,,flying ,,machines ,,today ,hitherto aviation has been almost monopolized by that much-overpraised and much-overtrusted person1 'the practical man4' ,it is much in need of the services of the theorist--the engineer with his mathematical calculations of how a flying machine ought to be built and of how the material used in its construction should be distributed to give the greatest possible amount of strength and efficiency4 --,from the ,new ,york ,times1 ,january #af1 #aiaa4 ,illustration3 ,,the ,,fall ,,of ,,icarus ,,flying ,,machines ,,today ,,by ,,william ,,duane ,,ennis ,professor of ,mechanical ,engineering in the ,polytechnic ,institute of ,brooklyn #abc ,,illustrations ,illustration3 ,,van ,,nostrand ,,logo ,,new ,,york ,d4 ,,van ,,nostrand ,,company #bc ,,murray ,,and #aiaa #bg ,,warren ,,sts4 ,copyright1 #aiaa1 by ,d4 ,,van ,,nostrand ,,company ,,the ,,plimpton ,,press ,,norwood ,,mass ,u ,s ,a ,to ,,my ,,mother ,,preface ,speaking with some experience1 the writer has found that instruction in the principles underlying the science and sport of aviation must be vitalized by some contemporaneous study of what is being accomplished in the air4 ,no one of the revolutionizing inventions of man has progressed as rapidly as aerial navigation4 ,the truths of today are the absurdities of tomorrow4 ,the suggestion that some grasp of the principles and a very fair knowledge of the current practices in aeronautics may be had without special technical knowledge came almost automatically4 ,if this book is comprehensible to the lay reader1 and if it conveys to him even a small proportion of the writer's conviction that flying machines are to profoundly influence our living in the next generation1 it will have accomplished its author's purpose4 ,,polytechnic ,,institute ,,of ,,brooklyn1 ,,new ,,york1 ,april1 #aiaa4 ,,contents ,,page ,,the ,,delights ,,and ,,dangers ,,of ,,flying4--,dangers of ,aviation4--,what it is ,like to ,fly #a ,,soaring ,,flight ,,by ,,man4--,what ,holds it ,up8--,lifting ,power4--,why so ,many ,sails8--,steering #ag ,,turning ,,corners4--,what ,happens when ,making a ,turn4-- ,lateral ,stability4--,wing ,warping4--,automatic ,control4-- ,the ,gyroscope4--,wind ,gusts #cc ,,air ,,and ,,the ,,wind4--,sailing ,balloons4--,field and ,speed #dc ,,gas ,,and ,,ballast4--,buoyancy in ,air4--,ascending and ,descending4--,the ,ballonet4--,the ,equilibrator #eg ,,dirigible ,,balloons ,,and ,,other ,,kinds4--,shapes4-- ,dimensions4--,fabrics4--,framing4--,kee ping the ,keel ,horizontal4--,stability4--,rudders and ,planes4--,arrangement and ,accessories4--,amateur ,dirigibles4--,the ,fort ,omaha ,plant4--,balloon ,progress #ga ,,the ,,question ,,of ,,power4--,resistance of ,aeroplanes4-- ,resistance of ,dirigibles4--,independent ,speed and ,time-,table4--,the ,cost of ,speed4--,the ,propeller #aja ,,getting ,,up ,,and ,,down2 ,,models ,,and ,,gliders2 ,,aeroplane ,,details4--,launching4--,descending4-- ,gliders4--,models4--,balancing4--,weigh ts4-- ,miscellaneous4--,things to ,look ,after #aba ,,some ,,aeroplanes4--,,some ,,accomplishments #adc ,,the ,,possibilities ,,in ,,aviation4--,the ,case of the ,dirigible4--,the ,orthopter4--,the ,helicopter4--,composite ,types4--,what is ,promised #agj ,,aerial ,,warfare #ahi ,,list ,,of ,,illustrations ,,page ,the ,fall of ,icarus ,frontispiece ,the ,aviator #c ,the ,santos-,dumont ,demoiselle #d ,view from a ,balloon #i ,anatomy of a ,bird's ,wing #aj ,flight of a ,bird #aa ,in a ,meteoric ,shower #ac ,how a ,boat ,tacks #ae ,octave ,chanute #ah ,pressure of the ,wind #ai ,forces ,acting on a ,kite #bj ,sustaining ,force in the ,aeroplane #bc ,direct ,lifting and ,resisting ,forces #bd ,shapes of ,planes #bf ,balancing ,sail #bh ,roe's ,triplane at ,wembley #cj ,action of the ,steering ,rudder #ca ,recent ,type of ,wright ,biplane #ca ,circular ,flight #cc ,the ,aileron #ce ,wing ,tipping #cf ,wing ,warping #cg ,the ,gyroscope #ci ,diurnal ,temperatures at ,different ,heights #de ,seasonal ,variation in ,wind ,velocities #dg ,the ,wind ,rose for ,mt4 ,weather1 ,va4 #di ,diagram of ,parts of a ,drifting ,balloon #ea ,glidden and ,stevens ,getting ,away in the ,boston #eb ,relative and ,absolute ,balloon ,velocities #ec ,field and ,speed #ec ,influence of ,wind on ,possible ,course #ed ,count ,zeppelin #ee ,buoyant ,power of ,wood #eg ,one ,cubic ,foot of ,wood ,loaded in ,water #eh ,buoyant ,power of ,hydrogen #ei ,lebaudy's ,jaune #fj ,air ,balloon #fb ,screw ,propeller for ,altitude ,control #ff ,balloon with ,ballonets #fg ,construction of the ,zeppelin ,balloon #fh ,the ,equilibrator #fi ,henry ,giffard's ,dirigible #ga ,dirigible of ,dupuy de ,lome #gb ,tissandier ,brothers' ,dirigible ,balloon #gc ,the ,baldwin #gd ,the ,zeppelin on ,lake ,constance #ge ,the ,patrie #gg ,manufacturing the ,envelope of a ,balloon #gi ,andre's ,balloon1 ,l',oernen #hj ,wreck of the ,zeppelin #hb ,car of the ,zeppelin #hd ,stern ,view of the ,zeppelin #hf ,the ,clment-,bayard #hg ,the ,ville de ,paris #hh ,car of the ,libert #hi ,the ,zodiac ,no4 #b #ib ,united ,states ,signal ,corps ,balloon ,plant at ,fort ,omaha #ic ,the ,caroline #id ,the ,ascent at ,versailles1 #aghc #ie ,proposed ,dirigible #if ,the ,rpublique #ig ,the ,first ,flight for the ,gordon-,bennett ,cup #ii ,the ,gnome ,motor #ajb ,screw ,propeller #ajc ,one of the ,motors of the ,zeppelin #ajd ,the ,four-,cycle ,engine #aje ,action of ,two-,cycle ,engine #ajf ,motor and ,propeller #ajh ,two-,cylinder ,opposed ,engine #aaj ,four-,cylinder ,vertical ,engine #aaj ,head ,end ,shapes #aac ,the ,santos-,dumont ,dirigible ,no4 #b #aae ,in the ,bay of ,monaco3 ,santos-,dumont #aag ,wright ,biplane on ,starting ,rail #aba ,launching ,system for ,wright ,aeroplane #abb ,the ,nieuport ,monoplane #abd ,a ,biplane #abe ,ely at ,los ,angeles #abf ,trajectory ,during ,descent #abg ,descending #abh ,the ,witteman ,glider #acj ,french ,monoplane #acb ,a ,problem in ,steering #acc ,lejeune ,biplane #acd ,tellier ,monoplane #ace ,a ,monoplane #acg ,cars and ,framework #aci ,some ,details #aci ,recent ,french ,machines #ada ,orville ,wright at ,fort ,myer #adc ,the ,first ,flight ,across the ,channel #add ,wright ,motor #ade ,voisin-,farman ,biplane #adg ,the ,champagne ,grand ,prize ,flight #adh ,farman's ,first ,biplane #adi ,the ,june ,bug #aej ,curtiss ,biplane #aea ,curtiss' ,hydro-,aeroplane at ,san ,diego ,bay #aeb ,flying ,over the ,water #aec ,blriot-,voisin ,cellular ,biplane with ,pontoons #aed ,latham's ,antoinette #aee ,james ,j4 ,ward at ,lewiston ,fair #aef ,marcel ,penot in the ,mohawk #aeg ,santos-,dumont's ,demoiselle #aei ,blriot ,monoplane #afj ,latham's ,fall into the ,channel #afa ,de ,lesseps ,crossing the ,channel #afc ,the ,maxim ,aeroplane #afd ,langley's ,aeroplane #afe ,robart ,monoplane #aff ,vina ,monoplane #afg ,blanc ,monoplane #agj ,melvin ,vaniman ,triplane #aga ,jean de ,crawhez ,triplane #aga ,a ,triplane #agb ,giraudon's ,wheel ,aeroplane #age ,brguet ,gyroplane 7,helicopter7 #agg ,wellman's ,america #aha ,the ,german ,emperor ,watching the ,progress of ,aviation #ahi ,automatic ,gun for ,attacking ,airships #aic ,gun for ,shooting at ,aeroplanes #aig ,santos-,dumont ,circling the ,eiffel ,tower #aii ,latham1 ,farman and ,paulhan #bjb ,,flying ,,machines ,,today ,,the ,,delights ,,and ,,dangers ,,of ,,flying ,few things have more charm for man than flight4 ,the soaring of a bird is beautiful and the gliding of a yacht before the wind has something of the same beauty4 ,the child's swing2 the exercise of skating on good ice2 a sixty-mile-an-hour spurt on a smooth road in a motor car2 even the slightly pass bicycle3 these things have all in their time appealed to us because they produce the illusion of flight--of progress through the intangible air with all but separation from the prosaic earth4 ,but these sensations have been only illusions4 ,to actually leave the earth and wander at will in aerial space--this has been1 scarcely a hope1 perhaps rarely even a distinct dream4 ,from the days of ,ddalus and ,icarus1 of ,oriental flying horses and magic carpets1 down to ,darius ,green and his flying machine1 free flight and frenzy were not far apart4 ,we were learnedly told1 only a few years since1 that sustention by heavier-than-air machines was impossible without the discovery1 first1 of some new matter or some new force4 ,it is now 7#aiaa7 only eight years since ,wilbur ,wright at ,kitty ,hawk1 with the aid of the new 787 matter--aluminum--and the new force--the gasoline engine--in three successive flights proved that a man could travel through the air and safely descend1 in a machine weighing many times as much as the air it displaced4 ,it is only five years since two designers--,surcouf and ,lebaudy--built dirigible balloons approximating present forms1 the ,ville de ,paris and ,la ,patrie4 ,it is only now that we average people may confidently contemplate the prospect of an aerial voyage for ourselves before we die4 ,a contemplation not without its shudder1 perhaps2 but yet not altogether more daring than that of our grandsires who first rode on steel rails behind a steam locomotive4 ,the ,dangers of ,aviation ,we are very sure to be informed of the fact when an aviator is killed4 ,comparatively little stir is made nowadays over an automobile fatality1 and the ordinary railroad accident receives bare mention4 ,for instruction and warning1 accidents to air craft cannot be given too much publicity2 but if we wish any accurate conception of the danger we must pay regard to factors of proportion4 ,there are perhaps a thousand aeroplanes and about sixty dirigible balloons in the world4 ,about #ejj men--amateurs and professionals--are continuously engaged in aviation4 ,the ,aero ,club of ,france has issued in that country nearly #cjj licenses4 ,in the ,united ,states1 licenses are held by about thirty individuals4 ,we can form no intelligent estimate as to the number of unlicensed amateurs of all ages who are constantly experimenting with gliders at more or less peril to life and limb4 ,a ,french authority has ascertained the death rate among air-men to have been--to date--about #f4 ,this is equivalent to about one life for #djjj miles of flight3 but we must remember that accidents will vary rather with the number of ascents and descents than with the mileage4 ,four thousand miles in #ajj flights would be much less perilous1 under present conditions1 than #djjj miles in #ajjj flights4 ,illustration3 ,,the ,,aviator ,there were #bf fatal aeroplane accidents between ,september #ag1 #aijh1 and ,december #c1 #aiaj4 ,yet in that period there were many thousands of ascents3 #acjj were made in one week at the ,rheims tournament alone4 ,of the #bf accidents1 #a was due to a wind squall1 #c to collision1 #f 7apparently7 to confusion of the aviator1 and #ab to mechanical breakage4 ,an analysis of #dj ,british accidents shows #ac to have been due to engine failures1 #aj to alighting on bad ground1 #f to wind gusts1 #e to breakage of the propeller1 and #f to fire and miscellaneous causes4 ,these casualties were not all fatal1 although the percentage of fatalities in aeronautic accidents is high4 ,the most serious results were those due to alighting on bad ground2 long grass and standing grain being very likely to trip the machine and throw the occupant4 ,french aviators are now strapping themselves to their seats in order to avoid this last danger4 ,illustration3 ,,the ,,santos-,,dumont ,,demoiselle 7,from ,the ,aeroplane1 by ,hubbard1 ,ledeboer and ,turner7 ,practically all of the accidents occur to those who are flying2 but spectators may endanger themselves4 ,during one of the flights of ,mauvais at ,madrid1 in ,march of the present year1 the bystanders rushed through the barriers and out on the field before the machine had well started4 ,a woman was decapitated by the propeller1 and four other persons were seriously injured4 ,nearly all accidents result from one of three causes3 bad design1 inferior mechanical construction1 and the taking of unnecessary risks by the operator4 ,scientific design at the present writing is perhaps impossible4 ,our knowledge of the laws of air resistance and sustention is neither accurate nor complete4 ,much additional study and experiment must be carried on2 and some better method of experimenting must be devised than that which sends a man up in the air and waits to see what happens4 ,a thorough scientific analysis will not only make aviation safer1 it will aid toward making it commercially important4 ,further data on propeller proportions and efficiencies1 and on strains in the material of screws under aerial conditions1 will do much to standardize power plant equipment4 ,the excessive number of engine breakdowns is obviously related to the extremely light weight of the engines employed3 better design may actually increase these weights over those customary at present4 ,great weight reduction is no longer regarded as essential at present speeds in aerial navigation3 we have perhaps already gone too far in this respect4 ,bad workmanship has been more or less unavoidable1 since no one has yet had ten years' experience in building aeroplanes4 ,the men who have developed the art have usually been sportsmen rather than mechanics1 and only time is necessary to show the impropriety of using safety pins and bent wire nails for connections4 ,the taking of risks has been an essential feature4 ,when one man earns #ajj1jjj in a year by dare-devil flights1 when the public flocks in hordes--and pays good prices--to see a man risk his neck1 he will usually aim to satisfy it4 ,this is not developing aerial navigation3 this is circus riding--looping-the-loop performances which appeal to some savage instinct in us but lead us nowhere4 ,men have climbed two miles into the clouds1 for no good