottom the air would bring it practically to a stop4 ,imagine a heavy automobile traveling at #acb miles per hour and brought down to a standstill in half a city block6 ,the passengers would be hurled out of their seats1 but in an elevator the passengers are standing and can brace themselves against the pressure produced by their own momentum4 ,the velocity acquired in falling #edc feet to the air pocket must be overcome in #acg feet or of the distance4 ,this means that the weight of each passenger is multiplied by four4 ,a man who weighed #aej pounds would find that his pressure on the floor of the car had mounted to #fjj pounds4 ,one of the inventors of the pneumatic cushion for elevators was killed when testing out a car1 not because of the impact of the car1 but because he was foolish enough to sit in a chair4 ,the chair gave way under his suddenly acquired weight and the poor man was fatally stabbed by one of the splinters4 ,air jets are used for a variety of purposes ranging from tamping railway tracks to painting buildings4 ,when a track is depressed under the tamping action of trains passing over it the ties must be raised and new ballast introduced under them so as to bring them up to level4 ,in order to save hand labor and insure the perfect filling of all cavities a pneumatic tamper is sometimes used4 ,the ballast1 consisting of sand or gravel up to inch in diameter1 is fed out of a hopper and meets a blast of air that hurls it into place like shot from an air rifle4 ,this furnishes a very solid and compact road bed4 ,it is in much the same way that weather-stained stone walls are cleansed by means of a sand blast4 ,the sand particles projected by the jet of air act like myriads of tiny bullets which chip away the face of the stone4 ,,laying ,,cement ,,with ,,an ,,airgun ,it is after this same fashion that the cement gun is used to project cement against wire reenforcement to form walls of buildings4 ,carl ,e4 ,akeley was led to the invention of the cement gun by his efforts to find an expeditious and economical method of mounting specimens of large animals for the ,field ,museum in ,chicago4 ,he constructed a pneumatic device for spraying cement and water upon a canvas-covered framework1 thus building up a body upon which the skin of the animal could be mounted4 ,this machine was improved and tried out successfully1 on a large scale1 in constructing buildings4 ,the machine as now constructed consists of a hopper into which a proper mix of sand and cement is introduced4 ,compressed air blows this mixture out of a nozzle4 ,here it meets a jet of water also propelled by compressed air4 ,the water1 sand1 and cement combine and strike the wall or surface to be coated with such an impact as to make a compact fine-grained coating known to the trade as 8gunite40 ,large surfaces can be painted much more readily and more evenly with compressed air than with a brush4 ,a widely spreading air jet is used which draws the paint out of a receptacle1 breaking it up into minute droplets that are projected as a mist against the surface1 covering it with a uniform coating4 ,,air ,,as ,a ,,tension ,,spring ,so far we have been considering air as a compression spring4 ,it may also be employed in a manner somewhat analogous to a tension spring4 ,when air is exhausted from a receptacle we have a partial vacuum which will produce work1 but in the opposite direction from that produced by compressed air4 ,of course there is no such thing as suction1 and it is the pressure of the atmosphere which is employed to do the work4 ,we are apt to overlook the fact that a vacuum cleaner depends upon atmospheric pressure to drag the dust and dirt out of a carpet4 ,a vacuum cleaner would not work on the moon1 where there is no atmospheric pressure4 ,the apparatus consists of an air pump1 usually driven by an electric motor1 which exhausts1 or partially exhausts1 the air from a foot piece that is dragged along the carpet4 ,as the air under atmospheric pressure rushes in through the carpet to take the place of the air that has been pumped out1 it carries with it all loose particles of dirt4 ,the dirt is filtered out of the air or a mechanical trap is provided to catch and retain the dirt while the air is allowed to escape4 ,large-scale vacuum cleaners are used for cleaning city streets4 ,the dirt is loosened by revolving brushes and is then drawn up by atmospheric pressure into a tank4 ,another use of atmospheric pressure is to be found in the pneumatic tubes which convey mail from one post office to another4 ,air is exhausted from the tube and when a carrier is inserted which fits the tube closely the atmospheric pressure behind it forces the carrier along to its destination4 ,the same system is used to carry money to and from the cashier's office in department stores4 ,in later developments of the pneumatic mail carrier compressed air was used back of the carrier1 but the principle of operation was not altered4 ,in either case propulsion is effected by the difference of air pressure on the opposite sides of the car4 ,in #ahfi ,alfred ,e4 ,beach built an experimental subway line under ,broadway1 ,new ,york1 near ,warren ,street4 ,the line was only #bjj feet long4 ,a cylindrical car large enough to hold eighteen people1 fitted the bore snugly and was propelled in one direction by compressing the air in the tunnel and in the other direction by exhausting the air4 ,,chapter ,,ix ,,power ,,from ,,heat ,,the ,,term 8water power0 is a misnomer4 ,there is no power inherent in water4 ,it is gravity that makes water fall in cataracts or flow down a river bed1 and hence it is the force of gravity that is responsible for the turning of our turbines and ,pelton wheels4 ,water is merely the medium through which the force of gravity acts4 ,in the steam engine1 water1 again1 serves as a medium and it is the energy of heat that is actually the working force4 ,a closed vessel is partly filled with water and heat is applied to it4 ,the water grows hotter and hotter until at a temperature of #bab degrees it begins to vaporize4 ,the temperature of the water remains stationary until the space above the water is completely filled with steam at a pressure equal to that of normal air pressure4 ,the steam gauge then registers zero4 ,continued application of heat raises the pressure of the steam and also raises the temperature of the water4 ,when the steam gauge shows a pressure of #be pounds per square inch1 the water temperature is nearly #bfg degrees2 at #ajj pounds it is over #ccg degrees2 at #bjj pounds it is #chg degrees2 at #ejj pounds it is about #dfg degrees4 ,as steam is drawn off from the boiler a proportionate amount of water turns immediately into steam to take its place4 ,if the boiler should burst1 the entire mass of water would instantly flash into steam because its temperature is far above the boiling point at normal air pressure4 ,that is why the explosion of a steam boiler is so violent4 ,if the boiler were entirely filled with steam the effect of an explosion would not begin to be so destructive as if the boiler were half full of water4 ,it is really the explosion of water that does such serious damage4 ,when the steam pressure in a boiler corresponds to the temperature of the water it is said to be saturated4 ,the water in a boiler boils violently when the steam is drawn off rapidly and tiny droplets of water are carried off in the steam1 producing what is known as wet steam4 ,steam that carries no water particles in suspension is called dry steam4 ,when the steam is heated above the temperature of the water by means of an auxiliary heating device or by some peculiar construction of the boiler1 it is called superheated steam4 ,in order to economize fuel it is highly important that as much water surface be exposed to the heat as possible4 ,this may be done either by passing the heat in tubes through the water or by passing the water in tubes through the fire4 ,locomotive boilers are of the fire-tube type4 ,the flaming gases of the furnace pass through the boiler through a series of tubes that lead to the stack4 ,in the water-tube boilers it is highly important that a good and rapid circulation of water be maintained1 otherwise there might be local generation of steam with serious consequences4 ,,the ,,giffard ,,injector ,illustration3 ,,fig4 #de4--;,,injector ,,for ,,introducing ,,water ,,into ,a ,,steam ,,boiler ,as steam is used from a boiler the water is slowly exhausted and it must be replenished with a fresh supply4 ,in early days of the steam engine1 water was pumped in against the boiler pressure by the use of powerful pumps1 but in #aheh a man named ,giffard invented a most ingenious apparatus by which steam of the boiler was used to force water in directly against its own pressure4 ,this seems like lifting oneself by one's boot straps4 ,when the injector was first invented it seemed so impossible for it to work that engineers would not accept it until it had repeatedly demonstrated its operativeness4 ,even after it was accepted and in common use its mysterious operation was a subject of discussion for years4 ,a sectional view of a ,giffard injector is shown in ,figure #de4 ,steam from the boiler comes down the tube ,a and passes out in a jet from the nozzle ,b4 ,a needle valve ,c may be moved into the nozzle to reduce or shut off the jet of steam4 ,the jet enters a conical chamber ,d which has a tube ,e that runs down into the water reservoir4 ,the steam jet blows the air out of chamber ,d1 producing a partial vacuum which draws water up the tube ,e and into the chamber ,d4 ,when the water reaches the steam jet it is driven out of the chamber across a short open space into a slightly diverging tube or receiving cone ,f and through a check valve ,g into the boiler4 ,at ,h there is a glass window through which the action of the water jet as it rushes into the receiving tube may be watched4 ,i is an overflow pipe leading back to the reservoir4 ,when the steam flows into the cone ,b it gathers momentum and issues from the nozzle in a jet of high velocity4 ,on striking the water it combines with the water and condenses1 but at the same time it imparts its momentum to the water so that the water is given more than enough momentum to drive it into the boiler against the pressure in the boiler4 ,the pressure of steam is utilized to drive the piston of an engine or the steam may be set in motion by letting it issue from a nozzle1 when its momentum may be employed to drive a steam turbine in the same way that a water jet drives a ,pelton wheel but in either case it is heat that does the work4 ,the steam expands as it moves the piston and as it passes through the nozzle its expansion is accompanied by a corresponding loss of heat4 ,as we have already noted1 it was for the purpose of raising water that inanimate powers were first set to work4 ,it was with the same object in view that steam was first employed4 ,,hero',s ,,steam ,,engine ,to be sure the first steam engine was invented by ,hero1 the disciple of ,ctesibius1 in the second century before ,christ1 and it was not a water-raising machine4 ,it consisted of a hollow sphere 7see ,figure #df71 mounted to rotate and fed with steam that entered it through the journals4 ,the steam issued from opposite sides of the sphere through two bent tubes4 ,the steam in issuing from the tubes reacted against the tubes1 pushing them back and causing the sphere to revolve4 ,every action is accompanied by an equal and opposite reaction4 ,a bullet fired from a gun kicks the gun back4 ,in order to push the bullet out of the barrel1 the powder must have something to push against and the push against the gun is equal to the push against the bullet4 ,even if there were no bullet to be pushed the discharge of the powder would react against the gun4 ,in order to push its own gases out of the gun1 the powder must push back against the gun4 ,illustration3 ,,fig4 #df4--;,,hero',s ,,steam ,,engine ,in ,hero's engine1 the steam1 in order to push itself out of the sphere1 must push against the bent tubes4 ,we have a similar reaction motor in the revolving lawn sprinkler4 ,the water issuing from the bent arms of the sprinkler forces them back and causes them to revolve4 ,were the arms radial and not bent the reaction would be there just the same1 but it would be exerted against the center of the wheel and hence there would be no rotation4 ,reaction has nothing to do with the pressure of the atmosphere as so many people imagine4 ,a gun would kick just as hard and the lawn sprinkler or ,hero's engine would operate just as well and as fast in a perfect vacuum4 ,it was to demonstrate the principle of reaction that ,hero built his steam engine4 ,as far as we know it was never put to useful work and remained merely a scientific toy4 ,,newcomen',s ,,atmospheric ,,engine ,the first practical use of steam power was applied to the pumping of water from the deep mines of ,cornwall4 ,newcomen's engine1 which antedated ,watt's by several decades1 was known as an atmospheric engine4 ,it consisted of a cylinder fitted with a piston1 but the top of the cylinder was open4 ,the piston was connected to one end of a lever or walking beam1 the other end of which was connected by a chain with the plunger of a pump situated at the bottom of the mine shaft4 ,little power was required to lift the piston because it was counterbalanced by the chain and plunger attached to the opposite end of the walking beam4 ,the real work was done in pushing the piston down and thereby raising the pump plunger4 ,steam under low pressure was let into the cylinder under the piston to raise it and then a jet of water was sprayed into the steam-filled cylinder4 ,this condensed the steam1 producing vacuum and the atmospheric pressure acting on the upper surface of the piston forced the piston down1 raising the pump plunger4 ,the engine ran very slowly1 making only about #ae strokes per minute4 ,later it was improved1 producing about #cj strokes per minute4 ,,watt',s ,,steam ,,engine ,watt was the first man to build an engine in which the real work was done by the pressure of steam as in modern steam engines4 ,as long as the steam engine was used for pumping water the reciprocating piston could be connected directly to the pump plunger and it was unnecessary to exert power on both sides of the piston1 but in #aghb ,watt obtained a patent on a double-acting engine4 ,steam was admitted first on one side of the piston and then on the other4 ,the walking beam was connected by means of a connecting rod to a crank on a shaft that carried a flywheel1 and the seesaw motion of the beam was converted into rotary motion of the wheel4 ,this opened up new industrial opportunities for the steam engine4 ,the steam was exhausted from the cylinder into a condenser1 i4e41 a chamber1 in which a spray of water converted the steam into water1 producing a vacuum1 thereby relieving the piston of back pressure and virtually adding that much more power to the steam operating on the opposite side of the piston4 ,a pump driven by the engine drew the water and the air liberated from the condensed steam out of the condenser4 ,watt invented an ingenious governor to control the flow of steam to the engine and insure a uniform motion4 7,see ,figure #dg47 ,this governor consisted of a pair of levers hinged to a revolving shaft and each provided with a ball weight at its free end4 ,the shaft was revolved by the engine and if the engine tended to run too fast the balls were thrown out by centrifugal action4 ,in so doing they operated a throttle valve cutting down the steam supply4 ,when the engine slowed down the balls would drop1 admitting more steam4 ,in this way the speed of the engine was kept within close limits4 ,the ball governor in improved form is still widely used in stationary engines4 ,,using ,,the ,,heat ,,in ,,the ,,steam ,illustration3 ,,fig4 #dg4--,,watt',s ,,ball ,,governor ,another of ,watt's inventions which has proved of highest importance in steam engineering was the cut off4 ,in his first engine the piston was subjected to the full boiler pressure throughout its stroke1 and the steam that poured out of the exhaust port of the cylinder at the end of the piston stroke was almost as hot as that which entered the cylinder at the beginning of the stroke4 ,the heat that goes out in the exhaust represents just so much wasted energy4 ,watt realized this and so he invented a valve which would cut off the flow from the boiler before the piston had completed its stroke4 ,then the steam back of the piston would continue to expand because of the heat within it and would keep on pushing the piston4 ,of course1 the pressure would gradually diminish and there would be less power in the stroke than if the full boiler pressure were pushing the piston all the way1 but this loss of power is offset by the saving in steam and in the fuel used to heat the steam4 ,the point at which the cut-off takes place depends largely upon the pressure of the steam4 ,if the steam is cut off when the piston has made only one-fifth of its stroke1 one-fifth as much steam will be used at each stroke as would be the case if the steam were used nonexpansively4 ,however1 in actual practice the expansion of the cut-off steam instead of being five times would be only about four times1 because of the clearance that must be allowed between the piston and the end of the cylinder4 ,if steam of #ajj pounds absolute pressure is used1 the average pressure throughout the piston will be only about #eg per cent of the full pressure of the steam in the boiler1 but each pound of steam will actually do 4#eg #d #b4bh times as much work as it would if used nonexpansively4 ,all sorts of valve gear have been invented to admit steam quickly and cut it off at the proper point to produce the most efficient result4 ,in low-pressure cylinders in order to prevent loss of heat through the wall of the cylinder1 the latter is steam-jacketed4 ,in other words1 there is an outer casing surrounding the cylinder and between this casing and the cylinder steam is admitted to keep the cylinder walls hot4 ,in order to make full use of the heat in steam it is1 in some engines1 sent through a series of two1 three1 and even four cylinders4 ,the exhaust from one cylinder goes into a second larger cylinder4 ,from here after doing work on a piston it discharges into a third still larger cylinder and from that may be led into a fourth cylinder4 ,the cylinders must be progressively larger to allow for the expansion of the steam4 ,the ordinary steam engine labors under the disadvantage of having to start and stop its pistons at the end of each stroke4 ,every body possesses inertia1 whether it be moving or at rest4 ,if it be at rest1 it takes much more energy to set it in motion than to keep it moving4 ,in fact it would keep on moving without further expenditure of energy were there no friction and no forces acting against it4 ,in order to stop the body energy must be expended to overcome its inertia4 ,the more rapidly a body is started and the more quickly it is stopped1 the more work must be done in overcoming its inertia4 ,in a steam engine not only the piston but other parts connected to it may be required to reciprocate several hundred times per minute4 ,a great deal of energy is uselessly expended in starting and stopping these parts4 ,many efforts have been made to produce a rotary engine in which the piston rotates instead of reciprocating1 thus doing away with the work of overcoming inertia4 ,however1 there are serious obstacles to the construction of such an engine1 and as yet no truly efficient and practical rotary engine has been built4 ,,de ,,laval',s ,,steam ,,turbine ,however1 there is another type of engine in which the steam is applied continuously and all the parts revolve4 ,such an engine was the reaction turbine invented by ,hero1 to which reference has already been made4 ,modern turbines1 however1 are of very different construction4 ,they resemble the ,pelton wheels and turbines used in developing water power1 differing from them mainly in the fact that use is made of the expansive energy of steam which is lacking in water4 ,in the ,de ,laval steam turbine a wheel is used which has a series of curved buckets all around its periphery that are closed at the outer end by a circular rim4 7,see ,figure #dh47 ,steam is directed against this bucket1 not tangentially as in a ,pelton wheel1 but from the side4 ,several steam nozzles are employed and as the steam jets strike the buckets and sweep around their curved surfaces they react against the buckets and drive the wheel around4 ,in order to operate efficiently the velocity of the steam must be very high and the wheel must also turn at high speed4 ,when steam flows through a diverging nozzle its velocity is greatly accelerated by its expansive effort4 ,such nozzles are used in the ,de ,laval turbines and the steam issues from them with a velocity which may be higher than that of a rifle bullet4 ,the buckets are forged and the hard-scale surface is left on them2 otherwise they would wear away quickly under the action of the powerful jets of steam4 ,illustration3 ,,fig4 #dh4--,,the ,,de ,,laval ,,steam ,,turbine ,the turbine wheel may revolve at a speed of #cj1jjj revolutions per minute4 ,such a tremendous speed has its disadvantages4 ,if a wheel is to run smoothly it must revolve on its center of gravity4 ,a lopsided wheel1 or one that is mounted a little off center1 produces a pounding action which imposes a serious strain upon the bearings and the revolving parts4 ,the wheel tries to turn on its own center of gravity and will do so if permitted to4 ,it is impossible to balance a wheel so perfectly that the axis it turns on passes exactly through its center of gravity4 ,at ordinary speeds this slight eccentricity is so slight that it is practically negligible1 but when we have to deal with #cj1jjj revolutions per minute the least divergence between the center of rotation and the center of gravity will produce dangerous strains4 ,for this reason the wheel of the ,de ,laval turbine is mounted on a flexible shaft and on floating bearings1 so that it will automatically find and turn on its own center of gravity4 ,in order to utilize the power developed in the wheel1 gearing must be used to step down the speed4 ,,parsons ,,expansion ,,turbine ,the ,parsons steam turbine resembles a water turbine in its action4 ,instead of having a few nozzles directing steam against the buckets there is a nozzle for each bucket1 and instead of a single wheel there is a series of them through which the steam passes1 successively passing through a set of nozzles between each wheel4 ,the nozzles are formed of blades on the periphery of stationary wheels4 ,these blades are curved in the opposite direction to the blades on the revolving wheels1 as shown in ,figure #di4 ,steam in passing through the ring of curved stationary blades is divided up into a series of jets which strike the curved blades of the first wheel4 ,in passing through this wheel the direction of the stream is reversed1 and it enters between the second set of stationary blades1 which turn it back again and direct it against the next wheel4 ,thus the steam pursues a sinuous course through the series of wheels4 ,to allow for the expansion of the steam the blades are made progressively longer and the wheels of progressively larger diameter from the inlet to the exhaust end of the engine4 ,illustration3 ,,fig4 #di4--,,peripheral ,,view ,,of ,,the ,,blades ,,of ,a ,,parsons ,,turbine ,the ,curtis turbine combines the ,de ,laval and the ,parsons principles4 ,the steam enters through a series of nozzles which are of the expanding type1 then it goes through a series of moving and stationary blades1 as in the ,parsons turbine1 from which it enters another set of expanding nozzles and gains velocity and momentum before passing through the second series or stage of moving and fixed blades4 7,see ,figure #ej47 ,steam turbines are particularly adapted for use in electric power plants4 ,the speed of rotation of the ,parsons and ,curtis types is much lower than that of the ,de ,laval and hence the electric generators may be directly driven by them without the interposition of any gearing4 ,they can be built of larger power than the reciprocating engines because they are so economical of space4 ,illustration3 ,,fig4 #ej4--,,peripheral ,,view ,,of ,,the ,,blades ,,and ,,nozzles ,,of ,a ,,curtis ,,turbine ,a good comparison of turbine versus reciprocating engines is offered by the #gdth ,street power station of the ,manhattan ,elevated ,railway1 ,new ,york4 ,this station1 which was completed in #aija1 was equipped with eight huge reciprocating engines1 each developing #h1jjj horsepower normally1 and capable of delivering a maximum of #ab1ejj horsepower4 ,the whole plant1 therefore1 had a maximum capacity of #ajj1jjj horsepower4 ,gradually these units have been giving way to steam turbines of much higher power1 and in #aiai there was installed one powerful turbine which alone was capable of developing as much power as the entire plant of #aija4 ,this is a triple-compound turbine comprising one high-pressure turbine and a low-pressure turbine at each side4 ,steam enters the high-pressure turbine at #bje pounds pressure to the square inch and then exhausts into the low-pressure turbines1 passing from them into condensers which operate under #bi inches vacuum4 ,each turbine drives a separate generator and the combined horsepower of the whole unit is about #ajj1jjj1 while the floor space occupied is only #ej by #eb feet4 ,the economy of space and of fuel offered by the steam turbine is of great value in the power plants of ships1 and this form of prime mover has been installed on modern high-speed passenger liners and also on high-speed war vessels4 ,while in certain respects the turbine is ideal for such service1 there are two handicaps which must be overcome4 ,in the first place1 the most efficient speed for the turbine is considerably higher than the efficient speed of the propeller and some means must be provided for stepping down the speed4 ,in the second place1 the turbine cannot be as economically controlled as a reciprocating engine and its direction of rotation cannot be reversed1 so that difficulties are encountered in maneuvering the ship in harbors4 ,it is no simple matter to gear down the high speed and enormous power of a turbine1 ,however1 an elaborate system of gearing has been provided for this purpose which has proved satisfactory even in powerful battle cruisers4 ,the ,british battle cruisers with a power plant of #acd1jjj horsepower are driven by geared turbines4 ,to reverse the propellers separate low-power turbines are used4 ,a more attractive system of control is to have the turbines drive electric generators and then use the electric power to drive the propellers through motors mounted on the propeller shafts4 ,the electric power can easily be controlled from the bridge and the propellers may be reversed by reversing the motors4 ,however1 the disadvantage of the electric system is that it occupies a great deal of space1 particularly in plants running over #ajj1jjj horsepower4 ,,chapter ,x ,,burning ,,fuel ,,in ,,the ,,engine ,,cylinder ,,one ,,of the handicaps of steam power is that the heat produced by the combustion of fuel is not used directly to drive the piston4 ,a large part of the heat energy in coal goes up the chimney or is wasted by radiation from the furnace walls4 ,with anthracite coal in the furnace the loss may be as low as #bb per cent in the very best types of boilers4 ,in the engine other serious losses occur1 so that in the best condensing reciprocating steam engines the power delivered is only #aj to #af per cent of that stored in the fuel4 ,in locomotives the efficiency is as low as #d to #f per cent4 ,in turbines the steam is used to better advantage and the actual power delivered may run up to #bj per cent of that in the fuel4 ,in internal-combustion engines the furnace and boiler losses are largely overcome by burning the fuel right in the cylinder1 where the heat energy of the combustion may be utilized directly upon the piston4 ,there are other losses1 however1 so that the most efficient gasoline engines deliver only #bh per cent of the energy in the fuel1 and coal-gas engines may run up to #ca per cent4 ,a wide range of fuels may be used in an internal-combustion engine4 ,they may be either gaseous1 liquid1 or even solid4 ,in stationary engines hydrogen1 coal gas1 natural gas1 blast-furnace gas1 and producer gas are employed to advantage4 ,volatile fuels1 such as alcohol1 bensol1 gasoline1 and kerosene1 are turned into a mist or vapor and then burned as a gas4 ,in engines of the ,diesel type any liquid fuel ranging down to thick crude oils may be employed1 and in one type of engine1 which1 however1 has not proved commercially practicable1 coal dust is burned in the cylinder4 ,,burning ,,air ,,in ,,the ,,automobile ,,engine ,owing to the widespread use of automobiles1 the general public is better acquainted with internal-combustion engines than with steam engines4 ,nevertheless1 there are many elementary facts in connection with gasoline engines that are not generally known4 ,the average motorist probably does not realize that he burns far more air in his motor than gasoline1 and he probably does not understand why it is that the mixture of gasoline vapor and air must be compressed before it is ignited1 or why only one out of four strokes of the piston is a power stroke4 ,if a volume of gasoline vapor be thoroughly mixed with an equal volume of air1 the mixture will not explode4 ,only when there is an excess of air will combustion take place1 and the most intensive explosion takes place when there are nine parts of air to one part of gasoline vapor4 ,where gasoline is vaporized in a carburetor the best mixture is one part of gasoline-saturated air to eight parts of pure air4 ,hence it is mainly air that is burned in an automobile engine4 ,the energy of combustion is much greater when the mixture is compressed4 ,the particles of gasoline and air are forced into more intimate contact by the compression4 ,the same thing is true of gunpowder4 ,if gunpowder is ignited in the open air1 it will burn quickly1 but not with explosive violence4 ,if1 on the other hand1 the powder is compressed in a cartridge and is then ignited1 an explosion takes place4 ,nearly twice as much gas was required in the early noncompression-type motors as is required to-day in the compression motors of the same power4 ,in an internal-combustion engine the cylinder serves as a furnace4 ,this 8furnace0 must be charged with fuel1 and after the fuel has been burned the 8ashes0--i4 e41 the products of combustion--must be removed4 ,the piston serves as the furnace stoker4 ,in the ordinary four-cycle engine the action of the piston is as follows3 ,on the first or down stroke of the piston a mixture of air and gasoline vapor is drawn into the cylinder2 on the next or rising stroke the charge is compressed4 ,then the charge is ignited by an electric spark1 and the rapid combustion of the charge produces gases which drive the piston down4 ,on the fourth stroke the piston rises again and pushes the burnt gases out of the cylinder4 ,the piston receives energy intermittently1 or only once out of four strokes1 and a flywheel has to keep it going the rest of the time4 ,it is just like propelling a bicycle with a single pedal and pushing the pedal every other time it comes out4 ,it can be done as long as the wheel is moving fast enough to carry itself along between power strokes4 ,naturally a single-cylinder motor cannot be slowed down very much without stalling1 and it will not start of itself because it needs outside help in stoking its furnace before it acquires the power to do this job alone4 ,illustration3 ,,fig4 #ea--,,sectional ,,view ,,of ,a ,,two-,,cycle ,,engine ,there is a two-cycle type of motor in which the burnt gases are removed from the cylinder1 not by the piston1 but by the injection of the unburnt fuel mixture4 ,on the upward or compression stroke the piston not only compresses the mixture in the cylinder1 but draws in a fresh charge of fuel into the crank case1 and when the piston is driven down by the combustion of the fuel in the cylinder1 the charge in the crank case is compressed until1 near the end of its stroke1 the piston uncovers a port in the cylinder through which the fuel from the crank case is forced in4 7,see ,figure #ea47 ,just before this occurs the piston uncovers an exhaust port in the opposite side of the cylinder1 and the burnt gases start to flow out before the fresh charge of fuel pours into the cylinder4 ,the incoming gas is directed upward so as to completely scavenge the cylinder of all burnt gases4 ,there are no bothersome poppet valves in this engine4 ,the piston itself acts as a valve1 opening and closing the inlet and exhaust ports as it slides by them4 ,every other stroke of the piston is a power stroke1 so that the engine acts like a one-pedal bicycle1 which receives a push every time the pedal comes around4 ,unfortunately1 the burnt gases are never completely scavenged1 and the fresh charge of fuel is always more or less diluted by the product of combustion remaining from the previous charge4 ,this represents just so much loss of power1 and may interfere with the ignition of the charge4 ,for this reason the four-cycle engine is generally considered more reliable and efficient1 and is far more generally used1 particularly on motor vehicles4 ,to overcome the intermittent character of the internal combustion engine a number of cylinders are used1 which come into play successively4 ,in the four-cylinder motor one piston is always on the power stroke4 ,in recent years the number of cylinders has progressively increased from four to six1 eight1 and twelve cylinders1 while in racing power boats the number of cylinders has gone up as high as twenty-four4 ,,cooling ,,the ,,cylinders ,the temperature of the combustion in a gasoline engine may be over #c1jjj degrees ,fahrenheit4 ,evidently it would melt the cylinder walls were not special provisions taken to keep them cool4 ,the usual method is to surround the cylinders with water which absorbs the heat1 and then cool the water by passing it through a radiator4 ,air driven by a fan through the radiator carries off the heat4 ,of course this represents just so much wasted energy and lowers the efficiency of the motor1 but it is the most convenient way of getting rid of the intense heat of combustion4 ,smaller motors1 such as are used on motorcycles1 have their cylinders cooled by direct action of air on the outer surface of the cylinder4 ,the heat radiated depends upon the surface exposed and the velocity of the air current4 ,the radiating surface of the cylinders is increased by forming them with external ribs or flanges1 so that the air that flows over them1 while the machine is in motion1 carries off enough heat to keep the temperature of the cylinders within safe limits4 ,in some systems1 particularly in the case of stationary engines1 to insure a good circulation1 the air is positively driven against the flanges by means of a fan4 ,there are serious disadvantages in using water to cool an engine4 ,besides the bother of keeping the water system supplied with water there is the danger of clogging the radiator with lime deposits1 and in extremely cold weather the water is liable to freeze and burst the water jackets or the radiator2 for this reason1 air cooling is recommended by some for automobile engines4 ,in certain air-cooled automobile engines the cylinders are air-jacketed2 that is1 they are surrounded with casings through which the air is sucked by a powerful fan driven by the engine shaft1 so that the air is bound to flow if the engine is turning4 ,the cylinders are ribbed1 so that they present a large radiating surface4 ,illustration3 ,copyright1 ,kadel ,herbert ,,giant ,,caproni ,,hydroaeroplane ,,which ,,was ,,wrecked ,,at ,,lago ,,maggiore ,seating capacity #ajj persons2 power1 eight #dej-;h4p4 ,liberty motors ,illustration3 ,a ,,boat ,,of ,,stone--,,the ,,concrete ,,steamship 8,,faith0 ,illustration3 ,,the 8,,virginian10 ,,the ,,largest ,,locomotive ,,in ,,the ,,world ,length over all1 #ig ft42 weight of engine1 #fhd1jjj lbs42 of tender1 #bad1cjj lbs42 tractive power1 simple1 #agf1fjj lbs42 compound1 #adg1bjj ,air-cooled engines have hotter cylinders than water-cooled engines and hence in cylinders of the same size less fuel is drawn into the air-cooled cylinder4 ,but the fuel is used more efficiently because less of its heat energy is wasted2 so that air-cooled engines show a slight fuel economy over water-cooled engines4 ,on the other hand1 when the air-cooled engine is overloaded or is run at very high speeds it is liable to become overheated and may ignite the incoming charge of gas prematurely4 ,,the ,,self ,,igniting ,,diesel ,,engine ,as has already been pointed out1 compression of gas generates heat1 and one of the reasons for cooling the cylinders of an internal combustion engine is to prevent the gas from exploding prematurely on the compression stroke of the piston4 ,in the ,diesel engine1 instead of avoiding such a critical temperature it is deliberately sought1 because it is the heat of compression1 instead of an electric spark1 which ignites the charge4 ,pure air is drawn into the cylinder on the suction stroke4 ,this air is under ordinary atmospheric pressure when it enters1 but on the return stroke of the piston it is compressed to about #ejj pounds per square inch4 ,this raises the temperature up to the neighborhood of #ajjj degrees ,fahrenheit4 ,into this highly heated air a spray of oil is injected by air at still higher pressure and immediately the oil flashes into flame and the gases resulting from the combustion drive the piston down4 ,this is a very economical type of motor4 ,any liquid fuel may be used1 from light gasoline to heavy crude oils1 or the oils that remain after the more volatile fuels have been distilled from them4 ,the heavy oils have more heat value in them than is to be found in light volatile fuels1 such as alcohol1 gasoline1 and kerosene1 and because the oils do not throw off any inflammable vapors unless highly heated1 they can be stored more safely4 ,this is of highest importance on submarines and ,diesel engines are commonly used for propulsion on the surface or to drive the generators which charge the storage batteries for submerged travel4 ,in order to inject the fuel into the cylinder against the pressure of air therein1 a powerful air pump is required4 ,this does not need to be of very large capacity1 but it must compress the air to from #gjj to #a1jjj pounds per square inch4 ,it may seem at first as if the work done by the engine in compressing the air in the cylinder and in operating the injector pump represents so much loss1 but a moment's consideration will show that it is all recovered4 ,the air in the cylinder acts like a spring1 rebounding when the piston starts down on its power stroke and adding its energy to that of the burning gases1 while the air from the injector pump also enters the cylinder and helps to push the piston down4 ,diesel engines are made to operate on the two-cycle as well as the four-cycle principle4 ,in one type of engine1 known as the semi-,diesel1 a lower compression is used in the cylinder4 ,this is not high enough to ignite the oil that is sprayed in1 and so a hot tube or bulb is employed at the top of the cylinder against which the fuel jet is directed4 ,this bulb is heated to a dark cherry red by means of a torch until the engine has developed enough heat to keep the bulb at the requisite temperature4 ,,the ,,double-,,acting ,,junker ,,engine ,illustration3 ,,fig4 #eb4--,,the ,,junker ,,engine ,,in ,,which ,,two ,,pistons ,,reciprocate ,,toward ,,and ,,away ,,from ,,each ,,other ,an interesting modification of the ,diesel engine is the ,junker engine 7,figure #eb7 in which the cylinder consists of a tube open at each end4 ,in this there are two pistons which reciprocate toward and away from each other4 ,air is compressed between them as they approach each other and fuel is injected into this air1 ignites and forces them apart4 ,both pistons are connected to the same crank shaft1 one pushing down and the other pulling up4 ,the pulling piston has a yoke on the end of the piston rod from which a pair of connecting rods run down at either side of the cylinder to a pair of cranks on the crank shaft4 ,between these cranks on the opposite side of the shaft is the crank to which the pushing piston is connected4 ,the advantages of this arrangement are that the moving masses are perfectly balanced1 the construction of the cylinder is very simple and especially adapted to high pressures1 and the reaction of the gases1 instead of being directed against a fixed part of the engine1 is directed against a moving piston1 thus reducing the strain on the structure4 ,of course the power is not doubled or increased1 because each piston moves only half as far as it would for a given expansion of gas were it operating in a cylinder closed by a cylinder head4 ,the efficiency of ,diesel engines1 although greater than that of the gas and gasoline engines1 is still very low4 ,the semi-,diesel will yield about #cj per cent of the energy in the fuel1 the ,junker engine about #cd per cent1 and the best ,diesel1 four-cycle engine in large units1 about #cf per cent4 ,this is a wonderfully high efficiency compared with that of a locomotive1 and yet it seems pitiably low when we consider that nearly two-thirds of the energy stored in the fuel is thrown away4 ,,silencing ,,the ,,noisy ,,exhaust ,the waste of energy is clearly evident in the exhaust pipe of an internal combustion engine4 ,the gases after doing their work on the piston rush out with such velocity as to produce a sharp explosive sound4 ,the noise of the exhaust is highly objectionable in automobiles and must be overcome1 but instead of utilizing the boisterous energy of the escaping gases and getting a little more useful work out of them1 means are provided for hushing their noise4 ,this is done by passing them through a series of baffles which reduces the pressure of the gases before they are discharged into the atmosphere4 ,by letting the gases expand gradually instead of bursting suddenly into the atmosphere the noise of the discharge is reduced4 ,however1 this must not be done at the expense of the engine power4 ,unless the gases pass quickly through the muffler they will choke and retard the exhaust and make the engine do useless work in driving them through4 ,even the best of mufflers will use up nearly #e per cent of the engine power4 ,the energy that escapes at the exhaust is not the only loss4 ,all the heat that radiates from the engine represents just so much wasted energy4 ,in our water and air-cooled systems we deliberately abstract heat from the burning gases and throw it away4 ,if we had materials that would stand the intense heat of burning gases and enable us to conserve all the heat developed in the cylinder we could use our fuels much more economically4 ,many attempts have been made to utilize the wasted heat of internal combustion engines1 but they have not met with any considerable degree of success1 with the exception of the invention of ,william ,joseph ,still4 ,this engine1 which was the result of many years of patient work1 was first made public in a paper read before the ,royal ,society of ,arts in ,london1 ,may #bf1 #aiai1 and when it was shown that the new engine had developed an efficiency of #ch to #da per cent it was realized that here was a remarkable advance over any other machine for turning heat into power4 ,,combined ,,steam ,,and ,,oil ,,engine ,the ,still engine is a combined steam and gas or oil engine4 ,the heat that is ordinarily thrown away in the water jacket and in the exhaust is utilized to produce steam1 and this steam is employed to return the piston to the top of the cylinder after the gases generated by the combustion of fuel have driven it down4 ,while in previous experiments some steam had been developed from the exhaust gases it had not been found possible to generate steam in the water jacket because of the low temperature that had to be maintained4 ,in the standard internal combustion engine the cylinder walls are made of cast iron1 thick enough to withstand the heavy pressures to which they are subjected should the charge be ignited prematurely4 ,around them the water circulates under practically no pressure and so the wall of the water jacket is made comparatively thin4 ,because of the thickness of the cylinder wall the water has to be maintained at a comparatively low temperature so as to keep the interior of the cylinder from growing too hot4 ,in the ,still engine the cylinder wall is from one-third to one-fourth the thickness of the standard cylinder wall1 while the water-jacket wall is of thick steel4 ,the cylinder wall is formed with ribs which extend to the water-jacket wall1 so that the latter will take care of any excessive loads due to premature ignition4 ,figure #ec shows how the cylinder and jacket of the ,still engine compare with those of the ordinary motor4 ,the thin cylinder wall and the ribs furnish a far better conduction of heat to the water which circulates between the ribs4 ,the necessary cooling of the cylinder can be maintained with water at a much higher temperature than in the ordinary engine4 ,illustration3 ,,fig4 #ec4--,,section ,,through ,,the ,,cylinder ,,and ,,water ,,jacket ,,of ,,the ,,still ,,engine ,illustration3 ,,fig4 #ed4--;,,diagrammatic ,,view ,,of ,,the ,,still ,,engine ,a diagrammatic representation of a ,still engine of the two-cycle heavy-oil type is shown in ,figure #ed4 ,this is shown with an auxiliary boiler heated by an oil burner4 ,the piston of this engine has a sleeve which fits into an annular steam cylinder4 ,the latter is an extension of the combustion cylinder4 ,surrounding the steam and combustion cylinders are the steam and water jackets4 ,the drawing shows the piston at the end of its