purpose whatever4 ,all that we need to know of high altitude conditions is already known or may be learned by ascents in anchored balloons4 ,records up to heights of sixteen miles have been obtained by sounding balloons4 ,if these high altitudes may under certain conditions be desirable for particular types of balloon1 they are essentially undesirable for the aeroplane4 ,the supporting power of a heavier-than-air machine decreases in precisely inverse ratio with the altitude4 ,to fly high will then involve either more supporting surface and therefore a structurally weaker machine1 or greater speed and consequently a larger motor4 ,it is true that the resistance to propulsion decreases at high altitudes1 just as the supporting power decreases3 and on this account1 given only a sufficient margin of supporting power1 we might expect a standard machine to work about as well at a two-mile elevation as at a height of #bjj feet2 but rarefaction of the air at the higher altitudes decreases the weight of carbureted mixture drawn into the motor1 and consequently its output4 ,any air-man who attempts to reach great heights in a machine not built for such purpose is courting disaster4 ,flights over cities1 spectacular as they are1 and popular as they are likely to remain1 are doubly dangerous on account of the irregular air currents and absence of safe landing places4 ,they have at last been officially discountenanced as not likely to advance the sport4 ,all flights are exhibition flights4 ,the day of a quiet1 mind-your-own-business type of aerial journey has not yet arrived4 ,exhibition performances of any sort are generally hazardous4 ,there were nine men killed in one recent automobile meet4 ,if the automobile were used exclusively for races and contests1 the percentage of fatalities might easily exceed that in aviation4 ,it is claimed that no inexperienced aviator has ever been killed4 ,this may not be true1 but there is no doubt that the larger number of accidents has occurred to the better-known men from whom the public expects something daring4 ,probably the best summing up of the danger of aviation may be obtained from the insurance companies4 ,the courts have decided that an individual does not forfeit his life insurance by making an occasional balloon trip4 ,regular classified rates for aeroplane and balloon operators are in force in ,france and ,germany4 ,it is reported that ,mr4 ,grahame-,white carries a life insurance policy at #ce premium--about the same rate as that paid by a crowned head4 ,another aviator of a less professional type has been refused insurance even at #dj premium4 ,policies of insurance may be obtained covering damage to machines by fire or during transportation and by collisions with other machines2 and covering liability for injuries to persons other than the aviator4 ,on the whole1 flying is an ultra-hazardous occupation2 but an occasional flight by a competent person or by a passenger with a careful pilot is simply a thrilling experience1 practically no more dangerous than many things we do without hesitation4 ,nearly all accidents have been due to preventable causes2 and it is simply a matter of science1 skill1 perseverance1 and determination to make an aerial excursion under proper conditions as safe as a journey in a motor car4 ,men who for valuable prizes undertake spectacular feats will be killed as frequently in aviation as in bicycle or even in automobile racing2 but probably not very much more frequently1 after design and workmanship in flying machines shall have been perfected4 ,the total number of deaths in aviation up to ,february #i1 #aiaa1 is stated to have been forty-two4 ,what ,it ,is ,like to ,fly ,we are fond of comparing flying machines with birds1 with fish1 and with ships3 and there are useful analogies with all three4 ,a drifting balloon is like a becalmed ship or a dead fish4 ,it moves at the speed of the aerial fluid about it and the occupants perceive no movement whatever4 ,the earth's surface below appears to move in the opposite direction to that in which the wind carries the balloon4 ,with a dirigible balloon or flying machine1 the sensation is that of being exposed to a violent wind1 against which 7by observation of landmarks7 we find that we progress4 ,it is the same experience as that obtained when standing in an exposed position on a steamship1 and we wonder if a bird or a fish gradually gets so accustomed to the opposing current as to be unconscious of it4 ,but in spite of jar of motors and machinery1 there is a freedom of movement1 a detachment from earth-associations1 in air flight1 that distinguishes it absolutely from the churning of a powerful vessel through the waves4 ,illustration3 ,,view ,,from ,a ,,balloon ,illustration3 ,,anatomy ,,of ,a ,,bird',s ,,wing 7,from ,walker's ,aerial ,navigation7 ,illustration3 ,,flight ,,of ,a ,,bird ,birds fly in one of three ways4 ,the most familiar bird flight is by a rapid wing movement which has been called oar-like1 but which is precisely equivalent to the usual movement of the arms of a man in swimming4 ,the edge of the wing moves forward1 cutting the air2 on the return stroke the leading edge is depressed so as to present a nearly flat surface to the air and thus propel the bird forward4 ,a slight downward direction of this stroke serves to impel the flight sufficiently upward to offset the effect of gravity4 ,any man can learn to swim1 but no man can fly1 because neither in his muscular frame nor by any device which he can attach thereto can he exert a sufficient pressure to overcome his own weight against as imponderable a fluid as air4 ,if air were as heavy as water1 instead of #gjj times lighter1 it would be as easy to fly as to swim4 ,the bird can fly because of the great surface1 powerful construction1 and rapid movement of its wings1 in proportion to the weight of its body4 ,but compared with the rest of the animal kingdom1 flying birds are all of small size4 ,helmholz considered that the vulture represented the heaviest body that could possibly be raised and kept aloft by the exercise of muscular power1 and it is understood that vultures have considerable difficulty in ascending2 so much so that unless in a position to take a short preliminary run they are easily captured4 ,every one has noticed a second type of bird flight--soaring4 ,it is this flight which is exactly imitated in a glider4 ,an aeroplane differs from a soaring bird only in that it carries with it a producer of forward impetus--the propeller--so that the soaring flight may last indefinitely3 whereas a soaring bird gradually loses speed and descends4 ,illustration3 ,,in ,a ,,meteoric ,,shower ,a third and rare type of bird flight has been called sailing4 ,the bird faces the wind1 and with wings outspread and their forward edge elevated rises while being forced backward under the action of the breeze4 ,as soon as the wind somewhat subsides1 the bird turns and soars in the desired direction4 ,flight is thus accomplished without muscular effort other than that necessary to properly incline the wings and to make the turns4 ,it is practicable only in squally winds1 and the birds which practice sailing--the albatross and frigate bird--are those which live in the lower and more disturbed regions of the atmosphere4 ,this form of flight has been approximately imitated in the manoeuvering of aeroplanes4 ,comparison of flying machines and ships suggests many points of difference4 ,water is a fluid of great density1 with a definite upper surface1 on which marine structures naturally rest4 ,a vessel in the air may be at any elevation in the surrounding rarefied fluid1 and great attention is necessary to keep it at the elevation desired4 ,the air has no surface4 ,the air ship is like a submarine--the dirigible balloon of the sea--and perhaps rather more safe4 ,an ordinary ship is only partially immersed2 the resistance of the fluid medium is exerted over a portion only of its head end3 but the submarine or the flying machine is wholly exposed to this resistance4 ,the submarine is subjected to ocean currents of a very few miles per hour1 at most2 the currents to which the flying machine may be exposed exceed a mile a minute4 ,put a submarine in the ,whirlpool ,rapids at ,niagara and you will have possible air ship conditions4 ,a marine vessel may tack1 i4e41 may sail partially against the wind that propels it1 by skillful utilization of the resistance to sidewise movement of the ship through the water3 but the flying machine is wholly immersed in a single fluid1 and a head wind is nothing else than a head wind1 producing an absolute subtraction from the proper speed of the vessel4 ,illustration3 ,,how ,a ,,boat ,,tacks ,the wind always exerts a pressure1 perpendicular to the sail1 which tends to drift the boat sidewise 7,r7 and also to propel it forward 7,l74 ,sidewise movement is resisted by the hull4 ,an air ship cannot tack because there is no such resistance to drift4 ,aerial navigation is thus a new art1 particularly when heavier-than-air machines are used4 ,we have no heavier-than-water ships4 ,the flying machine must work out its own salvation4 ,,soaring ,,flight ,,by ,,man ,flying machines have been classified as follows3-- ,lighter than ,air ,fixed balloon1 ,drifting balloon1 ,sailing balloon1 ,dirigible balloon rigid 7,zeppelin71 ballonetted4 ,heavier than ,air ,orthopter1 ,helicopter1 ,aeroplane monoplane1 multiplane4 ,we will fall in with the present current of popular interest and consider the aeroplane--that mechanical grasshopper--first4 ,what ,holds ,it ,up8 ,illustration3 ,,octave ,,chanute 7,,died #aiaj7 ,to the researches of ,chanute and ,langley must be ascribed much of ,american progress in aviation4 ,when a flat surface like the side of a house is exposed to the breeze1 the velocity of the wind exerts a force or pressure directly against the surface4 ,this principle is taken into account in the design of buildings1 bridges1 and other structures4 ,the pressure exerted per square foot of surface is equal 7approximately7 to the square of the wind velocity in miles per hour1 divided by #cjj4 ,thus1 if the wind velocity is thirty miles1 the pressure against a house wall on which it acts directly is #cj #cj #cjj #c pounds per square foot3 if the wind velocity is sixty miles1 the pressure is #fj #fj #cjj #ab pounds3 if the velocity is ninety miles1 the pressure is #ij #ij #cjj #bg pounds1 and so on4 ,illustration3 ,,pressure ,,of ,,the ,,wind ,if the wind blows obliquely toward the surface1 instead of directly1 the pressure at any given velocity is reduced1 but may still be considerable4 ,thus1 in the sketch1 let ab represent a wall1 toward which we are looking downward1 and let the arrow ,v represent the direction of the wind4 ,the air particles will follow some such paths as those indicated1 being deflected so as to finally escape around the ends of the wall4 ,the result is that a pressure is produced which may be considered to act along the dotted line ,p1 perpendicular to the wall4 ,this is the invariable law3 that no matter how oblique the surface may be1 with reference to the direction of the wind1 there is always a pressure produced against the surface by the wind1 and this pressure always acts in a direction perpendicular to the surface4 ,the amount of pressure will depend upon the wind velocity and the obliquity or inclination of the surface 7ab7 with the wind 7,v74 ,now let us consider a kite--the immediate ancestor of the aeroplane4 ,the surface ab is that of the kite itself1 held by its string cd4 ,we are standing at one side and looking at the edge of the kite4 ,the wind is moving horizontally against the face of the kite1 and produces a pressure ,p directly against the latter4 ,the pressure tends both to move it toward the left and to lift it4 ,if the tendency to move toward the left be overcome by the string1 then the tendency toward lifting may be offset--and in practice is offset--by the weight of the kite and tail4 ,illustration3 ,,forces ,,acting ,,on ,a ,,kite ,we may represent the two tendencies to movement produced by the force ,p1 by drawing additional dotted lines1 one horizontally to the left 7,r7 and the other vertically 7,l72 and it is known that if we let the length of the line ,p represent to some convenient scale the amount of direct pressure1 then the lengths of ,r and ,l will also represent to the same scale the amounts of horizontal and vertical force due to the pressure4 ,if the weight of kite and tail exceeds the vertical force ,l1 the kite will descend3 if these weights are less than that force1 the kite will ascend4 ,if they are precisely equal to it1 the kite will neither ascend nor descend4 ,the ratio of ,l to ,r is determined by the slope of ,p2 and this is fixed by the slope of ab2 so that we have the most important conclusion3 not only does the amount of direct pressure 7,p7 depend upon the obliquity of the surface with the breeze 7as has already been shown71 but the relation of vertical force 7which sustains the kite7 to horizontal force also depends on the same obliquity4 ,for example1 if the kite were flying almost directly above the boy who held the string1 so that ab became almost horizontal1 ,p would be nearly vertical and ,l would be much greater than ,r4 ,on the other hand1 if ab were nearly vertical1 the kite flying at low elevation1 the string and the direct pressure would be nearly horizontal and ,l would be much less than ,r4 ,the force ,l which lifts the kite seems to increase while ,r decreases1 as the kite ascends3 but ,l may not actually increase1 because it depends upon the amount of direct pressure1 ,p1 as well as upon the direction of this pressure2 and the amount of direct pressure steadily decreases during ascent1 on account of the increasing obliquity of ab with ,v4 ,all of this is of course dependent on the assumption that the kite always has the same inclination to the string1 and the described resolution of the forces1 although answering for illustrative purposes1 is technically incorrect4 ,it seems to be the wind velocity1 then1 which holds up the kite3 but in reality the string is just as necessary as the wind4 ,if there is no string1 and the wind blows the kite with it1 the kite comes down1 because the pressure is wholly due to a relative velocity as between kite and wind4 ,the wind exerts a pressure against the rear of a railway train1 if it happens to be blowing in that direction1 and if we stood on the rear platform of a stationary train we should feel that pressure3 but if the train is started up and caused to move at the same speed as the wind there would be no pressure whatever4 ,one of the very first heavier-than-air flights ever recorded is said to have been made by a ,japanese who dropped bombs from an immense man-carrying kite during the ,satsuma rebellion of #ahfi4 ,the kite as a flying machine has1 however1 two drawbacks3 it needs the wind--it cannot fly in a calm--and it stands still4 ,one early effort to improve on this situation was made in #ahef1 when a man was towed in a sort of kite which was hauled by a vehicle moving on the ground4 ,in ,february of the present year1 ,lieut4 ,john ,rodgers1 ,u4,s4,n41 was lifted #djj feet from the deck of the cruiser ,pennsylvania by a train of eleven large kites1 the vessel steaming at twelve knots against an eight-knot breeze4 ,the aviator made observations and took photographs for about fifteen minutes1 while suspended from a tail cable about #ajj feet astern4 ,in the absence of a sufficient natural breeze1 an artificial wind was thus produced by the motion imparted to the kite2 and the device permitted of reaching some destination4 ,the next step was obviously to get rid of the tractive vehicle and tow rope by carrying propelling machinery on the kite4 ,this had been accomplished by ,langley in #ahif1 who flew a thirty-pound model nearly a mile1 using a steam engine for power4 ,the gasoline engine1 first employed by ,santos-,dumont 7in a dirigible balloon7 in #aija1 has made possible the present day aeroplane4 ,illustration3 ,,sustaining ,,force ,,in ,,the ,,aeroplane ,what keeps it up1 in the case of this device1 is likewise its velocity4 ,looking from the side1 ab is the sail of the aeroplane1 which is moving toward the right at such speed as to produce the equivalent of an air velocity ,v to the left4 ,this velocity causes the direct pressure ,p1 equivalent to a lifting force ,l and a retarding force ,r4 ,the latter is the force which must be overcome by the motor3 the former must suffice to overcome the whole weight of the apparatus4 ,travel in an aeroplane is like skating rapidly over very thin ice3 the air literally doesn't have time to get away from underneath4 ,illustration3 ,,direct1 ,,lifting1 ,,and ,,resisting ,,forces ,if the pressure is #aj lbs4 when the wind blows directly toward the surface 7at an angle of #ij degrees71 then the forces for other angles of direction are as shown on the diagram4 ,the amounts of all forces depend upon the wind velocity3 that assumed in drawing the diagram was about #ee miles per hour4 ,but the relations of the forces are the same for the various angles1 no matter what the velocity4 ,if we designate the angle made by the wings 7ab7 with the horizontal 7,v7 as ,b1 then ,p increases as ,b increases1 while 7as has been stated7 the ratio of ,l to ,r decreases4 ,when the angle ,b is a right angle1 the wings being in the position ab1 ,p has its maximum value for direct wind--#a_/cjj of the square of the velocity1 in pounds per square foot2 but ,l is zero and ,r is equal to ,p4 ,the plane would have no lifting power4 ,when the angle ,b becomes zero1 position ab1 wings being horizontal1 ,p becomes zero and 7so far as we can now judge7 the plane has neither lifting power nor retarding force4 ,at some intermediate position1 like ab1 there will be appreciable lifting and retarding forces4 ,the chart shows the approximate lifting force1 in pounds per square foot1 for various angles4 ,this force becomes a maximum at an angle of #de 7half a right angle74 ,we are not yet prepared to consider why in all actual aeroplanes the angle of inclination is much less than this4 ,the reason will be shown presently4 ,at this stage of the discussion we may note that the lifting power per square foot of sail area varies with the square of the velocity1 and the angle of inclination4 ,the total lifting power of the whole plane will also vary with its area4 ,as we do not wish this whole lifting power to be consumed in overcoming the dead weight of the machine itself1 we must keep the parts light1 and in particular must use for the wings a fabric of light weight per unit of surface4 ,these fabrics are frequently the same as those used for the envelopes of balloons4 ,since the total supporting power varies both with the sail area and with the velocity1 we may attain a given capacity either by employing large sails or by using high speed4 ,the size of sails for a given machine varies inversely as the square of the speed4 ,the original ,wright machine had #ejj square feet of wings and a speed of forty miles per hour4 ,at eighty miles per hour the necessary sail area for this machine would be only #abe square feet2 and at #afj miles per hour it would be only #ca-a_/d square feet3 while if we attempted to run the machine at ten miles per hour we should need a sail area of #hjjj square feet4 ,this explains why the aeroplane cannot go slowly4 ,it would seem as if when two or more superposed sails were used1 as in biplanes1 the full effect of the air would not be realized1 one sail becalming the other4 ,experiments have shown this to be the case2 but there is no great reduction in lifting power unless the distance apart is considerably less than the width of the planes4 ,in all present aeroplanes the sails are concaved on the under side4 ,this serves to keep the air from escaping from underneath as rapidly as it otherwise would1 and increases the lifting power from one-fourth to one-half over that given by our #a_/cjj rule3 the divisor becoming roughly about #bcj instead of #cjj4 ,illustration3 ,,shapes ,,of ,,planes ,why are the wings placed crosswise of the machine1 when the other arrangement--the greatest dimension in the line of flight--would seem to be stronger8 ,this is also done in order to keep the air from escaping from underneath4 ,the sketch shows how much less easily the air will get away from below a wing of the bird-like spread-out form than from one relatively long and narrow but of the same area4 ,a sustaining force of two pounds per square foot of area has been common in ordinary aeroplanes and is perhaps comparable with the results of bird studies3 but this figure is steadily increasing as velocities increase4 ,why so ,many ,sails8 ,thus far a single wing or pair of wings would seem to fully answer for practicable flight3 yet every actual aeroplane has several small wings at various points4 ,the necessity for one of these had already been discovered in the kite1 which is built with a balancing tail4 ,in the sketch on page #ah it appears that the particles of air which are near the upper edge of the surface are more obstructed in their effort to get around and past than those near the lower edge4 ,they have to turn almost completely about1 while the others are merely deflected4 ,this means that on the whole the upper air particles will exert more pressure than the lower particles and that the center of pressure 7the point where the entire force of the wind may be assumed to act7 will be1 not at the center of the surface1 but at a point some distance above this center4 ,this action is described as the displacement of the center of pressure4 ,it is known that the displacement is greatest for least inclinations of surface 7as might be surmised from the sketch already referred to71 and that it is always proportional to the dimension of the surface in the direction of movement2 i4e41 to the length of the line ab4 ,illustration3 ,,balancing ,,sail ,if the weight ,w of the aeroplane acts downward at the center of the wing 7at o in the accompanying sketch71 while the direct pressure ,p acts at some point c farther along toward the upper edge of the wing1 the two forces ,w and ,p tend to revolve the whole wing in the direction indicated by the curved arrow4 ,this rotation1 in an aeroplane1 is resisted by the use of a tail plane or planes1 such as mn4 ,the velocity produces a direct pressure ,p on the tail plane1 which opposes1 like a lever1 any rotation due to the action of ,p4 ,it may be considered a matter of rather nice calculation to get the area and location of the tail plane just right3 but we must remember that the amount of pressure ,p can be greatly varied by changing the inclination of the surface mn4 ,this change of inclination is effected by the operator1 who has access to wires which are attached to the pivoted tail plane4 ,it is of course permissible to place the tail plane in front of the main planes--as in the original ,wright machine illustrated3 but in this case1 with the relative positions of ,w and ,p already shown1 the forward edge of the tail plane would have to be depressed instead of elevated4 ,the illustration shows the tail built as a biplane1 just as are the principal wings 7page #ada74 ,suppose the machine to be started with the tail plane in a horizontal position4 ,as its speed increases1 it rises and at the same time 7if the weight is suspended from the center of the main planes7 tilts backward4 ,the tilting can be stopped by swinging the tail plane on its pivot so as to oppose the rotative tendency4 ,if this control is not carried too far1 the main planes will be allowed to maintain some of their excessive inclination and ascent will continue4 ,when the desired altitude has been attained1 the inclination of the main planes will1 by further swinging of the tail plane1 be reduced to the normal amount1 at which the supporting power is precisely equal to the load2 and the machine will be in vertical equilibrium3 an equilibrium which demands at every moment1 however1 the attention of the operator4 ,in many machines1 ascent and tilting are separately controlled by using two sets of transverse planes1 one set placed forward1 and the other set aft1 of the main planes4 ,in any case1 quick ascent can be produced only by an increase in the lifting force ,l 7see sketch1 page #bd7 of the main planes3 and this force is increased by enlarging the angle of inclination of the main planes1 that is1 by a controlled and partial tilting4 ,the forward transverse wing which produces this tilting is therefore called the elevating rudder or elevating plane4 ,the rear transverse plane which checks the tilting and steadies the machine is often described as the stabilizing plane4 ,descent is of course produced by decreasing the angle of inclination of the main planes4 ,illustration3 ,,roe',s ,,triplane ,,at ,,wembley 7,from ,brewer's ,art of ,aviation7 ,steering ,if we need extra sails for stability and ascent or descent1 we need them also for changes of horizontal direction4 ,let ab be the top view of the main plane of a machine1 following the course xy4 ,at rs is a vertical plane called the steering rudder4 ,this is pivoted1 and controlled by the operator by means of the wires t1 u4 ,let the rudder be suddenly shifted to the position rs4 ,it will then be subjected to a pressure ,p which will swing the whole machine into the new position shown by the dotted lines1 its course becoming xy4 ,the steering rudder may of course be double1 forming a vertical biplane1 as in the ,wright machine shown below4 ,illustration3 ,,action ,,of ,,the ,,steering ,,rudder ,successful steering necessitates lateral resistance to drift1 i4e41 a fulcrum4 ,this is provided1 to some extent1 by the stays and frame of the machine2 and in a much more ample way by the vertical planes of the original ,voisin cellular biplane4 ,a recent ,wright machine had vertical planes forward probably intended for this purpose4 ,illustration3 ,,recent ,,type ,,of ,,wright ,,biplane ,it now begins to appear that the aviator has a great many things to look after4 ,there are many more things requiring his attention than have yet been suggested4 ,no one has any business to attempt flying unless he is superlatively cool-headed and has the happy faculty of instinctively doing the right thing in an emergency4 ,give a chauffeur a high power automobile running at maximum speed on a rough and unfamiliar road1 and you have some conception of the position of the operator of an aeroplane4 ,it is perhaps not too much to say that to make the two positions fairly comparable we should blindfold the chauffeur4 ,broadly speaking1 designers may be classed in one of two groups--those who1 like the ,wrights1 believe in training the aviator so as to qualify him to properly handle his complicated machine2 and those who aim to simplify the whole question of control so that to acquire the necessary ability will not be impossible for the average man4 ,if aviation is to become a popular sport1 the latter ideal must prevail4 ,the machines must be more automatic and the aviator must have time to enjoy the scenery4 ,in ,france1 where amateur aviation is of some importance1 progress has already been made in this direction4 ,the universal steering head1 for example1 which not only revolves like that of an automobile1 but is hinged to permit of additional movements1 provides for simultaneous control of the steering rudder and the main plane warping1 while scarcely demanding the conscious thought of the operator4 ,,turning ,,corners ,a year elapsed after the first successful