downward stroke1 having just been driven down by the gases of combustion4 ,in this position a scavenging-air port at the left is uncovered and the burnt gases are swept out by a blast of air1 passing out of the exhaust4 ,this consists of a bank of tubes or flues which pass through a water heater4 ,the gases leave the cylinder with a temperature of #ijj degrees ,fahrenheit and they issue from the exhaust with a final temperature of only #aej degrees ,fahrenheit4 ,steam now enters the annular steam cylinder from the steam jacket1 through the port shown at the lower right-hand side1 forcing the piston up and compressing the charge of air in the cylinder4 ,then oil is sprayed in through a nozzle1 not shown in the drawing1 and is ignited by the heat of the compressed air as in a ,diesel engine and the piston is driven down again by the gases of the combustion4 ,the water surrounding the combustion cylinder comes from the lower part of the boiler and flows by the exhaust flues4 ,it is maintained at a temperature of #cej degrees in the water jacket1 and here is turned into steam by the heat of the combustion4 ,thence it passes into the steam dome of the boiler4 ,on the downward stroke of the piston a slide valve1 shown at the lower right-hand side1 moves down and connects the steam port with an exhaust port through which the steam flows out into a condenser4 ,water from the hot well of the condenser enters the system at the combustion exhaust4 ,the arrows show the course of the steam and water and the temperature at various points is given4 ,as may be noted there are two systems of steam and water circulation3 one from the bottom of the boiler through combustion exhaust heater to the water jacket and back to the top of the boiler2 and the other from the steam dome of the boiler to the steam jacket1 to the steam cylinder1 to the steam exhaust1 to the condenser and back again from the condenser into the combustion exhaust heater1 whence it enters the boiler by way of the water jacket4 ,,latent ,,heat ,when water turns into steam a certain amount of heat is absorbed1 which does not show in the thermometer4 ,this is known as latent heat4 ,if cold water is placed in a kettle and is then heated the thermometer will gradually rise until the water reaches the boiling point4 ,then there will be no further rise of temperature1 although heat is still applied to the kettle1 until all the water is turned into steam1 after which the thermometer will begin to show a rise of temperature1 showing that the steam is beginning to grow sensibly hotter4 ,in the engine1 shown in ,figure #ed1 a boiler pressure of #abj pounds gauge pressure is maintained1 and therefore water will not boil until it reaches #cej degrees ,fahrenheit4 ,the water in the water jacket registers #cej degrees and is therefore far hotter than it could possibly be in the open atmosphere4 ,however1 the heat from the combustion does not raise the temperature of the water1 but expends its energy in converting the water into steam4 ,the cylinder wall is kept at a temperature of at least #cej degrees all the time1 so that the air that enters the cylinder gathers heat from the cylinder as well as from its own compression1 and its temperature at the end of the compression stroke is higher than it would be in a cold cylinder1 thereby insuring the ignition of the fuel when it is sprayed in4 ,the ,still engine can also be used as a common gasoline or gas engine of either two or four cycle and the efficiency in such types is from #ca to #cc per cent4 ,this is much better than the best airplane engines1 which show an efficiency under #bg per cent4 ,although #da per cent for the best ,still heavy-oil engine is a remarkable accomplishment1 yet it does not begin to compare with the efficiency of the best water turbines and ,pelton wheels1 which turn into useful power from #ge to #hg per cent of the kinetic energy in the water that drives them4 ,,chapter ,,xi ,,when ,,coal ,,and ,,oil ,,are ,,exhausted ,,in ,,previous chapters we have indulged in a great deal of historic retrospect4 ,it may be well at this point1 while we are dealing with the subject of power1 to look into the future and the prospects that it holds out to us4 ,it was about fifty thousand years ago1 according to conservative estimates1 that primitive man first began to use tools1 and he managed to exist and thrive and develop to a very high degree of civilization during practically the whole of that period without touching the stores of energy that lay beneath his feet4 ,it was only yesterday that the steam engine was invented1 and when it was discovered how to turn heat into work and what a wealth of power was stored up in the deposits of coal there started a lavish and profligate squandering of the precious heritage of the ,carboniferous era4 ,the fossilized vegetation of by-gone ages is now employed to drive our locomotives and steamships1 to turn our factory wheels1 to extract metals from the ore and help us shape them according to our needs and desires1 to convert iron into steel and to heat and light our houses4 ,we all know that there is a limited supply of coal in the world and that some day the stores will be exhausted1 yet we go on using larger quantities of the fuel each year4 ,for the last century our demands for coal have been doubling every ten years1 until to-day the world is using about #a1bjj million long tons per year4 ,it is conservatively estimated that if our demands for coal do not increase there is enough left in the whole world within a mile of the surface to last #a1ejj years4 ,fortunately this country is better supplied than many others1 and it is probable that we can get along on our present rations for #b1jjj years4 ,england1 however1 faces exhaustion of her coal supplies within two hundred years4 ,after living fifty millenniums on earth as a being clearly superior to other animals1 man comes into an inheritance which he squanders in one or at most two millenniums4 ,it is not creditable to our civilization that we have taken no precautions to ration out this precious store of fuel4 ,,our ,,waste ,,of ,,fuel ,as was shown in a previous chapter1 we utilize very little of the energy in coal4 ,our steam railroads squander from #id to #if per cent of the coal they burn and our best turbine power plants throw away about #hj per cent4 ,the coal we burn in domestic furnaces is most wastefully squandered4 ,maybe we shall learn how to use the energy in coal more efficiently and make it last longer1 but eventually it will all be gone and then what are we going to do8 ,of the other fuels available1 petroleum takes the leading place1 but we are hardly more economical in our use of this fuel and our oil supplies are diminishing much more rapidly than the stores of coal4 ,in #aiai the ,united ,states produced #cgf1jjj1jjj barrels of oil and consumed #dah1jjj1jjj barrels1 having had to draw on ,mexico for #db1jjj1jjj barrels4 ,natural gas cannot last much longer and peat bogs are estimated at about half of one per cent of the coal supplies4 ,where shall we turn for heat and power when all these stores of energy are gone8 ,it has been estimated that the water powers of the earth1 if fully developed1 would probably supply about half of the energy that we now get out of coal4 ,this is a never-failing supply of energy1 and no doubt before we have begun to scrape the bottom of our coal magazines every river on earth that is capable of turning a wheel will be doing so to the limit of its capacity4 ,then there will be a readjustment of the manufacturing centers of the earth and remote regions such as ,iceland1 for instance1 which has more available water power than ,switzerland1 will hum with machinery1 while such countries as ,great ,britain1 which is relatively poor in water powers1 will have to give up manufacture and revert to agricultural pursuits4 ,but are there not other powers that can be used8 ,if we could capture all the energy of the winds we should have ample power to do all the work that is now done on earth with a large margin to spare4 ,it has been estimated that the winds contain #e1jjj times as much energy as is obtained from coal1 but how may we capture so fickle a power as the wind4 ,it is so variable1 sometimes exerting enough power to lift houses from their foundations and uproot giant trees1 and again sinking to an absolute calm4 ,in some places wind power is turned into electricity and then stored up in batteries2 but the cost of doing this is high and at present uneconomical4 8,,blue ,,coal0 ,the ocean ,is a vast storehouse of energy4 ,the quiet but powerful rise and fall of ocean tides1 and the tremendous energy of ocean waves1 have been looked upon with envy by engineers4 ,all sorts of schemes have been devised for capturing a part of this energy and putting it into the service of man4 ,water power has been aptly called 8white coal0 and ocean power 8blue coal40 ,wave energy is but another form of wind energy and hence just as fickle4 ,there is plenty of power to be had1 but it is a costly matter to build a power plant on the shores of the ocean and any day a storm may arise which will dash the machinery to pieces and sweep away the whole plant or convert it into a pile of wreckage4 ,in a few places1 however1 ,nature has provided a plant which the ocean has been unable to destroy and man has adopted the plant to furnish him with power4 ,there is a rocky cave on the ,california coast which is exposed to the ocean swells4 ,as the swells sweep into the cave they compress the air therein and this compressed air is trapped in a reservoir4 ,then the air that has been pumped by the ocean is put to useful work4 ,there are similar caves on other rocky coasts which could be made to deliver power when coal becomes scarce and it becomes commercially practicable to exploit them1 but the amount of power they would furnish would be a mere drop in the bucket4 ,,setting ,,tides ,,to ,,work ,the ocean tides are also immensely powerful1 but the rise and fall of the water is so slight and so gradual in most places that an enormous plant is required to obtain any appreciable amount of power4 ,in certain regions1 however1 tidal power is actually in use to-day4 ,at high tide water flows into a large basin and at the ebb of the tide the outflow of the basin operates a water wheel or turbine4 ,power can be obtained while the basin is filling as well as while it is emptying4 ,one serious objection to this plan is that the turbine operates intermittently and at irregular intervals1 sometimes by day and sometimes by night1 depending upon the tide4 ,however1 tide mills need not be exposed to the fury of ocean storms as are plants that seek to employ the power of ocean waves4 ,in certain localities the conformation of the coast is such as to accumulate the tidal flow and produce enormous differences of level between ebb and flood tide4 ,in the ,bay of ,fundy1 for instance1 the tide rises seventy feet and an appreciable amount of power could be obtained from the flow of water into and out of the bay4 ,if a sea-level canal were dug across the ,isthmus of ,panama there would be a flow of water back and forth through it because the tides at the ,pacific side have a rise and fall of only two feet while on the ,atlantic side the tide rises twenty-two feet4 ,some power might be obtained from the tidal flow through this canal1 but a fall of twenty feet in fifty miles would not produce a very swift current4 ,illustration3 ,,fig4 #ee4--,,the ,,esnault ,,pelterie ,,plan ,,of ,,utilizing ,,tidal ,,power ,,in ,,the ,,english ,,channel ,if tidal power is to be utilized at all it must be done on a grand scale4 ,a ,french engineer1 ,r4 ,esnault ,pelterie1 has proposed a vast tidal power system in the ,english channel where the tide rises high4 7,see map ,fig4 #ee47 ,the plan is a most ambitious one1 but the power that could be obtained is enormous4 ,he proposes to build concrete dikes across the channel at the ,straits of ,calais inclosing a large basin about twenty miles wide and turbines would be operated by the flow of water into and out of this basin4 ,of course locks would have to be provided to permit the passage of ships through the basin4 ,other and larger basins could be formed by walling off the estuary of the ,thames and the bay of the ,seine on the ,french coast4 ,the ,gulf of ,st4 ,malo could be inclosed by running a dike from ,cape ,la ,hague to the island of ,guernsey and thence to the mouth of the ,trieux4 ,these basins would furnish a minimum of #hjj horsepower for each square mile1 hence the basin across the ,straits of ,calais alone would furnish nearly half a million horsepower while the ,gulf of ,st4 ,malo would furnish about a quarter of the power that ,france now uses in her industries4 ,the first cost of the installation would be heavy1 but there would be no expense for fuel and the supply of power would be endless4 ,it has been proposed to dam the estuary of the ,severn 7,england7 where the spring tides rise thirty feet1 and it has been estimated that half a million horsepower would be developed4 ,part of the power would be used to pump water into an elevated reservoir which would serve as a storage battery1 so that when the tidal plant was idle because of the turn of the tide1 water flowing out of the reservoir would operate an auxiliary plant1 thereby furnishing a continuous supply of power4 ,,power ,,from ,,sunshine ,with the exception of the tides all the energy we use on earth comes from the sun4 ,it is the sun's energy that is stored in coal beds and oil fields2 it is the sun's energy that raises water from the ocean to the tops of our mountains2 it is the sun's energy that makes the winds blow1 and through them disturbs the surface of the ocean1 and even the tides owe a part of their energy to the attraction of the sun4 ,why can we not utilize the energy of the sun directly1 instead of at second hand8 ,in the sunshine that beats upon the earth there is seventy-thousand times as much energy as we now obtain from coal4 ,unfortunately the energy of the sun is so widely dispersed that it cannot be used economically except in a very few places where clouds do not often interrupt the direct passage of the rays to the earth's surface4 ,near ,cairo1 ,egypt1 there is a plant erected by an ,american inventor1 ,mr4 ,frank ,shuman1 which develops about fifty horsepower4 ,this consists of a series of five huge trough-shaped mirrors that focus the sun's rays upon boilers and thus generate low pressure steam4 ,the mirrors measure #ac feet in width and #cjd feet in length and these are mounted on a light steel framework with their axes running north and south so that they may be turned from east to west to follow the course of the sun across the sky4 ,in order to prevent the mirrors from shading each other in the early morning and late afternoon they are set twenty-five feet apart4 ,mirrors are made of thin sheets of window glass1 silvered at the back4 ,the troughs are parabolic in cross section and at the focus of each is hung a tubular boiler painted black to absorb the heat rays4 ,the five boilers feed a common steam reservoir from which steam is fed to a pump4 ,this pump raises about #f1jjj gallons of water per minute1 which is used for irrigating purposes4 ,of course at night the supply of energy is cut off and on cloudy or rainy days no steam is generated1 but such days are few in the region of ,cairo1 and continuous operation is not essential to the operation of irrigating systems4 ,there are localities in ,africa1 ,asia ,minor1 and even in the ,united ,states where the lack of water and the pitiless rays of the sun have turned vast regions into deserts4 ,here the very rays which have parched vegetation may be utilized to pump water over the thirsty lands and convert them into rich agricultural regions4 ,there is another mighty source of power in the internal heat of the earth4 ,here and there all over the earth are vent holes through which the pent-up energy makes its escape in the form of steam1 gases1 or molten lava4 ,there is no question as to the enormous stores of energy in active volcanoes1 and as we appreciate the value of heat energy our eyes turn covetously to these great chimneys of the subterranean furnaces4 ,,harnessing ,,volcanoes ,it seems like the height of daring to attempt to harness the volcanoes1 and yet there is a plant in ,italy which utilizes volcanic energy and develops useful power from it4 ,at ,volterra1 in the province of ,tuscany1 there is a volcanic region where jets of very hot steam issue from cracks in the ground4 ,these steam jets1 known as soffioni1 are laden with gases and mineral matter4 ,for many years the boric acid that they contain was abstracted from them1 but the steam was allowed to escape4 ,in some few instances it was piped into houses and used for domestic heating4 ,in #aijh an attempt was made to convert the energy of the steam into useful power4 ,holes were bored into the earth and steam of a temperature of #cjb degrees ,fahrenheit came up the pipes4 ,this steam was applied directly to a forty horsepower steam engine1 and for the first time volcanic heat was set to work4 ,the steam1 however1 contained so many impurities that it was impracticable to use it directly in the engine4 ,the valves and cylinders were soon clogged with deposits of boric acid4 ,then instead of trying to obtain power directly from the steam1 the latter was used to heat a boiler in which pure steam was generated4 ,this plan proved perfectly practical and a #cjj horsepower condensing steam turbine was driven by the energy thus obtained indirectly from volcanic heat4 ,this power was converted into electricity and the power was transmitted to the surrounding villages4 ,after the ,world ,war broke out and ,italy began to feel the shortage of fuel1 the price of coal having risen to #ej per ton1 the use of volcanic power was extended4 ,a #c1jjj kilowatt plant was installed and electric current was transmitted to ,florence1 ,leghorn1 ,volterra1 and other towns of ,tuscany4 ,the exhaust steam from the boilers was utilized in the boric acid industries4 ,other projects for utilizing the internal heat of the earth have been given serious consideration in ,italy4 ,near ,naples there is the dormant volcano1 ,solfatara1 the crater of which is filled with a sea of very hot mud underlying a cool thin crust of earth4 ,holes bored into this mud to a depth of a few feet send forth steam hot enough to do useful work and a plan to utilize this store of energy is under way4 ,,power ,,from ,,the ,,core ,,of ,,the ,,earth ,there are regions where the ground is red-hot at a depth of a hundred feet4 ,while there is no water present to furnish steam1 it is a simple matter to sink a water pipe down to the heated earth and then1 around this pipe1 to drive a ring of smaller pipes through which steam may find its way up to the top and be fed either into water heaters or directly into steam engines4 ,in fact it has been suggested that such a scheme might be used almost anywhere4 ,if we bore into the earth1 we find that the temperature grows higher the deeper we go4 ,the rate of increase of temperature varies with different localities1 but it is very evident that anywhere on earth temperatures that will give a steam pressure of ten or more pounds per square inch can be obtained if we dig down far enough1 and when we find it worth while to do so we shall probably riddle the earth's crust with perforations through which water will be sent down to the subterranean furnaces and it will return to us laden with heat energy4 ,after all1 we shall not be plunged into dire want when our stores of coal are exhausted4 ,there will be other sources of power to draw upon1 most of which will be inexhaustible4 ,furthermore1 we have recently discovered in atoms of matter stores of energy incomparably greater than any that have heretofore been used to work the will of man4 ,how to utilize this energy we have not yet learned1 but the energy is there1 and no doubt1 some day1 probably long before coal takes its place in museum collections1 we shall be possessed of a new slave1 far more powerful than that which has served us so far4 ,,chapter ,,xii ,,invasion ,,of ,,the ,,sea ,,the ,,possibility that the wind was the first inanimate power utilized by man1 has already been referred to4 ,there are records of the use of sailing vessels in ,egypt that date as far back as #f1jjj years before ,christ4 ,navigators of that early date1 however1 could hardly claim to have mastered the wind4 ,they merely used wind power when the wind was disposed to help them4 ,if the winds were adverse1 they had no recourse other than to furl their sail1 step the mast and depend upon oars to propel them to the desired port4 ,it was not until thousands of years later that primitive mariners learned how to tack and pursue a zigzag course against the wind4 ,when this knowledge was acquired we do not know1 but it is certain that the ,phnicians1 who rounded the continent of ,africa #a1bjj years before ,christ1 knew how to make use of the power of opposing winds4 ,of course they could not explain how it was that a breeze could be made to drive a vessel in a direction across and even opposed to that in which it was blowing4 ,in order to understand this apparent paradox ourselves1 we must go back to the very elements of mechanics4 ,,elementary ,,mechanics ,the popular conception of force is something that produces motion1 but its true definition is 8that which tends to produce or resist motion40 ,there are forces in existence when there is no motion4 ,when you hold a weight in your hand there is a force tending to pull the weight to the earth1 but this force is opposed by an equal force exerted by your muscles in holding up the weight4 ,there is no motion because the two forces are perfectly balanced4 ,if they were unbalanced1 there would be motion in the direction of the greater force4 ,if the pull of the arm is greater than that of gravity1 the weight will be lifted1 and if the weight is too heavy for the arm to support1 it will go down despite muscular efforts to prevent it4 ,in one case the force of gravity will endeavor to destroy motion by opposing the lift of the arm1 and in the other case the arm will endeavor to resist motion by opposing the pull of gravity4 ,a book on a table is motionless and yet it is acted upon by two forces which are opposed to each other and hence balanced4 ,the table furnishes a force which resists and balances the force exerted by gravity4 ,if the book were heavy enough1 in other words1 if the force directed downward were great enough1 the table would be crushed4 ,when two forces are in perfect balance they must be equal and opposite4 ,unless the directions of the two forces are exactly opposite1 there will be motion in some new direction4 ,suppose we use an apparatus such as shown in ,fig4 #ef to study the result of three coacting forces4 ,it consists of a ,t-shaped frame with a pulley ,p at each end of the cross arm4 ,these pulleys turn very freely on their axes1 so that we need not be concerned with any appreciable amount of friction4 ,two fine cords running over these pulleys are knotted at ,o to a third short cord4 ,each cord is provided with a hook on which weights may be hung4 ,now if we put a pound weight on each cord the two ,a and ,b will raise the weight ,c until the angles between the cords at ,o are all equal4 ,in other words each force of one pound is balanced by two other forces of one pound each pulling at an angle of #abj degrees to it and to each other4 ,if we put a #c-pound weight at ,a1 a #d-pound weight at ,b and a #e-pound weight at ,c1 the cords will come to rest in the position shown in ,fig4 #eg4 ,the weight ,b being heavier than weight ,a will pull the knot ,o to the right until the angle between the cords running to these weights is a right angle4 ,illustration3 ,,fig4 #ef4--;,,balanced ,,forces--,,equal ,,weights ,,parallelogram ,,of ,,forces ,although a force is something that cannot be pictured it can be represented graphically by means of a line1 letting the direction of the line represent the direction of the force and the length of the line the strength of the force4 ,in ,figure #eh we may measure off #c inches from ,o to a to indicate the #c-pound force and #d inches from ,o to b to represent the #d-pound force and #e inches from ,o to c to represent the #e-pound force4 ,now if from a a line is drawn parallel to ,o b and from b a line is drawn parallel to ,o a we shall have a parallelogram a ,o b d1 and if we extend the line ,o c it will bisect the parallelogram1 running diagonally from ,o to d1 and this diagonal will be found to measure exactly #e inches which represents the #e-pound force4 ,this is what is known as the parallelogram of forces4 ,it shows us the resultant of any two forces that are not directly opposite and it gives us the direction as well as the strength or magnitude of this resultant4 ,it is only because we happen to choose the forces #c1 #d and #e that the angle at ,o is a right angle4 ,in ,figure #ei1 where the forces are all equal1 our parallelogram is lozenge-shaped and the line ,o d is just as long as the line ,o a and ,o b1 showing that its magnitude is the same as that of the two forces that balanced it4 ,illustration3 ,,fig4 #eg4--;,,balanced ,,forces--,,unequal ,,weights ,the greater the angle between the two lifting forces the less weight can they lift4 ,if two men are carrying a ten-pound satchel1 each will be lifting five pounds1 if the pull is directly upward2 but this is a rather inconvenient way of carrying the bag and usually they pull at a slight angle from the vertical1 and so each must carry more than half the weight4 ,if they move so far apart that the angle between them is more than #abj degrees1 each will be carrying more than the full weight of the bag4 ,illustration3 ,,figs4 #eh ,,and #ei4--,,parallelograms ,,of ,,forces ,,sailing ,,against ,,the ,,wind ,now that we know something about the parallelogram of forces we may return to the problem of sailing across and against the wind4 ,in ,fig4 #fj we are looking down on the deck of a ship and the wind is represented by the arrow4 ,the dotted line ,a ,b represents the direction in which the boat is traveling and the line ,c ,d represents the plane of a sail4 ,if the line ,e ,f represents the magnitude and direction of the force of the wind at the center of the sail1 then we can tell how much pressure is being exerted directly against the sail1 by drawing the line g ,f perpendicular to the sail and completing the parallelogram by drawing from ,e a line parallel to the sail intersecting g ,f at ,g and another line parallel to g ,f intersecting the plane of the sail at ,h4 ,then the length of the line ,g ,f represents the pressure against the sail4 ,if the line ,g ,f is half as long as the line ,e ,f1 then only half of the force of the wind is exerted in the direction ,g ,f4 ,in other words1 a wind pressure of one pound per square foot blowing in the direction of ,g ,f will do as much work as two pounds in the direction ,e ,f4 ,the force of the wind has been broken up into two 8components10 one 7,g ,f7 at right angles to the sail1 and the other 7,h ,f7 edgewise to the plane1 and of course the latter has no effect upon the propulsion of the boat4 ,illustration3 ,,fig4 #fj4--;,,forces ,,that ,,move ,a ,,sailboat ,if there were nothing to prevent it1 the boat would sail in the direction ,g ,f2 but the keel of the boat offers resistance to motion in this direction1 and we must construct another parallelogram around the force ,g ,f to find the magnitude of the force exerted in the direction ,a ,b4 ,the line ,k ,f is drawn at right angles to ,a ,b1 and then the parallelogram is completed by drawing a line from ,g to ,k parallel to the line ,a ,b and another from ,g to ,m parallel to ,k ,f4 ,we have then resolved to force ,g ,f into two components ,m ,f and ,k ,f4 ,the former tends to push the boat along its course while the latter tends to make it drift to leeward4 ,the length of the line ,m ,f is little more than a quarter of the length of the wind force ,e ,f and the leeward acting force ,k ,f is actually considerably greater than the forward acting force ,m ,f4 ,even with a deep keel there will be some drift to leeward4 ,this is corrected by means of the rudder of the ship which is turned to head the ship further into the wind so that although the boat does not actually travel in the direction of its axis it may be made to travel along the course ,a ,b4 ,of course the boat cannot sail directly against the wind1 but it can accomplish the same result by tacking alternately to port and starboard so that eventually it can reach a port that lies in the direction from which the wind comes4 ,,the ,,speedy ,,clipper ,before the advent of the steamship1 sailing vessels were developed to a high degree of efficiency4 ,the speedy clippers of #ahaf to #ahde used to cross the ,atlantic at an average speed of #f to #i miles per hour and sometimes even better1 which compares favorably with a common steam freighter of to-day4 ,the largest sailing vessel ever built was the ,thomas ,w4 ,lawson1 a seven-masted schooner4 ,she was launched in #aijb1 but foundered in #aijg off the ,scilly ,islands4 ,this great ship was a steel vessel #cie feet long1 with a displacement of #aj1jjj tons and a cargo capacity of #g1ejj tons4 ,she had a sail spread of #dj1fag feet4 ,,from ,,oars ,,to ,,propellers ,although a century has elapsed since the first steam-driven vessel made its way across the ,atlantic ,ocean1 sails have been as yet by no means swept off the face of the sea4 ,nevertheless1 even when sailing vessels had no competitors they did not furnish a perfectly satisfactory means of transportation4 ,the fickleness of wind power was felt in this application as well as in that of windmills1 and inventors racked their brains for some more certain means of propelling ships4 ,naturally1 when the steam engine was a proven success1 efforts were made to apply this newly discovered power to ships4 ,how to make steam drive a ship was a problem4 ,at first it was proposed to use a system of oars which would be moved back and forth in imitation of oarsmen and ,john ,fitch's first steamboat in #aghf was driven by a set of paddles operated in a manner similar to that of paddling a canoe4 ,it was a very natural evolution from oars to paddle wheel1 which consists of a series of oars mounted in a wheel so that they will come into play one after the other4 ,the propeller1 although not invented by ,col4 ,john ,stevens 7as has been popularly supposed71 was first applied by him to steam navigation when he constructed a small steamboat on the ,hudson ,river in #ahjd4 ,but the simplicity of the paddle wheel and its high efficiency1 particularly in quiet harbors and shallow inland waters1 gave it preference over the propeller4 ,in rough seas1 however1 the paddle wheel was far from ideal4 ,it was too easily broken by heavy waves and between #ahee and #ahfe the propeller displaced it completely for ocean-going vessels4 ,,water ,,jet ,,propulsion ,another curious form of propulsion1 which dates back to the eighteenth century and is still periodically revived by inventors1 is the water jet4 ,the idea was to have the engine operate a pump which would drive a stream of water out of the stern of the boat and drive the boat by reaction4 ,the ,british ,government actually built two jet-propelled steamers4 ,one of them1 called the ,waterwitch1 was a #a1ajj-ton vessel and the other1 the ,squirt1 was a small torpedo boat4 ,the latter attained a speed of but twelve knots while a sister ship of the same steam power driven by a propeller attained a speed of seventeen knots4 ,the ,waterwitch was even less efficient4 ,some years ago experimental water-jet vessels were built in ,new ,york in which a jet only inch in diameter with a pressure of #b1ejj pounds per square inch was used1 but the experiment proved a failure4 ,the propelling force of a jet is the reaction of the stream of water against the orifice from which it issues4 ,the action is just like ,hero's reaction steam turbine referred to on page #adc4 ,the propulsion would be the same were the jet discharged in the open air or in a vacuum or against a solid stone wall4 ,,water ,,and ,,air ,,resistance ,it takes very little power to move a boat slowly because the resistance that has to be overcome is merely the parting of the water at the bow and closing in of the water at the stern and the skin friction along the sides of the hull4 ,in addition to this there is a similar resistance offered by the air4 ,at very low speeds the resistances of the water and the air are practically negligible4 ,in perfectly quiet water with no air stirring the pull of a cord will move a ship weighing hundreds of tons1 but the motion will be very slow indeed4 ,unfortunately the speed of a ship does not increase directly in proportion to the power that drives it4 ,doubling the power does not double the speed4 ,if it takes ten horsepower to drive a vessel at a speed of ten knots it will take not #b but #b or #h times as much power to drive it at a speed of twenty knots4 ,in other words1 the horsepower goes up as the cube of the speed4 ,this is an average condition for ordinary speeds4 ,for very high speeds the horsepower may have to be increased as the #dth and even the #eth power of the speed4 ,the shape of the bow and the stern is of utmost importance4 ,the parting and displacement of the water at the bow and the replacement at the stern produce waves and the forming of these waves represents so much wasted energy4 ,the swell that is kicked up by a steamer is evidence of power uselessly expended4 ,much of this loss can be overcome by careful design of the ship's lines4 ,a vessel that kicks up a high bow wave--one that sails with a 8bone in its teeth0--may present a very pleasing spectacle and may seem to be traveling at high speed1 but the best designed vessel--the one that slips through the water with no fuss--is much more economical of power4 ,it is easy to understand that the bow must be carefully designed to cut through the water1 but it is not so apparent that the stern must also be shaped to permit the water to flow in readily and fill in the void behind the ship4 ,if the stern is not carefully shaped1 there will be a serious drag on the vessel4 ,the skin friction of the vessel is greatly increased by fouling of the hull with marine growths4 ,at high speeds the wind pressure on the superstructure is considerable4 ,every spar and line adds its quota4 ,a boat that is traveling in still air at a speed of twenty-two knots or twenty-five miles per hour is encountering the equivalent of a twenty-five mile wind which will exert a pressure of over three pounds per square foot of frontage4 ,,flying ,,on ,,water ,instead of cutting through the water modern speed boats are designed to ride over it4 ,the boats have flat bottoms which are arranged as a series of flat planes known as hydroplanes4 ,these planes form steps and are set at such an angle as to make the boat rise up on the water in the same way that a kite rises in the air4 ,the higher the speed the higher the boat rises so that at full speed it skims on the surface4 ,hence there is comparatively little power wasted in displacing the water4 ,some of these boats are driven by air propellers so that water resistance to the propeller gear is avoided4 ,these hydroplanes 7they must not be confused with hydroaeroplanes7 almost fly over the water4 ,,first ,,ocean ,,steamer ,it was in #ahjg that ,robert ,fulton built the ,clermont and established steam navigation by running a regular service between ,new ,york and ,albany1 and it was twelve years later that the ,atlantic ,ocean was first crossed by a steam-driven vessel4 ,it was an ,american vessel1 the ,savannah1 that made the trip4 ,she was a #chj-ton ship equipped with steam power to help her along when the wind failed4 ,seventy-five tons of coal and twenty-five cords of kindling wood were taken aboard to feed her furnace4 ,this was thought to be ample for the voyage1 but before the trip was completed the fuel was all gone4 ,the log of the ,savannah bears this entry the night before sighting the ,irish coast3 8#b ,a4 ,m4 ,calm4 ,no cole to get up steam40 ,however the captain did raise steam just before reaching ,kinsale1 ,ireland1 by burning wood4 ,watchers ashore beholding the smoke issuing from her stack were convinced that the vessel was afire and boats were dispatched to the rescue4 ,the ,savannah made the trip from ,savannah to ,kinsale in #bc days and was under steam propulsion for only #hj hours of this time4 ,regular trans-,atlantic steam service was not inaugurated until #ahch1 but for many decades steamers were equipped with sails to assist them when the wind was favorable4 ,the most notable of early steamships was the ,great ,eastern1 a combined screw and paddle-wheel ship1 #fib feet long1 built in #aheh4 ,she held the record for size until #ahii when the ,oceanic1 #gjd feet long1 was put into service4 ,at present the ,leviathan1 formerly the ,vaterland1 holds the record with a length of #ibj feet4 ,it is difficult to judge of the size of a vessel out on the open water4 ,if the ,leviathan were placed in ,broadway1 ,new ,york1 she would span nearly four blocks4 ,because of her #ajj-;foot beam she would be too wide to be wedged in between the skyscrapers that border lower ,broadway4 ,if she were set up on end she would tower #aeh feet above the pinnacle of the ,woolworth ,building4 ,her power plant consists of four turbines which total #ij1jjj horsepower and the huge vessel is driven at a speed of #be4h knots or nearly thirty miles per hour4 ,the wonder of these huge floating structures lies not merely in their gigantic proportions but in the fact that they are able to weather the terrific wrenching strains of heavy ocean storms4 ,a skyscraper is built to withstand only the steady and direct pull of gravity and the variable thrust of the wind which1 except in western cyclones1 seldom amounts to thirty pounds per square foot4 ,bridge building is more difficult because of the leverage of the parts overhanging the foundations4 ,wind pressures must be calculated and also the live load of objects moving over the structure4 ,in naval architecture enter the problems of building construction combined with those of bridge building1 complicated by the fact that there is no fixed foundation for the structure to rest upon4 ,at one moment a ship may be spanning a trough in the seas and at the next it may be seesawing over the crest of the wave4 ,of course the bottom of the boat is seldom if ever out of the water and a certain amount of support is provided throughout the length of the vessel1 but the ship is subjected to the strains of a cantilever bridge when she is passing over a wave1 and to the strains of a truss bridge when spanning a wave trough4 ,these strains are increased by the fact that the structure is in constant motion4 ,a certain degree of flexibility is demanded of the materials which go into the structure and of the joints between the frame members4 ,,boats ,,of ,,artificial ,,stone ,originally wood was used for the hulls of ships2 then between #ahde and #ahee iron supplanted wood1 ,between #ahge and #ahhe steel supplanted iron and to-day efforts are being made to supplant steel with concrete4 ,the advantages offered by concrete are cheapness and speed of construction4 ,the first large vessel built of this material was the ,faith1 an #h1jjj-ton ship4 ,this boat stood up very well in heavy weather despite the rigidity of her structure4 ,it is doubtful1 however1 that a large boat comparable in size to the ,leviathan could weather a severe ocean storm4 ,the proposal to build ships of cement created almost as much of a popular sensation as did the first iron boat4 ,although the public had accepted iron and then steel as a perfectly proper material for shipbuilding1 concrete seemed too much like stone and it did not seem possible that artificial stone could be made to float4 ,they did not realize that a cubic foot of steel weighs four times as much as the same volume of concrete4 ,of course concrete does not begin to have the tensile strength of steel and consequently the walls of a concrete ship must be made relatively thick4 ,for this reason a concrete vessel is heavier than a steel vessel4 ,she draws more water and requires a larger power plant1 and because of her greater mass she is not so readily maneuvered4 ,,submarine ,,navigation ,as was explained in ,chapter ,,vi1 a body will float only so long as it is lighter than the volume of water it displaces4 ,it is almost impossible to keep a body suspended in water unless some portion of it is exposed above the surface4 ,if it starts sinking it will keep on going down until it reaches the bottom of the sea4 ,there is a popular notion that at great depths water becomes dense enough to float solid iron1 but water is practically incompressible and its density at a depth of five miles is only slightly greater than that at the surface4 ,an object must therefore either float on the surface or sink to the bottom1 unless its weight is exactly equal to the difference between the upward pressure of the water under it and the downward pressure of the water above it4 ,such an ideal balance it is practically impossible to obtain unless the object itself is compressible4 ,how then can a submarine navigate under water without sinking to the bottom8 ,a ,,submarine ,,of ,,the ,,seventeenth ,,century ,the first solution to this problem dates back to the seventeenth century4 ,doctor ,cornelius ,van ,drebel1 a ,netherlander1 who was a guest at the court of ,king ,james ,i of ,england1 built three submarines between #afbj and #afbd4 ,these were rowboats covered over with a water-tight deck and propelled by twelve oarsmen4 ,it is recorded that ,van ,drebel discovered a means of holding the boats submerged by observing some fishermen towing baskets full of fish up the ,thames4 ,the barks to which the baskets were attached by cables were weighted down by the load they were towing1 but when the cables slackened the boats rose a little bit4 ,van ,drebel's method of applying this principle was evidently to attach a weight to the boat which trailed along the bottom4 ,when the oarsmen propelled the boat1 she was pulled down under the surface by the drag1 but when the rowing ceased the boat would float up to the surface4 ,king ,james himself is said to have made a journey of several hours' duration in one these boats1 which was kept at a depth of twelve to fifteen feet below the surface4 ,progress must have been very slow because the range of the submarine was given as five or six miles4 ,during the ,revolutionary ,war ,david ,bushnell built a submarine with which attempts were made to sink a ,british frigate lying in the ,hudson ,river4 ,this submarine was driven by a hand-operated screw propeller4 ,the boat was provided with water ballast tanks1 and by pressing a valve with one foot he could let in water enough to submerge the boat while with the other foot he could operate a pump to empty the tanks and bring the boat to the surface4 ,when the boat was ballasted so that she would barely float1 a vertical screw propeller was operated to raise or lower her as much as desired4 ,a #bjj-pound lead weight was attached to a long cable which passed up through the bottom of the boat1 and by letting out this cable the submarine could be made to rise instantly in case of an accident4 ,,fulton',s ,,hand-,,propelled ,,submarine ,to ,robert ,fulton1 however1 belongs the credit of building the first submarine operating on the principle that is now universally used4 ,his boat was also driven by a hand-operated screw propeller and was furnished with water tanks which could be filled or pumped out at will1 but after the submarine was weighted until only the conning tower showed above water1 she was submerged or raised by means of horizontal rudders or hydroplanes which could be tilted to any angle desired4 ,of course these rudders1 like any other rudders1 would not operate unless the boat were in motion4 ,such is the case with modern submarines4 ,like bicycles1 they must keep on going or they will fall4 ,if they are heavy1 they will fall to the bottom1 and if light they will 8fall0 to the surface4 ,when in motion the hydroplanes will either hold them down or lift them up according to the angle to which these horizontal rudders are tipped4 ,robert ,fulton's ,nautilus had a fish-shaped hull of copper plating on iron ribs and was twenty-one feet three inches long by six feet five inches at her greatest diameter4 ,the screw propeller was operated by two men4 ,when the boat was on the surface a sail was raised to assist in driving the boat4 ,this sail could be folded up like a fan when it was desired to submerge4 ,fulton deserves full credit for anticipating so many of the essential features of the modern submarine1 but of course the ,nautilus was a mere toy compared to the marvelous machines which swim under the surface of the sea to-day4 ,the ,german ,u-boats at the outbreak of the war were #aej feet long and could make only nine knots submerged and twelve knots on the surface1 but later they grew to a length of #cjj feet with a submerged speed of twelve knots and a surface speed of eighteen knots4 ,the ,british in the meantime developed a submarine that was #cdj feet long and had a displacement submerged of #b1gjj tons as against #hjj for the largest ,german ,u-boats4 ,the speed of this big ,british boat is twenty-four knots on the surface and ten knots submerged4 ,,submarines ,,as ,,surface ,,boats ,despite their name1 submarines are really surface boats4 ,only when necessity demands are they submerged4 ,during the war even the ,u-boats did #ij per cent of their sailing on the surface4 ,origially submarines were built primarily for submerged travel and consequently they were given the form of a fish or of a fat cigar1 but such a shape was not adapted for surface sailing4 ,water piled up on the nose of the boat and tended to bear her down4 ,to overcome this1 submarines are