flight at ,kitty ,hawk before the aviator became able to describe a circle in the air4 ,a later date1 #aijg1 is recorded for the first ,european half-circular flight3 and the first complete circuit1 on the other side of the water1 was made a year after that2 by both biplane and monoplane4 ,it was in the same year that ,louis ,blriot made the pioneer cross-country trip of twenty-one miles1 stopping at will en route and returning to his starting point4 ,what ,happens ,when ,making a ,turn ,illustration3 ,,circular ,,flight ,we are looking downward on an aeroplane ab which has been moving along the straight path cd4 ,at d it begins to describe the circle de1 the radius of which is od1 around the center o4 ,the outer portion of the plane1 at the edge b1 must then move faster than the inner edge a4 ,we have seen that the direct air pressure on the plane is proportional to the square of the velocity4 ,the direct pressure ,p 7see sketch on page #bb7 will then be greater at the outer than at the inner limb2 the lifting force ,l will also be greater and the outer limb will tend to rise1 so that the plane 7viewed from the rear7 will take the inclined position shown in the lower view3 and this inclination will increase as long as the outer limb travels faster than the inner limb2 that is1 as long as the orbit continues to be curved4 ,very soon1 then1 the plane will be completely tipped over4 ,necessarily1 the two velocities have the ratio om3om2 the respective lifting forces must then be proportional to the squares of these distances4 ,the difference of lifting forces1 and the tendency to overturn1 will be more important as the distances most greatly differ3 which is the case when the distance om is small as compared with mm4 ,the shorter the radius of curvature1 the more dangerous1 for a given machine1 is a circling flight3 and in rounding a curve of given radius the most danger is attached to the machine of greatest spread of wing4 ,lateral ,stability ,this particular difficulty has considerably delayed the development of the aeroplane4 ,it may1 however1 be overcome by very simple methods--simple1 at least as far as their mechanical features are concerned4 ,if the outer limb of the plane is tilted upward1 it is because the wind pressure is greater there4 ,the wind pressure is greater because the velocity is greater4 ,we have only to increase the wind pressure at the inner limb1 in order to restore equilibrium4 ,this cannot be done by adjusting the velocity1 because the velocity is fixed by the curvature of path required3 but the total wind pressure depends upon the sail area as well as the velocity2 so that by increasing the surface at the inner limb we may equalize the value of ,l1 the lifting force1 at the two ends of the plane4 ,this increase of surface must be a temporary affair1 to be discontinued when moving along a straight course4 ,illustration3 ,,the ,,aileron ,let us stand in the rear of an aeroplane1 the main wing of which is represented by ab4 ,let the small fan-shaped wings c and d be attached near the ends1 and let the control wires1 e1 f1 passing to the operator at g1 be employed to close and unclasp the fans4 ,if these fans are given a forward inclination at the top1 as indicated in the end view1 they will when spread out exert an extra lifting force4 ,a fan will be placed at each end4 ,they will be ordinarily folded up3 but when rounding a curve the aviator will open the fan on the inner or more slowly moving limb of the main plane4 ,this represents one of the first forms of the aileron or wing-tip for lateral control4 ,the more common present form of aileron is that shown in the lower sketch1 at s and t4 ,the method of control is the same4 ,illustration3 ,,wing ,,tipping ,the cellular ,voisin biplanes illustrate an attempt at self-sufficing control1 without the interposition of the aviator4 ,between the upper and lower sails of the machine there were fore and aft vertical partitions4 ,the idea was that when the machine started to revolve1 the velocity of rotation would produce a pressure against these partitions which would obstruct the tipping4 ,but rotation may take place slowly1 so as to produce an insufficient pressure for control1 and yet be amply sufficient to wreck the apparatus4 ,the use of extra vertical rudder planes1 hinged on a horizontal longitudinal axis1 is open to the same objection4 ,wing ,warping ,in some monoplanes with the inverted ,v wing arrangement1 a dipping of one wing answers1 so to speak1 to increase its concavity and thus to augment the lifting force on that side4 ,the sketch shows the normal and distorted arrangement of wings3 the inner limb being the one bent down in rounding a curve4 ,an equivalent plan was to change the angle of inclination of one-half the sail by swinging it about a horizontal pivot at the center or at the rear edge3 some machines have been built with sails divided in the center4 ,the obvious objection to both of these plans is that too much mechanism is necessary in order to distort what amounts to nearly half the whole machine4 ,they remind one of ,charles ,lamb's story of the discovery of roast pig4 ,illustration3 ,,wing ,,warping ,the distinctive feature of the ,wright machines lies in the warping or distorting of the ends only of the main planes4 ,this is made possible1 not by hinging the wings in halves1 but by the flexibility of the framework1 which is sufficiently pliable to permit of a considerable bending without danger4 ,the operator1 by pulling on a stout wire linkage1 may tip up 7or down7 the corners cc of the sails at one limb1 thus decreasing or increasing the effective surface acted on by the wind1 as the case may require4 ,the only objection is that the scheme provides one more thing for the aviator to think about and manipulate4 ,automatic ,control ,let us consider again the condition of things when rounding a curve1 as in the sketch on page #cb4 ,as long as the machine is moving forward in a straight line1 the operator sits upright4 ,when it begins to tip1 he will unconsciously tip himself the other way1 as represented by the line xy in the rear view4 ,any bicyclist will recognize this as plausible4 ,why not take advantage of this involuntary movement to provide a stabilizing force8 ,if operating wires are attached to the aviator's belt and from thence connected with ailerons or wing-warping devices1 then by a proper proportioning of levers and surfaces to the probable swaying of the man1 the control may become automatic4 ,the idea is not new2 it has even been made the subject of a patent4 ,the ,gyroscope ,illustration3 ,,the ,,gyroscope ,this device for automatic control is being steadily developed and may ultimately supersede all others4 ,it uses the inertia of a fast-moving fly wheel for control1 in a manner not unlike that contemplated in proposed methods of automatic balancing by the action of a suspended pendulum4 ,every one has seen the toy gyroscope and perhaps has wondered at its mysterious ways4 ,the mathematical analysis of its action fills volumes3 but some idea of what it does1 and why1 may perhaps be gathered at the expense of a very small amount of careful attention4 ,the wheel acbd1 a thin disc1 is spinning rapidly about the axle o4 ,in the side view1 ab shows the edge of the wheel1 and oo the axle4 ,this axle is not fixed1 but may be conceived as held in some one's fingers4 ,now suppose the right-hand end of the axle 7o7 to be suddenly moved toward us 7away from the paper7 and the left-hand 7o7 to be moved away4 ,the wheel will now appear in both views as an ellipse1 and it has been so represented1 as afbe4 ,now1 any particle1 like x1 on the rim of the wheel1 will have been regularly moving in the circular orbit cb4 ,the tendency of any body in motion is to move indefinitely in a straight line4 ,the cohesion of the metal of the disc prevents the particle x from flying off at a straight line tangent1 xy1 and it is constrained1 therefore1 to move in a circular orbit4 ,unless some additional constraint is imposed1 it will at least remain in this orbit and will try to remain in its plane of rotation4 ,when the disc is tipped1 the plane of rotation is changed1 and the particle is required1 instead of 7so to speak7 remaining in the plane of the paper--in the side view--to approach and pass through that plane at b and afterward to continue receding from us4 ,under ordinary circumstances1 this is just what it would do3 but if1 as in the gyroscope1 the axle oo is perfectly free to move in any direction1 the particle x will refuse to change its direction of rotation4 ,its position has been shifted3 it no longer lies in the plane of the paper3 but it will at least persist in rotating in a parallel plane3 and this persistence forces the revolving disc to swing into the new position indicated by the curve hg1 the axis being tipped into the position pq4 ,the whole effect of all particles like x in the entire wheel will be found to produce precisely this condition of things3 if we undertake to change the plane of rotation by shifting the axle in a horizontal plane1 the device itself will 7if not prevented7 make a further change in the plane of rotation by shifting the axle in a vertical plane4 ,a revolving disc mounted on the gyroscopic framework therefore resists influences tending to change its plane of rotation4 ,if the device is placed on a steamship1 so that when the vessel rolls a change of rotative plane is produced1 the action of the gyroscope will resist the rolling tendency of the vessel4 ,all that is necessary is to have the wheel revolving in a fore and aft plane on the center line of the vessel1 the axle being transverse and firmly attached to the vessel itself4 ,a small amount of power 7consumed in revolving the wheel7 gives a marked steadying effect4 ,the same location and arrangement on an aeroplane will suffice to overcome tendencies to transverse rotation when rounding curves4 ,the device itself is automatic1 and requires no attention1 but it does unfortunately require power to drive it and it adds some weight4 ,the gyroscope is being tested at the present time on some of the aeroplanes at the temporary army camps near ,san ,antonio1 ,texas4 ,wind ,gusts ,this feature of aeronautics is particularly important1 because any device which will give automatic stability when turning corners will go far toward making aviation a safe amusement4 ,inequalities of velocity exist not only on curves1 but also when the wind is blowing at anything but uniform velocity across the whole front of the machine4 ,the slightest flaw in the wind means an at least temporary variation in lifting force of the two arms4 ,here is a pregnant source of danger1 and one which cannot be left for the aviator to meet by conscious thought and action4 ,it is this1 then1 that blindfolds him3 he cannot see the wind conditions in advance4 ,the conditions are upon him1 and may have done their destructive work1 before he can prepare to control them4 ,we must now study what these conditions are and what their influence may be on various forms of aerial navigation3 after which1 a return to our present subject will be possible4 ,,air ,,and ,,the ,,wind ,the air that surrounds us weighs about one-thirteenth of a pound per cubic foot and exerts a pressure1 at sea level1 of nearly fifteen pounds per square inch4 ,its temperature varies from #cj below to #ajj above the ,fahrenheit zero4 ,the pressure of the air decreases about one-half pound for each thousand feet of altitude2 at the top of ,mt4 ,blanc it would be1 therefore1 only about six pounds per square inch4 ,the temperature also decreases with the altitude4 ,the weight of a cubic foot1 or density1 which1 as has been stated1 is one-thirteenth of a pound ordinarily1 varies with the pressure and with the temperature4 ,the variation with pressure may be described by saying that the quotient of the pressure by the density is constant3 one varies in the same ratio as the other4 ,thus1 at the top of ,mt4 ,blanc 7if the temperature were the same as at sea level71 the density of air would be about #f_/ae #a_/ac #b_/fe3 less than half what it is at sea level4 ,as to temperature1 if we call our ,fahrenheit zero #dfj1 and correspondingly describe other temperatures--for instance1 say that water boils at #fgb--then 7pressure being unchanged7 the product of the density and the temperature is constant4 ,if the density at sea level and zero temperature is one-thirteenth pound1 then that at sea level and #dfj ,fahrenheit would be 7#j #dfj7_/7dfj #dfj7 #a_/ac #a_/bf4 ,these relations are particularly important in the design of all balloons1 and in computations relating to aeroplane flight at high altitudes4 ,we shall be prepared to appreciate some of their applications presently4 ,generally speaking1 the atmosphere is always in motion1 and moving air is called wind4 ,our meteorologists first studied winds near the surface of the ground3 it is only of late years that high altitude measurements have been considered practically desirable4 ,now1 records are obtained by the aid of kites up to a height of nearly four miles3 estimates of cloud movements have given data on wind velocities at heights above six miles3 and much greater heights have been obtained by free balloons equipped with instruments for recording temperatures1 pressures1 altitude1 time1 and other data4 ,when the ,eiffel ,tower was completed1 it was found that the average wind velocity at its summit was about four times that at the base4 ,since that time1 much attention has been given to the contrasting conditions of surface and upper breezes as to direction and velocity4 ,air is easily impeded in its movement1 and the well-known uncertainties of the weather are closely related to local variations in atmospheric pressure and temperature4 ,when near the surface of the ground1 impingement against irregularities therein--hills1 cliffs1 and buildings--makes the atmospheric currents turbulent and irregular4 ,where there are no surface irregularities1 as on a smooth plain or over water1 the friction of the air particles passing over the surface still results in a stratification of velocities4 ,even on a mountain top1 the direction and speed of the wind are less steady than in the open where measured by a captive balloon4 ,the stronger the wind1 the greater1 relatively1 is the irregularity produced by surface conditions4 ,further1 the earth's surface and its features form a vast sponge for sun heat1 which they transfer in turn to the air in an irregular way1 producing those convectional currents peculiar to low altitudes1 the upper limit of which is marked by the elevation of the cumulus clouds4 ,near the surface1 therefore1 wind velocities are lowest in the early morning1 rising to a maximum in the afternoon4 ,illustration3 ,,diurnal ,,temperatures ,,at ,,different ,,heights 7,from ,rotch's ,the ,conquest of the ,air7 ,every locality has its so-called prevailing winds4 ,considering the compass as having eight points1 one of those points may describe as many as #dj of all the winds at a given place4 ,the direction of prevalence varies with the season4 ,the range of wind velocities is also a matter of local peculiarity4 ,in ,paris1 the wind speed exceeds thirty-four miles per hour on only sixty-eight days in the average year1 and exceeds fifty-four miles on only fifteen days4 ,observations at ,boston show that the velocity of the wind exceeds twenty miles per hour on half the days in winter and on only one-sixth the days in summer4 ,our largest present dirigible balloons have independent speeds of about thirty-four miles per hour and are therefore available 7at some degree of effectiveness7 for nearly ten months of the year1 in the vicinity of ,paris4 ,in a region of low wind velocities--like western ,washington1 in this country--they would be available a much greater proportion of the time4 ,to make the dirigible able to at least move nearly every day in the average year--in ,paris--it must be given a speed of about fifty-five miles per hour4 ,figures as to wind velocity mean little to one unaccustomed to using them4 ,a five-mile breeze is just pleasant4 ,twelve miles means a brisk gale4 ,thirty miles is a high wind3 fifty miles a serious storm 7these are the winds the aviator constantly meets73 one hundred miles is perhaps about the maximum hurricane velocity4 ,as we ascend from the surface of the earth1 the wind velocity steadily increases2 and the excess velocity of winter winds over summer winds is as steadily augmented4 ,thus1 ,professor ,rotch found the following variations3 ,altitude in ,feet ,annual ,average ,wind ,velocity1 ,feet per ,second #fef #bc4ae #a1hjj #cb4aj #c1bhj #ce4 #h1aij #da4 #aa1ddj #ej4h #ag1fhj #ha4g #bj1igj #hi4 #ca1ajj #aag4e ,average ,wind ,velocities1 ,altitude in ,feet ,feet per ,second ,summer ,winter #fef to #c1bhj #bd4ee #bh4hj #c1bhj to #i1haj #bf4he #dh4ag #i1haj to #af1djj #cd4fe #ga4jj #af1djj to #bb1iej #fb4fj #afa4e #bb1iej to #bi1ejj #gg4jj #agg4j ,illustration3 ,,diurnal ,,temperatures ,,at ,,different ,,heights ,these results are shown in a more striking way by the chart4 ,at a five or six mile height1 double-barreled hurricanes at speeds exceeding #bjj miles per hour are not merely possible2 they are part of the regular order of things1 during the winter months4 ,the winds of the upper air1 though vastly more powerful1 are far less irregular than those near the surface3 and the directions of prevailing winds are changed4 ,if #ej of the winds1 at a given location on the surface1 are from the southwest1 then at as moderate an elevation as even #ajjj feet1 the prevailing direction will cease to be from southwest2 it may become from west-southwest2 and the proportion of total winds coming from this direction will not be #ej4 ,these factors are represented in meteorological papers by what is known as the wind rose4 ,from the samples shown1 we may note that #dj of the surface winds at ,mount ,weather are from the northwest2 while at some elevation not stated the most prevalent of the winds 7#bb of the total7 are westerly4 ,the direction of prevalence has changed through one-eighth of the possible circle1 and in a counter-clockwise direction4 ,this is contrary to the usual variation described by the so-called ,broun's ,law1 which asserts that as we ascend the direction of prevalence rotates around the circle like the hands of a watch2 being1 say1 from northwest at the surface1 from north at some elevation1 from northeast at a still higher elevation1 and so on4 ,at a great height1 the change in direction may become total3 that is1 the high altitude winds blow in the exactly opposite direction to that of the surface winds4 ,in the temperate regions1 most of the high altitude winds are from the west3 in the tropics1 the surface winds blow toward the west and toward the equator2 being northeasterly in the northern hemisphere and southeasterly in the southern3 and there are undoubtedly equally prevalent high-altitude counter-trades4 ,illustration3 ,,the ,,wind ,,rose ,,for ,,mount ,,weather1 ,,va4 7,from the ,bulletin of the ,mount ,weather ,observatory1 ,,ii1 #f7 ,the best flying height for an aeroplane over a flat field out in the country is perhaps quite low--#bjj or #cjj feet3 but for cross-country trips1 where hills1 rivers1 and buildings disturb the air currents1 a much higher elevation is necessary2 perhaps #bjjj or #cjjj feet1 but in no case more than a mile4 ,the same altitude is suitable for dirigible balloons4 ,at these elevations we have the conditions of reasonable warmth1 dryness1 and moderate wind velocities4 ,sailing ,balloons ,in classifying air craft1 the sailing balloon was mentioned as a type intermediate between the drifting balloon and the dirigible4 ,no such type has before been recognized3 but it may prove to have its field1 just as the sailing vessel on the sea has bridged the gap between the raft and the steamship4 ,it is true that tacking is impossible1 so that our sailing balloons must always run before the wind3 but they possess this great advantage over marine sailing craft1 that by varying their altitude they may always be able to find a favorable wind4 ,this implies adequate altitude control1 which is one of the problems not yet solved for lighter-than-air flying machines3 but when it has been solved we shall go far toward attaining a dirigible balloon without motor or propeller2 a true sailing craft4 ,illustration3 ,,diagram ,,of ,,parts ,,of ,a ,,drifting ,,balloon ,this means more study and careful utilization of stratified atmospheric currents4 ,professor ,rotch suggests the utilization of the upper westerly wind drift across the ,american continent and the ,atlantic ,ocean1 which would carry a balloon from ,san ,francisco to southern ,europe at a speed of about fifty feet per second--thirty-four miles per hour4 ,then by transporting the balloon to northern ,africa1 the northeast surface trade wind would drive it back to the ,west ,indies at twenty-five miles per hour4 ,this without any motive power3 and since present day dirigibles are all short of motive power for complete dirigibility1 we must either make them much more powerful or else adopt the sailing principle1 which will permit of actually decreasing present sizes of motors1 or even possibly of omitting them altogether4 ,our next study is1 then1 logically1 one of altitude control in balloons4 ,illustration3 ,,glidden ,,and ,,stevens ,,getting ,,away ,,in ,,the ,,boston 7,leo ,stevens1 ,n4,y47 ,field and ,speed ,illustration3 ,,relative ,,and ,,absolute ,,balloon ,,velocities ,illustration3 ,,field ,,and ,,speed ,an aerostat 7non-dirigible balloon71 unless anchored1 drifts at the speed of the wind4 ,to the occupants1 it seems to stand still1 while the surface of the earth below appears to move in a direction opposite to that of the wind4 ,in the sketch1 if the independent velocity of a dirigible balloon be ,,pb1 the wind velocity ,,pv1 then the actual course pursued is ,,pr1 although the balloon always points in the direction ,,pb1 as shown at #a and #b4 ,if the speed of the wind exceed that of the balloon1 there will be some directions in which the latter cannot progress4 ,thus1 let ,,pv be the wind velocity and ,,tv the independent speed of the balloon4 ,the tangents ,,px1 ,,px1 include the whole field of action possible4 ,the wind direction may change during flight1 so that the initial objective point may become unattainable1 or an initially unattainable point may be brought within the field4 ,the present need is to increase independent speeds from thirty or forty to fifty or sixty miles per hour1 so that the balloon will be truly dirigible 7even if at low effectiveness7 during practically the whole year4 ,illustration3 ,,influence ,,of ,,wind ,,on ,,possible ,,course ,suppose a dirigible to start on a trip from ,new ,york to ,albany1 #aej miles away4 ,let the wind be a twenty-five mile breeze from the southwest4 ,the wind alone tends to carry the balloon from ,new ,york to the point d in four hours4 ,if the balloon meanwhile be headed due west1 it would need an independent velocity of its own having the same ratio to that of the wind as that of de to fd1 or about seventeen and one-half miles per hour4 ,suppose its independent speed to be only twelve and one-half miles2 then after four hours it will be at the position b1 assuming it to have been continually headed due west1 as indicated at a4 ,it will have traveled northward the distance fe1 apparently about sixty-nine miles4 ,illustration3 ,,count ,,zeppelin ,after this four hours of flight1 the wind suddenly changes to south-southwest4 ,it now tends to carry the balloon to g in the next four hours4 ,meanwhile the balloon1 heading west1 overcomes the easterly drift1 and the balloon actually lands at c4 ,unless there is some further favorable shift of the wind it cannot reach ,albany4 ,if1 during the second four hours1 its independent speed could have been increased to about fifteen and a half miles it would have just made it4 ,the actual course has been fbc3 a drifting balloon would have followed the course fdh1 dh being a course parallel to bg4 ,,gas ,,and ,,ballast ,a cubical block of wood measuring twelve inches on a side floats on water because it is lighter than water2 it weighs1 if yellow pine1 thirty-eight pounds1 whereas the same volume of water weighs about sixty-two pounds4 ,any substance weighing more than sixty-two pounds to the cubic foot would sink in water4 ,illustration3 ,,buoyant ,,power ,,of ,,wood ,if our block of wood be drilled1 and lead poured in the hole1 the total size of wood-and-lead block being kept constantly at one cubic foot1 the block will sink as soon as its whole weight exceeds sixty-two pounds4 ,ignoring the wood removed by boring 7as1 compared with the lead which replaces it1 an insignificant amount71 the weight of lead plugged in may reach twenty-four pounds before the block will sink4 ,this figure1 twenty-four pounds1 the difference between sixty-two and thirty-eight pounds1 then represents the maximum buoyant power of a cubic foot of wood in water4 ,it is the difference between the weight of the wood block and the weight of the water it displaces4 ,if any weight less than this is added to that of the wood1 the block will float1 projecting above the water's surface more or less1 according to the amount of weight buoyed up4 ,it will not rise entirely from the water1 because to do this it would need to be lighter1 not only than water1 but than air4 ,illustration3 ,,one ,,cubic ,,foot ,,of ,,wood ,,loaded ,,in ,,water ,buoyancy in ,air ,there are gases1 if not woods1 lighter than air3 among them1 coal gas and hydrogen4 ,a bubble of any of these gases1 if isolated from the surrounding atmosphere1 cannot sink but must rise4 ,at the same pressure and temperature1 hydrogen weighs about one-fifteenth as much as air2 coal gas1 about one-third as much4 ,if a bubble of either of these gases be isolated in the atmosphere1 it must continually rise1 just as wood immersed in water will rise when liberated4 ,but the wood will stop when it reaches the surface of the water1 while there is no reason to suppose that the hydrogen or coal gas bubbles will ever stop4 ,the hydrogen bubble can be made to remain stationary if it is weighted down with something of about fourteen times its own weight 7thirteen and one-half times1 accurately74 ,perhaps it would be better to say that it would still continue to rise slowly because that additional something would itself displace some additional air2 but if the added weight is a solid body1 its own buoyancy in air is negligible4 ,illustration3 ,,buoyant ,,power ,,of ,,hydrogen ,our first principle is1 then1 that at the same pressure and temperature1 any gas lighter than air1 if properly confined1 will exert a net lifting power of 7n-#a7 times its own weight1 where n is the ratio of weights of air and gas per cubic foot4 ,illustration3 ,,lebaudy',s ,,jaune ,if the pressures and temperatures are different1 this principle is modified4 ,in a balloon1 the gas is under a pressure slightly in excess of that of the external atmosphere3 this decreases its lifting power1 because the weight of a given volume of gas is greater as the pressure to which it is subjected is increased4 ,the weight of a given volume we have called the density3 and1 as has been stated1 if the temperature be unchanged1 the density varies directly as the pressure4 ,the pressure in a balloon is only about #a greater than that of the atmosphere at sea level1 so that this factor has only a slight influence on the lifting power4 ,that it leads to certain difficulties in economy of