now shaped more like a boat with a bow high enough to part the waves without burrowing into them4 ,,power ,,plant ,,of ,a ,,submarine ,the gasoline engines that were formerly used for propelling the boats have now given way to heavy oil or ,diesel engines1 because of the greater efficiency of these engines and the greater safety of handling heavy oil4 ,some submarines have been equipped with steam power plants4 ,such is the power used on the big ,british submarines above referred to4 ,of course any power that involves the burning of fuel can only be used on the surface4 ,as has already been explained1 an internal combustion engine burns seven to nine times as much air as oil and it would be impossible to store enough air on board to keep the engines going very long2 hence they can be operated only while the hatches are open to the atmosphere4 ,coupled to the shafts of the engines are dynamos which generate electricity and feed it to storage batteries4 ,a dynamo will serve as a generator when turned by some mechanical power and on the other hand when current is fed into it1 it serves as a motor1 so that when traveling submerged and fuel can no longer be used1 the generators are disconnected from the engines but remain connected to the propeller shafts and driven by the very current they previously stored in the batteries4 ,,the ,,collapsible 8,,eye0 ,,of ,,the ,,submarine ,amidships there is a bridge from which the vessel can be navigated when on the surface and a conning tower from which she can be navigated when running awash4 ,most of the submerged travel is maintained at a comparatively shallow depth so that the submarine can keep an 8eye0 on the surface4 ,the eye is the periscope of which there are two so that in case of damage to one the other may be used4 ,periscopes date back to the 8,fifties0 when they were used on some experimental ,european submarines4 ,in the ,civil ,war1 when the river monitor ,osage ran aground in the ,red ,river1 her captain1 now ,rear-,admiral ,thomas ,o4 ,selfridge1 rigged up a periscope with which he could look over the high banks of the river and direct the fire of his guns upon a ,confederate force that was attacking him4 ,this periscope consisted merely of a three-inch pipe with a hole at each end cut in opposite sides of the pipe4 ,small mirrors were set in the pipe so that the light coming in through the upper hole was reflected down through the pipe and out of the lower hole4 ,this crude periscope is the same in principle as the modern submarine periscopes except that the latter are provided with lenses to gather and focus all the light possible on the eyepiece so that the operator will have a perfectly clear view4 ,periscopes extend fifteen to twenty feet above the roof of the conning tower4 ,while periscopes are insignificant objects on the broad seas when a submarine is moving very slowly1 they are made conspicuous by the wake of foam that follows them when the boat is traveling even at a moderate speed4 ,for this reason during the war the ,germans developed a telescoping periscope which could be shot up to the surface whenever desired in order to give the commander a glimpse of his surroundings4 ,the submarine is submerged by letting water into the ballast tanks and then turning the hydroplanes to a diving angle4 ,there is an after as well as a forward pair of diving rudders4 ,when running completely submerged the submarine is blind and solely dependent upon the chart and compass4 ,it is impossible to see far under water4 ,searchlights are of no value at all4 ,they will not make visible an object a hundred feet away4 ,the submarine commander cannot see even the bow of the boat he is piloting4 ,the ordinary magnetic compass will not operate when entirely incased in steel as it is in the hull of the submarine and so a gyroscope compass has to be used instead4 ,while the compass serves as a guide for travel in the horizontal plane the depth gauge must be watched to see that the boat does not dive too deeply4 ,the pressure of the sea increases at the rate of #fd pounds per foot of depth4 ,two hundred feet below the surface the pressure amounts to about six tons on every square foot of the surface of the submarine4 ,few submarines can stand a greater pressure than that without being crushed or at least springing serious leaks4 ,when coming to the surface the hydroplanes are used and if the boat is to remain on the surface water is blown out of the ballast tanks4 ,,the 8,,ears0 ,,of ,a ,,submarine ,although submarines may be blind under water they are not deaf4 ,sound detectors are used which enable them to locate other vessels by the throbbing of their engines or the beat of their propellers and so they can avoid collisions when coming up to the surface4 ,despite the perfection of the submarine the sea is still a great mystery to us4 ,we know only its surface and its shallows4 ,we have sounded a few deep holes and brought up samples of deep-sea life1 but we have not been able to penetrate in person its profound depths and explore with our eyes and hands the world that is buried beneath its waves4 ,three quarters of the globe is covered by water and if we are to claim complete mastery of the earth we must find some way of descending into the heart of the ocean and exploring its deepest valleys4 ,,chapter ,,xiii ,,sliding1 ,,rolling1 ,,walking1 ,,and ,,creeping ,,in ,,all forms of transportation friction plays a most important part4 ,if there were no such thing as friction1 it would be impossible for us to set an object in motion by the means that are now commonly in use1 and once the object were moving it would be impossible to stop it except by bringing it up against a wall set squarely across its path4 ,in transportation on land friction is a much more serious bar to motion than it is in marine or aerial transportation4 ,there are two kinds of friction that we have to contend with2 sliding friction when two contacting surfaces are dragged by each other2 and rolling friction when one surface rolls upon another4 ,it is impossible to obtain two surfaces that are absolutely smooth2 there are minute elevations in each that sink into minute depressions of the other like intermeshing teeth and a grinding action takes place as these microscopic inequalities are broken away4 ,oil reduces the friction by filling up these inequalities1 but the oil itself offers a certain amount of friction just as water does along the sides of a moving ship4 ,,rolling ,,friction ,rolling friction is of a different kind4 ,the intermeshing inequalities or microscopic teeth are lifted out of contact with1 one another just as the teeth of gear wheels are carried out of mesh4 ,but there is another cause of friction due to the fact that no objects are so microscopic that they do not sink into each other to some extent4 ,a wheel is always rolling out the surface it is turning on just as a rolling pin rolls out dough4 ,if the surface is of elastic material such as a steel rail1 it springs back into place immediately after the passage of the wheel1 but the wheel must constantly travel in the trough of a wave which accompanies it along the rail4 ,there is a similar wave in the wheel itself and this ironing-out action produces heat in the wheel and the rail4 ,it is particularly noticeable in the flexible tires of automobiles which1 after a run on even a smooth road1 become too hot to be grasped with the bare hand merely because of the waves of compression and decompression to which they are subjected4 ,both rolling and sliding friction are increased by pressure because the depression is greater and because inequalities are brought into more intimate engagement with one another4 ,the degree of friction also depends upon the nature of the substances in contact1 but theoretically the area of contact does not make any difference4 ,it is just as hard to push a block along a smooth surface on its edge as on its side4 ,,putting ,,rollers ,,between ,,load ,,and ,,road ,as intimated in ,chapter ,i the forerunner of the wheel was probably the roller4 ,it was much easier to move a heavy object on rollers because rolling friction was substituted for sliding friction1 but the rollers would not stay under the object2 they traveled only half as fast as the load they carried4 ,to make them keep up with the load they had to be mounted on axles which were fastened either directly to the load or to a cart body on which the load was supported4 ,thus the wheel came to be invented1 but except for the fact that it stays by its load and does not roll out from under it a common wheel is not to be compared with a roller for efficiency4 ,to be sure1 it substitutes rolling friction for sliding friction where it contacts with the road1 but the friction at the axle is sliding rather than rolling4 ,however1 drawing an object on wheels is a decided improvement over sliding it along the road1 for two reasons3 the sliding friction at the axle is reduced to a minimum by choosing materials that will slide upon each other with comparatively little resistance1 by polishing them smooth and by lubricating them4 ,but even if these precautions were not taken there would be a distinct advantage in the use of wheels because of the relatively shorter travel at the axle than at the rim of the wheel4 ,if a wheel is thirty inches in diameter and turns on an axle one inch in diameter1 it will travel thirty times as far at the rim as it does at the axle2 hence the sliding friction at the axle is far less than it would be at the point of contact with the ground1 were the wheel locked so that it could not turn4 ,but it is not necessary to have any sliding friction at the axle if we revert to the old roller system that prevailed before the day of the wheel4 ,the axle may be considered the load and the axle bearing the road4 ,we can then put rollers between load and road4 ,because the road is a circular one that travels with the load we can line it with rollers throughout its length1 and the load will never lack for rollers to roll upon4 ,thus we have the roller bearing which is so widely used in modern vehicles4 ,ball bearings operate on the same principle except that the balls furnish less contacting surface and are not so suitable for supporting heavy loads1 as are rollers4 ,sliding friction is almost completely eliminated and unless heavily loaded a wheel on ball bearings will not heat even when the bearings are not lubricated4 ,,reducing ,,road ,,friction ,while there is little friction between a wheel and the roadway upon which it travels1 the roughness of the road is a very important factor4 ,every time a wheel goes over a stone the entire vehicle must be lifted2 this represents so much wasted energy4 ,the advantage of the pneumatic tire lies in the fact that it absorbs small inequalities without making it necessary for the entire vehicle to rise over them4 ,this means less load lifted and hence less work done4 ,large wheels are better than small ones because they do not sink so deeply into depressions and because they surmount small obstacles more readily4 ,on a steel track the size of the wheel does not make so much difference as it does on a road because the track surface is smooth and is but little depressed by the wheel4 ,it has been estimated that a horse can pull ten times as great a load on rails as on an ordinary macadamed road4 ,some years ago broad steel tracks were laid in some of our city streets for the use of horse-drawn trucks4 ,they served very well as far as the vehicles were concerned4 ,the road friction was reduced considerably1 but the fact was overlooked that the horses needed a good friction surface under their feet4 ,two horses could not pull a truck along the track without walking on the track and the smooth steel made such slippery footing that the tracks had to be torn out and replaced with common paving4 ,,increasing ,,track ,,friction ,the difference between sliding and rolling friction is well illustrated in a locomotive4 ,the driving wheels are turned around by steam power4 ,they must either roll or slide on the track and the load they will pull without slipping is a measure of the excess of sliding friction over rolling friction4 ,to increase the traction or the adhesion of the locomotive to the track it is provided with a number of driving wheels4 ,in some of our largest locomotives driving wheels are placed under the tender so as to obtain a maximum of traction4 ,,ancient ,,lineage ,,of ,,the ,,automobile ,when it was first proposed to substitute steam propulsion for the horse it was not realized that a rail would furnish enough traction to permit of hauling heavy loads1 and some of the early locomotives that ran on rails were provided with toothed wheels that engaged in racks alongside the rails4 ,in fact1 the earliest locomotives were not built to run on rails but on ordinary roads2 in other words1 they were automobiles4 ,the motor car can therefore boast of a more ancient lineage than the railroad engine4 ,joseph ,cugnot of ,france is said to have built a three-wheeled steam carriage in #agfi which was so top-heavy that it upset when making a sharp turn at three miles per hour4 ,several steam carriages were built in ,england in the eighteenth century1 but they were not successful4 ,the real father of steam traction was ,richard ,trevithic1 of ,camborne1 ,cornwall1 whose first steam carriage1 built in #ahja1 carried eight passengers4 ,his third machine1 built in #ahjd1 was the first to run on rails4 ,this was strictly a locomotive intended to haul cars4 ,it ran with its load at the astonishing speed of five miles an hour4 ,trevithic was the first to exhaust the steam from the cylinders into the smoke-stack and thereby increase the draft through the furnace and generated steam at higher pressure4 ,all the early locomotives used toothed gears to turn the driving wheels until ,george ,stephenson introduced connecting rods to drive the driving wheels direct from the pistons4 ,george ,stephenson's 8,rocket10 built in #ahbi1 won a prize of #ejj pounds in a speed contest when it established a record of #bd #a-f miles per hour4 ,it also established the doubtful honor of being the first mechanical speed monster to exact the toll of human life4 ,on its prize run it ran over a man and killed him4 ,,stephenson',s ,,link ,,motion ,illustration3 ,,fig4 #fa4--,,stephenson',s ,,link ,,motion ,stephenson's son ,robert is commonly credited with the invention of an ingenious link motion1 although the invention is also claimed for ,w4 ,t4 ,james of ,new ,york4 ,we must pause a moment for a description of this ingenious link motion1 because it became a standard in locomotive construction that is still in service4 ,as explained in ,chapter ,,ix steam should be used expansively in order to obtain a maximum of efficiency4 ,after a certain amount of steam has been admitted into the cylinder it is cut off from the boiler and it pushes the piston by its own expansion4 ,the speed of the locomotive must be varied by varying the point of cut-off1 and the direction of motion of the locomotive is reversed by reversing the motion of the valve4 ,in the ,stephenson link motion this is all effected by the operation of a single lever4 ,fig4 #fa shows the arrangement4 ,the valve is moved back and forth by the rod ,a which is connected to the arm ,b suspended from the frame of the locomotive4 ,the drive shaft is shown at ,c and it carries two eccentrics projecting on opposite sides of the shaft which move the rods ,d and ,e back and forth4 ,the outer ends of these rods are connected to opposite ends of a curved link ,f and a pin ,g on the arm ,b engages a slot in the link4 ,the link is held up by a rod ,h4 ,as the drive shaft rotates the slotted link is oscillated back and forth on its own center4 ,when the link is lowered so that the pin ,g is at the center of the slot there is no motion of the valve rod ,a1 but when the pin is at the top or at the bottom of the slot the valve rod has its greatest motion4 ,as the top of the link is moving in one direction while the bottom is moving in the other direction1 it will be plain that the action of the valve when ,g is at the top of the link will be the reverse of the action when ,g is at the bottom4 ,the link is raised and lowered by means of a lever ,i which is connected to one arm of a ,t-shaped lever ,j which on one side of its fulcrum is connected to the rod ,h and on the other to the counterweight ,k4 ,there are certain defects in the ,stephenson link motion that we cannot discuss here4 ,these became serious as engines grew larger and more powerful so that to-day it has been largely superseded by other valve gears4 ,the most important of these is the ,walschaerts gear1 invented by a ,belgian engineer4 ,this gear1 unlike ,stephenson's1 is conspicuously placed outside the drivers and is particularly noticeable because of its peculiar grasshopper motion4 ,the action of the gear is so complicated that a description of it would be out of place in this book4 ,,modern ,,locomotives ,we cannot enter minutely into the development of the locomotive from the crude machine of ,trevithic's time to monsters of to-day4 ,there has been a progressive growth of locomotives in power and in speed4 ,our biggest freight engines are so powerful that they cannot be used for pulling alone because they can pull a greater load than the draw-bars of the cars can stand4 ,if placed at the head of a long train they would yank the forward cars loose from the rest4 ,hence they are placed at the rear of the train to act as pushers or in the middle of the train where half their energy is expended in pushing the cars ahead of them and the other half in pulling the rest of the train4 ,the most powerful steam locomotive of to-day 7#aiba7 weighs #cdb tons and its tender #ajg making a total of #ddi tons4 ,its length is #aje feet and its boiler #h feet #g inches in diameter4 ,its low pressure cylinders 7#d feet in diameter7 are larger than the locomotive boilers of #ej years ago4 ,its high pressure cylinders are #cj inches in diameter and the stroke is #cb inches4 ,it may be operated either compound or simple1 i4 e41 the smaller cylinders may exhaust into the larger ones or they may take steam direct from the boiler4 ,the tractive effort compound is #adg1bjj pounds and simple #agf1fjj pounds and the total horsepower developed is #e1jdj4 ,each cylinder drives five coupled drivers1 in other words there are twenty power-driven wheels with a pair of trailers and a pair of pilot wheels4 ,six and a half tons of coal are consumed per hour4 ,in the matter of speed a mile per minute has become common and regular scheduled runs over long distances at an average well above sixty miles per hour have been maintained1 but the present tendency is to reduce speed somewhat in favor of safety4 ,there are two inventions that have made possible the high speeds of modern railroad travel3 the air brake1 which has already been described2 and the block signal system4 ,the latter1 of which there are a number of different types1 being electrical1 does not properly belong in this book4 ,stoking a large freight engine or a high speed passenger locomotive is strenuous work4 ,three tons of coal per hour is not an uncommon rate of consumption4 ,the fireman on a fast express train gets little rest4 ,to relieve him of this exhaustive work automatic stokers are now being used4 ,these convey the coal from the tender to the fire box and feed the fuel at a uniform rate4 ,in place of solid fuel1 oil is extensively used in regions where it may readily be obtained4 ,this simplifies the task of firing the locomotives4 ,there has also been some use of powdered coal which is blown into the furnace in much the same way as oil is4 ,to-day steam locomotives have found a serious competitor in the electric locomotive1 which is steadily increasing in favor4 ,where traffic is heavy1 where long tunnels make the smoke and gases of a steam locomotive dangerous1 where electric power is plentiful1 the steam locomotive must give place to electricity4 ,as the cost of coal mounts1 the electrification of railroads will spread and it will be only a matter of time before the electric locomotive1 which is far more economical in its use of power1 will completely supplant the steam locomotive4 ,,first ,,automobile ,,accident ,as we have already noted1 the automobile antedated the railway locomotive4 ,it was an accident that took the primitive steam carriage off the high roads and put it on rails4 ,in #ahjb ,richard ,trevithic1 while speeding along a road at the frightful speed of ten miles per hour1 lost control of his machine1 ran into a fence and ripped off a number of palings4 ,that accident spelled the doom of the early automobile4 ,so dangerous a machine was not allowed to run at large4 ,special tolls and restrictions were placed on power-driven road vehicles4 ,as late as #ahif when the automobile had become a practical machine in ,france and was being rapidly developed in this country1 ,england still had a law prohibiting any power-propelled vehicle to travel over the highways at a higher speed than four miles per hour and required further that the vehicle be preceded by a man bearing a red flag4 ,the most important early ,american road car was that built by ,richard ,dudgeon in #ahee1 which made a record speed of forty miles per hour4 ,in #ahhi ,serpollet1 in ,france1 invented the flash boiler and interest in steam-driven automobiles was revived4 ,in a flash boiler water is turned into steam as it is used by injecting small quantities at a time in a red-hot tube4 ,in the meantime1 however1 the internal combustion engine was being developed4 ,lenoir1 in ,france1 was the first to build a motor car driven by an internal combustion engine4 ,he obtained a patent on such a vehicle in #ahfj4 ,however1 the real father of the modern automobile was ,gottlieb ,daimler of ,germany1 who patented a motor vehicle in #ahhd driven by an internal combustion engine4 ,the next year ,karl ,benz1 another ,german1 built an automobile4 ,,american ,,pioneers ,,of ,,the ,,motor ,,car ,pioneer work in this country began with ,charles ,e4 ,duryea in #ahia4 ,five years later he took one of his machines to ,england1 where it entered a fifty-two-mile race between ,london and ,brighton4 ,there were many entrants from ,france1 ,germany1 and other ,european countries4 ,the ,american car won the race by nearly an hour over its nearest competitor4 ,commercial building of automobiles began in ,america in #ahid4 ,however1 it was not until the opening of the twentieth century that ,america took hold of the motor car in real earnest4 ,since then the rise of the automobile industry has been phenomenal4 ,american methods of manufacture were applied and cars were turned out in quantity4 ,in #aiaf the annual production exceeded a million and to-day the production is about two million passenger cars and over three hundred thousand trucks4 ,the motor car industry is largely responsible for the wonderful progress in ,american machine tools that has been made in the past two decades4 ,on the race track the motor car has established a record speed of #aca miles per hour1 but of greater utility has been the motor truck which now competes with railroads in the transportation of freight4 ,owing to ,new ,york's inadequate terminal facilities1 it takes less time to haul a load from ,new ,york to ,philadelphia by motor truck than to take the same load from the warehouse1 transport it across the ,hudson ,river1 and load it on a freight car4 ,it has made the country a part of the city4 ,a short run brings the farmer's produce to the markets and his passenger car keeps him in close touch with city life4 ,the motor tractor has lightened his work on the farm and has enabled him to conduct farming operations over vast areas4 ,animal power is gradually giving way to mechanical power4 ,this1 however1 is a special branch of automotive engineering which we must look into4 ,,wheels ,,vs4 ,,legs ,the success of the automobile depends upon the character of the roads it has to traverse4 ,wheels provide the best form of transportation over a smooth1 hard road1 but if the road is soft1 the wheel will sink into the surface and will be greatly impeded4 ,in traveling over mud or sand runners are preferable to wheels because they have a broader and longer bearing surface4 ,in the snowy regions of the north and the sandy regions of ,africa and ,asia ,minor1 sledges are used in place of wheeled vehicles4 ,sliding friction is less than rolling friction under such conditions4 ,in fact1 only where man has constructed special roads is it possible to use wheeled locomotion4 ,it is because in nature we must contend with all sorts of surface conditions1 soft and hard and seldom smooth1 that the rolling principle of locomotion is not to be found in any species of animal4 ,the legs of an animal are levers1 just as a wheel is a system of levers1 but in the former case the levers can be folded or extended to adapt themselves to all the unevennesses of the ground4 ,no animal can begin to run as fast as an automobile on a good road1 but on the other hand we have yet to build a machine which will run as fast as a horse on soft and uneven ground4 ,,walking ,,machines ,farm operations must be conducted on loose and broken surfaces for which the ordinary wheeled vehicle is unfitted4 ,in some cases broad wheels are used to keep them from sinking into the soil and they are furnished with cleats so as to give them a good grip on the ground1 but long ago it was realized that if the horse was to be completely displaced on the farm a more adaptable form of locomotion than that of wheels must be furnished4 ,inventors sought to make machines that would walk4 ,one interesting machine of this class which met with a certain degree of success attempted to combine walking and rolling4 ,large wheels were used which were provided with a series of feet or tread plates connected by knuckle joints to the wheel rims4 ,as the wheels revolved1 these treads came successively into contact with the ground and the machine actually walked on its feet4 ,the feet were broad enough to prevent the machine from sinking into the ground and they adapted themselves to inequalities in the surface4 ,instead of having to roll over a rock that lay in its path the machine would plant its feet on the rock and lift itself over4 ,a very curious machine of the walking type has been developed for excavating machines that operate in soft swampy ground4 ,the machine actually walks over surfaces that a light carriage could not negotiate4 ,it consists of a large central turntable flanked on each side by a pair of broad and long tread plates which serve as feet4 ,when the dredge is to be moved1 it plants the feet on the ground1 lifts up the turntable1 moves it forward1 and sets it down again2 then the feet are lifted1 moved forward1 and planted on the ground again while the turntable is moved forward again4 ,when it is desired to make a turn the machine is swiveled around to the desired direction while sitting on the turntable with its feet raised clear of the ground4 ,of course the speed of such a machine is very low1 but transportation is of secondary consideration4 ,the main purpose of the machine is to excavate ditches in soft ground and only occasionally does it have to move its position4 ,the turntable provides a broad base that distributes the load over a comparatively large area which prevents the machine from sinking into the mud1 and if it should sink into a soft spot it lifts itself out vertically instead of having to roll out4 8,,caterpillar0 ,,traction ,long ago it occurred to inventors that a machine could travel over trackless wastes if they carried their own tracks with them4 ,the idea dates back more than a century1 but only in comparatively recent times has it been developed to a practical stage4 ,the track-laying mechanism takes different forms1 but in one prominent type it consists of a series of plates linked together to form a chain or belt that passes around a series of wheels4 ,as the machine progresses the plates are successively laid down in front of the wheels and picked up behind them4 ,the wheels consist of a large number of rollers whose axles are spring-supported so that they are capable of a certain amount of vertical movement and as the belt they roll upon is made up of separate plates they can adjust themselves to irregularities of the ground and creep over an uneven surface4 ,its close resemblance to the creeping locomotion of a caterpillar has led to the adoption of the trade name 8caterpillar0 by one of the large tractor manufacturers4 ,the tractor belt is driven by spur wheels at each end and the rollers serve merely to distribute the weight of the machine along the belt4 ,the traction is exceedingly great because the belt is broad and long1 giving it a large gripping surface4 ,for the same reason it will not sink into plowed ground4 ,because of its flexible tread surface it will creep over rocks and stumps1 waddle down into a ditch and climb up the opposite bank4 ,so powerful is it that it will crash through underbrush with ease and even small trees yield before it4 ,it will run over soft mud1 deep sand1 and even snow with equal facility4 ,the tread belts on either side of the tractor are separately driven and by making one belt run faster than the other it is possible to steer the machine4 ,in fact it can be made to turn around in its own length by stopping the belt on one side and driving the belt on the other4 ,such a machine is ideal for plowing and other are hauled with ease over the soft plowed ground4 ,for ordinary farming purposes speed is not essential1 but the possibility of rapid travel with tread-belt traction was demonstrated in the ,world ,war when small 8tanks0 were built which could run at the rate of twelve miles per hour4 ,,chapter ,,xiv ,,invasion ,,of ,,the ,,sky ,,from the day when man began to assert his superiority over other animals he began to cast longing eyes at the sky4 ,fired with ambition and stirred with a spirit of mastery he chafed at the bonds that bound him to earth2 but the heavens remained a forbidden kingdom to him4 ,many a bold adventurer who dared to emulate the birds paid the penalty of his temerity with a broken limb and even with his life4 ,it seemed as if man were destined forever to grovel on the bed of the atmospheric ocean with never a chance to rise except in dreams and fancy4 ,it was not until near the close of the eighteenth century that a means of rising off the earth was discovered4 ,two brothers1 ,stephen and ,joseph ,montgolfier1 of ,annonay1 ,france1 were sitting before a fire1 watching the smoke curl up the chimney1 when it occurred to one of them that smoke might serve as a vehicle to carry them up into the air4 ,they belonged to a prominent paper-manufacturing family and naturally turned to that material as the most suitable for trapping and harnessing the smoke4 ,they began their experiments with a large bag of thin paper which they filled with smoke and floated up to the ceiling4 ,the next step was to fasten a dish filled with burning embers to the bag1 so that the balloon carried its own smoke generator4 ,the experiment was tried in the open air and the balloon arose to a great height4 ,larger bags were made of linen and paper and on the fifth clay of ,june1 #aghb1 a public exhibition was given4 ,a pit was dug in the ground in which a fire was lighted and over this was placed a huge balloon which weighed #cjj pounds4 ,eight men were required to hold it down while it was filling with heated air and1 when released1 it shot up to an elevation of about #f1jjj feet and came to earth about a mile and a half away4 ,,the ,,first ,,hydrogen ,,balloon ,when the news of this event reached ,paris a professor of physics named ,charles suggested that hydrogen1 being much lighter than air1 would raise the balloon without the use of fire4 ,by a popular subscription funds were raised to defray the expenses of securing enough iron filings and sulphuric acid to generate the hydrogen necessary to fill a balloon of #bb1jjj cubic-foot capacity4 ,on the #bgth of ,august1 #aghc1 a flight was attempted4 ,the big bag arose without mishap and disappeared in the clouds4 ,three quarters of an hour later it landed in a field fifteen miles away much to the astonishment of the villagers thereabout who gathered around the strange bobbing monster with mingled fear and curiosity4 ,one of the number1 more daring than the rest1 advanced and shot the balloon1 whereupon the crowd closed in and tore it to pieces with their pitchforks4 ,in ,november of the same year the ,montgolfier brothers built a balloon #dh feet in diameter and #gd feet high1 and ,jean ,franois ,pilatre de ,rozier1 a professor of natural history1 made several ascents with the balloon held captive4 ,then1 in company with the ,marquis d',arlandes1 the balloon was cut loose and the balloon voyage was undertaken4 ,below the car of the balloon was an iron vessel in which a fire was maintained to furnish the heated air4 ,the aeronauts each carried a bundle of fuel to feed the fire and a wet sponge to extinguish sparks that might ignite the bag4 ,despite this precaution a number of holes were burnt in the envelope1 but nevertheless the flight was successful and the daring voyagers came to earth without mishap after a short journey4 ,m4 de ,rozier's career as an aeronaut was a short one4 ,the first man to be carried up in a balloon1 he was also the first balloon victim4 ,he undertook to combine the ,montgolfier and the ,charles systems by building a balloon that employed both the hot air and the hydrogen principles1 but the balloon took fire and ,de ,rozier with his companion1 the ,marquis de ,maisonfort1 were both killed4 ,two months after ,de ,rozier's first balloon ascension a flight was made at ,lyons in a huge fire balloon which carried seven passengers4 ,this big bag was #ajj feet in diameter and #acj feet high1 with a capacity of #eij1jjj cubic feet4 ,the invasion of the air was now well under way1 although for a time it made little real progress4 ,owing to the danger of fire1 hot air eventually gave way to hydrogen and later to coal gas1 which1 although it did not have half the lifting power of hydrogen1 possessed the advantage of being much cheaper4 ,,the ,,weight ,,of ,,air ,it seems hardly necessary in this day and generation to explain that a balloon rises because it is lighter than the air it displaces1 but it does seem astonishing that a balloon weighing several tons may yet be lighter than an equal volume of air4 ,we do not ordinarily think of air as having any weight4 ,we know that the ocean of air bears on the earth with a pressure of about #ad pounds per square inch1 or about a ton per square foot at sea level4 ,this amounts to #bh millions tons per square mile and1 when we multiply this figure by the number of square miles of surface in the total area of the earth1 we find that the whole ocean of air has a weight of #e1ejj1jjj1jjj1jjj1jjj tons--a figure which is far beyond our conception1 but it does impress us with the fact that air is a ponderable substance4 ,of course1 the atmosphere that exerts a pressure of #ad pounds per square inch is scores of miles deep1 but even a small quantity of air has appreciable weight4 ,if weighed in a vacuum a cubic foot of air would tip the scales at #a ounces1 and #ajj cubic feet would weigh close to #h pounds4 ,the air in an empty room #aj feet square and with a #aj-;foot ceiling weighs nearly #hj pounds at a temperature of #cb degrees ,fahrenheit4 ,in other words1 if we had a box measuring #aj feet on each side and weighing less than #hj pounds in a vacuum it would float in the atmosphere when the thermometer was down to the freezing point1 provided there was no air in the box to weigh it down4 ,vacuum balloons were proposed long before the time of the ,montgolfier1 but the problem was to construct a vessel strong enough to resist the crushing pressure of the atmosphere4 ,the best bracing for the walls of the vessel is some gas dense enough to exert a pressure equal to that of the atmosphere but whose weight is less than that of the air4 ,the weight of the vessel must then not exceed the difference between the weight of the gas and an equal volume of air4 ,the ,montgolfier brothers used heated air to keep their box or envelope distended4 ,air expanded by heat is lighter than cold air4 ,however1 it does not make a very good filler because #a1jjj cubic feet of air heated to #bab degrees ,fahrenheit weighs #ei pounds1 leaving only #ba pounds on a freezing cold day for the absolute weight of our #a1jjj-;cubic-foot box4 ,coal gas1 on the other hand1 weighs about #dj pounds per #a1jjj cubic feet at #cb degrees ,fahrenheit1 while the same volume of hydrogen weighs only #e pounds4 ,if coal gas were used to brace our box against the pressure of the air we should have a surplus of about #dj pounds for the weight of the box1 while hydrogen would allow us #gd pounds4 ,of course1 the weight of a volume of gas depends upon its density4 ,no matter how small a weight of gas we placed in the box it would fill the box completely1 but when we speak of a #a1jjj cubic feet of gas or hydrogen we mean a volume sufficiently dense to bear against the container with the same pressure that the atmosphere presses outside2 i4 e41 #ad pounds per square inch4 ,temperature also affects the pressure4 ,in the case of fire balloons the hot air inside the envelope is less dense and hence lighter than cool air outside1 but the pressure is equal because the former is expanded by heat4 ,the volume of gas in a hydrogen or coal-gas balloon varies greatly with the temperature to which it is subjected4 ,for instance1 if on rising through a cloud or a blanket of fog1 the balloon should encounter the rays of the sun1 the heat would burst open the envelope were no vent provided4 ,the mouth of the bag is kept open1 however1 for just such emergencies so that the surplus gas may escape4 ,on the other hand1 sudden chilling of the gas will contract it and send it down to earth1 or the balloon might encounter a downward current of air1 when the only salvation of the aeronaut is to throw out the ballast4 ,,balloon ,,navigation ,balloons seem like very helpless craft1 and yet they are capable of skillful navigation at the hands of an experienced pilot4 ,although the balloonist has no means of self-propulsion and must drift with the winds1 he is capable of controlling motion in the vertical direction and can choose the particular air currents on which he desires to ride4 ,by throwing out sand ballast the bag may be made to rise and by letting out the gas it may be made to descend1 and a pilot who is familiar with prevailing currents of the atmosphere or able to interpret meteorological indications1 may locate the air stream that will carry him to his destination4 ,sand is the balloonist's fuel2 when that is gone the balloon may as well come to earth at once4 ,its course can no longer be directed and there is nothing to prevent it from being suddenly dashed to earth should it run into an 8air hole10 which is another name for a downward air current4 ,when a balloon comes to earth it is liable to be dragged by the wind and many accidents from dragging occurred in the early days of aeronautics until ,john ,wise1 an ,american1 invented the rip panel by which the envelope may be ripped open by pulling a cord1 thus freeing the gas and permitting the bag to collapse instantly4 ,illustration3 ,a ,,loom ,,provided ,,with ,a ,,jacquard ,,attachment ,note the belt of cards that determine the pattern that is to be woven ,illustration3 ,a ,,battery ,,of ,,mule-,,spinning ,,frames ,illustration3 ,,jacquard ,,attachment ,,for ,,looms ,,seven ,,miles ,,above ,,the ,,earth ,the greatest altitude ever attained by a balloon has been claimed for ,glaisher and ,coxwell1 who in #ahfb went up to a height of seven miles4 ,both men were overcome by the extreme rarity of the atmosphere4 ,coxwell1 however1 although nearly paralyzed and unable to move his arms1 succeeded in seizing the safety valve rope in his teeth and pulled it before he lost consciousness4 ,the balloon was then at an altitude of #bi1jjj feet and rising at the rate of #a1jjj feet per minute4 ,thirteen minutes elapsed before he regained his senses1 and then the balloon was falling at the rate of #b1jjj feet per minute4 ,from the data furnished1 it has been estimated that an altitude of #cg1jjj feet was reached4 ,while there has been much dispute as to the authenticity of this record1 the altitude of #ce1ajj feet established in #aija by ,professor ,berson and ,dr4 ,suring in the ,german balloon ,preussen1 probably represents a higher ascent than that of ,glaisher's balloon4 ,the new system of aerial transportation proved very useful in the nineteenth century4 ,during the siege of ,paris1 in #ahgj-ahga1 sixty-six balloons arose out of the beleaguered city1 and all but seven made their escape in safety4 ,in our own ,civil ,war captive balloons were first used to direct the fire of artillery4 ,it was in one of these balloons that ,friedrich von ,zeppelin1 who was a ,german military attach with the ,union forces1 made his first aerial ascent4 ,he was so impressed with the advantages of military observation from such a lofty aerie that he became from that moment an aeronautical enthusiast1 and on his return to ,germany urged upon the military authorities the importance of the balloon in war4 ,it was then that he began his aeronautic studies and experiments which culminated in the construction of the gigantic ships of the air with which ,germany undertook to carry the terror of war into ,england4 ,,kite ,,balloons ,in the ,world ,war captive balloons were extensively used by both sides1 an important development being the kite balloon4 ,the common spherical captive balloon is very unsteady except in perfectly still air4 ,it bobs around and swings and turns1 making an unfavorable base for careful observation4 ,in heavy winds it is liable to be dashed to earth by sudden gusts4 ,the kite balloon is held up not only by its own buoyancy1 but also by the wind in the same way that a kite is supported4 ,the bag is elongated 7sausage-shaped7 and is fastened to the anchor line in such a way that it is tilted like a kite4 ,to assist in holding it in this position the balloon is ballasted at the after end and the ballast1 if you please1 is air4 ,a big air-filled bag hangs from the stern of the balloon and serves as a rudder while two other horizontal bags serve as stabilizing fins4 ,,self-,,propelled ,,balloons ,no sooner had the ,montgolfier brothers proved that it was possible to rise off the earth upon a bubble of hot air1 than inventors began to devise schemes of propelling the bubble and controlling its course4 ,the first dirigible balloon was built in #aghd and1 strangely enough1 oars were used to propel it4 ,the balloon had a fish-shaped body1 just like that of modern airships1 and the bag was kept inflated by means of air as it is to-day4 ,it was realized even at that early date that the envelope must retain its shape if it is to plow through the air with a minimum of friction4 ,as the gas would gradually leak out of the envelope the bag would become flabby and present a crumpled bow to the ocean of the air and1 to overcome this1 a double envelope was provided and air was introduced between the inner and outer skin4 ,means were provided for pumping air in as the gas slowly escaped1 thus keeping the envelope fully inflated4 ,as the air was pumped in sand ballast was thrown overboard so that the buoyancy of the airship was not impaired4 ,to-day air is used to keep gas envelopes inflated1 but instead of placing the air in an outside envelope it is introduced into a small bag inside called a 8ballonet40 ,from time to time other means of propulsion were proposed and tried4 ,in #aheb ,henri ,giffard1 who is known as the ,fulton of aerial navigation1 built and operated a dirigible driven by a steam engine1 which he hung at a considerable distance below the gas bag1 so that the fire box would not be liable to ignite the highly inflammable gas4 ,a draft was maintained in the fire box as it is in a locomotive by letting the steam discharge into the smoke stack1 but in this case the stack was inverted and the smoke and gases were blown downward and away from the coal gas with which the balloon was inflated4 ,the danger of fire and the difficulty of building a power plant light enough to be carried aloft and powerful enough to give the craft any material headway were the chief obstacles that had to be overcome4 ,at the close of the nineteenth century1 ,santos ,dumont1 a ,brazilian inventor1 built a balloon that was driven by a gasoline engine4 ,despite the apprehension of other aeronauts this machine proved an unqualified success4 ,two years later1 in #aijj1 ,count ,zeppelin introduced the rigid dirigible1 which to-day is the standard for large airships4 ,,three ,,types ,,of ,,dirigibles ,there are three types of dirigible airships2 the flexible1 the semirigid1 and the rigid4 ,in the flexible type1 as we have observed1 the envelope must be kept tightly filled in order to hold its shape when driven against the air4 ,the car is suspended from the gas bag4 ,in the semirigid type a rigid frame or backbone serves as a keel for the gasbag and helps to prevent it from crumpling up4 ,in the rigid type a casing incloses the gas or rather bags2 for the gas ,is contained in a number of separate bags fitted into separate compartments4 ,the casing is composed of a framework of duralumin1 which is an alloy of aluminum1 with a percentage of copper and nickel4 ,it weighs but little more than aluminum1 but is five times as strong4 ,over the duralumin framework is stretched a sheathing of rubberized fabric4 ,because of the weight of this casing rigid dirigibles must be made in large size4 ,,across ,,the ,,atlantic ,,in ,a ,,dirigible ,before the war large ,zeppelins were built that were fitted with luxurious cabins and dining rooms and made regular scheduled voyages4 ,the big ,british dirigibles are of the ,zeppelin type4 ,the ,r-#cd1 