gas will1 however1 soon be seen4 ,the temperature of the gas in a balloon1 one might think1 would naturally be the same as that of the air outside3 but the surface of the balloon envelope has an absorbing capacity for heat1 and on a bright sunny day the gas may be considerably warmed thereby4 ,this action increases the lifting power1 since increase of temperature 7the pressure remaining fixed7 decreases the density of a gas4 ,to avoid this possibly objectionable increase in lifting power1 balloons are sometimes painted with a non-absorbent color4 ,one of the first ,lebaudy balloons received a popular nickname in ,paris on account of the yellow hue of its envelope4 ,suppose we wish a balloon to carry a total weight1 including that of the envelope itself1 of a ton4 ,if of hydrogen1 it will have to contain one fifteenth of this weight or about #acc pounds of that gas1 occupying a space of about #bc1jjj cubic feet4 ,if coal gas is used1 the size of the balloon would have to be much greater4 ,if hot air is used--as has sometimes been the case--let us assume the temperature of the air inside the envelope such that the density is just half that of the outside air4 ,this would require a temperature probably about #ejj4 ,the air needed would be just a ton1 and the balloon would be of about #eb1jjj cubic feet4 ,it would soon lose its lifting power as the air cooled2 and such a balloon would be useful only for short flights4 ,illustration3 ,,air ,,balloon 7,photo by ,paul ,thompson1 ,n4,y47 ,built by some ,germans in the backwoods of ,south ,africa ,the #bc1jjj cubic foot hydrogen balloon1 designed to carry a ton1 would just answer to sustain the weight4 ,if anchored at sea level1 it would neither fall to the ground nor tug upward on its holding-down ropes4 ,in order to ascend1 something more is necessary4 ,this something more might be some addition to the size and to the amount of hydrogen4 ,let us assume that we1 instead1 drop one hundred pounds of our load4 ,thus relieved of so much ballast1 the balloon starts upward1 under the net lifting force of one hundred pounds4 ,it is easy to calculate how far it will go4 ,it will not ascend indefinitely1 because1 as the altitude increases1 the pressure 7and consequently the density7 of the external atmosphere decreases4 ,at about a #bjjj-;foot elevation1 this decrease in density will have been sufficient to decrease the buoyant power of the hydrogen to about #aijj pounds1 and the balloon will cease to rise1 remaining at this level while it moves before the wind4 ,there are several factors to complicate any calculations4 ,any expansion of the gas bag--stretching due to an increase in internal pressure--would be one2 but the envelope fabrics do not stretch much2 there is indeed a very good reason why they must not be allowed to stretch4 ,the pressure in the gas bag is a factor4 ,if there is no stretching of the bag1 this pressure will vary directly with the temperature of the gas1 and might easily become excessive when the sun shines on the envelope4 ,a more serious matter is the increased difference between the internal pressure of the gas and the external pressure of the atmosphere at high altitudes4 ,atmospheric pressure decreases as we ascend4 ,the difference between gas pressure and air pressure thus increases1 and it is this difference of pressure which tends to burst the envelope4 ,suppose the difference of pressure at sea level to have been two-tenths of a pound4 ,for a balloon of twenty feet diameter1 this would give a stress on the fabric1 per lineal inch1 of twenty-four pounds4 ,at an altitude of #bjjj feet1 the atmospheric pressure would decrease by one pound1 the difference of pressures would become one and two-tenths pounds1 and the stress on the fabric would be #add pounds per lineal inch--an absolutely unpermissible strain4 ,there is only one remedy3 to allow some of the gas to escape through the safety valve2 and this will decrease our altitude4 ,ascending and ,descending ,to ascend1 then1 we must discard ballast3 and we cannot ascend beyond a certain limit on account of the limit of allowable pressure on the envelope fabric4 ,to again descend1 we must discharge some of the gas which gives us lifting power4 ,every change of altitude thus involves a loss either of gas or of ballast4 ,our vertical field of control may then be represented by a series of oscillations of gradually decreasing magnitude until finally all power to ascend is gone4 ,and even this situation1 serious as it is1 is made worse by the gradual but steady leakage of gas through the envelope fabric4 ,here1 in a word1 is the whole problem of altitude regulation4 ,air has no surface of equilibrium like water4 ,some device supplementary to ballast and the safety valve is absolutely necessary for practicable flight in any balloon not staked to the ground4 ,a writer of romance has equipped his aeronautic heroes with a complete gas-generating plant so that all losses might be made up2 and in addition1 heating arrangements were provided so that when the gas supply had been partially expended its lifting power could be augmented by warming it so as to decrease its density below even the normal4 ,there might be something to say in favor of this latter device1 if used in connection with a collapsible gas envelope4 ,methods of mechanically varying the size of the balloon1 so as by compressing the gas to cause descent and by giving it more room to increase its lifting power and produce ascent1 have been at least suggested4 ,the idea of a vacuum balloon1 in which a rigid hollow shell would be exhausted of its contents by a continually working pump1 may appear commendable4 ,such a balloon would have maximum lifting power for its size2 but the weight of any rigid shell would be considerable1 and the pressure tending to rupture it would be about #ajj times that in ordinary gas balloons4 ,it has been proposed to carry stored gas at high pressure 7perhaps in the liquefied condition7 as a supplementary method of prolonging the voyage while facilitating vertical movements3 but hydrogen gas at a pressure of a ton to the square inch in steel cylinders would give an ultimate lifting power of only about one-tenth the weight of the cylinders which contain it4 ,these cylinders might be regarded as somewhat better than ordinary ballast3 but to throw them away1 with their gas charge1 as ballast1 would seem too tragic4 ,liquefied gas might possibly appear rather more desirable1 but would be altogether too expensive4 ,illustration3 ,,screw ,,propeller ,,for ,,altitude ,,control ,if a screw propeller can be used on a steamship1 a dirigible balloon1 or an aeroplane to produce forward motion1 there is no reason why it could not also be used to produce upward motion in any balloon2 and the propeller with its operating machinery would be a substitute for twice its equivalent in ballast1 since it could produce motion either upward or downward4 ,weight for weight1 however1 the propeller and engine give only 7in one computed case7 about half the lifting power of hydrogen4 ,if we are to use the screw for ascent1 we might well use a helicopter1 heavier than air1 rather than a balloon4 ,the ,ballonet ,the present standard method of improving altitude regulation involves the use of the ballonet1 or compartment air bag1 inside the main envelope4 ,for stability and effective propulsion1 it is important that the balloon preserve its shape1 no matter how much gas be allowed to escape4 ,dirigible balloons are divided into two types1 according to the method employed for maintaining the shape4 ,in the ,zeppelin type1 a rigid internal metal framework supports the gas envelope4 ,this forms a series of seventeen compartments1 each isolated from the others4 ,no matter what the pressure of gas1 the shape of the balloon is unchanged4 ,in the more common form of balloon1 the internal air ballonet is empty1 or nearly so1 when the main envelope is full4 ,as gas is vented from the latter1 air is pumped into the former4 ,this compresses the remaining gas and thus preserves the normal form of the balloon outline4 ,illustration3 ,,balloon ,,with ,,ballonets ,but the air ballonet does more than this4 ,it provides an opportunity for keeping the balloon on a level keel1 for by using a number of compartments the air can be circulated from one to another as the case may require1 thus altering the distribution of weights4 ,besides this1 if the pressure in the air ballonet be initially somewhat greater than that of the external atmosphere1 a considerable ascent may be produced by merely venting this air ballonet4 ,this involves no loss of gas2 and when it is again desired to descend1 air may be pumped into the ballonet4 ,if any considerable amount of gas should be vented1 to produce quick and rapid descent1 the pumping of air into the ballonet maintains the shape of the balloon and also facilitates the descent4 ,illustration3 ,,construction ,,of ,,the ,,zeppelin ,,balloon ,the ,equilibrator ,illustration3 ,,the ,,equilibrator ,,in ,,neutral ,,position ,suppose a timber block of one square foot area1 ten feet long1 weighing #chj pounds1 to be suspended from the balloon in the ocean1 and let mechanism be provided by which this block may be raised or lowered at pleasure4 ,when completely immersed in water it exerts an upward pressure 7lifting force7 of #bdj pounds1 which may be used to supplement the lifting power of the balloon4 ,if wholly withdrawn from the water1 it pulls down the balloon with its weight of #chj pounds4 ,it seems to be equivalent1 therefore1 to about #fbj pounds of ballast4 ,when immersed a little over six feet--the upper four feet being out of the water--it exerts neither lifting nor depressing effect4 ,the amount of either may be perfectly adjusted between the limits stated by varying the immersion4 ,in the ,wellman-,vaniman equilibrator attached to the balloon ,america1 which last year carried six men 7and a cat7 a thousand miles in three days over the ,atlantic ,ocean1 a string of tanks partly filled with fuel was used in place of the timber block4 ,as the tanks were emptied1 the degree of control was increased2 and this should apparently have given ideal results1 equilibration being augmented as the gas supply was lost by leakage3 but the unsailorlike disregard of conditions resulting from the strains transferred from a choppy sea to the delicate gas bag led to disaster1 and it is doubtful whether this method of control can ever be made practicable4 ,the ,america's trip was largely one of a drifting rather than of a dirigible balloon4 ,the equilibrator could be used only in flights over water in any case3 and if we are to look to water for our buoyancy1 why not look wholly to water and build a ship instead of a balloon8 ,,dirigible ,,balloons ,,and ,,other ,,kinds ,shapes ,illustration3 ,,henry ,,giffard',s ,,dirigible 7,the first with steam power7 ,the cylindrical ,zeppelin balloon with approximately conical ends has already been shown 7page #fh74 ,those balloons in which the shape is maintained by internal pressure of air are usually pisciform1 that is1 fish-shaped4 ,studies have actually been made of the contour lines of various fishes and equivalent symmetrical forms derived1 the outline of the balloon being formed by a pair of approximately parabolic curves4 ,illustration3 ,,dirigible ,,of ,,dupuy ,,de ,,lome 7,man ,power7 ,the first flight in a power driven balloon was made by ,giffard in #aheb4 ,this balloon had an independent speed of about ten feet per second1 but was without appliances for steering4 ,a ballonetted balloon of #abj1jjj cubic feet capacity was directed by man power in #ahgb3 eight men turned a screw thirty feet in diameter which gave a speed of about seven miles per hour4 ,electric motors and storage batteries were used for dirigible balloons in #ahhc-'hd3 in the latter year1 ,renard and ,krebs built the first fish-shaped balloon4 ,the first dirigible driven by an internal combustion motor was used by ,santos-,dumont in #aija4 ,illustration3 ,,tissandier ,,brothers' ,,dirigible ,,balloon 7,electric ,motor7 ,dimensions ,the displacements of present dirigibles vary from #bj1jjj cubic feet 7in the ,united ,states ,signal ,corps airship7 up to #dfj1jjj cubic feet 7in the ,zeppelin74 ,the former balloon has a carrying capacity only about equivalent to that of a ,wright biplane4 ,while anchored or drifting balloons are usually spherical1 all dirigibles are elongated1 with a length of from four to eleven diameters4 ,the ,zeppelin represents an extreme elongation1 the length being #dej feet and the diameter forty-two feet4 ,at the other extreme1 some of the ,english military dirigibles are thirty-one feet in diameter and only #aab feet long4 ,ballonet capacities may run up to one-fifth the gas volume4 ,all present dirigibles have gasoline engines driving propellers from eight to twenty feet in diameter4 ,the larger propellers are connected with the motors by gearing1 and make from #bej to #gjj turns per minute4 ,the smaller propellers are direct connected and make about #abjj revolutions4 ,speeds are usually from fifteen to thirty miles per hour4 ,illustration3 ,,the ,,baldwin ,dirigible of the ,united ,states ,signal ,corps ,the present-day elongated shape is the result of the effort to decrease the proportion of propulsion resistance due to the pressure of the air against the head of the balloon4 ,this has led also to the pointed ends now universal2 and to avoid eddy resistance about the rear it is just as important to point the stern as the bow4 ,as far as head end resistance alone is concerned1 the longer the balloon the better3 but the friction of the air along the side of the envelope also produces resistance1 so that the balloon must not be too much elongated4 ,excessive elongation also produces structural weakness4 ,from the standpoint of stress on the fabric of the envelope1 the greatest strain is that which tends to break the material along a longitudinal line1 and this is true no matter what the length1 as long as the seams are equally strong in both directions and the load is so suspended as not to produce excessive bending strain on the whole balloon4 ,in the ,patrie 7page #gg71 some distortion due to loading is apparent4 ,the stress per lineal inch of fabric is obtained by multiplying the net pressure by half the diameter of the envelope 7in inches74 ,illustration3 ,,the ,,zeppelin ,,entering ,,its ,,hangar ,,on ,,lake ,,constance ,ample steering power 7provided by vertical planes1 as in heavier-than-air machines7 is absolutely necessary in dirigibles3 else the head could not be held up to the wind and the propelling machinery would become ineffective4 ,fabrics ,the material for the envelope and ballonets should be light1 strong1 unaffected by moisture or the atmosphere1 non-cracking1 non-stretching1 and not acted upon by variations in temperature4 ,the same specifications apply to the material for the wings of an aeroplane4 ,in addition1 for use in dirigible balloons1 fabrics must be impermeable1 resistent to chemical action of the gas1 and not subject to spontaneous combustion4 ,the materials used are vulcanized silk1 gold beater's skin1 ,japanese silk and rubber1 and cotton and rubber compositions4 ,in many ,french balloons1 a middle layer of rubber has layers of cotton on each side1 the whole thickness being the two hundred and fiftieth part of an inch4 ,in the ,patrie1 this was supplemented by an outside non-heat-absorbent layer of lead chromate and an inside coating of rubber1 all rubber being vulcanized4 ,the inner rubber layer was intended to protect the fabric against the destructive action of impurities in the gas4 ,illustration3 ,,the ,,patrie4 ,,destroyed ,,by ,a ,,storm ,fabrics are obtainable in various colors1 painted1 varnished1 or wholly uncoated4 ,the rubber and cotton mixtures are regularly woven in ,france and ,germany for aeroplanes and balloons4 ,the cars and machinery are frequently shielded by a fabricated wall4 ,weights of envelope materials range from one twenty-third to one-fourteenth pound per square foot1 and breaking stresses from twenty-eight to one hundred and thirty pounds4 ,pressures 7net7 in the main envelope are from three-fifths to one and a quarter ounces per square inch1 those in the ballonets being somewhat less4 ,the ,patrie of #aijg had an envelope guaranteed not to allow the leakage of more than half a cubic inch of hydrogen per square foot of surface per twenty-four hours4 ,illustration3 ,,manufacturing ,,the ,,envelope ,,of ,a ,,balloon ,illustration3 ,,inspecting ,,the ,,envelope ,,of ,,andr,e',s ,,balloon ,l',,oernen ,the best method of cutting the fabric is to arrange for building up the envelope by a series of strips about the circumference1 the seams being at the bottom4 ,the two warps of the cloth should cross at an angle so as to localize a rip or tear4 ,bands of cloth are usually pasted over the seams1 inside and out1 with a rubber solution2 this is to prevent leakage at the stitches4 ,framing ,in the ,zeppelin1 the rigid aluminum frame is braced every forty-five feet by transverse diametral rods which make the cross-sections resemble a bicycle wheel 7page #fh74 ,this cross-section is not circular1 but sixteen-sided4 ,the pressure is resisted by the framework itself1 the envelope being required to be impervious only4 ,the seventeen compartments are separated by partitions of sheet aluminum4 ,there is a system of complete longitudinal bracing between these partitions4 ,under the main framework1 the cars and machinery are carried by a truss about six feet deep which runs the entire length4 ,the cars are boat-shaped1 twenty feet long and six feet wide1 three and one-half feet high1 enclosed in aluminum sheathing4 ,these cars1 placed about one hundred feet from the ends1 are for the operating force and machinery4 ,the third car1 carrying passengers1 is built into the keel4 ,illustration3 ,,wreck ,,of ,,the ,,zeppelin ,in non-rigid balloons like the ,patrie1 the connecting frame must be carefully attached to the envelope4 ,in this particular machine1 cloth flaps were sewed to the bag1 and nickel steel tubes then laced in the flaps4 ,with these tubes as a base1 a light framework of tubes and wires1 covered with a laced-on waterproof cloth1 was built up for supporting the load4 ,braces ran between the various stabilizing and controlling surfaces and the gas bag2 these were for the most part very fine wire cables4 ,the weight of the car was concentrated on about seventy feet of the total length of #bjj feet4 ,this accounts for the deformation of the envelope shown in the illustration 7page #gg74 ,the frame and car of this balloon were readily dismantled for transportation4 ,in some of the ,english dirigibles the cars were suspended by network passing over the top of the balloon4 ,keeping the ,keel ,horizontal ,in the ,zeppelin1 a sliding weight could be moved along the keel so as to cause the center of gravity to coincide with the center of upward pressure in spite of variations in weight and position of gas1 fuel1 and ballast4 ,in the ,german balloon ,parseval1 the car itself was movable on a longitudinal suspending cable which carried supporting sheaves4 ,this balloon has figured in recent press notices4 ,it was somewhat damaged by a collision with its shed in ,march3 the sixteen passengers escaped unharmed4 ,a few days later1 emergency deflation by the rip-strip was made necessary during a severe storm4 ,in the ordinary non-rigid balloon1 the pumping of air between the ballonets aids in controlling longitudinal equilibrium4 ,the pump may be arranged for either hand or motor operation3 that in the ,clment-,bayard had a capacity of #ahjj liters per minute against the pressure of a little over three-fifths of an ounce4 ,the ,parseval has two ballonets4 ,into the rear of these air is pumped at starting4 ,this raises the bow and facilitates ascent on the principle of the inclined surface of an aeroplane4 ,after some elevation is attained1 the forward ballonet is also filled4 ,illustration3 ,,car ,,of ,,the ,,zeppelin 7,from the ,transactions of the ,american ,society of ,mechanical ,engineers7 ,stability ,besides proper distribution of the loads1 correct vertical location of the propeller is important if the balloon is to travel on a level keel4 ,in some early balloons1 two envelopes side by side had the propeller at the height of the axes of the gas bags and midway between them4 ,the modern forms carry the car1 motor1 and propeller below the balloon proper4 ,the air resistance is mostly that of the bow of the envelope3 but there is some resistance due to the car1 and the propeller shaft should properly be at the equivalent center of all resistance1 which will be between car and axis of gas bag and nearer the latter than the former4 ,with a single envelope and propeller1 this arrangement is impracticable4 ,by using four 7or even two7 propellers1 as in the ,zeppelin machine 7page #fh71 it can be accomplished4 ,if only one propeller is employed1 horizontal rudder planes must be disposed at such angles and in such positions as to compensate for the improper position of the tractive force4 ,even on the ,zeppelin1 such planes were employed with advantage 7pages #ff and #gc74 ,perfect stability also involves freedom from rolling4 ,this is usually inherent in a balloon1 because the center of mass is well below the center of buoyancy3 but in machines of the non-rigid type the absence of a ballonet might lead to both rolling and pitching when the gas was partially exhausted4 ,illustration3 ,,stern ,,view ,,of ,,the ,,zeppelin ,what is called route stability describes the condition of straight flight4 ,the balloon must point directly in its 7independent7 course4 ,this involves the use of a steering rudder1 and1 in addition1 of fixed vertical planes1 which1 on the principle of the vertical partitions of ,voisin1 probably give some automatic steadiness to the course4 ,to avoid the difficulty or impossibility of holding the head up to the wind at high speeds1 an empennage or feathering tail is a feature of all present balloons4 ,the empennage of the ,patrie 7page #gg7 consisted of pairs of vertical and horizontal planes at the extreme stern4 ,in the ,france1 thirty-two feet in maximum diameter and nearly #bjj feet long1 empennage planes aggregating about #djj square feet were placed somewhat forward of the stern4 ,in the ,clment-,bayard1 the empennage consisted of cylindro-conical ballonets projecting aft from the stern4 ,a rather peculiar grouping of such ballonets was used about the prolonged stern of the ,ville de ,paris4 ,illustration3 ,,the ,,cl,,ment-,,bayard ,illustration3 ,,the ,,ville ,,de ,,paris ,rudders and ,planes ,the dirigible has thus several air-resisting or gliding surfaces4 ,the approximately horizontal 7actually somewhat inclined7 planes permit of considerable ascent and descent by the expenditure of power rather than gas1 and thus somewhat influence the problem of altitude control4 ,each of the four sets of horizontal rudder planes on the ,zeppelin1 for example1 has1 at thirty-five miles per hour1 with an inclination equal to one-sixth a right angle1 a lifting power of nearly a ton2 about equal to that of all of the gas in one of the sixteen compartments4 ,illustration3 ,,car ,,of ,,the ,,libert ,movable rudders may be either hand or motor-operated4 ,the double vertical steering rudder of the ,ville de ,paris had an area of #aej square feet4 ,the horizontally pivoted rudders for vertical direction had an area of #acj square feet4 ,arrangement and ,accessories ,the motor in the ,ville de ,paris was at the front of the car1 the operator behind it4 ,this car had the excessive weight of nearly #gjj pounds4 ,the ,patrie employed a non-combustible shield over the motor1 for the protection of the envelope3 its steering wheel was in front and the motor about in the middle of the car4 ,the gasoline tank was under the car1 compressed air being used to force the fuel up to the motor1 which discharged its exhaust downward at the rear through a spark arrester4 ,motors have battery and magneto ignition and decompression cocks1 and are often carried on a spring-supported chassis4 ,the interesting ,parseval propeller has four cloth blades which hang limp when not revolving4 ,when the motor is running1 these blades1 which are weighted with lead at the proper points1 assume the desired form4 ,balloons usually carry guide ropes at head and stern1 the aggregate weight of which may easily exceed a hundred pounds4 ,in descending1 the bow rope is first made fast1 and the airship then stands with its head to the wind1 to be hauled in by the stern rope4 ,for the large ,french military balloons1 this requires a force of about thirty men4 ,the ,zeppelin descends in water1 being lowered until the cars float1 when it is docked like a ship 7see page #hd74 ,landing skids are sometimes used1 as with aeroplanes4 ,the balloon must have escape valves in the main envelope and ballonets4 ,in addition it has a rip-strip at the bottom by which a large cut can be made and the gas quickly vented for the purpose of an emergency descent4 ,common equipment includes a siren1 megaphone1 anchor pins1 fire extinguisher1 acetylene search light1 telephotographic apparatus1 registering and indicating gages and other instruments1 anemometer1 possibly carrier pigeons2 besides fuel1 oil and water for the motor1 and the necessary supplies for the crew4 ,the glycerine floated compass of ,moisant must now also be included if we are to contemplate genuine navigation without constant recourse to landmarks4 ,amateur ,dirigibles ,the ,french ,zodiac types of aerial runabout displace #gjj cubic meters1 carrying one passenger with coal gas or two passengers with a mixture of coal gas and hydrogen4 ,the motor is four-cylinder1 sixteen horse-power1 water-cooled4 ,the stern screw1 of seven feet diameter1 makes #fjj turns per minute1 giving an independent speed of nineteen miles per hour4 ,the machine can remain aloft three hours with #afe pounds of supplies4 ,it costs #ejjj4 ,hydrogen costs not far from a cent per cubic foot 7twenty cents per cubic meter7 so that the question of gas leakage may be at least as important as the tire question with automobiles4 ,illustration3 ,,the ,,zodiac ,,no4 #b ,may be deflated and easily transported ,the ,fort ,omaha ,plant ,the ,signal ,corps post at ,fort ,omaha has a plant comprising a steel balloon house of size sufficient to house one of the largest dirigibles built1 an electrolytic plant for generating hydrogen gas1 having a capacity of #cjjj cubic feet per hour1 a #ej1jjj cubic foot gas storage tank1 and the compressing and carrying equipment involved in preparing gas for shipment at high pressure in steel cylinders4 ,illustration3 ,,united ,,states ,,signal ,,corps ,,balloon ,,plant ,,at ,,fort ,,omaha1 ,,neb4 7,from the ,transactions of the ,american ,society of ,mechanical ,engineers7 ,balloon ,progress ,illustration3 ,,the ,,caroline ,,of ,,robert ,,brothers1 #aghd ,the ascent terminated tragically ,the first aerial buoy of ,montgolfier brothers1 in #aghc1 led to the suggestion of ,meussier that two envelopes be used2 the inner of an impervious material to prevent gas leakage1 and the outer for strength4 ,there was perhaps a foreshadowing of the ,zeppelin idea4 ,captive and drifting balloons were used during the wars of the ,french ,revolution3 they became a part of standard equipment in our own ,war of ,secession and in the ,franco-,prussian conflict4 ,the years #aijf to #aijh recorded rapid progress in the development of the dirigible3 the record-breaking ,zeppelin trip was in #aiji