was #fgb feet long and #gi feet in diameter4 ,it was fitted with nineteen gas bags and had a total capacity of over two million cubic feet of hydrogen4 ,it was driven by five engines1 each developing from #bej to #bge horsepower1 and was capable of making from #ej to #ge miles per hour1 depending upon whether or not the engines were pushed4 ,the big dirigible left the ,royal ,naval ,air ,station1 near ,edinburgh1 on the #b;d of ,july1 #aiai1 and landed at the ,roosevelt ,field near ,mineola on the #fth1 having made the trip in four days and two hours4 ,the course covered about #c1ajj sea miles1 but the actual air mileage was about #f1cjj miles because head winds were encountered4 ,in aeronautic voyages it is the distance through the air that must be reckoned rather than the distance over the ground or sea4 ,an airship may be traveling at the rate of #ej miles per hour through the air1 but if there is a wind of #cj miles per hour blowing against the course of the dirigible1 the latter will be making only #bj miles per hour over the ground1 or if the wind is blowing with the airship it will be making #hj miles per hour over the ground4 ,because of the head winds the transatlantic flight of the ,r-#cd was so much longer than had been anticipated that its stores of fuel were almost completely exhausted4 ,and yet1 when the airship started out from ,edinburgh1 it carried #ha tanks of gasoline1 each containing nearly #gj gallons1 or a total of #d1ijj gallons4 ,this fuel weighed nearly #af tons4 ,almost a ton of oil and #c tons of water added to the load and the baggage and crew amounted to #d tons more4 ,the total weight carried was over #bd tons and the dirigible fully loaded weighed altogether about #fj tons4 ,when the dirigible started out it had to fly low1 but as the fuel was consumed it grew lighter and rose higher4 ,the surplus hydrogen had to be pumped into steel tanks where1 owing to its compression1 it was heavy and served as ballast which could at any time be fed back into the gas bags to increase the buoyancy of the airship4 ,we can no longer think of air as having no weight when we consider that all this tonnage was supported by air4 ,the ,r-#cd was by no means the largest dirigible built1 but we dare not boast of the size of the airships of to-day when the aeronautics is in its in-fancy1 because our present dirigibles may seem puny alongside the big aircraft that may be built to-morrow4 ,the dimensions of the ,r-#cd have been given because of the historic interest in this first dirigible to span the ,atlantic ,ocean4 ,,heavier-,,than-,,air ,,machines ,marvelous as was the achievement of the ,montgolfiers and wonderful as were the aeronautic developments that followed the invention of the balloon1 the dominion of the birds was not really conquered until man had learned how to fly in a machine heavier than the air4 ,captive aeroplanes date back to the remote ages of ancient history4 ,kites are really 8heavier-than-air machines40 ,they maintain themselves in the air because they travel through the air at a considerable velocity4 ,true1 a kite may be stationary1 or practically so with respect to the ground1 but if we detach ourselves from the ground and view the situation from a drifting balloon1 the earth will appear to be moving under us and the kite will rush past us as it is dragged by the earth to which it is tied4 ,the idea of propelling a kite through the air1 not by tying it to the earth1 but by furnishing it with its own propeller and power plant1 was conceived long ago1 but the problem was to find a power plant light enough4 ,the honor of being the first man to rise off the ground in an aeroplane belongs to ,c4 ,ader1 who made several short flights between #ahij and #ahif in a machine driven by a twenty-horsepower steam engine4 ,our own ,s4 ,p4 ,langley did some most important pioneer work in flying and built a man-lifting1 steam-driven machine in #aijc which would have flown had it not been for an accident to its launching gear4 ,in fact1 this very model was flown successfully a number of years later4 ,however1 it was not until the gasoline engine was developed that the power plant problem was solved4 ,the internal-combustion motor was made more and more powerful in proportion to its weight until now there are several types that weigh less than two pounds per horsepower4 ,but the power plant was only one obstacle to be overcome4 ,the real problem was to learn how to control the machine after it rose into the air4 ,otto ,lilienthal attempted to learn how to fly in a motorless flying machine4 ,he provided himself with wings and1 jumping off a height or running down a slope1 depended upon gravity to furnish him with the necessary propulsion through the air4 ,unfortunately after five years of gliding experiments a fatal accident terminated his aeronautic research4 ,,the ,,wright ,,brothers ,in this country the ,wright brothers1 ,orville and ,wilbur1 took up the work of ,lilienthal and they1 too1 undertook to learn to fly before they built a flying machine4 ,in all his years of experiment1 ,lilienthal did not have more than five hours of experience in the air4 ,the ,wright brothers determined to spend more time in the air and less in theoretical speculations at home1 so they built a gliding machine that would sustain a man at a speed of eighteen miles per hour and picked out a spot on the ,atlantic coast where they were assured of fairly constant winds of sixteen to twenty-five miles per hour4 ,at first the machine was used as a kite and various experiments were made in balancing it4 ,then short gliding flights were made from the tops of the sand dunes4 ,not until the art of balancing the glider and controlling it in unsteady air currents was any attempt made at building a motor-driven flying machine4 ,it was by these experiments that the ,wright brothers discovered the system of warping the wings so as to preserve the lateral balance of the machine4 ,after several seasons of experimental gliding1 and not until they felt that they had learned how to fly1 was a power machine built4 ,this made its first flight on ,december #ag1 #aijc4 ,the first flight lasted only twelve seconds1 while the fourth flight lasted fifty-nine seconds4 ,many months were spent in perfecting the machine and in solving the various problems of flight1 and not until ,september1 #aije1 did the ,wright brothers feel that they had mastered the art of flying4 ,after that three years elapsed before the world was actually convinced of the reality of airplane flight and recognized the work of the pioneers4 ,,transatlantic ,,aeroplane ,,flights ,the development of the heavier-than-air machine is so recent and is still advancing so rapidly that we dare not give more than a brief outline of its progress here4 ,the more important advances are familiar to most of us and a record of achievements to-day will be hopelessly out of date to-morrow4 ,the war gave a tremendous impetus to flying4 ,pilots were trained by the thousand4 ,machines grew in speed up to #aej miles per hour4 ,huge bombing machines were built1 with a wing spread of over #abe feet1 and weighing ten to fifteen tons4 ,these were capable of carrying a load of four to five tons4 ,the first flight across the ,atlantic was made in ,june1 #aiai1 by the ,united ,states navy flying boat ,,nc-#d1 which flew to ,newfoundland1 then to the ,azores1 and from there to ,lisbon1 ,portugal4 ,the trip was finally completed by a flight to ,plymouth1 ,england4 ,the first nonstop flight was made in the same month by a ,vickers ,vimy bomber which1 with a favoring wind of thirty miles per hour1 made the trip in less than eighteen hours at a rate of #abj miles per hour4 ,to-day all-metal aeroplanes are being flown successfully4 ,plans are under way to build aeroplanes for service at extremely high altitudes1 where greater speeds are possible owing to the tenuity of the air and the consequent lowering of head resistance4 ,these machines are to have inclosed bodies in which air at normal pressure will be maintained by means of blowers4 ,the blowers would also furnish the engines with air necessary for proper combustion of the fuel4 ,we are not going to give a history of the progress of aviation since the invention of the ,wright biplane1 but instead we shall look briefly and in a very elementary way into the principles underlying the flight of heavier-than-air machines4 ,,why ,a ,,kite ,,stays ,,up ,what is it that makes a plane or a kite stay in the air8 ,the answer is inertia4 ,the balloon shows us that air possesses weight2 the aeroplane shows us that air possesses inertia4 ,this is a natural consequence4 ,every body possesses inertia and the heavier the body the greater its inertia4 ,by inertia we mean resistance to change of motion or rest4 ,the pressure of air against the face of a fan is due to its resistance to a change from state of rest to a state of motion1 while the pressure of wind against a surface represents the resistance of air in motion to being brought to a state of rest4 ,the more sudden the change the higher is the resistance or pressure developed4 ,if an open newspaper be laid over one half of a ruler1 while the other half extends beyond the edge of the table1 the ruler may be broken by a sharp blow on the overhanging end1 not because the other end is held down by the weight of the newspaper1 but because the inertia of the air bearing on the broad area of the paper prevents the ruler under the paper from rising in response to the sudden blow at the overhanging end4 ,it is the inertia of the air1 i4 e41 its resistance to rapid displacement that keeps a parachute from falling like a solid shot to earth4 ,figure #fb shows how a kite is maintained in the air4 ,the line ,,ab represents the plane of the kite1 the line ,,co at right angles to this plane is the pressure against the center of the kite surface4 ,the wind pressure ,,do is resisted by the pull of the kite string and exerts a lift ,,eo1 which resists the vertical pull of gravity4 ,the sum of the forces ,,do and ,,eo must be equal to the force ,,co4 ,if ,,eo is greater than the force of gravity the kite will rise1 and if it is less the kite will fall4 ,the magnitude of the force ,,eo depends upon the velocity of the wind ,,do and the angle of the kite ,,ab to the wind4 ,if the plane of the kite were parallel to the direction of the wind the angle would be zero and the lift would also be zero4 ,,forces ,,that ,,support ,,an ,,aeroplane ,illustration3 ,,fig4 #fb4--;,,forces ,,which ,,hold ,,up ,a ,,kite ,in an aeroplane conditions are just the same as in a kite1 except that a propeller drives the plane through the air with a force equal to ,,co4 ,the plane is slightly curved1 so that air which is deflected or forced down at the forward edge will continue to press against the plane all the way to the rear edge4 ,the shape of the top of the plane is also important4 ,as the plane is driven through the air a partial vacuum is formed above the plane1 so that the difference in pressure between the two sides is increased and there is a greater lifting effect4 ,this partial vacuum is known as 8cavitation40 ,in the early days of the aeroplane it was not realized how important was the effect of cavitation on rapidly moving objects4 ,every spar and member of the airplane as it plows through the air builds up a head resistance in front and is followed by a wake of rarefied air unless it is given a stream-line construction4 ,this is illustrated in ,figure #fc1 which shows at the left a rectangular body traveling through the air and at the right a stream-lined body4 ,the flow of the air is indicated by the lines and it is evident that head resistance and cavitation are reduced by forming the body with a bulging bow and tapering stern4 ,to-day all the exposed parts of aeroplanes are stream-lined as far as possible4 ,in the early ,wright machines wire braces were extensively used4 ,it was not supposed that a wire would offer much resistance to the air1 but1 upon investigation1 it was found that the wire braces would vibrate laterally and present virtually a broad surface which materially increased the head resistance4 ,illustration3 ,,fig4 #fc4--;,,flow ,,of ,,air ,,around ,a ,,rectangular ,,body ,,and ,a ,,stream-,,lined ,,body ,the angle of the plane determines to a large extent the head resistance of the plane4 ,if the plane is horizontal the head resistance is at a minimum1 but the lift is also very slight4 ,if the wing planes were perfectly flat1 there would be no lift at all1 but because of the curve of the wings there is a certain amount of lift when they are horizontal1 and even when they are tipped slightly downward1 provided the machine is traveling at high speed4 ,the angle of an aeroplane's wings is therefore much flatter than that of a kite4 ,,maintaining ,,the ,,equilibrium ,,of ,,an ,,aeroplane ,in order to maintain itself in equilibrium the center of gravity must coincide with the center of pressure1 otherwise there will be a turning action about the center of gravity and the machine will upset4 ,the location of the center of pressure depends upon the angle of the plane4 ,the greater the angle the farther it is from the forward edge of the plane and the pilot can maintain fore-and-aft equilibrium by tilting the horizontal planes of his rudder so as to change the angle of the machine1 and hence of the main or forward planes4 ,unfortunately the air is a turbulent ocean filled with invisible air currents and the aeroplane must be capable of adjustment to meet the variations of pressure due to sudden gusts of wind4 ,this is particularly true of lateral balance4 ,a gust coming from the side will put a greater pressure on one side of the aeroplane than on the other4 ,to meet this the angle of the plane at one side must be less than that at the other4 ,this was discovered by the ,wright brothers and their method of overcoming the lateral variations of pressure was the key to their early success4 ,they warped their wings or twisted them so that the angle of the wing was reduced on the side from which the gust came and was increased on the other1 and thus the center of pressure over the whole wing was kept on the line of the center of gravity4 ,at the same time there was a variation in head resistance which had to be corrected by moving the rudder1 and the ,wright brothers used a single lever to warp the wings and at the same time to operate the rudder so as to keep the aeroplane on its course4 ,before the ,wright brothers made public their invention other aeronauts had great difficulty in making turns4 ,when turning1 one side naturally has to move through the air faster than the other4 ,this produces an increase of pressure on one side over the other which may be counterbalanced by warping the wings4 ,the same effect is produced by the use of small wing planes1 called 8ailerons10 at each side of the main planes4 ,an automatic means of stabilizing an aeroplane has also been devised1 a description of which will be found in ,chapter ,,xxi4 ,,chapter ,,xv ,,helping ,,the ,,farmer ,,the ,,first efforts at directing the forces of nature and employing them in the service of man were made by the farmer4 ,the task of growing food was quite the most important of primitive occupations1 and although the virgin soil was rich and the yield abundant there were regions where crops could not be raised except at the expense of constant toil4 ,infrequent rains made it necessary to carry water by hand from wells and rivers and pour it over thirsty lands4 ,as the grain fields grew more extensive1 irrigating ditches were used which saved the toil of carrying the water1 although it still had to be raised by hand4 ,then machines were invented by which water could be raised by animal power and1 finally1 as we have already seen1 automatic water-lifting machines were constructed by which the river itself was constrained to lift a part of itself and pour this part into the irrigation ditches4 ,while it is true that the earliest machines were built to lighten the work of the farmer1 the attention of inventors was soon attracted to other fields of endeavor and the farmer was left to toil slavishly from daybreak to sundown with no further mechanical aid4 ,the tools he used were improved in form and quality4 ,oxen were used to draw the plow4 ,the wooden plow made out of a forked stick gave way to a bronze plow and1 finally1 to one of iron4 ,the curved knife or sickle went through a similar process of evolution from flint to iron4 ,it was the only implement used for cutting the standing grain1 and not until comparatively recent times did it give way to the scythe4 ,practically all the work of tilling1 seeding1 cultivating1 harvesting and threshing was done by hand in practically the same way and with practically the same tools from the time of the ,pharaohs down to the end of the eighteenth century4 ,,the ,,first ,,harvesting ,,machine ,to be sure1 there is a record of a harvesting machine built in ,gaul1 while that province was under ,roman dominion4 ,pliny described this machine in #gj ,a4 ,d4 ,it consisted of an ox cart which was pushed through a field of grain1 instead of being pulled by the ox4 ,this cart carried a rack or comb which caught the heads of the standing grain1 tearing them off and delivering them into the body of the cart4 ,unfortunately this primitive1 but useful1 harvester was not extensively employed and in time it was lost to agriculture4 ,farmers reverted to the time-honored method of reaping by hand and the ox-pushed machine was forgotten4 ,from time to time in recent years this machine has been reinvented and a machine similar in principle is used to-day to gather clover seed4 ,the scythe was a distinct improvement over the sickle4 ,it enabled a man to use two hands at the work of reaping instead of one4 ,it provided a much longer and heavier blade1 and hence a much broader swath was cut at each stroke4 ,a distinctly ,american improvement on the scythe is the grain cradle1 consisting of a set of fingers above the blade which catch the grain and lay it in a swath at the end of the stroke4 ,this important improvement rapidly spread to all parts of the world and is still used to-day where it is impracticable to use a mechanical reaper4 ,it is claimed that one man can cut and bind more grain with the cradle than three men could with the sickle4 ,,evolution ,,of ,,the ,,plow ,the plow has undergone important developments in comparatively recent years4 ,wooden plows were still in use in ,america in ,revolutionary times2 usually the point was shod with wrought iron4 ,however1 these wooden plows speedily gave way to metal when iron came to be manufactured in considerable quantity in this country4 ,a plow has to contend with two conditions of service that apparently conflict with each other4 ,the constant friction of the soil against the blade tends to wear it away very rapidly1 hence a very hard surface is requisite4 ,on the other hand1 the plow is apt to encounter buried stones and rocks which will shatter it unless it is soft4 ,the problem then is to make the plow both hard and soft4 ,the chilled iron plow was invented by ,oliver1 in #ahee1 to meet the first condition4 ,when molten iron is poured into an iron mold the surface that comes into contact with the mold is suddenly chilled1 producing a very hard surface that takes a good polish4 ,this effect is accentuated by using a hollow mold through which water is circulated4 ,the hard surface of the chilled iron wears well in sandy and gravelly soil1 it does not rust deeply1 and it clears well in sticky soil4 ,however1 it is very brittle and is liable to break if struck a sharp blow4 ,a more recent improvement is the soft-center steel plow4 ,this is both hard and soft4 ,it is composed of three layers of metal2 the outer layers are of hard cast steel and the center one of soft steel4 ,these metal layers are heated to a welding heat and then rolled together1 producing a plow that has a hard outer wearing surface and at the same time is tough because the center layer of soft steel acts as a cushion to absorb sharp blows4 ,to increase the wearing qualities of the plow still further a patch of very hard cast steel is welded over the point of the share4 ,thus both conflicting requirements of softness and extreme hardness are met4 ,we think of the plow as a very simple tool1 but the modern implement is a product resulting from a vast amount of study and research into the materials most suitable for its construction and into the best form of share and moldboard4 ,in place of a single plow for all purposes the modern farmer is offered a large assortment to suit various classes of work4 ,at least three different kinds of plows are indispensable on every farm2 the sod plow1 the stubble plow1 and the corn-cultivating plow4 ,the sod plow is used for turning over the sod and breaking the clod4 ,this is provided with a jointer or diminutive plow point set above the share1 which turns over the edge of the furrow to prevent grass from growing up between the furrows4 ,the stubble plow has a moldboard with less twist than that of the sod plow4 ,this is used for plowing land that was under cultivation during the previous year4 ,the plow of to-day has become more than a hand-guided1 horse-drawn tool4 ,it has developed into a real machine1 mounted on wheels1 with a disk or coulter wheel that cuts the furrow cleanly1 means for leveling the plow and regulating the depth of the plow1 and a seat for the plowman4 ,it works upon soil with the same precision that a planer works upon a slab of cast iron4 ,the furrow is neatly sliced1 lifted1 and turned over with mechanical accuracy4 ,as the furrow slice slides over the moldboard of the plow the soil is pulverized by friction4 ,the front furrow wheel runs in the furrow previously cut which serves as a track to guide the machine4 ,the front and rear furrow wheels are inclined from the vertical so as to balance the thrust of the plow and they may be given a lead toward or from the 8land0 or unplowed part of the ground to regulate the steering automatically4 ,the proper adjustment and balancing of a plow calls for considerable skill4 ,agricultural operations are now conducted on such a vast scale that the single plow cannot begin to do the necessary work4 ,instead1 sets of gang plows are used so that from a dozen to two dozen furrows may be turned at a time4 ,steam or gasoline tractors of the wheel or track-laying type are required to furnish the tractive effort needed to haul these huge plows4 ,the larger tractors are so powerful that they haul not only the plow but a harrow behind the plow to break up the clods and a seeder behind the harrow to sow and cover the seed so that all three operations are performed simultaneously4 ,the disk type of plow is used in very dry and hard soil and also in very sticky soil4 ,a rolling disk takes the place of the moldboard and share1 and in this way friction is reduced very materially1 with the result that less tractive effort is required to draw the machine4 ,there is scarcely any agricultural operation for which a machine has not been designed4 ,we cannot attempt to describe them all4 ,for tilling the soil there are plows1 harrows1 drags1 and rollers of many different varieties2 for seeding and planting there are grain and seed drills1 corn planters1 potato planters1 etc42 for cultivating or working the growing crops there are cultivators1 weeders1 fertilizer drills1 corn plows1 etc42 and for harvesting or gathering the crops there are mowers1 hay rakes and tedders1 reapers and binders1 potato diggers1 corn binders and huskers1 corn shellers1 etc4 ,,invention ,,of ,,the ,,reaper ,most interesting of all are the reapers because they represent the first successful efforts to introduce machinery into farming operations4 ,toward the close of the eighteenth century the ,royal ,agricultural ,society of ,england offered a prize for the invention of a successful reaper1 which stimulated inventive effort in this field4 ,but although many patents on reaping machines were granted by the ,british patent office1 nothing was produced that completely met the requirements4 ,in fact even as late as #ahea when a ,world's ,fair was held in ,london the ,british had no really successful reaper to exhibit4 ,in the meantime1 ,american inventors had been at work and two inventors in particular1 ,obed ,hussey of ,maryland and ,cyrus ,mc,cormick of ,virginia1 had developed machines which had so far proved their worth that they were extensively used on ,american farms4 ,these two inventors1 working independently1 produced machines that were very similar in basic principles4 ,as our patent regulations of that period did not call for an extensive search of the prior art there was no official investigation to show which was entitled to the honor of priority of basic principles or whether both did not include in their applications much that was old4 ,hussey filed his patent on the last day of #ahcc and ,mc,cormick in ,june of #ahcd4 ,the main stumblingblocks of earlier inventors of reaping and mowing machines was in finding a suitable method of cutting the grain4 ,revolving combs for tearing off the heads of grain1 fingers for gathering the grain and holding it against a revolving cutter1 horizontally reciprocating knives--all these methods were tried without success4 ,nearly three years before ,hussey obtained his patent1 ,manning1 of ,plainfield1 ,new ,jersey1 solved the problem by inventing a reciprocating cutter with spear-shaped blades cooperating with a finger bar that guided and held the grain against the blades4 ,this invention was apparently unknown to either ,hussey or ,mc,cormick and their patents show cutting means that were broadly the same as that of ,manning4 ,,the 8,,fulton0 ,,of ,,agricultural ,,machinery ,of the two rivals1 ,mc,cormick showed the better business ability in perfecting his invention and promoting it so that he eventually became to be considered the 8,fulton0 of agricultural machinery and the public forgot the pioneer work of ,hussey4 ,as a matter of fact1 ,mc,cormick built his first successful reaper three years before he obtained his patent4 ,four horses were hitched to the machine and he went out into a neighboring field of oats to demonstrate it4 ,in less than half a day he had reaped six acres1 which was a remarkable performance when we consider that a single acre was considered a day's work for one man4 ,mc,cormick's machine had a reel above the cutter to hold the grain against the knife and as the grain was cut it dropped upon a platform4 ,a man walked alongside the machine and removed the grain with a rake4 ,and so the reaper with two men to operate it did the work that had formerly required twelve men with the cradle4 ,the next important improvement was to provide a seat at one side of the reaper so that the man with the rake could ride4 ,while this reduced the labor of the man it did not materially increase the efficiency of the machine4 ,the next step1 however1 was of material importance4 ,in place of raking off the hay by hand an automatic rake was furnished and the services of the extra man were dispensed with4 ,one man could then do the work of twelve4 ,mc,cormick had had difficulty in introducing his machine into public use1 but now its superiority over hand labor was so marked that reapers came to be extensively employed on ,american farms4 ,the reaper had reached this stage of its development when the ,world's ,fair of #ahea was held in ,london and ,mc,cormick's machine was sent across the ,atlantic to be displayed at the exhibition4 ,at the same time ,hussey sent over one of his machines which had reached the same stage of development4 ,there was a ,british machine also on exhibition based on the invention of ,rev4 ,patrick ,bell of ,scotland in #ahbf1 but in a competition with the ,american machines it could not begin to compare in efficiency4 ,the work of the ,american machines was a revelation to the ,british farmers4 ,the prize was carried off by ,mc,cormick's machine1 which was declared by the judges to be worth the whole cost of the exposition4 ,unfortunately ,hussey was not on hand to direct the operation of his machine1 which may have had something to do with its failure1 for in another test the ,hussey reaper was found superior to the ,mc,cormick4 ,the excellence of ,american reapers was now well established and their fame spread throughout ,europe4 ,in a competitive test held near ,paris in #ahee1 ,america won the highest honors by cutting an acre of oats in twenty-two minutes as against sixty-six minutes for a ,british machine and seventy-two for an ,algerian machine4 ,in #ahgh ,mc,cormick was made a member of the ,french ,academy of ,sciences in honor of his achievements4 ,,tying ,,knots ,,by ,,machine ,after the self-raker was introduced the next important improvement was in the binding of the grain4 ,at first the cut grain was raked into a receptacle which was dumped by the driver of the machine when enough had accumulated to form a bundle and the bundles were bound by men following the machine4 ,as in the evolution of the raker1 the next step was to provide a platform for these men on the machine so that they could ride as they bound the grain and finally in #ahgc a self-binding attachment was invented which increased the efficiency of the machine manifold4 ,this self-binder1 however1 called for the use of wire which did not meet with favor as a binding material because of the difficulty of cutting it without a special tool4 ,efforts were therefore made to introduce twine instead4 ,but twine cannot be fastened by mere twisting2 it has to be tied and a mechanical means of tying a knot was far from an easy problem to solve4 ,while it is true that the human body is a machine and every movement of which it is capable may be reproduced by mechanical means1 the difficulty is to copy many operations without involving such complexity of members as to make the mechanism wholly impracticable4 ,the human hand is really a very intricate piece of mechanism which by long generations of evolution and development has become wonderfully deft4 ,it exhibits this deftness and complexity of movement in tying knots and the very intricacy of this operation was enough to baffle the majority of inventors4 ,there was one inventor1 however1 who was not to be thwarted even by so formidable an obstacle as this4 ,in #ahfd ,jacob ,behel secured a patent on an attachment for binders which would actually tie a knot4 ,the mechanism passed the twine around the gavel of grain1 formed a loop in the two ends1 and tied a simple overhand knot in much the same way that the hand ties this knot4 ,ten years later ,marquis ,l4 ,gorham improved the mechanism and built a successful twine binder4 ,finally in #ahgi ,john ,f4 ,appleby perfected the binding mechanism1 completing the last stage in the development of the modern automatic self-binding reaper4 ,to keep pace with the reaper1 other agricultural machines had to be invented and developed4 ,the vast quantity of grain harvested could not be threshed by hand and the old-fashioned flail had to give way to the steam-driven threshing machine4 ,finally to meet the requirements of the vast western wheat fields1 the combined harvester and thresher was developed which1 with a crew of four men1 will reap1 thresh1 and bag between two and three thousand bushels per day4 ,according to statistics of the ,u4 ,s4 ,department of ,agriculture it took a man three hours and a half to produce a bushel of wheat in #ahcj as against ten minutes in #ahif4 ,surely the world owes a tremendous debt to ,hussey and particularly to ,mc,cormick for introducing machinery into agriculture and starting the train of inventions which in the space of two-thirds of a century have led up to the present remarkable era of machine farming4 ,there still remains one task of the farmer that has not yet been accomplished with unqualified success by machine4 ,the harvesting of the corn crop is a tedious and disagreeable task and one which the farmer would only too gladly turn over to the machine4 ,to be sure1 many corn-harvesting machines have been built and put into service with more or less success1 but none has reached the perfection of other classes of agricultural machinery4 ,the difficulty lies not in the machine1 but in the fact that corn is so easily beaten down by storms that at harvest time the machine seldom finds the stalks all standing up in nice straight rows4 ,machines must therefore be provided with means for lifting up the fallen stalks to vertical position4 ,the stalks are cut and bound into bundles and stood up in shocks4 ,even more difficult than cutting and binding is the task of husking the corn4 ,this work was always dreaded by farm hands1 but now machines are provided to husk the ears and shred the stalks for fodder4 ,thus the farm is being relieved of its drudgery4 ,unfortunately it is only the large western farms that can afford to avail themselves of the latest agricultural machinery4 ,on small eastern farms it does not pay to purchase a machine which can be used for only a few weeks in the year and then must be stored away until the next season1 but small farmers are now cooperating and clubbing together to buy the less frequently used machines and so even the small farm is being relieved of its drudgery1 and the arduous burdens which have always had a tendency to drive young men away from the farm are now being assumed by the unfeeling machine4 ,,chapter ,,xvi ,,machining ,,the ,,earth ,,the ,,albanian people have a story that the ,creator recently visited the earth and was astonished to find how it had changed4 8,why1 this is not the earth ,i created10 ,he said4 8,everything has changed4 ,my forests are cut down2 ,my rivers have been diverted from their courses2 ,my hills have been blasted away1 and ,my mountains have been robbed of their minerals4 ,the whole face of the earth has been altered40 ,but in the course of ,his roamings1 the ,creator suddenly came upon the land of ,albania4 8,ah60 ,he exclaimed in delight4 8,here is a bit of earth untouched by man4 ,it is still just as ,i made it40 ,man's ambition to make over the face of the earth to his own liking dates far back of the present age of machinery4 ,however1 the work of the ancient engineer was accomplished only at the expense of decades and generations of hard manual labor4 ,to-day1 with powerful and gigantic machinery to do our bidding1 we do not hesitate to change the course of rivers1 to level off the hills1 to carve highways through the mountains and pierce them with tunnels1 to bore into their depths for treasure and drive deep holes into the bowels of the earth in quest of liquid fuel4 ,we are able to machine the earth in much the same way as a piece of metal is machined in the machine shop4 ,in fact1 the drill1 the circular saw1 the slotter1 and even the milling machine have their counterpart in the excavating machinery of to-day4 ,of course we cannot expect to find the counterpart of such machines as the lathe1 boring mill1 and planer1 in which the work revolves against the tool1 because this planet of ours is rather too big a piece of stock to be placed between lathe centers or to be bolted to a planer bed4 ,,mechanical ,,monsters ,the twentieth century finds this planet again stocked with monsters larger and more powerful than the gigantic saurians that dominated the earth in the ,jurassic and ,cretaceous epochs1 but our mighty fire-breathing1 steel-sinewed beasts are humbly subservient to the will of man4 ,the spectacle of a large steam shovel at work makes one feel at once very small and very big4 ,before the work of this monster the human shoveler shrinks to the proportions of a mere insect4 ,seven to eight cubic yards shoveled into a cart is considered a fair day's work for a laborer1 but a big steam shovel can easily gobble up as much material in two bites4 ,however1 when we contemplate that this mammoth machine is a human creation and an absolute slave to human command1 we are rather inclined to be puffed up with the greatness of man4 ,steam shovels are ideal machines for excavating railroad cuts and were primarily developed for just such work4 ,the general operation of the machine is very similar to that of hand shoveling4 ,the shovel proper consists of a big scoop or dipper and a dipper handle which correspond respectively to the blade and handle of a hand shovel4 ,like the shovel1 the dipper is supported at two points4 ,the dipper is suspended by a chain from the end of a boom while the handle of the dipper is also supported in the boom4 ,by loosening the hoisting chain the dipper is lowered to the ground1 and by moving the handle forward the toothed cutting edge is made to bite into the ground or sand bank4 ,the hoisting chain then hauls up the dipper1 making it scoop out the bank1 after which it is swung to one side over a car on an adjoining track4 ,the rear of the bucket is fitted with a door which is opened by a spring latch and the contents are emptied out4 ,some of the largest steam shovels for ordinary grading have dippers with a capacity of #e cubic yards4 ,they are not confined to railroad grading1 but are applicable to any excavation where a firm footing is provided for the heavy machine4 ,they are even used for excavating the cellars of large city buildings4 ,the machine must be supported on road wheels or on skids4 ,when used for excavating sewer trenches1 it is sometimes mounted on a platform spanning the trench4 ,however1 the steam shovel is rather limited in its reach4 ,the largest ordinary steam shovels have a clear lift of but sixteen feet and can make a cut only sixty feet wide at the top4 ,for more extensive excavating as well as for digging ditches and trenches the drag-line excavator has recently come in to use4 ,in these machines a scraper takes the place of the dipper4 ,this is suspended from the end of a long crane and it is dragged along the ground by a cable1 scooping up a load of earth4 ,in some cases the scoop or scraper is merely attached to a cable leading from the hoisting engine to an anchorage and back to the engine4 ,to adapt excavating machines for service in soft ground they are mounted on broad wheels or on track-laying tractor surfaces4 ,one peculiar form of walking traction used by a drag-line excavator was described in ,chapter ,,xiii4 ,,ditching ,,and ,,trenching ,,machines ,for digging narrow ditches and trenches1 particularly for sewers1 water mains1 gas-pipe lines1 etc41 a number of very interesting machines have been invented which are of two general types1 the endless chain and the wheel excavators4 ,the first type consists of a traction engine with a ladder at the rear that drops down into the trench4 ,about this ladder runs an endless chain which carries a series of scoops or buckets4 ,these are dragged up against the breast of the work and carry the excavated earth to the top of the ladder where it is dumped upon a transverse belt conveyor and carried to one side of the trench4 ,with the larger sizes of chain excavators1 trenches may be dug to a depth of twenty feet and the width of the trench may be from two to six feet wide4 ,the wheel type of trenching machine is similar in principle to the chain excavator4 ,instead of the chain of buckets1 it has a wheel fitted with buckets4 ,in one prominent type the wheel has no hub or spokes1 but consists of a rim that is supported on and is turned by four friction rollers mounted in a rigid frame4 ,this frame is mounted on a boom which can be raised or lowered as desired4 ,such machines can commonly dig to a depth of a dozen feet or so4 ,a ditch differs from a trench in the fact that its side walls are sloping instead of vertical4 ,a trench is usually a temporary excavation for the laying of pipes or conduits while the ditch is left open and serves for irrigation or drainage4 ,there are chain ditching machines in which the chain of buckets runs laterally across the course of the ditch1 dipping into the earth to form a ,v-shaped channel4 ,in connection with the draining of the ,everglades of ,florida1 a peculiar wheel type of ditcher was built4 ,the wheel is of gigantic proportions1 consisting of a series of radiating shovels or scoops shaped to conform to the outline of the ditch4 ,as the wheel revolves it scoops up the mud which slides down toward the hub of the wheel and is carried to one side by a traveling conveyor4 ,,floating ,,excavators ,the main difficulty in drainage work is to provide a good footing for the machine which must necessarily be very heavy4 ,broad caterpillar tread surfaces are about the only means of locomotion4 ,in very soft swampy regions dredges have to be used4 ,dredges are merely floating excavators4 ,in them the problem of support and locomotion disappear and there are no limitations of size and weight to be considered4 ,floating excavators are therefore much more powerful than excavators that run on land4 ,the ordinary dipper dredge is merely a floating steam shovel with a much longer dipper handle and much larger dipper4 ,when work on the slides of the ,panama ,canal had proceeded far enough to admit of using dredges in place of steam shovels material progress was made4 ,two enormous dipper dredges were built1 each provided with a dipper that had a capacity of fifteen cubic yards or about twenty tons at a single lift4 ,the dipper was big enough to hold thirty men4 ,the dipper handle was seventy-two feet long and it could reach down to a depth of fifty feet4 ,a smaller dipper of ten cubic yards capacity was also provided4 ,the power of these huge dredges was illustrated when one of them1 while using its ten-yard bucket1 picked up an enormous bowlder weighing forty tons4 ,it was much bigger than the dipper that had raised it and it was far too big to be placed on the mud scow that was receiving the spoil brought up by the dredge4 ,had it been rolled off on the scow it would have crashed right through the bottom of the boat and so the big rock had to be drilled and broken up on the dipper before it could be dumped into the scow4 ,for work on a soft bottom1 grab buckets are used in place of dippers4 ,these may be made of two scoops as in the clam-shell bucket or of four leaves as in the orange-peel bucket4 ,no rigid handle is provided for these scoops4 ,they are spread open as they are lowered into the water and on hauling in the hoisting cable1 the scoops or leaves come together biting into the bottom and lifting up a load of mud4 ,grab buckets are largely used for picking up coal1 ore1 gravel1 etc4 ,the equivalent of the chain trench-digging machine is found in the ladder dredge4 ,a ladder is hung over the stern of the dredge and carries a chain of buckets which dig into the bottom and bring up the mud or sand4 ,,gold ,,mining ,,with ,a ,,dredge ,it is a dredge of this type that is put to the peculiar task of gold mining4 ,the dredge eats its way into gold-bearing sands1 the material passing through a system of separators which extract the gold and then being discharged at the rear of the dredge4 ,the dredge floats in a pool of water that it carries with it1 for as it excavates ahead it builds up sand banks behind4 ,in this way it may travel far from the river from which it first started4 ,illustration3 ,,digging ,a ,,trench ,,with ,a ,,chain ,,type ,,machine ,illustration3 ,,multiple ,,plowing ,,on ,a ,,western ,,wheat ,,field--,,turning ,,fifty ,,furrows ,,at ,,once ,,suction ,,dredges ,suction dredges are particularly adapted for excavating sandy bottoms4 ,one type used for dredging channels consists of a large steam vessel with large bins into which the dredged material is pumped4 ,at each side of the boat there is a long pipe which may be let down into the water4 ,each pipe terminates in a drag or footpiece with grated opening which is designed to be dragged along the bottom as the vessel slowly steams ahead4 ,powerful pumps suck a stream of water up the pipes which carries with it a quantity of sand4 ,the sand and water flow into the bins1 the solid matter settling to the bottom while the liquid flows out over the top4 ,when the settlings have filled the tanks1 the drags are pulled up and the vessel steams out to sea4 ,here doors in the bottom of the bins are opened and the material drops through4 ,the idea of opening up the bottom of a boat to empty it seems rather startling until we consider that the bins are sealed off from the rest of the boat and do not contribute to its buoyancy4 ,the sand that is dumped out of them is much heavier than the water that takes its place when the bin doors are opened4 ,,canal ,,digging ,,under ,,water ,the ,ambrose channel in lower ,new ,york ,bay was dredged by means of suction dredges4 ,the channel is forty feet deep at low water and the bottom had to be excavated from ten to twenty-five feet to attain this depth4 ,about seventy million cubic yards of material had to be excavated or nearly a third as much as was excavated in the ,panama ,canal4 ,the ,ambrose channel is seven miles long while the ,panama ,canal is forty-five miles in length4 ,two of the larger dredges each had a capacity of forty-five hundred cubic yards in their bins or enough to load a train about a mile long1 composed of #age cars4 ,it took less than three hours to fill the bins4 ,the openings in the gratings of the drags measured about eight by nine inches and any stones or solid matter small enough to pass through them was easily sucked up into the bins4 ,when a pile of stones of larger diameter was encountered a deep hole was dredged around it and then by means of a water jet the stones were forced into the hole4 ,the material sucked up by a dredge is sometimes dumped into a scow alongside4 ,this makes the structure of the dredge less expensive1 but where work has to be conducted in bodies of water exposed to storms it is more expedient to let the dredge collect the material within its own hull4 ,,land ,,building ,,with ,,dredges ,the sand drawn up by a suction dredge is valuable material for land building4 ,in fact1 a suction dredge is often used for the double purpose of excavating and filling in low land4 ,sometimes its only purpose is to fill in tide flats to above tide level4 ,the material is discharged through a pipe line which may be over a mile in length4 ,this pipe line is supported on a string of wooden or steel pontoons4 ,the pipe sections are connected by means of heavy rubber sleeves so as to make the line flexible4 ,this permits the dredge to move about and also allows of moving the discharge end about to distribute the sand properly4 ,unfortunately all dredging does not consist of sand and mud4 ,sometimes snags and matted roots are encountered which give trouble4 ,for handling such material rotary cutters are used4 ,the bow of the dredge is fitted with a hinged ladder about sixty to seventy feet long in which the cutter is mounted4 ,the ladder also carries the suction pipe close to the cutter4 ,the ladder is lowered to the bottom and the revolving cutter chops up the roots into pieces which are drawn up into the suction pipe4 ,the size of the pieces that are sometimes sucked up is remarkable4 ,the greater part of the area of the ,new ,orleans ,inner ,harbor ,navigation ,canal was filled with stumps and matted cypress roots4 ,the cutters tore up and cut these roots and stumps and the pieces were transported through a pipe line about #fjj feet long4 ,stumps that were too large to be handled in this way were undercut and sunk below grade4 ,cutters are used also for loosening packed hard bottoms and some of them will dig into hard pan and even soft rock4 ,a pressure of #ajj to #aej pounds per square inch is maintained in a discharge pipe twenty to twenty-four inches in diameter1 which is enough to carry along heavy bowlders dug up by the cutter4 ,,the ,,deepest ,,mine ,,shaft ,so far we have dealt only with surface conditions1 but man has not been content to stay on the surface of this planet4 ,true1 we have scarcely begun to explore the crust of the earth4 ,the deepest mine in the world is the ,morro ,velho in the province of ,minas ,geraes1 ,brazil4 ,here the earth has been penetrated to a depth of #f1dbf feet in quest of gold4 ,this is a depth of less than a mile and a quarter and it shrinks into insignificance when we reflect that we must go more than #c1jjj times that distance to reach the center of the earth4 ,however1 we have made material progress in shaft-sinking in recent years1 and it is quite likely that the lure of scientific research may prove even more powerful than that of gold and that some day we shall be induced to dig many miles into the crust of the earth just to learn something more about this globe that whirls us through space4 ,we have not yet reached the point at which hand labor may be dispensed with in tunnel work1 but there are machines which will do what formerly could only be accomplished with the manually wielded pick and shovel4 ,we have already 7in ,chapter ,,vii7 described the pneumatic tunnel shield and explained how it is sometimes driven forward through soft silt by means of hydraulic jacks without any excavation of material4 ,this method of tunneling which is analogous to driving a punch through soft metal1 has a very limited field of application4 ,it is impossible to force the shield in this manner through sand or through any but very soft silt4 ,,tunneling ,,by ,,machine ,the city of ,cleveland takes its drinking water from ,lake ,erie4 ,in order to obtain water that is not contaminated by the refuse of the city1 tunnels are carried out under the bottom of the lake about two miles from the shore where they terminate in water intakes far enough below the surface to avoid floating impurities and far enough above the bottom to avoid impurities that have settled to the lake bed4 ,the material through which the tunnels pass is a stiff clay1 that cuts like cheese4 ,so uniform is this material that a special machine was built to bore the tunnel through it4 ,this machine is somewhat similar to a boring mill4 ,it has an arm that revolves against the face of the tunnel heading and carries a cutter that travels along the arm so that it cuts a continuous spiral ribbon of clay4 ,the clay ribbon passes back through the machine and is loaded into a train of dump cars4 ,for boring tunnels in hard rock many different machines have been invented1 but not one of them as yet has proved an unqualified success4 ,one very interesting machine1 which was tried on the ,new ,york subway excavation at #db;d ,street and ,lexington ,avenue1 consisted of a series of chipping hammers which1 by means of pneumatic mechanism1 were made to hammer and pulverize the face of the rock with repeated blows4 ,the hammers were arranged in a circle and were revolved as they hammered so that the whole surface of the heading was attacked and a circular tunnel was cut through the rock4 ,a serious disadvantage under which the machine labored was the fact that the rock had to be crushed to a powder or into small chips before it could be removed4 ,in ordinary rock excavation holes are bored into the heading and the rock is then blown out by means of dynamite or some other explosive4 ,large fragments of rock are then broken up into pieces small enough to be handled readily1 but no energy is wasted in reducing the material to a powder4 ,the percussion drills with which the rock is bored have already been briefly described4 ,when boring holes for a blast in soft material1 such as bituminous coal1 a drill is used which resembles in many respects an ordinary twisted auger bit except that it is many feet in length4 ,it is driven by hand into the coal by the use of a common bit brace4 ,percussion drills or punches are also used4 ,these are driven either by pneumatic or electric power4 ,,coal-,,cutting ,,machinery ,when excavating coal the heading is first undercut1 that is1 a deep slot is cut in the wall of coal along the floor line4 ,then blast holes are bored into the coal above this cut so that when the charges are fired the coal will be broken downward4 ,to undercut the coal special machines are used1 driven by compressed air or electricity4 ,these have endless chains fitted with chisel or pick points that bite into and cut the coal4 ,after the material has been shattered and reduced to fragments of convenient size special machinery may be employed to shovel it away from the heading and into dump cars4 ,one electrically driven shoveling machine which was tried out on some of the ,catskill aqueduct excavation had a broad open shovel which could be driven into the pile of rock fragments under the control of an operator and would scoop up the material1 delivering it upon a traveling belt conveyor which carried it on to the train cars4 ,many types of mechanical shoveling and loading machines have been built for use in mines4 ,they are driven either by pneumatic or electric power4 ,,exploring ,,subsurface ,,conditions ,in all engineering work it is highly important to explore subsurface conditions before starting any construction or even drawing up plans4 ,the ordinary pneumatic percussion drill will not serve for deep holes4 ,instead a rotary boring motion is requisite4 ,the tool is mounted with black diamond cutters which cut through the hardest rock4 ,water is introduced into the hole to lubricate the tool and also to wash out the abraded material4 ,by trapping this material the character of the rock penetrated may be determined4 ,the material1 however1 is pulverized and does not furnish1 as a general rule1 a fair sample of the rock4 ,when it is highly important to determine the exact nature of the rock or other material a core drill is used4 ,in other words the drill is a hollow tube set with cutting crystals about its periphery4 ,as the tool is revolved it cuts an annular slot in the rock leaving a central core standing4 ,this core is broken off and drawn to the surface and furnishes a true sample of the material encountered by the drill4 ,there is an interesting type of core drill in which steel shot is used in place of diamonds4 ,the cutting end of the drill is a collar with a notched edge4 ,steel balls are fed into the drill and under the cutting head4 ,the balls are caught in the notches and rolled around against the rock surface4 ,there is also a partial dragging action4 ,the friction is sufficient to wear away the rock4 ,as the balls wear away they are replaced with new ones4 ,very evidently such drilling costs less for upkeep than diamond drilling1 but it is not as rapid as the latter4 ,,locating ,,rock ,,under ,,hudson ,,river ,a notable illustration of exploration drilling was furnished by the surveys for the ,hudson crossing of the ,catskill ,aqueduct4 ,to bring water from the ,catskill ,mountains to ,new ,york ,city it was necessary to cross the ,hudson ,river4 ,in order to furnish a permanent conduit it was decided to carry the water in an inverted siphon bored through solid rock4 ,it was necessary to obtain a profile of the rock at the point where a crossing seemed most feasible4 ,borings were therefore made from a barge anchored in the river1 but it was impossible with such an unsteady working base to carry on the boring to any considerable depth4 ,tides1 the wash of passing steamers1 floating ice1 all combined to obstruct the work4 ,drills were constantly broken4 ,finally it was decided to do the boring from opposite banks of the river at such an angle that bore holes would meet or pass each other under the middle of the river4 ,the exploration boring from the barges indicated that solid rock lay at a considerable depth below the river bed and that the bore holes would have to be set at a sharp angle to keep from breaking through rock4 ,the river at that point is about #c1jjj feet wide and a boring from the surface at the middle of the river had been driven to a depth of #gfh feet without striking solid rock4 ,two shafts were sunk to a depth of about #bej feet and from these diamond drill borings were started at such an angle that they would cross at a depth of #a1ejj feet4 ,excellent rock was encountered throughout the boring4 ,then a second set of borings was made which crossed at a depth of #iej feet without encountering any appreciable amount of water4 ,it was accordingly decided to carry the aqueduct in vertical shafts1 one at each side of the river1 at a depth of #a1ajj feet below water level1 and then connect these shafts with a horizontal tunnel4 ,it was important to have a good solid rock cover over the tunnel because the aqueduct reaches the river with a head of #djj feet which added to the #a1ajj feet of depth of the inverted siphon gave a total head of #a1ejj feet or a hydraulic pressure of about forty-two tons per square inch4 ,although the diamond drill borings just mentioned were remarkable because of their inclination and because of the cramped quarters from which they were driven1 they do not begin to compare in depth with some of the borings made in search of water and of oil4 ,the deepest boring in the world to date is near ,fairmount1 ,west ,virginia1 where a hole six inches in diameter was driven to a depth of #g1egi feet or nearly a mile and a half4 ,at that point an earth slide stopped further borings4 ,,boring ,,for ,,oil ,the time-honored method of boring for oil known as the percussive system is to hammer through the earth and rock with a heavy steel drill4 ,the drill really consists of a long string of parts measuring altogether as much as sixty feet in length4 7,see ,figure #fd47 ,the drill proper or bit has a cutting edge adapted for the character of the material it is to penetrate4 ,the bit is attached to a steel bar known as the 8auger stem0 which may be from twelve to forty-five feet in length4 ,then come the 8jars0 or a link member which allows a play of about sixteen inches4 ,the purpose of this is to assist in freeing the bit from the material it is penetrating by jarring it upward on the upstroke of the drill4 ,above the jars there is another bar known as the sinker1 and this is provided with a rope socket to which is attached the cable that carries the string of drill parts4 ,the cable passes over a pulley to a walking beam which gives the necessary up-and-down motion4 ,illustration3 ,,fig4 #fd4--;,a ,,string ,,of ,,well-,,drilling ,,tools ,the loose material in the bore is removed by a sand pump4 ,to protect the bore from caving a casing of steel pipe must be lowered into the well4 ,the boring may proceed at the rate of ten to sixty feet per day1 depending upon the material penetrated and the depth of the well4 ,all sorts of difficulties are liable to interrupt the work4 ,the cable may break1 the string of tools may become unscrewed1 or the casing may drop into the hole1 and then follows the tedious process of fishing for the lost parts and hauling them up out of the well4 ,as the drilling proceeds1 the bore becomes progressively smaller and casings of smaller diameter must be used4 ,the well is completed by lowering a pipe within the casing through which the oil flows to the surface and is carried to the storage tanks and thence by pipe lines to the refineries4 ,while the percussive system of drilling is very generally used throughout the ,american oil fields1 rotary methods of drilling are largely employed in ,california4 ,,chapter ,,xvii ,,from ,,fiber ,,to ,,fabric ,,it ,,is ,,not very long since the spinning wheel and the clacking loom were an indispensable furnishing of every farmhouse and of many city dwellings as well4 ,with infinite patience the fleece of sheep1 the lint of flax1 the filaments of silk and the fibers of cotton were spun into yarn and then woven into cloth1 and it was the nimble fingers of the housewife that carried the process through from the matted raw product to the finished garment4 ,it is comparatively easy to comprehend the development of machines for dealing with such gross material as earth1 rock1 iron1 and wood1 but when we come to consider the infinitely delicate and almost imponderable fibers that go to make up our textiles1 the marvel is that any but highly skilled human hands1 guided by keen eyesight1 could combine the tangled and obstreperous filaments into fine yarn and weave this yarn into complicated patterns of cloth4 ,but the spinning wheel and hand loom could not stand long in the path of power-driven machinery1 and now huge1 blind machines1 with stiff1 unbending fingers of metal1 comb out the matted masses of raw material1 remove the dirt and twigs1 straighten out the snarls far quicker and better than could be done by hand1 and transform the fibers into beautiful fabrics such as in former days would have been the envy of kings4 ,we cannot attempt to describe all the machinery involved in the spinning and weaving of yarn1 but it is highly important that every well-informed person have a general knowledge of textile machinery4 ,because cotton cloth is more widely used than either linen or wool1 we shall confine ourselves to the cotton branch of the textile industry1 particularly as the difference between the treatment of cotton and other textile materials lies chiefly in the preparation of the thread or yarn4 ,the predominance of cotton among textiles may be traced back to the invention of a young ,new ,englander fresh from college1 who went to ,georgia as a private tutor1 only to find when he got there that some one else had been engaged in his stead1 leaving him stranded and practically penniless in a strange land4 ,we had occasion to refer to this man in ,chapter ,,iii4 ,eli ,whitney was a born mechanic1 and before entering college had not only shown great skill but had actually built up a thriving business in the manufacture of nails1 hatpins and knife blades4 ,,invention ,,of ,,the ,,cotton ,,gin ,the agricultural condition of ,georgia and its neighboring ,states at the time that ,whitney arrived there was very poor4 ,there was no market for their products4 ,a splendid cotton1 with fibers from #a to #b inches long1 was growing on the islands along the coast1 but this cotton could not be raised inland4 ,the upland product1 known as 8green seed0 cotton1 had a fiber only half as long as the 8,sea ,island0 cotton1 but the principal drawback to its use was the difficulty of separating the fiber from the seed4 ,it was a day's work for one woman to separate a single pound of the 8green seed0 cotton fiber4 ,his attention having been brought to this matter1 ,whitney undertook to design a machine which would remove the fiber from the seed in a small fraction of the time required by hand labor4 ,he was visiting at the time at the plantation of ,mrs4 ,greene1 widow of ,general ,nathaniel ,greene1 of ,revolutionary fame1 and he set himself to the task with such limited materials and tools as he could find on the estate4 ,in a couple of weeks he had built a model which contained all the essentials of the modern cotton gin1 with which a single man could separate more cotton in a day than could be produced by hand in a whole season4 ,this was in the winter of #agib4 ,the effect of the invention was felt immediately4 ,cotton production had been falling off steadily4 ,in #agia1 #ahi1caf pounds of cotton had been exported4 ,the next year there was a falling off to #ach1cbh pounds1 but following the introduction of the cotton gin exports rose to #dhg1jjj pounds in #agic1 #a1fha1jjj in #agid1 and #f1bgf1jjj in #agie4 ,fifty years later the world production amounted to #a1afi1fjj1jjj1 nearly seven-eighths of which was contributed by the ,united ,states1 and of this only a small amount was ,sea ,island cotton4 ,a cotton gin 7,fig4 #fe7 consists of a gang of circular saws 7,a71 with forwardly pointed teeth which pass between the ribs of an inclined grating 7,b7 that forms the floor of a chamber 7,c7 known as a roll box4 ,in this box is mounted a toothed roller 7,d74 ,the cotton is fed into the box and the fibers are seized by the teeth of the saws and dragged through the grating while the seeds1 being too large to pass through1 are left behind and1 rolling down the grating1 drop into a hopper4 ,the action of the saws is such as to impart a rolling motion to the mass of cotton1 and hence to the roller in the roll box4 ,this tends to drag the cotton into the roll box and bring fresh supplies to the saws4 ,the fleece carried by the saw teeth is beaten off by a wheel 7,e7 fitted with wire brushes4 ,these brushes1 traveling in the same direction as the saw teeth1 but at a higher velocity1 readily disengage the fibers from the teeth and create an air blast that blows the cotton fleece out of the gin4 ,illustration3 ,,fig4 #fe--,,sectional ,,view ,,of ,a ,,cotton ,,gin ,,preparing ,,cotton ,,for ,,the ,,spinning ,,mule ,cotton as it comes from the bale is a compact1 matted mass1 mixed with bits of seed1 leaves1 sand1 and other impurities1 and it must pass through a number of machines before it comes out as a pure1 light1 fleecy product1 with the fibers combed parallel4 ,even for a medium yarn a dozen machines are required to prepare the cotton for the spinning mule4 ,a system of 8counts0 is used to indicate the size of yarn and it is based on the number of hanks it takes to make a pound4 ,a hank is always #hdj yards and #ej's would mean that the yarn is of such fineness that it would take #ej #hdj yards 7#d1bjj yards7 of it to weigh a pound4 ,yarn below #cj's is graded as coarse2 between #cj's and #fj's as medium and above #fj's as fine4 ,to prepare cotton as it comes from the bale for a fine yarn of1 say1 #ajj's1 it must go through no less than sixteen machines before it reaches the mule4 ,we have not the space to describe all of these machines1 but in general it will suffice to say that the cotton is graded by passing it through a series of pickers4 ,these machines throw out the fibers and beat them so as to knock out the impurities and1 at the same time1 a blast of air blows out the dust4 ,the cotton is treated by a number of such machines in succession and is finally delivered in a broad sheet known as a 8lap10 after which it passes through the carding machine which combs out the tangled bunches and removes further impurities from the lap4 ,the lap is then gathered into a compact rope known as a 8sliver40 ,the sliver goes through the drawing rolls which serve to parallelize the fibers and make the sliver of even thickness1 and at the same time to give a moderate amount of twist so that it will hold together1 and it issues from the machine as 8roving40 ,in the case of fine yarn the sliver issuing from the carding machine goes through a combing machine so as to remove the finer fibers4 ,the bobbins of the roving are then placed in the spinning machine1 which may be either the spinning mule or the ring spinning machine4 ,the principal difference between the two is that the spinning mule is intermittent in its operation1 while the ring spinner not only spins the roving into yarn but at the same time winds it up on a bobbin4 ,illustration3 ,,fig4 #ff4--;,,arkwright',s ,,drawing ,,rolls ,,arkwright',s ,,drawing ,,rolls ,the first advance over the old-fashioned spinning wheel1 which dates back to the fifteenth century1 was in #aggj1 when the first spinning jenny was invented by ,hargreaves4 ,this consisted practically of a multiple spinning wheel by which one man could spin a large numbers of bobbins of yarn at the same time4 ,it was at about the same time that ,arkwright invented the drawing rolls which have played a most important part in the preparation of yarn1 and this invention is worthy of our attention because it contains an interesting mechanical principle4 ,as shown in ,figure #ff1 a number of pairs of rolls are provided through which the roving passes1 but successive pairs operate at higher velocities4 ,thus1 the second pair of rollers through which the roving passes run at a little higher speed than the first pair1 the third a little higher than the second pair1 and so on4 ,as a result1 the roving is drawn out by the operation and issues from the last pair of rollers at a higher speed than it entered the first pair of rollers4 ,the only way in which it can accommodate itself to this accelerated motion is to be attenuated or drawn out4 ,weights are used1 as shown in the drawing1 to press the upper rollers against the lower ones4 ,,the ,,spinning ,,mule ,shortly after ,arkwright's invention came the mule spinner1 invented by ,crompton between #aggd and #aggi4 ,machines operated on the same general principle as this are in general use to-day4 ,in the old-fashioned method of spinning by hand the worker took a small quantity of cotton1 pulled it out into a long sliver1 attached one end to a bobbin and gave the bobbin a twirl between his hands in order to spin the fiber into yarn2 then the yarn was wound up on the bobbin and the process was repeated4 ,the spinning mule does practically the same thing1 but infinitely faster and on a much larger scale4 ,as shown in ,figure #fg1 the bobbins of roving 7,a7 are mounted on a stand and passed through a set of drawing rolls 7,b7 which are regulated to pull the rovings out to the desired thickness of yarn4 ,the roving then passes to the nose of a 8cop10 or spindle 7,c71 which is revolved at very high speed4 ,the cop is carried by a carriage 7,d7 which moves away from the bobbins of roving to the position indicated by dotted lines1 while the cop is revolving4 ,the cop has a travel of about five feet during the time the yarn is drawn out and spun4 ,then the carriage moves back toward the stand upon which the bobbins of roving are mounted and the spun yarn is wound up on the cop4 ,the reason the yarn does not wind up on the cop while it is spinning is because it runs to the nose of the cop and1 at each turn of the cop1 the coil twists on the nose and slips off4 ,on the return of the carriage1 however1 a set of wires 7,e71 called 8fallers10 press the yarn down so that the revolving cop will wind up the slack4 ,illustration3 ,,fig4 #fg4--;,,details ,,of ,a ,,spinning ,,mule ,the continuously operating ring-spinning machine is provided with a ring frame 7,figure #fh7 around the cop or spindle4 ,this frame1 together with the spindle1 revolves at high speed1 but as the ring revolves a little more slowly than the spindle it winds the yarn comparatively slowly upon the spindle or bobbin4 ,,woven1 ,,braided1 ,,knitted1 ,,and ,,net ,,goods ,having now produced our yarn1 we may pause to consider the different types of fabric into which it may be formed1 and to draw a distinction between1 woven1 braided1 knitted1 and net goods4 ,in weaving we have two sets of threads1 one set running transversely to the other2 in braided materials the threads all run longitudinally and are arranged to cross each other diagonally1 so that they are interwoven2 in knitting and netting there is a single thread4 ,in the case of netting this thread is knotted where it loops back upon itself1 whereas in knitting it is merely looped without knotting4 ,,the ,,loom ,the loom can trace its genealogy away back to early ,babylonian times1 and the modern power-driven machine does not differ in its broad principles of operation from its ancient progenitor--the hand loom4 ,illustration3 ,,fig4 #fh4--,,ring-,,spinning ,,frame ,illustration3 ,,fig4 #fi4--,,the ,,heddles ,,of ,a ,,loom ,every industry has a vocabulary of its own to furnish names for its machine parts and products peculiar unto itself1 and in this respect the textile industry is by no means an exception4 ,the threads that run lengthwise in a piece of woven cloth are known as the 8weft10 8woof0 or 8filling40 ,in the loom the warp threads are threaded through loops on what are known as 8heddles02 in fact1 there are two 8heddles10 ,a and ,b1 ,figure #fi4 ,alternate warp threads 7,c7 pass through the loops of one heddle1 and the other threads through the loops on the other heddle4 ,when one heddle is raised and the other lowered1 the threads form a wedge-shaped space 7,d7 which is known as a 8shed40 ,the filling thread is sent through the shed and is then pressed closely into the wedge-shaped space against the cloth already woven by means of a 8reed0 7,e7 which is a comblike member with teeth or flat pieces of metal that pass between the warp threads4 ,this done1 the position of the heddles is reversed1 so that ,a is now lowered and ,b raised1 thus binding the warp thread in place and forming another shed for the next warp thread2 and thus the process continues4 ,the filling thread is placed in a shuttle 7,f7 which carries a bobbin on which the thread is wound4 ,as the shuttle is thrown back and forth through the shed1 the thread is unwound and trails behind it4 ,formerly the shuttle was thrown back and forth by hand1 but years ago1 long before the invention of the steam engine1 the flying shuttle was invented4 ,in other words1 a mechanism was provided for striking the shuttle a blow and throwing it across the warp from side to side4 ,by this means the speed of operations was greatly increased4 ,about the middle of the eighteenth century the drop box was invented4 ,this consists of a receptacle for shuttles carrying different colors of thread which may be selected in a definite order and thrown back and forth so as to vary the pattern of the cloth4 ,in present looms a special machine is provided for taking the threads from the bobbins or cops and laying them in an even sheet to form the warp of the loom4 ,these are wound on a beam and the machine is known as a beam warper4 ,as the threads are apt to be somewhat fuzzy it is necessary to size them1 and a machine known as a slasher is employed for this purpose4 ,this machine coats each thread of warp yarn with a sizing compound or an adhesive and dries the sheet of warp preparatory to its use in the loom4 ,in common weaving the weft or filling threads run alternately under and over the warp threads with perfect regularity4 ,a pattern can be formed by passing the weft threads under and over alternate groups of warp threads1 and this is effected in the ordinary loom by threading the weft in groups through the heddles1 i4 e41 instead of having every second thread pass through one heddle and the intervening threads through the other heddle2 the threads are arranged in alternate groups of two or more4 ,this gives a regular pattern1 but it may be varied to form ornamental designs if the groups are varied4 ,such designs used to be worked out by hand very slowly and laboriously1 with the result that figured weaving was very expensive4 ,,the ,,jacquard ,,loom ,at the ,french ,exposition of #ahja a loom was exhibited that made a sensation4 ,with seemingly human intelligence it selected individual warp threads or groups of threads and raised them or lowered them so as to work out elaborate ornamental designs4 ,the inventor1 ,joseph ,marie ,jacquard1 of ,lyons1 received a medal for his marvelous invention and was decorated with the ,cross of the ,legion of ,honor4 ,the 8brains0 of the ,jacquard loom is a set of pasteboard cards that are perforated in accordance with a prearranged design4 ,the warp threads1 instead of being passed through the loops of two heddles1 are passed through what might be termed individual heddles1 one for each thread1 or for a small group of threads4 ,these consist of cords in each of which is an eyelet through which the warp thread passes4 ,the cord is weighted at its lower end and its upper end is fastened to a hook in a box at the top of the machine4 ,the hooks engage transverse bars known as 8griffes0 or 8knives10 and when the griffes are raised1 the hooks engaging them are also raised4 ,in this way the warp threads that pass through the eyelets that are connected to the hooks are raised4 ,but running horizontally across the hooks there are 8needles0 or rods with eyelets or bends in them through which the hooks pass4 ,these needles may be moved lengthwise to make the hoops engage or disengage the knives4 ,the mechanism is illustrated in ,figure #gj1 where the knives are shown in section at ,a1 the hooks at ,b and the needles at ,c4 ,for the sake of simplicity only eight hooks and needles are shown2 in actual practice there are hundreds in a single machine4 ,at the right-hand end of each needle there is a spring which pushes the needle toward the left1 thereby bringing the hook through which it passes into position to be lifted by its griffe4 ,at the left-hand side of the machine there is a card 7,d7 which presses back the needles and thereby bends the hooks out of position to engage the griffes4 ,however1 there are perforations in the card through which certain of the needles can pass1 letting the hooks they control engage the needles4 ,the cards thus select the particular weft threads that are to be raised4 ,in our illustration most of the needles have entered holes in the card1 but the second1 fourth and sixth from the top have been pushed back by the blank wall of the card and their hooks have been bent back clear of the griffes4 ,only four cards are shown in the drawing arranged in a four-sided box or 8cylinder10 and the cards are successively presented to the needles4 ,for more elaborate designs a large number of cards are used1 arranged in a slatted belt1 and these come successively into position4 ,as many as thirty thousand cards have been employed to carry out a single pattern4 ,illustration3 ,,fig4 #gj4--;,,detail ,,of ,a ,,jacquard ,,loom ,,invention ,,of ,,the ,,knitting ,,machine ,we are wont to call ,necessity the ,mother of ,invention2 in many cases ,laziness has given rise to valuable inventions1 but according to legend1 ,cupid played the leading rle in the development of the knitting machine4 ,it is said that in #aehi ,william ,lee of ,england fell in love1 but the girl who was the object of his devotion was always so busy with her knitting that she could not give him the attention he sought or thought he deserved4 ,however1 ,lee was not to be thwarted in this fashion1 so he built a machine to do the knitting in order that the girl could devote herself more completely to him4 ,there is another less pleasant version of the story to the effect that ,lee became so attached to his knitting machine that he neglected the girl4 ,however1 in either case1 love was somehow mixed up in the invention of the knitting machine4 ,we are not going to attempt to delve into the complicated mechanism of a modern knitting machine1 but will merely call attention to the fact that modern machines perform automatically practically all the movements of the human hand in hand knitting4 ,the tendency of modern machinery has been to relieve the housewife of the tedious work she formerly performed and to take such work away from the home to the factory4 ,there is one important machine1 however1 which has been introduced into the home1 apparently to stay2 for in the majority of houses it is still considered indispensable4 ,it is a fact that the introduction of labor-saving machinery into the household has1 until recently1 met with stern opposition on the part of the housewife4 ,it is all the more remarkable1 therefore1 that in the middle of the nineteenth century the sewing machine began successfully to invade the home4 ,,howe',s ,,invention ,,of ,,the ,,sewing ,,machine ,it was in #ahdd that ,elias ,howe hit upon the brilliant idea of putting an eye at the point of a needle4 ,this enabled him to produce a successful sewing machine1 because it was unnecessary for him to pass the needle completely through the cloth in order to pull the thread through it4 ,when the needle point penetrated the cloth a shuttle passed through the loop of thread that was carried through with the point4 ,this shuttle carried a second thread which interlocked with the thread of the needle forming what is known as a 8lock stitch40 ,in ,howe's machine the cloth was held vertically and the needle which was curved was carried by a lever4 ,the needle was driven through the cloth with a swinging motion1 somewhat like that of a pick-ax4 ,the shuttle was driven back and forth by a pair of strikers after the manner of the flying shuttle of a loom4 ,george ,fisher1 a friend of ,howe1 furnished #ejj with which the first successful machine was built in #ahde1 and with this machine ,howe sewed two suits of clothes1 one for ,mr4 ,fisher and the other for himself4 ,a public exhibition was held at which the machine1 crude as it was1 beat five of the best hand-sewers that could be found4 ,in #ahfc ,howe was reaping a fortune in royalties from his machine which were estimated at #d1jjj per day4 ,the next notable improvement in sewing machinery was that of the rotary bobbin1 invented by ,a4 ,b4 ,wilson1 which was patented in #aheb4 ,this did away with the flying shuttle and simplified the machine considerably4 ,it made the sewing machine comparatively quiet1 thus adapting it for domestic use4 ,in ,wilson's machine1 a rotating hook passed through the loop of thread and carried it around the bobbin on which the lower thread was wound4 ,wilson also invented the four-motion feed for feeding the cloth under the needle4 ,sewing machines up to that time had been operated by hand1 but ,isaac ,merritt ,singer introduced a foot-power machine and by progressive business methods built up a thriving industry and did much to establish the sewing machine1 not only at home1 but abroad as well4 ,,the ,,single-,,thread ,,sewing ,,machine ,the single-thread machine was invented by a ,virginia farmer who had never seen a sewing machine4 ,james ,e4 ,a4 ,gibbs had seen a picture of a sewing machine and1 unaware of the fact that there was a shuttle carrying a second thread on the rear1 or under side of the cloth1 fell to puzzling over the problem of what happened to the thread carried by the needle through the cloth4 ,somehow1 it seemed to him1 the loop of thread must be held until the next stitch carried another loop of thread through it1 thus forming a chain stitch4 ,this led him to invent an ingenious revolving hook4 ,with infinite patience he whittled out a model of his invention1 and it is this hook that is the outstanding feature of the ,wilcox and ,gibbs machine4 ,,machine-,,made ,,embroideries ,a notable modern development of the sewing machine is its adaptation to the making of embroideries and even laces4 ,in the common domestic sewing machine the cloth is fed step by step under the needle1 and the length of the step regulates the size or length of the stitches4 ,the feed may be set for short or long stitches4 ,it is evident that if a greater range of length of stitch were provided1 and if1 while the machine was operating1 the stitch could be varied at will1 not only in length but in the direction as well1 it would be possible to work out elaborate patterns of embroidery4 ,this is what is done on the power-driven embroidery machines4 ,like the original ,howe machine1 the cloth is held vertically and a series of needles are used which pass horizontally through the cloth4 ,as the needle retreats1 the thread it carries forms a loop on the rear or 8wrong0 side of the cloth1 and through this a shuttle is driven which carries a thread wound upon a bobbin4 ,between stitches the cloth is moved this way and that1 in accordance with a prearranged pattern1 and thus the design is embroidered4 ,a single machine may have several hundred needles and1 as they all work in unison1 each needle repeats the design4 ,the arrangement is such that one needle starts where the next one leaves off1 so that the embroidery is continuous4 ,the shuttles which operate on the wrong side of the cloth are small1 boat-shaped parts which the ,swiss have named 8schiffli0 or 8little ships10 and this name has come to be applied to the whole machine4 ,the guiding of the cloth to produce the required design is accomplished either by hand or automatically4 ,in the hand-guided schiffli machine a skilled 8stitcher0 seated at one side of the machine operates a pantagraph1 tracing an enlarged design mounted on a board before him4 ,as he moves the lever vertically and horizontally the frame carrying the cloth is correspondingly moved before the needles4 ,an expert stitcher can put a great deal of individuality into the work1 which is impossible in the strictly automatic machine2 accordingly the pantagraph is used for the finer grades of embroideries4 ,in the automatic machines a perforated roll like that of a piano player is used4 ,the perforations control the movements of the frame that carries the fabric4 ,,fine ,,needlework ,,by ,,machine ,these machines are of ,swiss and ,german design1 but ,american inventors have recently developed a machine for producing fine needlework which imitates very closely the work of the hand4 ,in this machine the needle passes completely through the fabric as in ordinary hand sewing1 but it does not have to be turned around for the return stitch because it is pointed at each end and has the eye in the middle4 ,the needles are held by spring clips in a swinging frame4 ,when the frame swings toward the cloth the needles are pushed through the fabric and their points are caught by spring clips in a frame on the opposite side4 ,the latter frame draws the needles completely through and a set of hooks catch the thread and pull the stitch taut4 ,the advantage of this type of machine is that it produces the same design on each side of the cloth2 in other words1 there is no 8wrong0 side to the embroidery4 ,the design is controlled by a 8stitcher0 operating a pantagraphic system of levers and by skillful manipulation he can completely overcome the flat machinelike appearance of the automatic schiffli machine4 ,laces are very ingeniously produced on schiffli machines by using the 8burnt-out0 system invented forty years ago by a ,german1 named ,beckel4 ,this consists in the use of thread of a different material from that of the fabric1 and after the embroidery is completed the fabric is removed either chemically or by the application of heat1 leaving only the stitching1 which forms a delicate lace4 ,for instance1 cotton thread may be embroidered on a groundwork of wool1 or silk thread is used on a fabric of cotton4 ,laces made in this way are known as ,plauen laces1 taking their name from the city where ,beckel invented the process1 and they form a large part of the machine-made laces that are now so widely used4 ,illustration3 ,,sawing ,,logs ,,into #af-;,,inch ,,lengths ,,prior ,,to ,,grinding ,,them ,,into ,,pulp ,illustration3 ,copyright ,kadel ,herbert ,,the ,,heater ,,in ,a ,,pulp ,,mill ,,where ,,the ,,wood ,,pulp ,,is ,,mixed ,,with ,,clay ,illustration3 ,a ,,modern ,,fourdrinier ,,paper-,,making ,,machine ,,chapter ,,xviii ,,the ,,making ,,of ,,paper ,,the ,,making of paper is closely related to that of textiles4 ,in each case the same basic materials are used4 ,a mass of interlacing fibers is formed into a continuous sheet1 but the method of interlacing the fibers and holding them together is entirely different4 ,paper resembles felt more closely than any other form of fabric4 ,the fibers are not woven but are matted together and compressed4 ,in the case of felt the fibers of wool or hair are held together mainly by the microscopic barbs that they possess while paper fibers are held together by means of sizing4 ,although paper gets its name from papyrus the latter was not paper1 for it was a felt of pith rather than fiber4 ,the ancients produced a very fair writing material from the rushlike plants that grew in the swamps along the ,nile4 ,the stem of the papyrus was stripped of its bark and the pith was cut into thin ribbons which were laid side by side to form a sheet4 ,over these and at right angles to them was laid another layer of pith ribbons4 ,the material was then soaked in water1 pressed into a continuous sheet and dried4 ,these sheets were then pasted together and rolled up into scrolls4 ,unquestionably they played a most important part in the civilization of ancient ,egypt1 providing1 as they did1 a ready means of recording knowledge and disseminating it among the people4 ,,chinese ,,invention ,,of ,,paper ,like so many inventions that are of vital importance to modern civilization1 paper is a ,chinese invention4 ,the ,chinese made paper from the fibers of trees1 a material to which we have reverted in recent years4 ,the invention dates from about #aej ,a4 ,d41 when some one devised a process of reducing the bark of the mulberry tree to a pulp1 beating it and boiling it in lye and then matting the fibers on a screen and pressing them into a finished sheet4 ,the process was introduced into ,europe by the crusaders in the #abth ,century4 ,in #aaej a paper-making plant was established in ,italy and soon the new writing material was being made in increasing quantities and became a common article throughout ,europe4 ,it was not until the end of the #ahth ,century that machinery for making paper came into use4 ,in the old hand process which is still used to a very limited extent for special papers1 the pulp1 after being reduced to a thin milky fluid1 was dipped out of a vat with a rectangular sieve which had a wire screen bottom of fine mesh4 ,the water drained off1 leaving the fibers upon the screen4 ,as the pulp was draining the sieve was shaken about to distribute the fibers evenly and interlace them as much as possible4 ,the depth of the sieve determined the amount of pulp that was dipped out and hence the thickness of the paper4 ,the soft1 matted mass of fibers was turned out upon a felt mat and left to dry4 ,soon other fibers came to be used and the finest grades of paper were made from linen and cotton rags4 ,the rags were carefully sorted out and washed after which they were stored in a damp place to rot for a number of weeks4 ,then they were cut and shredded and boiled until they were converted into a pulp4 ,the complete process of making fine paper by hand took from two to three months4 ,paper was made in small sheets limited by the size of sieve that could readily be operated by hand4 ,the first man to make a continuous web of paper was ,nicholas ,louis ,robert1 a ,frenchman who received a reward of #h1jjj francs from his government for his invention4 ,robert's patent rights were acquired by the ,fourdrinier ,brothers 7,henry and ,sealy71 of ,england4 ,they developed and perfected the machine and to them is ascribed the honor of founding the modern paper industry4 ,,uses ,,of ,,paper ,paper is more commonly and extensively used to-day than any other product of manufacture and is employed for an astonishing variety of purposes1 ranging from milk bottles to suits of clothing4 ,one very novel use we might mention1 in passing1 is to be found on the sugar plantations of ,hawaii4 ,after the cane is planted the fields are covered with a thick paper made1 by the way1 from sugar-cane fiber4 ,this covering prevents the weeds from growing1 but the sharp spikes of the sugar sprouts pierce the paper and grow through it4 ,by the time the paper has disintegrated and the weeds have a chance to grow1 the cane has such a start on them that they are kept shaded and cannot compete with or choke out the cane4 ,,turning ,,forests ,,into ,,pulp ,before we proceed to describe the modern ,fourdrinier machine1 we must look into present day methods of preparing pulp4 ,the finest papers are still made from linen and cotton rags4 ,esparto grass is largely used in ,europe4 ,this comes from ,spain and ,north ,africa4 ,but by far the greater part of the paper produced to-day is made from the fiber of trees4 ,particularly is this true of our own country1 which consumes half of the world's output of paper4 ,it used to be that only the poorest grades of paper were made from wood pulp2 now however not only newspapers but nearly all books and magazines are printed on a forest product4 ,formerly only spruce wood was considered suitable for paper manufacture1 but the rapid depletion of this raw material led to the employment of many other species of trees and our ,government scientists are constantly searching for and experimenting with new woods for this purpose4 ,because of the insatiable appetites of our large newspaper printing presses and because a newspaper is not intended to be an imperishable document but a fleeting record of passing events1 quality is of little importance in the preparation of pulp for newsprint and everything must be sacrificed for speed4 ,the pulp is made of 8ground0 wood as distinguished from the chemically prepared wood pulp known as 8sulphite40 ,the wood is first stripped of its bark and then cut into pieces running from two to four feet in length1 depending upon the size of the magazine of the grinder4 ,the wood is pressed against a revolving grindstone by hydraulic pressure and at such an angle that the fibers torn off will be as long as possible4 ,the fibers are borne off by a stream of water which carries them through a set of screens4 ,these remove any unground slivers1 and eventually the pulp is drained of water and pressed into laps1 or1 if it is to be used immediately1 it goes directly to the beating engine4 ,here it is mixed with a certain amount of 8sulphite pulp10 usually from #bj to #be per cent4 ,to correct the yellowish color of the pulp1 a small amount of blue and red coloring is added4 ,to give body to the paper from #e to #ae per cent of clay is mixed into the pulp and1 to bind the fibers together and give the paper a finish that will be at least partly nonabsorbent1 a quantity of rosin and soda ash is added with enough alum to precipitate the rosin upon the fibers4 ,the beater thoroughly mixes the mass of material and converts it into a fluid of the consistency of thin milk1 which then passes on to the ,fourdrinier machine4 ,,getting ,,down ,,to ,,the 8,,bones0 ,,of ,,the ,,wood ,paper made from ground wood pulp soon discolors and becomes brittle owing to the presence of the lignin and resin of the tree4 ,the superiority of sulphite pulp is due to the fact that chemical processes are used to remove these disturbing ingredients1 leaving only the 8bones0 of the tree1 that is1 the pure cellulose fiber4 ,spruce wood is usually used and after being freed of its bark and thoroughly cleaned1 all knots are cut out and it is sawed into short lengths which are then split and cut up into little chips from to inch long4 ,these chips are boiled under pressure in a solution of sulphur dioxide and slaked lime4 ,the 8digesters0 in which the chips are boiled are large steel cylinders lined with brick set in cement and coated with litharge and glycerin1 so as to prevent the sulphite liquor from coming into contact with the metal4 ,a steam pressure of seventy to eighty pounds is maintained for eight to ten hours and then the digesters are discharged into vats4 ,the sulphite liquor in which the resinous matter is dissolved is drained away and the pulp is washed4 ,soft woods1 such as poplar1 basswood1 etc41 are boiled in caustic soda1 producing what is known as 8soda pulp40 8,sulphate pulp0 is made by boiling in a solution of sodium sulphate1 to which a certain amount of sodium carbonate and caustic soda are added4 ,this process is used for producing pulp for so-called 8,kraft0 paper and brown wrapping paper4 ,formerly pulp was always made in the paper mill and hence the mills had to be located near the source of wood supply1 but to-day the making of pulp is carried on as an independent industry in remote forest regions where water power is plentiful4 ,the pulp is pressed into laps and compressed into bales weighing about #djj pounds4 ,these are sent over long distances by rail or steamship to paper mills located in or near the big cities1 so that the paper may be made near the points of consumption4 ,baled paper pulp has to be reconverted into a smooth milklike fluid4 ,a shredding machine is used for this purpose1 which tears the pulp apart and mixes it with water4 ,then it goes to the beater where it receives its quota of sulphite pulp1 coloring matter1 clay1 and sizing1 as explained before4 ,after an hour of treatment in the beater1 it passes on to a tank in which it is further diluted with water and is then put through a ,jordan engine4 ,this consists of a conical cylinder in which is placed a conical roll4 ,both cylinder and roll are formed with knives that extend longitudinally1 but the revolving knives are set at a slight angle to the fixed knives1 somewhat after the fashion of a lawn mower4 ,the conical form permits of careful adjustment of the roller in the cylinder4 ,the pulp mixture enters at the smaller end and discharges at the larger end4 ,this machine gives the pulp its final beating and reduces it to a very smooth consistency4 ,,the ,,fourdrinier ,,paper-,,making ,,machine ,from the ,jordan engine the pulp is passed on into the ,fourdrinier machine1 which we are now ready to investigate4 ,the principal element of this machine is a traveling belt of copper wire gauze which takes the place of the screen or sieve used in the hand process4 ,to confine the pulp to the belt there are two endless bands of rubber1 known as 8deckles10 along each edge of the screen1 which travel with the screen4 ,to insure proper interlacing of the fibers1 as in the hand process1 the screen is shaken laterally at the rate of about #cjj vibrations per minute4 ,the fluid pulp enters the machine through a flow box1 where a constant hydraulic head is maintained1 so as to preserve a uniform discharge to the wire gauze4 ,the milky stream issues through a narrow opening in the flow box1 known as a 8slicer40 ,this may be adjusted to alter the width and also the thickness of the stream4 ,no one would suspect from the appearance of the milky fluid that it is filled with fibers1 but a microscopic examination of a drop of the thin liquid shows that it is filled with tiny particles floating in the water like logs in a river4 ,it is interesting to watch this stream1 as it passes out upon the screen1 change magically before one's eyes1 from a milky stream into solid mass of pulp4 ,illustration3 ,,fig4 #ga4--;,,diagrammatic ,,view ,,of ,,the ,,fourdrinier ,,paper-,,making ,,machine ,a4 ,flow ,box ,b4 ,copper ,gauze ,belt ,c4 ,rollers ,d4 ,deckles ,confining ,pulp ,,ee4 ,pulleys ,,ff4 ,drums ,g4 ,suction ,boxes ,h4 ,dandy ,roll ,i4 ,the ,final ,suction ,box for ,drying ,j4 ,couch ,roll ,k4 ,canvas ,belt ,in ,figure #ga1 which is a diagrammatical view of a portion of a ,fourdrinier machine1 the flow box is shown at ,a and the copper gauze belt at ,b4 ,this belt is supported on a series of rollers1 ,c4 ,the deckles which confine the pulp along the margins of the screen are shown at ,d4 ,these belts travel with the wire gauze for a certain distance and then pass back over the pulleys1 ,,ee1 while the wire cloth passes on and around the drums1 ,,ff4 ,as soon as the pulp flows out upon the wire gauze1 the water it contains begins to drain away through the gauze4 ,but it does not do this fast enough under the mere pull of gravity and it must be helped by means of suction4 ,at ,,gg there are boxes or troughs that fit against the under side of the wire gauze4 ,in them a partial vacuum is maintained by means of suction pumps and a large part of the water remaining in the pulp is sucked out here4 ,a dandy roll is shown at ,h1 which presses lightly upon the moist pulp1 squeezing out the moisture in it1 and at ,i there is a final suction box which further dries the web of fibers4 ,it is the dandy roll that puts a patterned surface on the paper4 ,if the face of the dandy roll is of finely woven wire cloth with diagonal mesh1 a 8wove0 paper is produced1 while if it is of such surface as to impress parallel lines in the half-formed paper1 8laid0 paper is produced4 ,water marks are also produced by placing a suitable raised or depressed pattern on the dandy roll1 producing a corresponding thickening or thinning of the pulp4 ,even after passing the last suction box1 the thin web of paper is still very wet and so flimsy that it cannot be handled4 ,right here comes the most delicate part of the whole process4 ,the web must be picked off the wire cloth and carried across a narrow gap to a felt belt which conducts it through another set of rollers1 ,a felt-covered roll1 ,j1 known as a 8couch0 roll1 presses down upon the web and the latter clings to the felt in place of the wire cloth which passes down around the roller ,f4 ,in starting a web of paper very skillful manipulation is required to transfer the web from the couch roll to the felt belt1 but after it has once bridged the gap it has enough tensional strength to pull itself across the gap4 ,the felt belt carries the web through a pair of heavy rollers which press out more of the water4 ,because the paper passes through the rolls with the felt belt it receives an impression from the felt on the under side4 ,this is now corrected by running the paper through a second pair of rolls in the reverse direction1 and on a second felt belt1 so that both sides of the paper receive the same impression4 ,from here on the paper passes through a long series of steam-heated drying rolls and emerges eventually as a perfectly dry sheet4 ,our largest ,fourdrinier machines make a web #bjj inches wide and they can be run at a rate of #hjj feet per minute1 or more than nine miles per hour4 ,the paper is made in lengths eight miles long1 which are wound up into rolls to be fed into the huge printing presses of our metropolitan newspaper plants4 ,the difference between the making of news print and finer papers lies chiefly in the quality of pulp used and the quantity of clay and sizing added4 ,after the finer grades have issued from the drying rolls1 they are put through calenders to give them a glazed surface4 ,this consists virtually in ironing the paper between smooth rolls of iron on one side and compressed paper or cotton on the other4 ,just as in ironing clothes1 the paper must be moistened before being ironed and steam is used to supply the necessary moisture4 ,in some cases a high glaze is given to one side only of the paper by means of friction4 ,the paper passes between two rollers of different size4 ,the smaller one travels faster than the larger one and consequently it slips on the paper1 giving it a very smooth surface4 ,,the ,,cylinder ,,machine ,,for ,,making ,,paper ,there is another type of paper-making machine which is used for coarse papers1 pasteboard1 etc4 ,this is known as a cylinder machine4 ,the wire gauze is formed into a cylinder which revolves in the liquid pulp4 ,a slight suction is maintained in the cylinder which causes the water to flow in through the gauze2 leaving the fiber drained on the surface4 ,the cylinder revolves1 carrying the drained pulp on its surface until it encounters a felt roll that picks off the web and carries it to the pressing and drying rolls4 ,one disadvantage of this type of machine is that the cylinder in dragging the drained pulp through the water causes the fibers to be combed in a direction parallel to the run of the paper web1 so that the paper1 while strong in the direction of its length1 is comparatively weak in the transverse direction4 ,this is corrected to a certain degree by the use of 8riffles0 or devices that produce eddies which disturb the even flow of the pulp4 ,in the making of pasteboard1 a number of cylinders contribute their webs to form a single sheet of several plies4 ,,chapter ,,xix ,,typesetting ,,and ,,printing ,,machinery 8,,who ,,won the war80 ,the question immediately brings forth numerous contenders who claim the honor1 respectively1 for the aviator1 the chemist1 the engineer1 the mechanic1 the farmer1 the shipbuilder1 etc4 ,as a matter of fact1 all these and many others as well were invaluable contributors to the final success1 and 8there is glory enough for all40 ,the question1 8,what branch of technology or what branch of machinery has done most for civilization80 finds a similar division of opinion1 with partisans in favor of the steam engine1 machine tools1 electrical machinery1 iron manufacture1 paper making1 printing1 etc4 ,again1 it is clearly evident that all have been most valuable contributors and none may carry off all the honors4 ,however1 partisans of the printing press are entitled to place that machine among the foremost because it has certainly been most useful in preserving and disseminating all classes of knowledge and in promoting the progress of civilization4 ,,early ,,chinese ,,printing ,it is hardly necessary for us to refer to ,johann ,gutenberg's invention in #adcf of separate type for each letter4 ,many centuries before that the ,chinese had made wood engravings of complete pages and printed them on paper4 ,their method was to prepare an ink copy on a sheet of paper and then transfer the copy by pressing the paper on the wood before the ink was dry1 after which they carved away all the surface except those parts which were inked4 ,this gave them a reverse plate from which any number of copies could be printed4 ,the invention of individual type which could be used over and over again for setting new copy was a marked improvement over the ,chinese system4 ,,development ,,of ,,printing ,,presses ,the primitive screw press saw little improvement except in minor details down to the end of the eighteenth century4 ,then steam began to take the place of hand power and the idea was conceived of using a rotary cylinder in place of a flat press4 ,the types were tapered so that they could be fitted about a cylinder4 ,the paper was fed between the type cylinder and a soft impression cylinder faced with leather4 ,the ink was applied to the type by means of a roller which was fed by an inking apparatus4 ,in #ahad two rotary presses were installed in the offices of the ,london 8,times10 making it possible to turn out that newspaper at the marvelous rate of #aa1jjj impressions per hour4 ,in this country1 ,richard ,marsh ,hoe invented a machine in which four1 six1 eight1 or ten impression cylinders operated on a single form of type1 thereby increasing the output of the press correspondingly4 ,the first machine1 a four-impression cylinder press1 was used by the ,philadelphia 8,ledger0 in #ahdf1 and it printed #h1jjj papers per hour4 ,next came the 8perfecting0 press that printed on both sides of the paper1 and then came the continuous web press1 in which the paper was fed from a roll as a continuous sheet and1 after receiving the type impression1 was cut1 folded1 and delivered as a complete newspaper4 ,,the ,,stereotype ,,plate ,meanwhile stereotyping was introduced into newspaper printing4 ,in stereotyping an impression in plastic material is made of the type face and then a casting is made from this impression which1 of course1 exactly duplicates the type face4 ,the type is thus relieved from wear in the press and it is immediately released for use in setting up other copy while the printing is done from the stereotype plate4 ,while the use of stereotyping in book printing dates back to the eighteenth century1 it was not thought practicable for newspaper printing because of the length of time taken in making the plate1 but in #ahfa papier-mach was introduced as a matrix material and a system of rapidly drying the mold was developed so that a plate could be cast in a comparatively short time2 furthermore1 impressions could be made from a flat face of type and then the mold could be bent so as to make curved stereotype plates for use on the cylinder presses4 ,in newspaper work it takes but five minutes to make a stereotype plate4 ,stereotype metal does not stand the wear of printing very long and the plates must be renewed from time to time4 ,this fits in well with newspaper requirements because clean cut work is not called for1 and as the news keeps coming in new editions must constantly be printed1 which means that new plates must be made from time to time4 ,for the finer printing of magazines and books1 copper-faced electrotype plates are used in place of the soft stereotype plates of newspaper printing4 ,,modern ,,newspaper ,,presses ,a modern large newspaper press is a bewildering sight to behold2 there is such a vast number of rolls and cylinders1 and the web of paper moves so rapidly4 ,but1 after all1 the machine is multiplex rather than complex4 ,it consists of a large number of printing cylinders1 all operating in a single frame4 ,take1 for instance1 a double-octuple1 color-combination press4 ,it consists really of two separate presses1 each operating on four webs of paper that feed from opposite ends toward the middle4 ,there are two type cylinders for each web1 one for each side of the paper4 ,each cylinder is long enough to take four stereotype plates side by side1 and since each plate extends but half way around the cylinder we have eight pages printed on each side of the web4 ,this makes sixteen pages per web or sixty-four for each half of the machine1 giving a total of #abh page impressions at each turn of the cylinders4 ,it is seldom that a #fd-page paper is required1 hence the webs are slit in two by a revolving knife blade and each section of the press has two folding mechanisms so that two sets of #af-page papers are printed1 folded1 and delivered by each section4 ,arrangements are provided whereby the product may consist of #cb-page papers4 ,the papers are delivered by a traveling conveyor and every fiftieth paper is pushed out ahead of the others so as to provide a simple method of keeping count of the product4 ,,printing #bdj1jjj ,,pages ,,per ,,hour ,the cylinders turn at the rate of #cjj revolutions per minute which means that the paper runs through the machine at nearly #ad miles per hour4 ,summing up all the webs we have a total consumption of #ajh miles of paper per hour4 ,the paper is #f feet wide and the weight of paper in an hour's run is about #ah tons and the hourly production is #aej1jjj sixteen-page papers4 ,when color is used1 the press will deliver #ej1jjj #bd-page papers per hour with the two outside pages printed in three colors and black4 ,the course of the color printed web must necessarily be different from that of the plain black printed web4 ,it must pass through a number of printings2 and to prevent the moist ink from transferring to the impression rolls and from them back to a succeeding page1 thus soiling or blurring the impression1 an extra roll of thin paper is passed between the printed web and the impression cylinders4 ,this acts in a measure as a blotter4 ,the offset paper is taken up on a roll and used over and over again4 ,it is used not only for color work1 but also when fine half tone engravings are to be printed so that a cleaner impression may be obtained4 ,the inking system of printing press is very elaborate4 ,it is highly essential that the ink be spread upon the type surface in just sufficient quantity to be picked up by the paper and that the ink be uniformly distributed over the whole surface4 ,there is an ink reservoir and a set of inking rollers for each cylinder4 ,the reservoir consists of a trough running the whole length of the cylinder4 ,at each turn a revolving roller dips into the ink and transfers a thin film of ink to a series of small rollers4 ,these are grouped about a large roller to which they deliver the ink4 ,the small rollers have an axial reciprocating motion whereby the ink is uniformly spread over the large roller4 ,the latter transfers its thin coating of ink to a pair of rollers known as 8form rollers0 and these in turn deliver the ink to the printing cylinder4 ,a ,,sea ,,captain',s ,,contribution ,the folding mechanism of a printing press is interesting4 ,the paper is first fed over a wedge-shaped form which folds the paper lengthwise and then it is given a cross-wise fold4 ,curiously enough the folding mechanism for printing presses was first invented by a ,yankee sea captain1 named ,cromwell1 who could not read a drawing but developed his invention by whittling out wooden models4 ,he also contributed other valuable improvements for the printing press worked out in the same primitive way4 ,the rotary press was evolved especially for the printing of daily papers and for a long time magazines continued to be printed on flat-bed presses4 ,but as the circulation of magazines grew into the hundreds of thousands it became necessary to build high speed presses to turn out these large editions4 ,accordingly rotary machines were constructed similar in design to newspaper presses1 but with refinements to enable them to produce the better class of work required of magazine printing4 ,although there are many magazines still printed on flat bed presses1 particularly those which publish small editions of less than a hundred thousand1 all the big national weekly journals and monthly magazines are printed on rotary presses and some of them even use web presses4 ,,gathering ,,and ,,binding ,,magazines ,when a newspaper leaves the press it is folded1 cut1 and ready for the news stand4 ,not so with the book and magazine press4 ,there are too many pages to be handled by a single press1 and1 furthermore1 the pages must be bound together4 ,some large magazines contain regularly more than #ejj pages and occasionally they will run over a thousand pages4 ,obviously no single press could handle so many pages and it takes the product of many presses to make up a single copy4 ,each press prints what is known as a form or signature and these signatures from the different presses are then gathered1 wire-stitched1 and bound into individual copies4 ,there are machines which will do this work of gathering and binding at the rate of sixty #a1jjj-page magazines or catalogues every minute4 ,the machines are adjustable for pages of different dimensions4 ,the forms may consist of four1 eight1 sixteen1 or thirty-two pages4 ,a separate compartment is provided for each signature4 ,a large machine will handle thirty-six #cb-page signatures4 ,the compartments are kept supplied by an operator1 there being usually six compartments for each operator to attend to4 ,the bottom signature in each compartment is brought into position by a suction device which seizes the signature and draws it out1 depositing it in a steel trough4 ,here a belt conveyor moves the signature along at the right speed to carry it before the next compartment just as a signature is being withdrawn therefrom4 ,thus the magazine or book is progressively built up and the signatures reach the end of their course properly assembled4 ,a very delicate adjustment is provided to insure the proper adjustment of signatures4 ,the grippers are adjusted to receive signatures of a certain thickness4 ,if the operator should make a mistake and put a signature of a wrong size in the compartment the whole machine would come to a standstill4 ,the adjustment is so delicate that even a variation of a single thickness of paper is enough to operate the stop mechanism4 ,each assembly of signatures as it reaches the end of the trough is squared up and then bound with wire stitching4 ,from this point it moves on to receive its cover4 ,a thin coating of hot glue is applied to the rear edge of the signatures4 ,the cover is automatically applied and firmly pressed into place4 ,the finished book is then carried on out of the machine and deposited neatly on a pile of previously bound books4 ,to operate such a machine there are required one chief operator and an assistant and six girls to feed the signatures to the compartments4 ,,setting ,,type ,,by ,,machine ,the publication of a modern daily newspaper with its many special editions would be well nigh impossible if we still had to depend upon hand setting of type4 ,tens of thousands of type characters are required to make up a single newspaper page1 and although skilled hand compositors work with extreme rapidity it would take a large corps of men to set type for even a small newspaper in the short time available4 ,speed is of prime importance in newspaper work and the task of handling thousands of little pieces of type metal and arranging them correctly into words and sentences was long recognized as a serious handicap1 but the problem of doing this work by machine was by no means simple one and baffled inventors for years4 ,one of the principal difficulties lay in the size and shape of the type and another was that of justifying the lines1 that is1 providing just the right width of spaces between words to fill out the lines completely so that they would all be of equal length1 giving a straight instead of a ragged margin to the column4 ,after that came the problem of redistributing the type4 ,the first really successful composing machine was the invention of ,ottmar ,mergenthaler in #ahhh4 ,mergenthaler overcame the difficulties that had balked other inventors by attacking the problem from a radically new angle4 ,instead of setting precast type1 his machine cast its own type from a set of matrices4 ,by operating a keyboard1 the matrices were assembled in a line which was justified automatically after the line was composed and then the whole line of type was cast in a single slug4 ,hence his machine earned the name 8linotype40 ,then the matrices were returned automatically distributed to the proper channels of the matrix magazine ready to be used over again for succeeding slugs4 ,,the ,,linotype ,,matrix ,,and ,,space ,,bar ,illustration3 ,,fig4 #gb--;,a ,,linotype ,,matrix ,a picture of a linotype matrix is shown in ,figure #gb4 ,it is a plate of brass formed with ears ,a at the four corners4 ,the type mold is shown at ,b and of course the thickness of the matrix varies with the width of the type letter it is designed to cast4 ,in the top of the matrix there is a ,v-shaped slot ,c formed with teeth which are designed to engage grooves in a ,v-shaped bar over the matrix magazine4 ,the teeth on the matrices are variously cut away and serve as keys to the different channels of the magazine4 ,there is a different combination of teeth for each letter of the alphabet and all matrices of the same letter have the same combination of teeth4 ,the teeth on the distributing bar are also cut away according to various combinations4 ,after the line has been cast the matrices are all raised by their ears and fed one by one upon the distributing bar4 ,each matrix moves along until it arrives over the channel it is designed to enter when it comes to a gap in the teeth of the bar that are supporting it and drops into the magazine4 ,although there are but seven teeth on each side of the ,v-shaped bar1 there are more than enough combinations possible to provide a characteristic one for every key of the keyboard4 ,a matrix always has at least one pair of teeth in engagement with the bar until it reaches the gap that lets it fall into its own special channel of the magazine4 ,the number of matrices of each character varies with the normal frequency of use of that letter4 ,for instance1 the letter e is very commonly used1 and there must be many more e matrices than z matrices1 but in any case the number need not be very large because the process of casting a line and redistributing the type does not take very long and the matrices are soon back in the magazine ready to be used over again4 ,the casting and distributing operations are entirely automatic and while they are in process the compositor is setting a new line4 ,the method of spacing which was a later development of the linotype is also very ingenious4 ,the compositor does not have to bother with the width of spaces required to fill out a line4 ,he merely touches the space key at the end of each word and and a space bar drops into place4 ,each space bar is formed of a pair of wedges and after the line has been assembled the space bars are automatically expanded to fill out the line completely by mechanism which holds down one wedge member 7,a1 ,figure #gc7 and slides up the other 7,b74 ,,individual ,,type ,,casting ,,and ,,composing ,illustration3 ,,fig4 #gc4--;,a ,,linotype ,,space ,,bar ,the difficulties of casting the linotype slug proved a serious handicap in the earlier days of the linotype4 ,the product of the machine could not compare in quality with precast hand-set individual type1 although it served very well for newspapers2 but the machine is now so far perfected that it is widely used for magazine and book composition4 ,however before this stage of perfection was reached the demand for a machine that could do a higher grade of work led to the invention of another machine known as the 8monotype40 ,the monotype consists actually of two machines1 one of which is operated by a compositor and the other operated entirely automatically by the product of the first machine4 ,the compositor operates a keyboard and thereby cuts perforations in a long strip of paper4 ,these perforations are arranged in characteristic groups one for each key4 ,the perforated paper is then run through the second machine and in accordance with the various perforations the separate types are cast and assembled into justified lines4 ,air flowing through the perforations operates a pneumatic mechanism which brings the proper molds into position and casts the separate types4 ,the method of justifying the lines is very interesting4 ,as in the linotype the operator merely touches a space key at the end of each word1 but at the end of the line the mechanism automatically estimates the spaces to be filled and divides this by the number of spaces so that a characteristic group of perforations is punched when the compositor shifts to the next line4 ,in the casting machine the paper ribbon runs through backward and the space group of perforations is encountered before the line is cast4 ,this automatically adjusts the mechanism to cast spaces of the requisite size to fill out the line exactly4 ,,writing ,,by ,,machine ,in one sense we have taken up the various machines employed in printing in reverse order4 ,of course the first machine used is the typewriter1 after which comes the composing machine1 and finally the press4 ,it was in #ahff that two inventors1 ,c4 ,latham ,sholes and ,samuel ,w4 ,soule1 undertook to make a machine for printing numbers in serial order upon the pages of a blankbook4 ,carlos ,glidden1 another inventor1 who was engaged in developing a spading machine designed to take the place of a plow1 saw their work and suggested that they make their machine write letters and words as well as numbers4 ,the three combined and proceeded to evolve the new machine4 ,by the end of the summer of #ahfg they had produced a typewriting machine that could be operated fairly rapidly and that produced fair work4 ,it was one of the letters written by this machine that brought ,james ,densmore into the enterprise4 ,he furnished the money needed to improve the crude typewriter and make it a commercial machine4 ,many models were built but nothing was produced that seemed good enough for commercial production4 ,this development work was too slow and discouraging for ,soule and ,glidden and they dropped out1 but ,sholes inspired by ,densmore persevered until at last in #ahgc he had produced a machine which he could offer for manufacture4 ,the typewriter was then taken to the ,remington factory at ,ilion1 ,n4 ,y41 and the next year it was placed on the market and began its public career4 ,such is the story of the early development of the typewriter4 ,it has become so widely used and is so indispensable a part of the business office that it arouses the utmost astonishment to learn that there still are a few old-fashioned houses so conservative and so far behind that they continue to write their business letters with the pen4 ,so common a machine1 it is hardly necessary for us to describe in detail except to mention two steps in the development of the machine1 namely the arrangement of the type bars whereby the typewriting is visible to the typist1 and secondly the effort to overcome noise by limiting the stroke of the type bar and making it impinge upon the paper with a pressure stroke rather than a hammer blow4 ,a recent development is the 8stenotype10 a small machine which prints shorthand characters1 thus expediting the taking of rapid dictation4 ,,chapter ,,xx ,,cast ,,iron1 ,,wrought ,,iron1 ,,and ,,steel ,,it ,,used to be that wars were fought for gold1 but nowadays the possession of rich iron mines is enough to arouse the cupidity of neighboring nations less favored by nature4 ,in fact1 even though an ounce of gold is worth twice as much as a ton of iron1 the value of the iron we dig out of the earth each year is far greater than that of gold4 ,when that rough ore is converted into iron and steel and then into thousands of useful articles1 its value mounts so high that it cannot be estimated4 ,the qualities of iron and its alloys are so excellent and so varied under different treatment that this metal may truly be said to form the foundation of all our mechanical progress4 ,on the one hand it spans our wide rivers1 carries the burden of heavy freight trains1 or1 in the form of armor plate1 resists the terrific impact of high-powered shells2 on the other hand the same metal1 spun into a hair spring1 governs the ship's chronometer1 or1 in the compass1 points a trembling finger to guide the navigator on his course4 ,,iron ,,in ,,ancient ,,days ,the first use of iron in the service of man dates far back into the ages4 ,an iron tool was found in the pyramid of ,kephron which must have been used #c1ejj years before ,christ4 ,however1 because of the difficulty of working it1 iron was not extensively employed except for swords and cutlery4 ,the conversion of iron into steel and the tempering of steel blades grew to be an art which gave ,damascus and ,toledo a world-wide reputation that dates back over a thousand years4 ,the ancients used to smelt their iron ore in what was known as a ,catalan forge because of its extensive use in ,catalonia1 ,spain4 ,whether the forge was invented there or not we cannot say4 ,similar forges have been found in ,india and other widely remote places4 ,they comprised an inclined tray leading to a pot which formed the furnace and in which a charcoal fire was kindled4 ,the ore and charcoal were placed on the tray and from time to time were raked down into the furnace and air was forced into the bottom of the furnace by means of bellows4 ,in an improved form of the ,catalan forge air was furnished by means of an air compressor operated by a stream of water4 ,this has already been referred to and illustrated on page #ij4 ,limestone served as a flux to melt the earthy matter4 ,the iron obtained from these primitive furnaces was not heated sufficiently to flow as a stream1 but was merely reduced to a pasty mass which was then hammered into shape by the blacksmith4 ,ten or twelve pounds of metal per day was considered a fair output for one of these forges4 ,,discovery ,,of ,,coke ,it was not until the middle of the #adth ,century that a blast furnace1 crudely similar to those we have to-day1 was first built and with it a temperature was obtained that was high enough to turn the metal into a liquid which could be cast in molds4 ,charcoal continued to be the fuel used until about four centuries later1 when ,abraham ,darby discovered that by baking coal to remove its free gases1 he could produce a new fuel known as coke which was a good substitute for charcoal4 ,this gave a wonderful impetus to the iron industry in ,england where there were ample deposits of coal adjacent to the iron mines4 ,shortly after that1 ,mr4 ,henry ,cort of ,gasport1 ,england1 invented the processes of puddling and rolling the product of the blast furnace1 thus converting the iron into a tough1 malleable metal4 ,,alloys ,,of ,,carbon ,,and ,,iron ,we must pause here to learn the difference between cast iron1 wrought iron and steel4 ,iron1 as we know1 has a high affinity for oxygen4 ,when exposed to air and moisture it oxidizes1 rusts very quickly4 ,the iron we find in nature is largely oxidized4 ,in other words1 it is rusty4 ,it is also found in combination with other elements as well4 ,the object of putting iron ore through a furnace is to rid it of oxygen and this is most readily accomplished by melting it in a carbon fire4 ,the highly heated carbon combines with the oxygen and passes off as carbon dioxide and carbon monoxide gas4 ,but a certain amount of carbon unites with the iron and it is this alloy of carbon and iron that makes cast iron so stiff and brittle4 ,the less carbon present the softer is the metal and pure iron is very ductile4 ,it was to rid cast iron of its carbon content that ,cort invented the puddling process4 ,as the metal came out of the blast furnace it ran into a 8reverberatory0 furnace where1 without coming in contact with coke or other carbon fuel1 it was exposed to flames from an adjoining furnace which burned out the carbon1 and then the carbon-free iron was cast into large pieces known as blooms which were hammered to rid them of slag4 ,the final product was known as wrought iron4 ,wrought iron then differs from cast iron in having no carbon4 ,steel1 on the other hand1 stands half way between wrought iron and cast iron in having a small percentage of carbon4 ,how steel is made will be described later4 ,,mechanical ,,handling ,,of ,,ore ,of course machinery plays a large part in the modern iron industry4 ,it would be an endless task even to load one of the big blast furnaces by hand and then the enormous output of molten metal--#dj tons for every pound produced by the old ,catalan furnaces--could not be handled without ponderous machines whose huge arms and fingers are not scorched and blistered by the intense heat4 ,along the ,great ,lakes vast loading machines fill the holds of ore vessels and at the plant there are enormous unloading machines that travel on rails4 ,these have long bridgelike arms that reach out over the ore boat and drop huge clam-shell buckets into their holds4 ,the buckets quickly unload the boats and dump the ore on shore where other buckets pick up the ore1 carry it back and pile it up in big heaps that look like mounds of reddish earth4 ,,the ,,modern ,,blast ,,furnace ,blast furnaces are towering cylindrical structures of steel lined with fire brick4 ,they are loaded from the top with alternate layers of coke and ore4 ,limestone also is added to act as a flux for the earthy matter1 as explained above4 ,running around the furnace near the base there is a large pipe known as the 8bustle0 pipe4 ,through this air is fed to a set of 8tuyeres0 which lead to the base of the furnace and admit blasts of air requisite to maintain combustion at an intense heat4 ,the gases of combustion are not allowed to escape freely into the atmosphere4 ,the top of the furnace through which the ore and fuel is admitted is closed by an air lock and the flaming hot gases are led into 8stoves0 where they give up a large part of their heat to preheat the air which is pumped to the blast furnace4 ,the gases being mainly composed of carbon monoxide are further combustible and may be used for heat1 light1 and power purposes4 ,in fact1 they are commonly used to drive the air compressors which feed the blast furnaces4 ,the blast furnace has two openings1 one above the other4 ,through the upper one slag is drawn off while the molten iron which trickles down and collects at the bottom of the furnace is tapped off through a hole near the base of the furnace4 ,the fiery stream pours out into a lot of small trough-shaped molds and is thus formed into 8pigs40 ,these pigs are all connected to the main body of the metal stream and must be broken off4 ,to save the time of cooling and of breaking off the pigs a machine is used which consists of a series of molds connected to form an endless belt4 ,the molten iron is poured into these molds which in their course dip into a trough of water4 ,here the iron is cooled and solidified4 ,the molds then run up an incline and finally dump the pigs directly into railway cars which haul them away4 ,,burning ,,out ,,the ,,carbon ,the production of steel economically and on a large scale dates back to the inventions of ,henry ,bessemer4 ,while searching for an improved method of making big guns1 ,bessemer hit upon the idea of forcing a blast of air through the molten iron and thus burning away carbon1 silicon1 and manganese in the cast iron4 ,no fuel was supplied except the carbon and silicon in the iron itself4 ,in burning out this carbon sufficient heat was generated to keep the metal fluid4 ,when ,bessemer made the announcement of his new process before the ,british ,association in #ahef1 his paper met with skepticism1 but he was able to demonstrate by actual experiment that cast iron could be converted into malleable iron in this way4 ,however1 when several firms operating under licenses from the inventor endeavored to reproduce his experiment on a commercial scale they were unsuccessful1 and after costly experiments the process was given up as a failure4 ,bessemer1 however1 persisted in his efforts and succeeded eventually in producing malleable iron of a quality equal if not superior to that on the market4 ,but iron makers after the failure of the first experiments would have nothing to do with the new process until ,bessemer began to turn out quantities of iron at #ajj a ton below the prevailing market price4 ,then iron makers woke up and ,bessemer had no difficulty in placing his process with numbers of firms on a very profitable royalty basis4 ,this process pertained to the making of iron and not steel4 ,when ,bessemer tried to produce steel he was confronted with serious difficulties4 ,the steel he obtained was very brittle4 ,he tried purer ores with little better success4 ,then a solution of his problem was offered by ,robert ,f4 ,mushet1 who discovered a compound which would be added to the molten metal to purify it4 ,this compound which is known as 8spiegeleisen0 is composed of iron1 carbon1 and manganese4 ,it removes the oxide of iron and the sulphur and regulates the amount of carbon in the steel4 ,a ,bessemer converter furnishes by far the most spectacular operation in steel manufacture4 ,the converter consists of a large bottle-shaped vessel lined with refractory material4 ,in the bottom of the vessel there are openings through which the air blast is admitted4 ,the molten metal is poured into the flask and then the air blast is turned on4 ,the metal begins to boil violently4 ,a dazzlingly brilliant blast of flame and sparks comes roaring out of the mouth of the converter4 ,bubbles of metal are thrown high into the air where they burst into showers of sparks4 ,the effect is similar to that of a volcanic eruption4 ,in from ten to twenty minutes the eruption subsides and then a quantity of spiegeleisen is added4 ,the converter is mounted on trunnions so that when the operation is completed the vessel is tilted over and the charge of molten metal now converted into steel is poured out4 ,,open ,,hearth ,,furnaces ,illustration3 ,,molten ,,metal ,,from ,a ,,blast ,,furnace ,illustration3 ,,bessemer ,,converter ,,blowing ,,air ,,through ,a ,,mass ,,of ,,molten ,,iron ,illustration3 ,a ,,steel ,,beam ,,passing ,,through ,,the ,,finishing ,,rolls ,,of ,a ,,steel ,,mill ,illustration3 ,,fig4 #gd4--,,sectional ,,view ,,of ,a ,,regenerative ,,open-,,hearth ,,furnace ,while the ,bessemer converter provides a very economical and expeditious method of converting cast iron into steel1 it is difficult to regulate the carbon content with great accuracy and hence the use of the open-hearth furnaces which furnish a slower method of burning out the carbon4 ,figure #gd is a diagrammatic representation of such a furnace4 ,below the hearth of the furnace there are two pairs of chambers1 ,a1 ,b and ,c1 ,d1 filled with a checkerwork of bricks4 ,gas is passed through one chamber ,a1 and air through the other ,b1 and they combine to form a very intense flame above the hearth ,e in which the metal is placed4 ,the burnt gases pass over and through the other pair of chambers1 ,c1 ,d1 on their way to the stack4 ,by this means the bricks in the latter chambers are raised to a white heat4 ,then the process is reversed2 air flows through the hot checkerwork of bricks in the chamber ,c and gas through the hot checkerwork in chamber ,d1 and after combustion in the furnace the burnt gases are drawn through the bricks of the first pair of chambers4 ,by alternating the direction of flow the air and gas fed to the furnace are always preheated by the stored-up heat of the previously burned gases4 ,while it takes but a few minutes to convert cast iron into steel in the ,bessemer converter1 the open-hearth process occupies from eight to twelve hours4 ,the steel produced in the open-hearth furnaces is poured into ingot molds4 ,these are approximately rectangular in section and slightly larger at the bottom than at the top4 ,they are open at the top and bottom1 but at the bottom rest upon a base plate4 ,as soon as the steel has hardened the plunger of a stripping machine holds down the glowing ingot while a pair of hooks lift off the mold1 leaving the ingot resting on the base plate4 ,,rolling ,,ingots ,,into ,,rails ,in the manufacture of railroad rails the ingots are placed on a traveling 8table0 consisting of a series of rapidly turning rollers4 ,these carry the ingot to a pair of large steel rolls between which it passes4 ,the rolls compress the ingot slightly and it is automatically turned over and passed through a second pair of rolls4 ,after passing through four 8stands0 of rolls1 turning over between each stand1 it is considerably reduced in cross-sectional area and correspondingly lengthened4 ,it is now termed a 8bloom40 ,the bloom goes through a series of rollers which gradually reduce its section until it is some forty feet long4 ,then it is cut in two and each section passes through other rolls1 until finally it is reduced to the required rail section4 ,each section is then about a hundred and twenty feet long and the glowing writhing rail passes on to the saws where it is cut into ten-yard lengths4 ,a similar process is employed in rolling other forms of rails and in making steel plates and sheets4 ,,steel ,,for ,,big ,,guns ,the largest machines employed in the steel industry are those used for the manufacture of armor and big guns4 ,a modern large high-powered gun is not a single solid casting or forging1 but is made up of a series of steel tubes that are shrunk one upon another so that the inner tube is compressed4 ,the reason for this is that the explosives used are so powerful that they would expand the inner tube or lining of the gun beyond its elastic limit and in that way enlarge the bore4 ,by having it compressed to start with it can expand farther without exceeding the elastic limit4 ,this expansion takes place so suddenly that the lining rebounds or returns to its original dimensions before the outer tubes have felt the full pressure and they too are thus prevented from being expanded too far4 ,in some cases the compression is effected by winding the gun with a heavy wire of rectangular cross section4 ,,squeezing ,,out ,,the 8,,pipes0 ,steel for guns and armor is made in the open-hearth furnace where the quality of the metal may be regulated to a nicety4 ,gun tubes are cast in vertical molds and during the cooling of the ingot it is subjected to pressure so as to prevent segregation and the forming of 8pipes40 ,pipes are cavities that are liable to form in the center of the ingot due to contraction during cooling4 ,steel1 as we have learned1 is not pure iron1 but an alloy1 and the various constituents have different temperatures of solidifying1 consequently they exhibit a tendency to segregate4 ,it is to overcome such tendencies that a so-called 8fluid0 compressor is used4 ,this is virtually a hydraulic press with a plunger that bears down on the fluid metal as it is solidifying4 ,modern big guns are enormously large4 ,a sixteen-inch #ej-;caliber gun1 for instance1 is nearly seventy feet long1 consequently the ingot must be even longer than this and the fluid compressor for so large a piece must be correspondingly powerful4 ,after the ingot has been cast and cooled1 the ends are cut off and it is bored to form a tube4 ,then it is placed in a furnace and raised to a white heat1 after which a bar or mandrel is inserted in the bore and the tube is placed under the hydraulic forge press4 ,this is a very powerful machine with an immense hammer that is actuated by hydraulic pressure4 ,the stroke of the hammer is carefully regulated so that the forging as it is turned in the forge is subjected to equal blows4 ,in the forge the tube is roughly formed to the dimensions it is eventually to have when finished4 ,the process of forging subjects the metal to strains which must be relieved and so the tube has to go to the annealing oven where it is raised to a temperature which destroys crystallization4 ,in this oven it is allowed to cool very slowly1 letting the molecules of the metal adjust and rearrange themselves4 ,when the temperature of the tube has been lowered to a certain point it is taken out and plunged into a bath of oil4 ,this sudden cooling tempers the metal1 giving it a high degree of elasticity and tensile strength4 ,again the tube must be annealed to relieve it of any strains occasioned by the tempering1 and then it goes to the shop to receive its finish boring and turning4 ,the process as here briefly described seems simple enough1 but we must not forget the enormous size of these pieces and their tremendous weight4 ,they would be difficult enough to handle when cold1 but much of the work is done while the pieces are at a white heat so that the men who control and operate the machinery that handles the big forgings must keep their distance4 ,the casting1 annealing1 and tempering operations are performed with the piece in vertical position1 and lofty machines and cranes are required to deal with these tall castings4 ,a visit to a plant which manufactures big guns is bound to impress the visitor with awe and give him increased respect for the men who are able to handle such huge masses of metal and also for the men who have conceived and developed such gigantic operations4 ,,chapter ,,xxi ,,animated ,,machinery ,,in ,,marked contrast to the massive machinery and apparatus described in the last chapter1 and fully as wonderful1 is a class of machinery to which we might apply the term 8animated40 ,by this we do not mean manikins or toys1 but certain higher types of machines which seem to be possessed of powers that we should expect to find only in living beings--machines that have a sense of touch1 sight1 and hearing--machines that will reason out a mathematical problem2 that will talk2 that have the equivalent of a memory4 ,in this broad classification we may include such widely different machines as the motion-picture camera and projector1 and that mysterious mechanism which seems animated with strange powers of its own--- the gyroscope4 ,,mathematical ,,machines ,adding1 subtracting1 multiplying1 dividing1 and the working out of complex mathematical problems by machine seems wonderful until we stop to reflect that mathematics is the most precise and mechanical of all sciences4 ,in the simpler forms these machines are mere counting mechanisms in which the counting is done very rapidly by the aid of intermeshing gears4 ,the adding machine is in no sense possessed of any reasoning power1 but blindly obeys the simplest of mechanical laws4 ,there are rows of wheels with numbers running from #j to #i printed on their peripheries4 ,one wheel represents 8digits10 the next 8tens10 the next 8hundreds10 etc4 ,the wheels are interconnected by means of gearing so that when the digits wheel makes a complete turn1 the tens wheel makes #a-ajth of a turn1 and when the tens wheel completes a rotation the hundreds wheel makes #a-ajth of a turn4 ,keys numbered from 8#j0 to 8#i0 are provided1 which respectively turn each wheel through angles from #a-ajth to #aj-ajths of a rotation4 ,thus suppose the digit wheel has already been turned through #i-ajths of a rotation and registers the figure 8#i10 and the 8#h0 key is depressed1 the wheel will be given an additional turn of #h-ajths of a rotation and will register the figure 8#g10 but the tens wheel to the left will also move through #a-ajth of a rotation1 so that the two wheels will register 8#ag40 ,such is the underlying principle of the adding machine1 but various refinements are added4 ,for instance1 the numbers that are being added are recorded in print1 and the total sum of the numbers is not printed until the operator desires to foot up the column4 ,more complicated1 of course1 are the mathematical machines which work out involved equations1 but they are all based on simple mechanical operations4 ,in the ,weather ,bureau at ,washington there is a tide-predicting machine1 which has been called a 8great brass brain40 ,its brass gears may be set to allow for all the varying factors of apparent solar and lunar motions1 and they will work out the tide for any past or future data in a few moments1 solving mechanically a mathematical problem that1 by hand1 would take hours and hours of weary figuring4 ,,hearing ,,and ,,talking ,,with ,a ,,mechanical 8,,ear0 ,it was in #ahgg that ,edison startled the world with a machine that could actually talk4 ,others had been working on this problem for years1 but they had been trying to copy the human mouth and organs of speech4 ,edison attacked the problem from a new angle4 ,he was not aiming to produce speech but to reproduce it4 ,let the human vocal organs modulate the sound waves so that they would produce spoken words2 he would provide a machine with no mouth but only an ear and a very retentive memory which would listen to these sound waves and make an impression of them on its soft tinfoil or wax brain4 ,then1 at any time by the principle of 8reversal10 the record could be made the transmitter instead of the receiver of sound waves1 and it would actuate the ear so that it would repeat the sound vibrations it had formerly received4 ,thus ,edison made the ear of his machine serve the double office of hearing and talking4 ,when ,edison's phonograph was listening it had a sharp needle attached to the ear-drum or diaphragm of the sound box1 which cut a hill and dale groove in the brain or cylinder record of the machine2 when reproducing1 a blunt needle was used which faithfully followed the hills and dales of the groove without cutting a path of its own4 ,the next notable improvement in the phonograph was that of ,emile ,berliner1 who in #ahhg invented the laterally vibrating needle which cut a zigzag groove in the record instead of a hill-and-dale groove4 ,in other words1 instead of having his recording needle move in and out as in the ,edison machine1 it moved sidewise4 ,he also invented the flat-disk record1 which has almost completely supplanted the cylindrical record4 ,,machines ,,that ,,picture ,,motion ,in a measure associated with the phonograph is the motion-picture machine1 a machine with an eye and a retentive memory1 which records on a sensitive retina a series of pictures that it is able to reproduce at any time4 ,the recording of still photographs is remarkable enough in itself1 but photography does not properly belong in a book on machinery4 ,the taking of motion pictures1 however1 and the projection of these pictures upon the screen1 involves the use of machinery1 and we must refer to these machines briefly1 owing to their widespread use at the present time4 ,long years ago it was observed that when a picture is suddenly flashed before the eye an image is impressed upon the retina1 which persists for a brief interval even after the picture itself has been withdrawn from view4 ,by preparing a series of pictures of a figure which show it in progressive positions and flashing these pictures in rapid succession before the eye1 persistence of vision will bridge the gaps between pictures and the figure will appear to move4 ,this principle was first used as early as #ahcd in an ingenious toy known as 8zoetrope10 which consisted of a cardboard cylinder with a series of pictures drawn on the inner surface4 ,there were slots cut in the cylinder through which these pictures on the opposite face of the cylinder could be seen4 ,as the cylinder was revolved the eye caught only momentary glimpses of these pictures1 one after the other1 producing a sense of motion4 ,in #ahgj1 ,henry ,heyl of ,philadelphia prepared a progressive series of photographs each separately posed before the camera4 ,from these he made glass positives and projected them on a screen in rapid succession so that the picture appeared to move4 ,in #ahhj1 ,edward ,muybridge set up a battery of cameras and took a succession of instantaneous pictures of a galloping horse4 ,the shutters were operated by strings stretched across the course and as these were successively snapped by the horse the pictures were progressively exposed4 ,glass positives of these pictures were thrown on the screen by means of a machine to which he gave the formidable name 8zopraxiscope40 ,,invention ,,of ,,the ,,photographic ,,film ,no one at that early date had thought of using anything but glass plates1 and they were difficult to handle1 both in the camera and in the projector4 ,it was not until #ahhg that the celluloid film was invented by ,rev4 ,hannibal ,goodwin1 and then it became possible for ,edison to invent a camera with a film that was intermittently moved so as to take a series of pictures4 ,from the negative thus obtained a positive film was then made and placed in a machine known as a 8kinetoscope40 ,looking through a peephole in this machine the pictures were flashed before the eye in rapid succession4 ,finally1 in #ahic1 ,c4 ,francis ,jenkins1 of ,washington1 developed a projector similar to those now in use by which the pictures could be thrown on a screen4 ,thus was born the motion-picture industry which has taken such a strong hold on the public4 ,it is now possible to project pictures in their natural color so as to add to their realism1 but one more step is needed to give a sense of real life4 ,the figures on the screen must talk as well as move4 ,efforts to combine the phonograph with motion pictures have so far been only partially successful4 ,perfect synchronism is very difficult to obtain1 but it is highly probable that obstacles which hitherto have been most troublesome and seemingly insurmountable will1 in time1 be overcome4 ,then the 8silent drama0 will no longer be silent and we shall have 8animated pictures0 that will be really animated4 ,in addition to machines that talk we have machines that hear--machines that will respond to sound waves4 ,a diaphragm flexed by sound waves closes an electric circuit and starts the operation of a machine4 ,some toys have been made which operate on this principle4 ,experiments have been made with a typewriter that will respond to a spoken message1 but so far they have not been attended with much success4 ,boats have been built whose steering gear may be controlled by sound waves1 but as yet nothing of commercial importance has been developed in machines controlled by sound4 ,,machines ,,that ,,see ,much more has been done with machines that see4 ,there is a delicate device known as a 8sun valve10 which is used on beacon lights so that as soon as it grows dark or very foggy the lamp is automatically lighted1 and when the day dawns or light breaks through the fog the light is extinguished4 ,the sun valve has two rods1 one brightly polished and the other a dead black4 ,light and its attendant radiant heat waves are absorbed by the black rod1 but are reflected from the bright rod4 ,as a consequence1 the black rod grows hotter than the polished rod and expands4 ,the difference of expansion between the two rods is utilized to operate a valve which controls the supply of gas to the lamp4 ,this valve is very sensitive and marvelously responsive to variations of light4 ,there is a chemical element called selenium1 which is peculiarly sensitive to light4 ,when light shines upon selenium its electrical resistance is lowered1 and hence it can be used as a light-operated valve to control the flow of electric current4 ,a ,,machine ,,that ,,reads ,,print ,one of the most marvelous machines of the present day is one which will actually read ordinary printed type1 uttering musical sounds that vary for each letter1 so that a blind man after learning this new musical language can read any book4 ,this machine1 known as the optophone1 is the invention of ,prof4 ,e4 ,fournier d',albe1 and was developed to a commercial success last year 7#aibj74 ,with it blind operators are able to read at the rate of twenty-five words per minute4 ,the operation of this wonderful machine can best be understood by reference to the accompanying diagrams1 ,figures #ge and #gf4 ,illustration3 ,diagrammatic ,arrangement of ,optophone4 ,,fig4 #ge4--;,,end ,,view ,,of ,,the ,,optophone ,illustration3 ,,fig4 #gf4--,,side ,,view ,,of ,,the ,,optophone ,there is an electric lamp in the machine before which there is a disk that is revolved by a small motor4 ,in this disk there are five circular rows of slots and the light shining through these slots is cut up into five pulsating beams of light4 ,these beams are brought to a focus in a vertical row upon the type page4 ,from the paper they are reflected to a selenium cell or bridge4 ,the selenium bridge forms part of the circuit of a telephone receiver and the diaphragm is thus made to vibrate at the same frequency as the light beams do4 ,by varying the number of slots in each row in the disk the beams of light are given different periods of pulsation or vibration and they produce a sound chord or 8scala0 in the telephone receiver4 ,the speed of the disk and the disposition of the slots is so chosen that the notes produced are ,g ,c ,d ,e ,g of the musical scale4 ,only white paper reflects the light beams2 the black surface of the printed type absorbs them4 ,thus1 as the row of beams is swept across a line of printed matter1 the beams will be extinguished in various orders of succession1 or simultaneously in accordance with the shape of the particular type-character they encounter4 ,the middle three beams correspond to notes ,c1 ,d and ,e1 and play upon the small letters1 while ,g plays up the upper part of capital letters1 and ,g upon the tails of such letters as y1 p1 etc4 ,if the scala passes over the letter 8,v10 for instance1 first the top note ,g is silenced1 then ,e1 ,d1 ,c1 ,d1 ,e and ,g in succession4 ,this arrangement constitutes what is known as the 8white sounding0 optophone1 because the full chord is sounded constantly1 except when the type matter is encountered4 ,to simplify the reading an improved type of optophone has been made1 which is known as the 8black-reading0 optophone1 ,with this machine there is no sound produced except when the type is encountered4 ,the letter 8,v0 is then identified by the sounding1 instead of the silencing of the notes ,g1 ,e1 ,d1 ,c1 ,e and ,g4 ,the letter 8,a0 produces the sounds ,c1 ,d1 ,,de1 ,,dg1 ,,de1 ,d and ,c4 ,this result is obtained by using two selenium bridges1 as shown better in the side view1 ,figure #gf4 ,there is a concave reflecting lens1 which reflects half of the light upon the second cell1 known as the balancer selenium bridge4 ,electric current passing through the balancer opposes the current passing through the main selenium bridge1 and hence there is silence in the telephone receiver when the scala passes over plain white paper1 but when type is encountered and certain of the beams are not reflected against the main selenium bridge the sounds are produced through the balancer bridge4 ,the success of the optophone leads one to hope that it may be but the forerunner of a machine that will translate the whole world of light and color into one of music1 and permit the blind not only to read by ear1 but also to see their friends and their surroundings through the sense of hearing4 ,in fact efforts to make such an apparatus preceded the invention of the optophone4 ,,the ,,willful ,,gyroscope ,as intimated above1 we have included the gyroscope among the higher type of machines1 because it seems possessed of a stubborn will of its own1 and apparently defies the laws of gravity4 ,there is nothing mysterious about its mechanism4 ,it is merely a wheel with a heavy rim and with its axis mounted in gimbals1 so that it may turn freely in any direction4 ,the wheel1 when at rest1 behaves no differently from any other mechanism4 ,but once the wheel is set to spinning at a high velocity it seems to acquire marvelous powers and obstinate notions of its own as to what it will do and what it won't do4 ,you may lift it1 or lower it1 or move it sideways in any direction1 and it will not show the least sign of rebellion so long as the plane of its rotation is not deflected1 but attempt to twist its plane of rotation and it will resist with the power of a giant4 ,the resistance that even a small gyroscope will develop is astounding4 ,a wheel weighing not more than #aj pounds may develop so much energy that a man twenty times as heavy pushing with all his might cannot turn it over4 ,not only does it resist the push1 but it actually leans back against the pusher4 ,then it has the peculiar habit of turning at right angles to the direction in which it is pushed4 ,suppose1 for instance1 the axis of the gyroscope is horizontal and it is resting freely on a pair of supports1 one at each end4 ,remove one of the supports and the gyroscope does not fall4 ,to do so it would have to swing around the other point of support as a center2 in other words1 the plane of rotation would have to be turned angularly and such a motion the gyroscope resists4 ,the unsupported end of the axis dips momentarily under the pull of gravity1 but immediately recovers and actually rises above the horizontal1 then it begins to revolve slowly in a horizontal circle about the supported end of the axis--a motion which is technically known as 8precession04 ,the pull of gravity exerted in a downward direction results in a horizontal motion at right angles thereto4 ,it seems as if the gyroscope was bidding defiance to laws that govern other objects1 but1 of course1 such is not the case4 ,the gyroscope is as submissively obedient to the laws of gravity as any other object or machine1 but the forces which act upon it are so complicated that it is difficult for one to comprehend them without study4 ,in fact1 it is almost impossible to explain the strange behavior of a gyroscope without the use of mathematics that is too involved to be presented in this book4 ,of course1 the underlying cause of gyroscopic action is inertia2 i4 e41 the tendency of a body to retain its state of rest or uniform motion4 ,a bullet is forced out of a gun by the sudden expansion of gases behind it1 but after it leaves the muzzle and the influence of the gases1 why does it keep on traveling8 ,we may just as well reverse the question and ask why it should ever stop4 ,having once acquired a certain velocity it keeps that velocity because of its inertia or mechanical helplessness1 and it would keep on going forever were it not for the resistance offered by the air and the pull of gravity1 which gradually draws it down to earth4 ,it takes a deal of energy to divert the bullet from its course4 ,in a gyroscope we have a similar condition4 ,,forces ,,developed ,,in ,a ,,gyroscope ,we may conceive of a gyroscope as consisting of a stream of bullets all tied to a center1 so that they fly around in a circle4 ,any effort to deflect the bullets out of their course will be resisted by each bullet as it comes to the deflector4 ,here each bullet acts individually1 but in a gyroscope wheel the equivalent of the stream of bullets is a solid rim1 each particle of which is rigidly connected to every other particle1 and so the whole wheel immediately feels the deflecting force and resists it4 ,as long as the wheel is maintained in its own plane of rotation1 or moved into parallel planes1 there is such a perfect balance of all forces that no more resistance is offered to the motion of the wheel as a whole than would be offered by any other object of equal mass4 ,but when the wheel's plane of rotation is moved angularly1 a complicated series of forces is developed4 ,illustration3 ,,fig4 #gg4--,,some ,,of ,,the ,,forces ,,developed ,,in ,a ,,gyroscope ,,when ,,its ,,plane ,,of ,,rotation ,,is ,,subjected ,,to ,,angular ,,motion ,some idea of the nature of these forces and why they give rise to precession may be understood by reference to the diagram1 ,figure #gg4 ,here we have a disk with a heavy rim turning on the axis ,x1 ,x4 ,at ,a1 ,b1 ,c and ,d are four particles whose flights we are going to consider4 ,suppose the wheel to be at rest2 then if ,x1 ,x is tilted in the direction of the arrows x x1 the wheel will turn about the line ,y ,y2 ,d will move forward toward ,d1 and ,b backward toward ,b1 but ,a and ,c will remain where they are4 ,now1 suppose1 the wheel to be revolving clockwise1 or in the direction ,a1 ,b1 ,c1 ,d1 then the particle ,a will pursue a spiral course that will bring it to ,b1 and ,c will pursue a spiral course that will bring it to ,d4 ,however1 particle ,d will have an irregular course1 as indicated by the dotted line1 starting first to move forward and then curving back toward ,a4 ,the same will be true of ,b1 except in the reverse direction4 ,the course of particles ,d and ,b is1 therefore1 materially different from that of ,a and ,c4 ,now1 the particle ,d will resist being deflected from its course and will develop an opposing force represented by the arrow d4 ,a moment later this is reversed as the particle bends back toward the axis ,y ,y1 and we may represent the new force by the arrow d4 ,it may be proved that the force d is more powerful than that of d4 ,the particle ,a in the meantime exerts a force opposing its deflection1 which is represented by the arrow a4 ,on the other half of the wheel there are similar but opposite forces1 b1 b and c4 ,the sum of these forces gives the wheel a tendency to turn about the axis ,z ,z4 ,to avoid complicating our diagram with too many arrows1 we had better refer to a new diagram 7,figure #gh7 which shows only the resultant of the forces developed4 ,the application of the forces x x1 which would have turned the wheel on the axis ,y ,y1 had it been stationary1 have resulted in the development of forces z z at right angles to x x1 tending to turn the wheel about the axis ,z ,z4 ,now1 if we go through the same processes of reasoning as before1 it will be evident that the forces z z will result in a third set of forces y y at right angles to z z tending to turn the wheel about the axis ,y ,y4 ,the forces y y exactly balance the forces x x1 and hence the wheel does not turn about the axis ,y ,y in response to the original forces1 but starts instead to revolve slowly about the axis ,z ,z4 ,because the forces x x and y y balance each other1 there is no fourth couple developed and hence no opposition to the forces z z4 ,illustration3 ,,fig4 #gh4--;,,diagram ,,explaining ,,precessional ,,movement ,,of ,a ,,gyroscope ,the gyroscope was used as a toy ages ago4 ,the top1 which is one form of gyroscope1 was a favorite plaything of ancient ,egypt4 ,but although known these many centuries1 it is only in the past few years that any real effort has been made to set the top to work4 ,because it persists in maintaining its plane of rotation it has proved most useful on submarine torpedoes to control the rudder and hold the torpedo on a true course to its target4 ,,the ,,gyroscope ,,as ,a ,,compass ,another most important use for the gyroscope is found in the submarine itself4 ,the needle of a magnetic compass is kept pointing north by action of the magnetic lines of force which surround this earth4 ,whenever a large mass of iron is placed near the compass the magnetic field is distorted and the compass needle is deflected from the true north4 ,on modern steel vessels the compass has to be carefully corrected by using iron masses to counterbalance other disturbing masses4 ,however1 in a submarine the whole shell of the vessel is of steel and the magnetic lines of force flow along this shell4 ,the compass needle is virtually insulated from the terrestrial magnetism by the surrounding steel hull4 ,but1 fortunately1 the gyroscope may be used as a compass and it is in no way affected by magnetism4 ,once the gyroscope is set spinning with its axis pointing to the ,north ,pole of the heavens it will continue to point in that direction no matter how devious a course the vessel may pursue4 ,if pointed in some other direction1 the precessional forces set up by the rotation of the earth will turn it due north4 ,as the vessel rolls or pitches1 disturbing precessional movements are likely to be set up4 ,these are overcome by special mechanism1 so that the gyroscopic compass may now be depended upon as a perfectly reliable instrument4 ,,preventing ,,ships ,,from ,,rolling ,one of the most remarkable recent developments of the gyroscope is its use as a stabilizer in ships to keep them from rolling in a heavy sea4 ,a comparatively small wheel is mounted in the hold of the vessel with perfect freedom to turn in any direction4 ,if the wheel is clamped so that it cannot precess1 the vessel will roll and pitch1 but the instant the gyroscope is released it exerts its wonderful powers4 ,the ship rides smoothly and its groaning and creaking ceases1 showing that it is no longer subjected to severe strains4 ,of course1 it rises and falls with the waves1 but it maintains an even keel as if sailing in smooth water4 ,the object of stabilizing a ship is not merely to cater to the comfort of passengers who are subject to seasickness1 but to save wear and tear on the vessel and also to economize time and fuel4 ,an unstabilized ship riding a heavy sea pursues a very sinuous course2 in other words1 it must travel farther than it would in smooth water4 ,the rudder must constantly be turned to keep the ship on its course1 and this acts as a drag on the progress of the ship1 slowing it down and wasting the power of the engine4 ,as the ship wallows in the sea it displaces much more water than it does when riding on an even keel and here there is a further loss4 ,it has been estimated that a #ae1jjj-ton vessel running at #ah knots may waste as much as #a1jjj to #a1bjj horsepower in a heavy sea4 ,if stabilized with a gyroscope1 practically all this wasted horsepower would be saved at the expense of a very small amount of power used in keeping the gyroscope spinning4 ,the first man to stabilize a ship with a gyroscope was ,dr4 ,schlick1 who demonstrated the powers of this mysterious mechanism in #aijf4 ,his stabilizer1 however1 was not sensitive enough to provide perfect stabilizing4 ,the ship had to roll some before the gyroscope exerted its corrective forces4 ,recently1 however1 ,mr4 ,elmer ,a4 ,sperry has improved the stabilizer1 making it so sensitive that there is practically no rolling or pitching of the vessel4 ,curiously enough1 the gyroscope may be used not only to keep a ship from rolling1 but also to make it roll4 ,should a vessel run upon a mud flat it may be rocked by braking or accelerating the precessional motion of the gyroscope4 ,in this way the ship may work itself out of the mud bank4 ,ice breakers are equipped with gyroscopes1 so that they may be rolled to prevent them from being frozen into an ice pack and to assist them in crushing their way through the ice4 ,,the ,,mono-,,rail ,,car ,in #aijg a sensation was created by the exhibition of a car which ran on a single rail4 ,the inventor of this monorail car was ,mr4 ,louis ,brennan4 ,the public was astonished at the ease with which this car maintained its balance on the rail1 leaning in as it rounded a curve to keep its equilibrium4 ,passengers could move about at will without the slightest danger of upsetting the car2 in fact1 if a heavy weight was placed on one side of the car that side would rise rather than fall4 ,the car could run with equal ease upon a cable of a crooked pipe line4 ,the gyroscope that maintained the balance of the car consisted of a couple of small wheels which revolved in a vacuum chamber at the rate of #g1jjj revolutions per minute4 ,once started1 little power was required to keep them going4 ,interesting as this car was1 it did not offer sufficient advantages over the present-day double rail cars and locomotives to justify its development on a commercial scale4 ,although witnesses of the exhibition marveled at the strange spectacle of this mechanical tight-rope walker1 they did not realize that they themselves had had gyroscopic cars in their midst for years4 ,the gyroscopic action of the wheels of a motorcycle is very marked4 ,it is this action which is mainly responsible for holding the machine upright4 ,the same is true of a bicycle1 although the gyroscopic effect is not quite so marked1 because of the lower velocity of the wheels4 ,however1 we all know that any tendency for the machine to fall to one side or the other may be corrected by a slight turn of the front wheel in that direction which at once has the effect of bringing the bicycle back to vertical position4 ,,the ,,automatic ,,aeroplane ,,pilot ,still another recent development of the gyroscope is its use as an 8automatic pilot0 on aeroplanes4 ,two sensitive gyroscopes are used to stabilize the aeroplane4 ,if a gust of wind tends to tilt the machine1 the gyroscopes immediately sense the deviation and by closing electrical circuits operate the ailerons to bring the machine back to a horizontal plane4 ,an aviator possesses a certain sense of balance which is highly developed by experience and long practice1 but at its best it does not begin to compare with sense of balance possessed by the gyroscope4 ,not only will it keep the machine from tipping laterally1 but it will also hold it on a level keel and can be used to steer the aeroplane in any desired direction1 so that the human pilot may surrender the helm to the faithful mechanical pilot with perfect confidence in the ability of this animated machine to hold the aeroplane on a true course despite the vagaries of the wind4 ,while this is theoretically possible1 in practice certain difficulties are encountered which up to the present have prevented gyroscopic control of aeroplanes from being entirely successful4 ,,chapter ,,xxii ,,heat ,,vacuums ,,in ,,the preceding chapter we dealt with high temperatures and their employment in melting1 molding1 and working steel into useful forms4 ,it will be well for us to pause here to consider temperatures at the other end of the thermometer scale1 how they are obtained1 and the important part they play in modern civilization4 ,it is not absolutely correct to speak of producing 8cold40 ,we are apt to forget that cold is merely absence of heat4 ,strictly speaking1 there is nothing cold on earth4 ,everything is more or less hot4 ,a piece of ice at #cb degrees ,f4 is hot compared with a lump of frozen alcohol1 and the latter at its freezing point is hot compared with a lump of frozen air1 while air at its freezing point is hot compared with a lump of solid helium4 ,in other words1 frozen alcohol will be melted by the heat in the ice2 frozen air will be melted by the heat in frozen alcohol1 and frozen helium will be fused by the heat in frozen air4 ,everything contains heat1 and one object is colder than another only because it contains less heat4 ,of course1 the temperature of ice may vary4 ,one block of ice may be ten1 fifty1 or a hundred degrees warmer than another1 but ice cannot be heated above #cb degrees ,f4 at the normal pressure of the atmosphere4 ,ice is really a partial heat vacuum1 a chamber partially exhausted1 into which heat will flow if it gets a chance4 ,we pack it away in sawdust1 granulated cork1 or other materials through which heat can with difficulty penetrate1 and then in hot weather cakes of ice are placed in our household refrigerators1 so that the heat that is in our food will have something to flow into4 ,when we place our hands near a cake of ice1 they feel cool and it seems as if ice radiated cold just as a stove radiates heat2 but1 of course1 such is not the case4 ,the heat of our hands radiates more rapidly in the direction of the cake of ice than in other directions1 because there is a partial heat vacuum for the heat to flow into and the result is a sensation of cold4 ,we no longer depend upon cold winters for our supply of ice4 ,we have learned how to pump heat and we can make heat vacuums1 anywhere and at any time1 even in the heart of the tropics1 and regions in which no natural ice is ever obtainable have the benefits of refrigeration4 ,furthermore1 we are not dependent upon ice for cooling foods4 ,in many cases it is not necessary or even desirable to reduce temperatures to the freezing point of water4 ,a moderate chilling is all that is required for certain foods4 ,by the proper use of refrigerating machinery any degree of temperature may be obtained and maintained4 ,to-day small refrigerating plants are constructed for domestic purposes1 so as to render the housewife independent of the ice man4 ,with refrigerator cars and refrigerating plants on shipboard1 fruit from the far west and from tropical lands may be brought to our breakfast table4 ,meats from northern slaughterhouses may be transported in perfect condition into hot southern climes4 ,there are also certain industries which are dependent on the use of the low temperatures4 ,in breweries1 dairies1 margarine factories1 etc41 refrigeration is of the utmost importance1 and refrigerating machinery is used for cooling and drying the air blast for blast furnaces4 ,in some few places refrigerating machinery is used to cool buildings in warm weather and make life more bearable in summer weather4 ,it is highly probable that refrigeration of dwellings will be more and more extensively developed4 ,in winter time we can make the climate in our houses anything we please4 ,why should we not control the indoor climate in summer time as well8 ,,absolute ,,zero ,the volume of a gas varies inversely in accordance with the pressure to which it is subjected1 and also directly according to the temperature4 ,if we start with a gas at the freezing point 7#cb degrees ,f47 and reduce its temperature #a degree 7or to #ca degrees ,f471 we find that the volume of the gas is reduced #a_/dib4f of its original volume1 provided1 of course1 that we do not vary the pressure on it4 ,in fact1 for every reduction of #a degree below the freezing point there is a reduction of #a_/dib4f of its volume1 and for every degree of increased temperature there is an increase of #a_/dib4f of the volume4 ,from this it is assumed that at #dib4f degrees below the freezing point1 or #dfj4f degrees below zero ,f41 we will reach the absolute zero1 or the point at which there is no more heat in the gas4 ,we have not yet succeeded in reaching the extreme of low temperature1 although we have come very near it in laboratory experiments4 ,helium is liquefied at -#ddh degrees ,f41 which is very near to the absolute zero4 ,at the other end of the scale we have attained enormously high temperatures4 ,the heat of the electric arc1 for instance1 is between #f1ejj and #g1bjj degrees ,f41 and that is the highest degree of temperature that we have been able so far to attain4 ,human life occupies a very limited zone in this range of temperatures4 ,we must maintain our blood at a temperature of #ih degrees ,f4 ,a variation of #h degrees either way is fatal4 ,by piling on heat insulators1 such as fur clothing1 to retain the heat of our bodies and keep it from flowing out too rapidly1 we can maintain the blood temperature at #ih while the surrounding atmosphere may be #gj or #hj degrees below zero4 ,there are internal fires within us that generate heat which radiates from the body1 and by checking this radiation by suitable clothing we can maintain our blood at the normal temperature4 ,but what can we do when the surrounding temperature is higher than blood heat8 ,the outside heat may be kept from flowing in by surrounding ourselves with heat-insulating clothing1 but the internal heat then has no means of radiating away from our bodies2 it accumulates1 and we become overheated4 ,however1 ,nature provides a cooling system in the perspiration which oozes from our pores1 and as this evaporates it cools the skin and enables us to maintain our normal blood heat1 although submerged in an atmosphere of a higher temperature4 ,if the air is dry1 the evaporation is more rapid and the cooling is greater than in a moist atmosphere4 ,that is why a temperature of #aje degrees on our ,western plains may be more endurable than a temperature of #ie degrees in the moist atmosphere of ,new ,york4 ,the importance of keeping down the temperature of the blood is particularly appreciated by physicians1 and for this reason the earliest attempts at artificial cooling were made by physicians4 ,,early ,,uses ,,of ,,low ,,temperatures ,very early in his history man discovered fire1 learned how to kindle it and how to use it for his good4 ,that discovery placed him immediately on a level far above the beasts4 ,however1 it is only in comparatively recent times that he has learned the uses of low temperatures4 ,nature's stores of ice were drawn upon1 and methods of preserving ice through warm weather were discovered in ancient times4 ,nero had ice houses built for him in ,rome1 but he could stock these buildings only with the ice that nature furnished him4 ,freezing mixtures of salt and ice1 such as we use in our ice-cream freezers to-day to obtain temperatures far below the freezing point of water1 were probably known in early times1 but the ancients did not know how to produce ice4 ,artificial ice was probably first made in ,india1 where it has long been the practice to produce ice by evaporation4 ,water is placed in shallow pans and then dry air is circulated over it1 causing so rapid a vaporization as to cool the water to the freezing point4 ,the idea of cooling water by evaporation belongs to very ancient times4 ,water placed in porous earthen vessels was found to be cooler than water kept in water-tight jars4 ,the moisture that escaped through the vessel would evaporate1 and in so doing draw heat out of the vessel and its contents4 ,to-day campers keep water cool by putting it in canvas buckets and hanging the buckets in the wind1 so that the moisture oozing through the canvas will evaporate quickly4 ,it was not until #agee that a mechanical means of producing low temperatures was developed4 ,the inventor was ,dr4 ,cullen1 and he used an evaporation system1 expediting the evaporation by producing a partial vacuum over the water4 ,but nearly a century elapsed before the first commercially successful refrigerating machine was built4 ,even then the advantages of artificial refrigeration were not fully realized1 and it was not until late in the last century that real progress was made4 ,since then the development of artificial refrigeration has been truly remarkable4 ,,heat ,,and ,,mechanical ,,energy ,there is a definite relation between heat and mechanical energy1 in fact the two are mutually convertible4 ,the amount of heat required to raise the temperature of a pound of water #a degree ,f4 is called a ,british thermal unit or a ,b4 t4 u4 ,this measure is taken at #ci4a degrees ,f41 because at that temperature water is at its densest4 ,since heat and mechanical energy are mutually convertible1 we can express foot-pounds or horsepower in ,b4 t4 u4 ,one ,b4 t4 u4 is equivalent to #ggh foot-pounds of energy4 ,in other words1 the amount of heat that would raise the temperature of a pound of water #a degree ,f4 would1 if converted into mechanical energy1 be sufficient to raise a weight of #ggh pounds to a height of one foot1 or one pound to a height of #ggh feet4 ,a horsepower is equivalent to #b1ede ,b4 t4 u4 per hour4 ,heat from burning coal is used to generate steam1 and this in turn is used to operate a steam engine and thus heat is converted into mechanical energy 7unfortunately most of the original heat units in the coal are wasted1 as was pointed out in a previous chapter72 but heat will not flow from one body into another of higher temperature without the expenditure of mechanical energy4 ,it always flows from a hot body into a cold one1 and not from the cold body into the hot one1 unless it is actually pumped up to the higher heat level by some mechanical means4 ,a refrigerating machine is actually a heat pump with which we produce a partial heat vacuum4 ,whenever a gas is compressed1 heat is generated4 ,anyone who has operated a tire pump knows how hot the pump becomes from the heat that is seemingly squeezed out of the compressed air4 ,as was noted in ,chapter ,,viii1 heat is liable to give trouble in an air compressor1 and sometimes the temperature rises to such a point that there is an explosion of the air and the vapors coming from the oil used to lubricate the machine4 ,the compressed air is therefore cooled by means of water jackets or coils of pipe through which water is passed4 ,in this way the excess heat is carried off4 ,when1 however1 cooled compressed air is relieved of pressure and allowed to expand again the process is reversed4 ,a partial heat vacuum is formed and heat from surrounding objects flows into the vacuum4 ,in other words1 the surrounding objects are cooled4 ,,cold ,,air ,,machines ,illustration3 ,,fig4 #gi4--;,,cold ,,air ,,machine ,it is a simple matter to make a machine which will alternately compress1 cool1 and expand air in such a way as to produce a lowered temperature4 ,such a machine is indicated diagrammatically in ,figure #gi4 ,there are two cylinders1 ,a and ,b1 and a condenser at ,c4 ,when the piston a in cylinder ,a descends it compresses the air in the cylinder2 this air flows into the condenser ,c4 ,there is a coil of pipe in this condenser through which water circulates4 ,this carries off the heat of compression and then a valve is opened which permits the cooler air to pass off into cylinder ,b4 ,as the air expands in this cylinder it becomes chilled4 ,this chilled air is then forced out of cylinder ,b by means of piston b and flows into the refrigerator or cold storage room ,d4 ,as the air is liable to take up moisture and to introduce objectionable vapors from oil used to lubricate the pumps1 it is usually confined in pipes in the refrigerator and then returned to the cylinder ,a4 ,illustration3 ,,compositor ,,at ,,work ,,on ,a ,,linotype ,,machine ,illustration3 ,,the ,,optophone ,an instrument which enables the blind to read common print ,illustration3 ,a ,,blind ,,man ,,reading ,,with ,,his ,,ears ,this is a type of a refrigerating machine that is used very extensively on ships for chilling perishable foods4 ,however1 air has only a very low capacity for heat1 and in order to obtain an appreciable amount of refrigeration very large volumes of air must be handled4 ,this means that cold-air machines must be very large and bulky4 ,the efficiency of such machines is low1 but they find favor on shipboard because there are no inflammable or poisonous gases to be dealt with4 ,in the standard machine of the ,united ,states ,navy air is compressed to #bfj pounds2 and in the expansion is raised to #fj pounds pressure1 which is enough to reduce the temperature to between #gj to #ij degrees below zero4 ,,latent ,,heat ,far more efficient are the machines which utilize latent heat4 ,as explained in a previous chapter1 whenever a solid is converted into a liquid or into a gas a certain amount of heat is absorbed and stored up in such a way as not to become apparent to the senses or to a thermometer4 ,such heat is known as 8latent heat40 ,for instance1 we can add a pound of water at #ej degrees temperature to a pound of water at #bjj degrees1 and the mixture will have a temperature of #abe degrees1 or the mean of #bjj #ej degrees4 ,but a pound of ice at #cb degrees mixed with a pound of water at #bjj degrees will not give us #aaf degrees 77#bjjcb7_/b71 but only #dd degrees4 ,in other words1 about #adc heat units will be rendered latent in converting solid water into liquid water1 reducing the temperature of the water to #eg degrees and then the mean of #eg and #cb is #dd4e 7#bjj-adceg1 7#egcb7_/b #dd74 ,a more striking experiment is to mix a pound of water cooled to #cb degrees ,f4 with a pound of water at #age degrees ,f41 and the result will be two pounds of water at #ajc4e degrees1 but if we mix a pound of chopped ice at #cb degrees ,f4 with a pound of water at #age degrees ,f41 the result will be two pounds of water cooled to the freezing point4 ,in passing from a liquid into a gas water absorbs far more heat and renders it latent4 ,for each pound of water converted into steam at atmospheric pressure #igj ,b4 t4 u4 are absorbed4 ,this storage of latent heat is utilized to good advantage in refrigerating machinery4 ,the vacuum machine invented by ,dr4 ,cullen in #agee was a latent heat machine4 ,,vacuum ,,machines ,as we have observed before1 the boiling point of a liquid depends upon the pressure to which it is subjected4 ,under the normal atmospheric pressure of #ad4g pounds per inch the boiling point of water is #bab degrees ,f41 but if the pressure be increased the boiling point rises1 and if it be reduced the boiling point is lowered4 ,in a partial vacuum of ten pounds absolute pressure the boiling point is #aic4b degrees1 at one pound it is #ajb4a degrees1 and if the pressure is reduced to 4#jhi pound water will boil at #cb degrees1 or its normal freezing point4 ,dr4 ,cullen1 by exhausting the air from a vessel containing water1 made the water boil or vaporize at a low temperature4 ,in order to boil it had to absorb heat1 and not being supplied with any external heat it had to draw upon itself1 thus producing ice4 ,illustration3 ,,fig4 #hj4--;,,diagrammatic ,,view ,,of ,a ,,vacuum ,,refrigerating ,,machine ,dr4 ,cullen's machine has been improved upon by using various chemical substances to absorb the water vapor4 ,such a machine is shown in ,figure #hj4 ,the vacuum chamber ,a is partly filled with brine1 which may be cooled below the freezing point of pure water without congealing4 ,a pump1 ,b1 maintains a vacuum in the chamber4 ,in the upper part of the vacuum chamber there is a vessel1 ,c1 into which sulphuric acid is sprayed from a reservoir1 ,d4 ,this acid has a strong affinity for water vapor and hastens the evaporation by absorbing the vapor with which it comes in contact4 ,the mixed sulphuric acid and water flows over into a receiver1 ,e4 ,the acid is reconcentrated by steam heat so that it can be used over again4 ,however1 this feature of the process is not shown in the diagram4 ,brine from the chamber ,a passes through a coil of pipe ,f in the tank ,g1 where the ice is made1 and it is returned to the vacuum chamber by an injector ,h1 which at the same time introduces fresh water into the chamber to take the place of that absorbed by the acid4 ,the fresh water and brine enter as a spray at ,i1 so as to increase the rate of evaporation4 ,illustration3 ,,fig4 #ha4--,,original ,,absorption ,,machine ,,the ,,absorption ,,process ,another form of refrigeration is known as the absorption system1 and strangely enough direct heat is applied to the machine in one place in order to abstract heat from it in another4 ,a diagrammatic representation of the first machine of this type 7which was invented by ,frederick ,carr7 is shown in ,figure #ha4 ,two vessels1 ,a and ,b1 are employed1 which are connected by a tube ,c4 ,the vessel ,a contains ammonia solution4 ,a lamp1 ,d1 is placed under the vessel ,a4 ,sufficient heat is produced to vaporize the ammonia1 whose boiling point is very low1 and distill it out of the water in the solution4 ,it passes through tube ,c into vessel ,b4 ,this vessel is surrounded by a tank1 ,e1 containing cold water1 which condenses the ammonia vapor into liquid ammonia1 then the process is reversed4 ,the circulation of water through tank ,e is checked and water from pipe ,f is sprayed on vessel ,a4 ,this cools the contents of vessel ,a1 producing a partial vacuum4 ,the ammonia in chamber ,b boils and its vapors pass back into chamber ,a1 where they are reabsorbed by the water in that chamber4 ,the rapid vaporization in chamber ,b absorbs heat from the immediate surroundings and will freeze water placed in the tank ,e4 ,in commercial practice the absorption system is very extensively employed4 ,the ammonia is placed in a large cylinder known as a generator and is heated by steam coils4 ,the ammonia vapor passes through an analyzer which traps any water vapor it may contain1 and then it goes through a series of condensing coils1 which are cooled by water4 ,in these condensing coils the ammonia vapor is liquefied by the pressure in the generator and collects in a receiver1 whence it passes through an expansion valve into the cooling coils in the brine tank4 ,from the cooling coils the ammonia gas passes back through an absorber which reverses the operation of the generator4 ,here weak aqua ammonia is sprayed on the ammonia gas and absorbs it4 ,the rich ammonia solution is then pumped into the generator4 ,there are several auxiliary apparatus which are omitted in this brief description in the interest of clarity4 ,,the ,,compression ,,system ,illustration3 ,,fig4 #hb4--;,,diagrammatic ,,view ,,of ,a ,,compression ,,machine ,one more type of refrigerating machine remains to be described and that is the compression type4 ,this was invented by ,jacob ,perkins in #ahcd1 but was not developed into a commercial machine until #ahej4 ,this machine is the most important of them all4 ,in some respects it is like the absorption process1 but in place of adding direct heat a compressing machine is employed4 ,figure #hb illustrates the system diagrammatically4 ,at ,a is the compressor which compresses ammonia gas4 ,the gas which is heated by the compressor is then cooled and liquefied in the condenser ,b4 ,thence it passes into a brine tank ,c1 where it expands and absorbs heat4 ,from this point it is drawn back into the compressor1 thus completing the cycle4 ,in other words1 the ammonia must absorb as much heat from the brine as is taken out of it at the condenser4 ,,chapter ,,xxiii ,,engines ,,of ,,destruction ,,at ,,the ,,very beginning of this book we observed that war is a most potent stimulus to invention among primitive men4 ,despite all our advances in civilization we still have our wars1 each more dreadful than the preceding one2 for each important conflict brings forth new engines of destruction or stimulates the invention of new death-dealing machines which are developed during intervals of peace4 ,so terrible has modern war become that with each great conflict it has seemed as if its very dreadfulness would stay the hand of the invader and make him hesitate to expose his men to the horrible monsters which science and invention have created4 ,to-day1 after a titanic struggle which cost millions of human lives1 which destroyed billions of dollars' worth of property1 and which made itself felt to the remotest corners of the earth1 serious efforts are being made to banish war1 but at the same time inventors here and abroad are busy inventing new and more powerful engines of death1 and the prospects are that the next big war1 should there ever be one1 will be even more horrible and destructive than the one we have just passed through4 ,fortunately engines of death are not the only inventions produced by war4 ,many machines1 apparatus1 and processes are originated or developed which have a distinct value in time of peace2 hence war is a great constructive as well as a destructive agency4 ,in this respect the great ,world ,war was no exception and we are already reaping benefits which in a small way compensate for the havoc that was wrought4 ,it advanced scientific research to a point it would not have reached in fifty years of peace4 ,the stimulus was felt in every field of science from chemistry to acoustics1 from geology to meteorology4 ,wonderful progress was made in radiotelephony1 in submarine navigation1 in aviation1 and there were scores of inventions which will add to our comfort and aid us in the mastery of ,nature4 ,many of these inventions have already been described2 others do not properly belong in this volume as they have to do chiefly with electricity or chemistry4 ,in this chapter we shall take up mainly the machines built for the purpose of destroying men and their works4 ,,primitive 8,,engines0 ,,of ,,war ,of course the main objects of war are offense and defense1 the destruction of the opponent and the protection of one's self4 ,this first fighting was a hand-to-hand struggle which gave way to fighting at a distance as spears and arrows were invented4 ,shields and armor were then invented to ward off these missiles4 ,cities were surrounded with walls to hold off the enemy4 ,then came the ,roman war 8engines10 catapults and battering rams1 to destroy the walls and towers which would enable the besiegers to fight on an equal level and in personal contact with the besieged4 ,although a battle might start with long-distance fighting it was always a hand-to-hand encounter that clinched the victory4 ,even to-day1 although we have our big guns which fight at ranges of five to twenty miles1 it is the rifle or bayonet which wins or loses the battle4 ,,invention ,,of ,,gunpowder ,the introduction of gunpowder from ,china in the fifteenth century did not immediately revolutionize warfare4 ,it was used only in cannon or mortars for hurling large stones at city walls4 ,the range of those cannon was so limited and the time it took to load and fire them was so great that they were of little use on an open battlefield4 ,a cannon1 although a comparatively powerful offensive weapon1 was helpless against attack and was only suitable for use in forts or behind breastworks4 ,later when its range was increased and it came to be used on the battlefield it had to be protected from capture by men supplied with small arms4 ,this defect of the cannon also applied to the use of the hand gun4 ,its range was small and consequently the blunderbuss type was invented to spread the charge of shot as much as possible so as to tear a wide gap in the enemy's line and prevent it from closing in upon the operator of the gun4 ,but the loading and firing of these early firearms was extremely slow and the battle-ax and even the arrow and the crossbow were much more effective weapons4 ,so unreliable were the muskets of our ,revolutionary ,war that in battle more dependence was placed upon the bayonet than the firearm4 ,,the ,,spinning ,,bullet ,three important improvements were necessary to make the small gun a really effective weapon4 ,first was the invention of a reliable means of igniting the powder2 second the rifling of the barrel so that the bullet would not tumble but would hold a true course1 and finally the invention of a cartridge and a rifle that could be loaded from the breech4 ,these improvements were not completely effected until the time of the ,civil ,war4 ,since then there have been further marked improvements3 ,the power of cartridges has been increased2 the bullets have been given a stream-line form so as to increase the range of the rifle and its power of penetration2 the rifle has been equipped with a magazine for carrying a number of cartridges2 and a simple mechanism has been provided for discharging empty shells and inserting fresh cartridges in a minimum of time4 ,gyroscopic action plays a very important part in the flight of a bullet or shell4 ,the spiral grooves cut in the bore of the rifle give the projectile a twist that sets it to spinning rapidly4 ,the spinning bullet is virtually a gyroscope and maintains its axis in the line of flight4 ,hence it is possible to use a long pointed bullet instead of the round ball of earlier days and to give the projectile a shape that will enable it to cut through the air with comparatively little resistance4 ,the same bullet fired from a smooth bore gun would begin to tumble and would encounter so much air resistance that it would fall short in the space of a few hundred feet1 besides which it would wander far off its course4 ,,machine ,,guns ,a rifle is really a machine for hurling small projectiles4 ,during the ,civil ,war a ,chicago physician named ,gatling fell to pondering over the inefficiency of using a machine that would fire only one bullet at a time with a considerable interval of time between shots for reloading1 and he hit upon the idea of developing a machine that would discharge a continuous stream of bullets4 ,so he built a ten-barrel revolving gun operated by a hand crank4 ,the barrels were automatically loaded and fired one after the other4 ,although it was slow to accept the ,gatling machine gun1 the ,u4 ,s4 ,army after once accepting it was loath to give it up even after better machine guns were invented4 ,,utilizing ,,the ,,kick ,,of ,a ,,gun ,in the ,gatling gun hand power was required to operate the loading1 firing and shell-ejecting mechanism1 but it occurred to another inventor that a small portion of the energy developed in exploding the cartridge could very well be utilized to replace the hand power and thus make the machine gun completely automatic4 ,it was ,hiram ,maxim who first carried out this idea to a successful conclusion4 ,when a rifle is fired the suddenly expanding gases push back against the breech of the gun with just as much pressure as they do against the bullet and this shows itself in the recoil or 8kick0 of the gun4 ,maxim utilized the kick of the gun to cock the gun1 open the breech1 eject the empty shell1 take a fresh cartridge out of a magazine belt1 insert it in the breech chamber1 lock the breech and fire the gun4 ,all these operations occupied but an instant of time and the gun kept on firing as long as the belt of cartridges held out4 ,john ,m4 ,browning1 inventor of the ,colt gun1 instead of using the recoil1 employed a small portion of the gases to operate the mechanism4 ,a minute hole in the barrel of the gun1 near the muzzle1 communicated with a small cylinder in which was a spring-pressed piston4 ,the gases pursuing the bullet out of the barrel would find this tiny hole and1 entering it1 push back the piston4 ,the pressure against the piston would be only a small fraction of that exerted against the bullet and would last for only the briefest part of a second1 from the time the bullet uncovered the hole to the time it emerged from the barrel and liberated the gases1 but this minute portion of the energy of the powder was sufficient to actuate the mechanism which performed all the operations necessary to reload and fire the gun4 ,,cooling ,,the ,,gun ,,barrel ,the advantage of these machine guns over ,gatling's lay not only in the saving of human labor1 but in the fact that a single barrel was employed in place of ten1 thereby greatly reducing the weight of the gun4 ,but a serious handicap was encountered in the heat developed by the burning powder4 ,dr4 ,gatling1 by using ten barrels1 could let nine be cooling while the tenth was discharging1 but even he found it necessary to place a water jacket about half the length of the barrels4 ,in the ,maxim machine gun a large water jacket enveloped the whole length of the barrel and when the gun was firing continuously at a moderate rate the #g pints of water contained in the water jacket would come to a boil inside of a minute and a half1 and thereafter more than a pint would be evaporated each minute of firing1 or about a pint and a half per thousand rounds4 ,the necessity of using water-cooling added considerably to the weight of the gun and made it occupy in the service an intermediate place between the shoulder rifle and the big gun4 ,another method of cooling was to use a barrel with a large outer diameter and depend upon the radiation of heat from the outer surface to prevent overheating4 ,this was later improved by putting flanges on the outer surface of the barrel1 so as to increase the radiating surface1 in the same way that the cylinders of a motorcycle are kept cool4 ,the barrel was made easily detachable and a spare one provided1 so that as soon as the barrel grew excessively hot it could be removed and replaced with a cool barrel4 ,the fault of overheating is not that it might explode the cartridge prematurely but that the bore will be enlarged by heat expansion so that the bullets will not take the rifling and will come out of the barrel as if from a smooth-bore gun4 ,in a test of a ,hotchkiss machine gun which was fired continuously the expansion was sufficient at the end of four minutes to make the course of the bullets very uncertain and in seven minutes the bullets1 emerging without any spin1 tumbled over and over and failed to carry more than three hundred yards4 ,a ,,gun ,,that ,,fans ,,itself ,the next marked step in the development of the machine gun was to make it fan itself and thus keep its barrel cool4 ,col4 ,i4 ,n4 ,lewis designed a gun operated by gas pressure somewhat on the principle of the ,colt gun and around the barrel he fitted sixteen deep flanges or fins of aluminum that ran lengthwise of the gun4 ,around these fins he fitted a casing1 thus forming #af long narrow chambers about the barrel4 ,the casing was open at the breech end1 but at the outer end was contracted into a narrow mouthpiece that extended beyond the muzzle4 ,the mouthpiece was so formed that as the bullets passed through it they sucked air through the chambers1 thereby cooling the gun4 ,the air travels through the casing at the rate of about seventy miles per hour4 ,this design permitted ,col4 ,lewis to build a very light gun4 ,its total weight was but #be pounds and it could be handled by a single man if the muzzle was supported on some sort of a rest4 ,it represented a marked step toward a shoulder machine gun which would increase enormously the efficiency of infantry equipped with this weapon4 ,the difference between rifle fire and machine-gun fire has been likened to the difference between trying to hit a tin can with a stone and with a stream of water from a hose4 ,in the latter case the hose may be raised or lowered to correct the course of the stream and bring it to bear on the target4 ,in the same way by watching the effect of the machine-gun bullets the leaden stream may be corrected to bring it directly upon the target4 ,the advantages of a weapon such as this1 which may be fired from the shoulder or from the hip1 are perfectly obvious4 ,as the war was nearing its end ,john ,m4 ,browning produced two machine guns1 one a water-cooled heavy model fired from a stand4 ,the total weight of this gun was #cd pounds and with the water jacket empty it weighed but #bb pounds4 ,it was operated by the recoil of the gun1 but the mechanism was greatly simplified and there were but few parts4 ,these could be taken apart and replaced with new ones in a minimum of time in case of breakage4 ,the other gun was a shoulder rifle weighing only #af pounds1 which carried a clip of twenty cartridges4 ,these could be fired singly or in rapid succession in the space of two and a half seconds4 ,only a second was required to replace the empty clip with a filled one4 ,no special cooling apparatus was provided because it was not likely that a shoulder rifle would be fired long enough at a time to become excessively heated4 ,,pocket-,,sized ,,machine ,,gun ,the latest development in machine guns is a pocket edition weapon--a firearm weighing only #g pounds and measuring but #bb inches over all4 ,this little gun which is too small to be classed as a rifle and yet rather large for a pistol1 has two grips so that it may be fired from the waist line1 and it may be fitted with a gun butt so that it may be fired from the shoulder4 ,it operates at the astounding rate of #a1ejj shots per minute or three times the speed of the average machine gun4 ,the cartridges are fed either from a box magazine containing #bj rounds or from a drum-shaped magazine loaded with #ej to #ajj cartridges4 ,the operating mechanism of this gun is entirely different from anything produced heretofore and depends upon a discovery made by ,commander ,blish of the ,united ,states ,navy4 ,he found that a wedge of a certain angle will hold a breechblock closed against the pressure of an exploding cartridge while the pressure is high1 but will slide when the pressure falls4 ,apparently at first the adhesion due to friction is too great to permit the wedge to move1 but the adhesion falls off more rapidly than the pressure does and a point is reached at which the wedge yields to the pressure4 ,in the 8submachine0 gun1 as the new weapon is called1 the barrel 7or rather an extension of the barrel7 and the receiver1 in which the operating mechanism is contained1 are locked together by a wedge4 ,the wedge slides in slots set at an angle of #hj degrees with the axis of the barrel4 ,when a cartridge is fired the wedge remains fast while the bullet is traveling through the bore1 but when it emerges and the pressure of the gases falls off the wedge slides1 unlocking the breech mechanism4 ,the gun is remarkable for its simplicity and the fewness of its parts4 ,it has been adopted by the ,police ,department of ,new ,york ,city4 ,,artillery ,,vs4 ,,armor ,as has been stated above1 gunpowder was first introduced in warfare not for the purpose of destroying men1 but for smashing city walls and fortifications1 so that infantry could pour through the breeches made by the heavy stone or iron projectiles4 ,as artillery grew more powerful and the aim more accurate walls of masonry gave way to earthworks and to masses of concrete and armored steel4 ,however the ,world ,war demonstrated the impossibility of building any fortifications above ground that would stand up against modern high-powered guns4 ,,guns1 ,,mortars1 ,,and ,,howitzers ,in military parlance a 8gun0 is a long-barreled piece that fires its projectiles with a flat trajectory1 that is1 the projectile is fired at a low angle and describes a long flat curve4 ,a 8mortar0 is a short-ranged weapon which fires at a high angle so as to land its projectile over the walls of a fortification4 ,the barrel of the mortar was formerly very short and had a smooth bore1 but later the barrel was extended and the bore rifled so as to give a greater range1 developing what is known as the 8howitzer40 ,the famous #db-;centimeter gun with which the ,germans started the war was a howitzer which fired a shell a yard and a half long weighing #b1ajh pounds4 ,we have big guns to defend our coasts which fire a shell #af inches in diameter1 which is half an inch less than #db centimeters1 and the weight of the shell is #b1djj pounds4 ,but the startling thing about the ,german big howitzers was that they were portable and could be brought up to smash fixed defenses4 ,as the war proceeded enormous guns as well as howitzers were set on railroad mounts and moved about from time to time to avoid discovery by spying aviators4 ,,the #gf-,,mile ,,gun ,the #gf-mile gun which bombarded ,paris fired projectiles of only #h4bg-;inch caliber4 ,the projectile described a wide curve which carried it about twenty-four miles above the surface of the earth or about #c times as high as the greatest altitude ever reached by man in an aeroplane4 ,had it pursued a perfectly straight line from the forest of ,st4 ,gobain to ,paris its course would have carried it #c1gej feet below the surface1 because of the curvature of the earth4 ,the range of the projectile was very materially increased by rising to such a great elevation because of the extreme tenuity of the atmosphere4 ,the air resistance that a shell is obliged to overcome is not generally appreciated4 ,in the denser strata of the lower atmosphere the resistance is very great1 but as a shell mounts to higher levels the air resistance falls off considerably and at twenty miles it is practically nonexistent4 ,it was not until the summer after the armistice that details of this gun were disclosed4 ,there were seven of these powerful guns that participated in the various bombardments4 ,they wore out very quickly under the terrific strain to which they were subjected and were rebored to a diameter of #i4d inches4 ,in the last bombardment a number of shells of this size reached ,paris4 ,the guns were fired at an angle of #ee degrees from the horizontal so as to pass quickly through the denser layers of the air4 ,the shell left the muzzle of the gun with the velocity of about #e1jjj feet per second and arrived in ,paris about three minutes later with a velocity of about half that amount4 ,the enormous muzzle velocity was obtained by using a very long gun so that the powder could keep pushing the projectile for a comparatively long time4 ,the guns were built out of worn-out #ae-;inch naval guns4 ,these guns which were #ef feet long were rebored1 fitted with a heavy tube and pieced out to a length of #aah feet4 ,the last #bj feet of the bore was not rifled and served as a guide to keep the shell in perfect axial alignment when it emerged from the muzzle4 ,a comparatively slow powder was used so as not to put too severe a strain on the gun at the breech1 but gradually to accelerate the shell in its travel through the bore4 ,spectacular as was the performance of these huge guns1 they were of little military value4 ,the slightest variation in the powder would cause a wide variation of range and they could not hope to hit a target smaller than a large city4 ,all seven guns fired a total of #cjc shells in #dd days of bombardment1 only #ahc of which fell within the city4 ,they killed #bef persons and wounded #fbj4 ,far more damage at far less expense could have been effected by dropping bombs from aircraft4 ,a #aba-,,mile ,,gun ,just as a problem in ordnance1 ,american officers designed a gun #bbe feet long which would fire a #djj-pound shell of #aj-;inch caliber4 ,it was estimated that with a charge of #a1ddj pounds of powder the shell would leave the muzzle with a velocity of #h1ejj feet per second and1 if fired at an angle of #ee degrees1 would have a range of #aba miles4 ,the shell would rise to a height of #df miles above the earth and would make the #aba miles in about #d minutes4 ,the gun was never built1 because its military value would in no way be commensurate with its cost of construction and operation4 ,the purpose of the ,german long-range bombardment was to produce a moral rather than a military effect4 ,the ,germans hoped to intimidate the ,french people by this spectacular performance1 and in this they failed completely4 ,,timed ,,and ,,percussion ,,shells ,in modern warfare large guns are used either to rain a storm of death upon infantry or to destroy their defensive works4 ,in earlier days the effectiveness of gunfire against a charging enemy was increased by the use of grapeshot4 ,a cannon was thus converted into a gigantic shotgun4 ,but although a wide dispersion of projectiles was obtained the range was very limited4 ,this handicap was then overcome by having the gun fire another gun which would discharge when it had reached the enemy's lines4 ,in other words1 the grapeshot or leaden balls were packed into a shell which was fired like a solid projectile1 and this exploded when it struck the target1 scattering death broadcast4 ,an improvement on this was the timed shell1 which would explode while still in the air and scatter its rain of lead over a wide area4 ,the time fuse of a shrapnel shell must be very delicately adjusted to explode at the desired instant4 ,a train of powder is used which may be short-circuited to give the exact length required for any given distance4 ,the powder is ignited by a cap which is exploded by concussion when the gun is fired4 ,the fuse then burns until it reaches the main charge of the shell4 ,this explodes1 bursting the shell open and scattering shell fragments as well as the scores of lead balls with which the shell is packed4 ,should the fuse fail1 a detonating pin is provided which will explode the shell when it reaches the ground4 ,where the object is to destroy defensive works the shell is charged with a high explosive which is detonated not by a time fuse1 but by concussion when the shell strikes its target4 ,the war brought forth many new types of projectiles3 shells loaded with lethal gases2 shells which left a trail of smoke whereby their course could be followed when fired at aircraft2 shells that illuminated the battlefield at night1 etc4 ,the searchlight shells carried a number of 8candles10 each furnished with a little parachute so that when the shell exploded the burning candles would settle slowly to the ground1 all the while casting a brilliant light on operations below4 ,,aerial ,,bombs ,obviously1 hurling projectiles from the air is a much simpler matter than projecting them from the ground4 ,no propellant is required to carry them to the target and no rifling is necessary to keep them head-on in the direction of flight4 ,they are pulled instead of being pushed and can easily be kept in their course by means of rudder planes4 ,but hitting a target from an aeroplane is like hitting a swiftly moving object from the ground4 ,the target is seemingly flying past the aeroplane and in calculating where the aerial bomb will strike the speed of the plane through the air and its height above the ground must all be taken into consideration4 ,naval warfare is a fight of fort against fort and consequently the high explosive projectile is the principal one used4 ,the shells must be able to penetrate heavy steel armor and explode within the hull of the vessel4 ,in addition to these we have the torpedoes fired by destroyers and submarines which explode an enormous quantity of high explosive against the hull of the vessel4 ,no attempt is made to penetrate the skin of the vessel1 but the explosive1 tamped by a considerable depth of water1 delivers a very heavy crushing blow against the side of the hull4 ,,automatic ,,control ,,of ,,submarine ,,torpedoes ,it is wrong to speak of firing a torpedo4 ,a torpedo is really an automatic1 self-propelled1 submarine boat4 ,all that the destroyer or submarine does is to set the steering gear in this little boat and then launch it at the enemy with a blast of air that ejects it from the torpedo tube4 ,most of the body of the torpedo is filled with compressed air which drives a small air motor coupled to a pair of propellers4 ,these propellers run in opposite directions so as to balance each other and they drive the torpedo through the water at a speed of about forty miles per hour4 ,the speed falls off gradually as the air supply is exhausted4 ,to hold the torpedo on its course horizontal and vertical rudders are employed4 ,the vertical rudder is controlled by a gyroscope which turns it this way or that according as the torpedo tends to veer off its course4 ,the value of a torpedo lies in its concealment4 ,were it to travel on the surface the vessel against which it was directed might be able to avoid it2 furthermore the action of the waves would tend to disturb the gyroscopic steering mechanism and the torpedo would pursue an erratic course4 ,for this reason it must travel under water at a depth sufficient to avoid surface disturbances4 ,there is also a distinct advantage in having a good cover of water over the torpedo when it strikes its target because the force of the explosion1 although felt in all directions1 is mainly expended along the line of the least resistance4 ,if the depth of water over the torpedo is slight1 most of the force will be expended upward and only a comparatively small part will act against the hull of the vessel4 ,it was the practice of the ,germans to set their torpedoes for a depth of about ten feet4 ,to hold a torpedo at a fixed depth a very delicate hydrostatic valve is employed which operates the diving rudders4 ,the valve is set for a certain depth or weight of water4 ,if the torpedo goes below this depth1 the weight of the water bearing on this valve presses it down and thereby tilts the diving rudders until the torpedo comes back to the required depth4 ,if it rises above the depth for which it is set1 the valve feels the reduction of water pressure and tilts the rudders in the opposite direction to correct the deviation from the predetermined line of travel4 ,once the valve has been set the torpedo takes care of itself automatically4 ,it may be discharged from any depth or be dropped from torpedo tubes on the deck of a ship and after a few undulations it will find its depth and hold it as long as it keeps running4 ,torpedoes have actually been discharged from aeroplanes and it is possible that in the next great war swiftly flying aeroplanes may actually bring death and destruction to powerful dreadnoughts4 ,in fact winged destroyers and battle cruisers of the air may render obsolete all our modern fighting machines4 ,as we have already observed1 it was war that first aroused the inventive instincts in man4 ,fortunately this instinct was not confined to destructive devices and engines1 and the mechanical conquest of the earth1 although it continues to derive much benefit from the stimulus of war1 may well afford to break off relations with so grim and horrible a partner and proceed to develop under the stimulus of its own successes4 ,,chapter ,,xxiv ,,summary ,,of ,,mechanical ,,progress ,,the ,,real beginning of the present age of machinery dates from ,watt's invention of the double-acting steam engine which was patented in #aghb4 ,prior to that date the steam engine was used merely for pumping water1 but now in its new form it was adapted for use in driving industrial machinery4 ,but1 as we have shown in another chapter1 it was not until ,john ,wilkinson invented his boring machine in #aggd that it was possible to bore the cylinders that ,watt used in his engine4 ,in the field of machine tools there were several notable inventions4 ,henry ,maudslay invented the slide rest for lathes and later in #agig the screwcutting lathe4 ,joseph ,bramah invented the hydraulic press and ,maudslay furnished the cup leather packing that made it a success4 ,woodworking machinery1 and particularly mortising machines for making pulley blocks1 were invented by ,samuel ,bentham and patented in #agia and #agic4 ,in the textile industry we find the spinning jenny invented by ,hargreaves in #aggj1 ,richard ,arkwright's roll-drawing spinning machine invented in #agfi and #agge1 and ,crompton's mule spinner invented between #aggd and #aggi1 but never patented4 ,in addition to this there was the invention of the cotton gin in #agid by our own ,eli ,whitney and ,dr4 ,cartwright's series of patents on the power-driven loom granted between #aghe and #aghh4 ,in #agii ,louis ,roberts invented a machine that would make a continuous web of paper4 ,the machine was developed in ,england by the ,fourdrinier ,brothers and has ever since borne their name4 #ahja-ahaj ,just before the ,nineteenth ,century dawned the patents on ,watt's steam engine expired and the invention became public property4 ,trevithic applied steam power to the propulsion of a coach in #ahja4 ,this was the forerunner of the automobile and it led to the invention of the first steam railway and locomotive three years later4 ,steam was also applied to the propulsion of boats in this decade and reached the practical stage when ,fulton built the ,clermont in #ahjg4 ,the first application of steam to the driving of a loom is accredited to ,william ,horrocks in #ahjc4 ,jacquard's loom attachment for producing various patterns was invented in #ahja4 ,the first knitting machine in which the latch needle was used was patented in ,france in #ahjf by ,jeandeau4 ,among the machine-tool developments the most important were ,bramah's invention of the planer in #ahjb and ,brunel's mortising machine in #ahja4 ,a process of making malleable iron castings was invented by ,lucas in #ahjd4 ,the percussion lock for guns was invented by ,forsyth in #ahjg4 #ahaa-ahbj ,the second decade saw a much wider application of steam and considerable development in locomotives4 ,hedley's 8,puffing ,billy0 was built in #ahac1 and ,stephenson's first locomotive in #ahad4 ,in the same year ,fulton built the first steam war vessel and five years later the ,atlantic was crossed for the first time by a steamer1 the ,savannah4 ,the rotary steam printing press belongs to this decade4 ,the circular knitting machine was invented by ,brunel in #ahaf4 ,about #ahah ,eli ,whitney invented the milling machine1 and in #ahai ,blanchard invented his 8gun-stocking0 lathe with which irregular forms could be turned out4 ,the breech-loading musket was patented in this country by ,thornton and ,hall in #ahaa4 #ahba-ahcj ,in this decade we find the conversion of electricity into mechanical motion and many other important electrical developments1 which1 however1 are omitted from this list as we are confining ourselves to mechanical inventions4 ,there were marked developments in steam railroads4 ,stephenson built the 8,rocket0 which won prizes on the ,liverpool and ,manchester ,railway1 and the first locomotive was imported into this country in #ahbi4 ,the tubular locomotive boiler was invented by ,seguin in #ahbh and ,ericsson's portable steam fire engine was built in #ahcj4 ,in the previous year an important improvement in spinning mules was made when ,john ,thorpe invented the ring frame4 #ahca-ahdj ,important railroad developments mark the opening of this decade4 ,the famous locomotive 8,john ,bull0 was imported from ,england in #ahca to operate on the ,camden and ,amboy ,railroad4 ,the following year saw the first ,american-built locomotive1 8,old ,ironsides10 which was built at ,philadelphia by the ,baldwin ,locomotive ,works4 ,stephenson's link motion1 also claimed by ,w4 ,t4 ,james1 was invented in #ahcb4 ,however1 the most important development of the decade was the invention of the reaper4 ,hussey's patent was obtained in #ahcc and ,mc,cormick's the following year4 ,colt's revolver 7#ahcf72 ,perkin's portable ice machine 7#ahcd72 ,anthony's 7#ahca71 ,tolle's 7#ahcd71 and ,burden's 7#ahce7 developments in machines for making horseshoes2 and ,isaac ,babbit's antifriction-bearing metal are other notable developments4 #ahda-ahej ,it was in #ahda that ,f4 ,e4 ,sickels invented the drop cut-off valve gear1 and the ,corliss valve gear was patented in #ahdi and #ahea4 ,nasmyth's steam hammer was invented in #ahdb4 ,hoe's revolving printing press was invented in #ahde4 ,the next year ,sloan patented the gimlet-pointed screw4 ,in #ahdg ,savage invented the time lock1 and in #ahdi ,hibbert patented the latch needle for knitting machines4 ,american machine-made watches appeared in #ahej4 ,however1 the most important invention of the decade was ,howe's sewing machine in #ahde4 #ahea-ahfj ,the year #ahea saw an important improvement in the harvester when ,seymour invented his self-raker1 also an advance in firearms when ,maynard invented the breech-loading rifle4 ,three years later ,smith ,wesson came forth with their magazine rifle which was the forerunner of the 8,winchester40 ,in that year ,wilson invented the four-motion feed for sewing machines4 ,one of the most notable inventions of the decade was ,bessemer's converter for producing steel 7#ahee71 and the following year ,siemens produced the regenerative furnace4 ,gifford's injector 7#aheh7 marked a most important advance in steam engineering4 ,the hand-turned turret for lathes was invented by ,stephen ,fitch about #ahec1 and the automatically revolving turret was brought out in #ahee4 ,other inventions of the decade were ,herman's diamond drill 7#ahed71 ,ericsson's air engine 7#ahee71 the pedal-operated bicycle by ,ernest ,michaux 7#ahee71 use of wood pulp in the manufacture of paper by ,voelter 7#aheh71 and the ammonia absorption ice machine invented by ,carr4 #ahfa-ahgj ,the ,civil ,war directed attention of inventors to military and naval improvements4 ,dr4 ,gatling invented his machine gun in #ahfb1 the same year that ,ericsson built the 8,monitor40 ,it is interesting to note that the revolving turret was patented in that year by ,theodore ,r4 ,timby4 ,dynamite was invented in #ahfg1 and the ,whitehead torpedo in the same year4 ,barbed wire was invented in #ahfa4 ,the same year saw the first passenger elevator invented by ,otis2 the shoe-sewing machine invented by ,mc,kay1 and ,col4 ,green's invention of the drive well1 which was brought about by the necessity of supplying his troops with water4 ,the pneumatic rock drill was invented by ,burleigh in #ahff1 and ,westinghouse invented the air brake in #ahfi4 ,the latter1 with ,sholes's invention of the typewriter in the previous year1 were undoubtedly the most notable inventions of the decade4 ,in #ahfe the cylindrical grinder marked a decided forward step in machine tools4 #ahga-ahhj ,this decade was marked by great activity1 particularly in the field of electricity4 ,while we are confining ourselves to mechanical inventions we cannot but mention ,bell's telephone 7#ahgf71 ,edison's carbon filament lamp 7#ahgh71 and ,berliner's transmitter and ,edison's carbon microphone which belong to the decade1 although their patents were not issued until #ahia and #ahib respectively4 ,the web printing press was invented by ,hoe in #ahga4 ,ingersoll's compressed air rock drill appeared in the same year4 ,a marked improvement in the ,westinghouse air brake was patented in #ahgb1 and the automatic car coupler appeared in #ahgc4 ,the positive motion loom was invented by ,lyall in #ahgb4 ,the harvester was improved by ,gorham's twine binder in #ahgd1 and in the same year a machine for making barbed wire was produced4 ,the ,centennial year saw an important development in milling processes when the roller mill was introduced to take the place of the time-honored millstones4 ,the middlings purifier was invented by ,george ,t4 ,smith in #ahge4 ,the hydraulic dredge was invented in #ahgf1 also the universal grinder1 and a machine for making cigarettes4 ,edison's invention of the phonograph and ,otto's invention of the gas engine give prominence to the year #ahgg and the ,remington typewriter to the year #ahgh4 #ahha-ahij ,the inventions of most far-reaching importance in this decade were ,mergenthaler's linotype machine1 which was invented in #ahhd and further developed into a practical machine in #ahij2 ,gottlieb ,daimler's invention of the automobile in #ahhc1 and ,j4 ,b4 ,dunlop's invention of the pneumatic tire in #ahij4 ,berliner in #ahhg invented the flat-disk talking machine known as the 8,gramophone40 ,the snapshot 8,kodak0 camera appeared in #ahhh4 ,in this year ,de ,laval invented his steam turbine1 while ,harvey invented his process for annealing armor plate4 ,the following year nickel steel was invented4 ,in #ahhc ,sir ,hiram ,maxim invented the machine gun4 ,hugo ,bilgram's generating system of gear cutting was invented in #ahha4 ,a less prominent1 though very important1 invention of the same year was the buttonhole machine patented by ,reece4 ,incidentally this decade saw the completion of the ,brooklyn ,suspension ,bridge in #ahhc1 and the ,great ,forth ,bridge in #ahij4 #ahia-aijj ,the last decade of the ,nineteenth ,century gave us ,parson's steam turbine 7#ahia7 and ,curtis's steam turbine 7#ahif72 also ,rudolf ,diesel's heavy-oil engine4 ,langley's model for a motor-driven airplane was built in #ahif and actually flew4 ,santos-,dumont made his first ascension in a dirigible in #ahih1 and ,count ,friedrich von ,zeppelin built his first rigid dirigible in #aijj4 ,j4 ,b4 ,holland built a steam-driven submarine1 and ,simon ,lake constructed the first submarine to be driven by an internal combustion engine4 ,this decade was largely devoted to the development of the automobile1 which gradually evolved into a truly commercial machine4 ,about #aijj1 ,benjamin ,holt invented the 8caterpillar0 tractor4 ,the decade also saw the invention of the ,lanston 8monotype10 and ,henry ,wise ,wood's 8autoplate0 machine which revolutionized stereotyping4 ,in #ahii ,william ,draper brought out a loom with an automatic shuttle-changing mechanism4 ,hulett invented the automatic ore unloader in #ahih4 ,improvements were also made in automatic machine tools4 ,j4 ,e4 ,gleason improved the ,bilgram gear cutter in #ahih1 and at the close of the century ,taylor and ,white brought out their high-speed cutting tools which revolutionized machine tools4 ,the decade was also remarkable for the invention of ,x-rays1 wireless telegraphy1 and certain chemical processes1 none of which really belong in this summary4 #aija-aiaj ,in this decade the automobile reached a marvelous state of perfection and a tremendous industry was built up which had a marked influence on the development of machine tools and the production of iron and steel4 ,james ,a4 ,gailey invented a dryblast process for steel production1 getting rid of the moisture in air by subjecting it to a freezing process4 ,fellow's gear-cutting machine was perfected and ,bullard brought out the vertical turret lathe4 ,there were important developments of the steam turbine4 ,there is one invention that makes this decade stand out from among all others4 ,on ,december #ag1 #aijc1 the ,wright brothers made a successful flight in a biplane driven by a gasoline engine1 and opened up a new world for conquest4 ,man took to wings and the dream of ages was realized4 ,during the decade rapid progress was made in developing the flying machine4 ,the invention of the monoplane soon followed4 ,it was in this decade that the gyroscope emerged from the laboratory and toy shop and began to be applied to practical uses4 ,schlick utilized the gyroscope to prevent ships from rolling4 ,the gyrocompass was invented and reached a commercial stage in #aiaj4 #aiaa-aibj ,it is difficult to pick out the most important inventions of this decade because sufficient time has not elapsed to determine which are most deserving of mention4 ,the ,great ,world ,war stimulated invention in all civilized lands4 ,aeronautics developed faster in the five years of war than it could in twenty-five years of peace4 ,of course1 engines of war developed to a remarkable degree4 ,among the lighter pieces we saw the development of the ,lewis gun1 and then the ,browning gun4 ,the most important invention was the tank4 ,many advances should be classed as remarkable developments rather than basically new inventions4 ,the war of and against the submarine brought forth many ingenious devices4 ,of the peace-time inventions1 the most remarkable is the optophone1 the instrument which enables the blind to read ordinary printed matter4 99 99 99 99 99 ,and thus the march of progress continues unchecked4 ,we are tempted to give our imaginations free play and forecast the developments that the future holds in store for us1 but unfortunately we cannot claim any prophetic instinct or inspiration4 ,,transcriber',s ,,note3 --,obvious print and punctuation errors were corrected4