and ,wellman's ,america exploit in ,october1 #aiaj4 ,unfortunately1 dirigibles have had a bad record for stanchness3 the ,patrie1 ,rpublique1 ,zeppelin 7,i and ,,ii71 ,deutschland1 ,clment-,bayard--all have gone to that bourne whence no balloon returns4 ,illustration3 ,,the ,,ascent ,,at ,,versailles1 #aghc ,the first balloon carrying living beings in the air ,illustration3 ,,proposed ,,dirigible ,investors were lacking to bring about the realization of this project ,it is gratifying to record that ,count ,zeppelin's latest machine1 the ,deutschland ,,ii1 is now in operation4 ,during the present month 7,april1 #aiaa71 flights have been made covering #ij miles and upward at speeds exceeding #bj miles per hour with the wind unfavorable4 ,this balloon is intended for use as a passenger excursion vehicle during the coming summer1 under contract with the municipality of ,dsseldorf4 ,illustration3 ,,the ,r,,publique ,at the present moment1 ,neale1 in ,england1 is reported to be building a dirigible for a speed of a hundred miles per hour4 ,the ,siemens-,schuckart non-rigid machine1 nearly #djj feet long and of #ejj horse-power1 is being tried out at ,berlin3 it is said to carry fifty passengers4,a ,fabrice1 of ,munich1 is experimenting with the ,inchard1 with a view to crossing the ,atlantic at an early date4 ,mr4 ,vaniman1 partner of ,wellman on the ,america expedition1 is planning a new dirigible which it is proposed to fly across the ocean before ,july #d4 ,the engine1 according to press reports1 will develop #bjj horse-power1 and the envelope will be more elongated than that of the ,america4 ,and meanwhile a ,chicago despatch describes a projected fifty-passenger machine1 to have a gross lifting power of twenty-five tons6 ,illustration3 ,,the ,,first ,,flight ,,for ,,the ,,gordon-,,bennet ,,cup4 ,won by ,lieut4 ,frank ,p4 ,lahm1 ,u4,s4,a41 #aijf4 ,figures on the map denote distances in kilometers4 ,the cup has been offered annually by ,mr4 ,james ,gordon-,bennet for international competition under such conditions as may be prescribed by the ,international ,aeronautic ,federation4 ,germany has a slight lead in number of dirigible balloons--sixteen in commission and ten building4 ,france follows closely with fourteen active and eleven authorized4 ,this accounts for two-thirds of all the dirigible balloons in the world4 ,great ,britain1 ,italy1 and ,russia rank in the order named4 ,the ,united ,states has one balloon of the smallest size4 ,spain has1 or had1 one dirigible4 ,as to aeroplanes1 however1 the ,united ,states and ,england rank equally1 having each about one-fourth as many machines as ,france 7which seems1 therefore1 to maintain a four-power standard74 ,germany1 ,russia1 and ,italy follow1 in order1 the ,united ,states4 ,these figures include all machines1 whether privately or nationally owned4 ,until lately1 our own government operated but one aeroplane4 ,a recent appropriation by ,congress of #abe1jjj has led to arrangements for the purchase of a few additional biplanes of the ,wright and ,curtiss types2 and a training school for army officers has been regularly conducted at ,san ,diego1 ,cal41 during the past winter4 ,the ,curtiss machine to be purchased is said to carry #gjj pounds of dead weight with a sail area of #ejj square feet4 ,it is completely demountable and equipped with pontoons4 ,,the ,,question ,,of ,,power ,in the year #ahaj1 a steam engine weighed something over a ton to the horse-power4 ,this was reduced to about #bjj pounds in #ahhj4 ,the steam-driven dirigible balloon of ,giffard1 in #aheb1 carried a complete power plant weighing a little over #ajj pounds per horse-power2 about the weight of a modern locomotive4 ,the unsuccessful ,maxim flying machine of #ahid brought this weight down to less than #bj pounds4 ,the gasoline engine on the original ,wright machines weighed about #e pounds to the horse-power2 those on some recent ,french machines not far from #b pounds4 ,pig iron is worth perhaps a cent a pound4 ,an ordinary steam or gas engine may cost eight cents a pound2 a steam turbine1 perhaps forty cents4 ,a high grade automobile or a piano may sell for a dollar a pound2 the ,gnome aeroplane motor is priced at about twenty dollars a pound4 ,this is considerably more than the price of silver4 ,the motor and accessories account for from two-thirds to nine-tenths of the total cost of an aeroplane4 ,a man weighing #aej pounds can develop at the outside about one-eighth of a horse-power4 ,it would require #abjj pounds of man to exert one horse-power4 ,considered as an engine1 then1 a man is 7weight for weight7 only one six-hundredth as effective as a ,gnome motor4 ,in the original ,wright aeroplane1 a weight of half a ton was sustained at the expenditure of about twenty-five horse-power4 ,the motor weight was about one-eighth of the total weight4 ,if traction had been produced by man-power1 #cj1jjj pounds of man would have been necessary3 thirty times the whole weight supported4 ,illustration3 ,,the ,,gnome ,,motor 7,aeromotion ,company of ,america7 ,under the most favorable conditions1 to support his own weight of #aej pounds 7at very high gliding velocity and a slight angle of inclination1 disregarding the weight of sails necessary71 a man would need to have the strength of about fifteen men4 ,no such thing as an aerial bicycle1 therefore1 appears possible4 ,the man can not emulate the bird4 ,illustration3 ,,screw ,,propeller 7,american ,propeller ,company7 ,the power plant of an air craft includes motor1 water and water tank1 radiator and piping1 shaft and bearings1 propeller1 controlling wheels and levers1 carbureter1 fuel1 lubricating oil and tanks therefor4 ,some of the weight may eventually be eliminated by employing a two-cycle motor 7which gives more power for its size7 or by using rotary air-cooled cylinders4 ,propellers are made light by employing wood or skeleton construction4 ,one eight-foot screw of white oak and spruce1 weighing from twelve to sixteen pounds1 is claimed to give over #djj pounds of propelling force at a thousand turns per minute4 ,illustration3 ,,one ,,of ,,the ,,motors ,,of ,,the ,,zeppelin ,the cut shows the action of the so-called four-cycle motor4 ,four strokes are required to produce an impulse on the piston and return the parts to their original positions4 ,on the first1 or suction stroke1 the combustible mixture is drawn into the cylinder1 the inlet valve being open and the outlet valve closed4 ,on the second stroke1 both valves are closed and the mixture is highly compressed4 ,at about the end of this stroke1 a spark ignites the charge1 a still greater pressure is produced in consequence1 and the energy of the gas now forces the piston outward on its third or working stroke1 the valves remaining closed4 ,finally1 the outlet valve is opened and a fourth stroke sweeps the burnt gas out of the cylinder4 ,illustration3 ,,action ,,of ,,the ,,four-,,cycle ,,engine ,in the two-cycle engine1 the piston first moves to the left1 compressing a charge already present in the cylinder at ,f1 and meanwhile drawing a fresh supply through the valve ,a and passages ,c to the space ,d4 ,on the return stroke1 the exploded gas in ,f expands1 doing its work1 while that in ,d is slightly compressed1 the valve ,a being now closed4 ,when the piston1 moving toward the right1 opens the passage ,e1 the burnt gas rushes out4 ,a little later1 when the passage ,i is exposed1 the fresh compressed gas in ,d rushes through ,c1 ,b1 and ,i to ,f4 ,the operation may now be repeated4 ,only two strokes have been necessary4 ,the cylinder develops power twice as rapidly as before3 but at the cost of some waste of gas1 since the inlet 7,i7 and outlet 7,e7 passages are for a brief interval both open at once3 a condition not altogether remedied by the use of a deflector at ,g4 ,a two-cycle cylinder should give nearly twice the power of a four-cycle cylinder of the same size1 and the two-cycle engine should weigh less1 per horse-power2 but it requires from #aj to #cj more fuel1 and fuel also counts in the total weight4 ,illustration3 ,,action ,,of ,,two-,,cycle ,,engine ,the high temperatures in the cylinder would soon make the cast-iron walls red-hot1 unless the latter where artificially cooled4 ,the usual method of cooling is to make the walls hollow and circulate water through them4 ,this involves a pump1 a quantity of water1 and a radiator 7cooling machine7 so that the water can be used over and over again4 ,to cool by air blowing over the surface of the cylinder is relatively ineffective3 but has been made possible in automobiles by building fins on the cylinders so as to increase the amount of cooling surface4 ,when the motors are worked at high capacity1 or when two-cycle motors are used1 the heat is generated so rapidly that this method of cooling is regarded as inapplicable4 ,by rapidly rotating the cylinders themselves through the air1 as in motors like the ,gnome1 air cooling is made sufficiently adequate1 but the expenditure of power in producing this rotation has perhaps not been sufficiently regarded4 ,illustration3 ,,motor ,,and ,,propeller 7,detroit ,aeronautic ,construction ,co47 ,possible progress in weight economy is destined to be limited by the necessity for reserve motor equipment4 ,the engine used is usually the four-cycle1 single-acting1 four-cylinder gasoline motor of the automobile1 designed for great lightness4 ,the power from each cylinder of such a motor is approximately that obtained by dividing the square of the diameter in inches by the figure #b-a_/b4 ,thus a five-inch cylinder should give ten horse-power--at normal piston speed4 ,on account of friction losses and the wastefulness of a screw propeller1 not more than half this power is actually available for propulsion4 ,the whole power plant of the ,clment-,bayard weighed about eleven pounds to the horse-power4 ,this balloon was #ahd feet long and #ce feet in maximum diameter1 displacing about #ajj1jjj cubic feet4 ,it carried six passengers1 about seventy gallons of fuel1 four gallons of lubricating oil1 fifteen gallons of water1 #fjj pounds of ballast1 and #acj pounds of ropes4 ,the motor developed #ajj horse-power at a thousand revolutions per minute4 ,about eight gallons of fuel and one gallon of oil were consumed per hour when running at the full independent speed of thirty-seven miles per hour4 ,the ,wellman balloon ,america is said to have consumed half a ton of gasoline per twenty-four hours3 an eight days' supply was carried4 ,the gas leakage in this balloon was estimated to have been equivalent to a loss of #ejj pounds of lifting power per day4 ,the largest of dirigibles1 the ,zeppelin1 had two motors of #agj horse-power each4 ,it made1 in #aiji1 a trip of over #hjj miles in thirty-eight hours4 ,the engine of the original ,voisin cellular biplanes was an eight-cylinder ,antoinette of fifty horse-power1 set near the rear edge of the lower of the main planes4 ,the ,wright motors are placed near the front edge4 ,a twenty-five horse-power motor at #adjj revolutions propelled the ,fort ,myer machine1 which was built to carry two passengers1 with fuel for a #abe mile flight3 the total weight of the whole flying apparatus being about half a ton4 ,illustration3 ,,two-,,cylinder ,,opposed ,,engine4 7,from ,aircraft7 ,illustration3 ,,four-,,cylinder ,,vertical ,,engine 7,the ,dean ,manufacturing ,co47 ,the eight-cylinder ,antoinette motor on a ,farman biplane1 weighing #age pounds1 developed thirty-eight horse-power at #ajej revolutions4 ,the total weight of the machine was nearly #abjj pounds1 and its speed twenty-eight miles per hour4 ,the eight-cylinder ,curtiss motor on the ,june ,bug was air cooled4 ,this aeroplane weighed #fej pounds and made thirty-nine miles per hour1 the engine developing twenty-five horse-power at #abjj turns4 ,resistance of ,aeroplanes ,the chart on page #bd 7see also the diagram of page #bc7 shows that the lifting power of an aeroplane increases as the angle of inclination increases1 up to a certain limit4 ,the resistance to propulsion also increases1 however3 and the ratio of lifting power to resistance is greatest at a very small angle--about five or six degrees4 ,since the motor power and weight are ruling factors in design1 it is important to fly at about this angle4 ,the supporting force is then about two pounds1 and the resistance about three-tenths of a pound1 per square foot of sail area1 if the velocity is that assumed in plotting the chart3 namely1 about fifty-five miles per hour4 ,but the resistance ,r indicated on pages #bc and #bd is not the only resistance to propulsion4 ,in addition1 we have the frictional resistance of the air sliding along the sail surface4 ,the amount of this resistance is independent of the angle of inclination3 it depends directly upon the area of the planes1 and in an indirect way on their dimensions in the direction of movement4 ,it also varies nearly with the square of the velocity4 ,at any velocity1 then1 the addition of this frictional resistance1 which does not depend on the angle of inclination1 modifies our views as to the desirable angle3 and the total resistance reaches a minimum 7in proportion to the weight supported7 when the angle is about three degrees and the velocity about fifty miles per hour4 ,this is not quite the best condition1 however4 ,the skin friction does not vary exactly with the square of the velocity3 and when the true law of variation is taken into account1 it is found that the horse-power is a minimum at an angle of about five degrees and a speed of about forty miles per hour4 ,the weight supported per horse-power may then be theoretically nearly a hundred pounds3 and the frictional resistance is about one-third the direct pressure resistance4 ,this must be regarded as the approximate condition of best effectiveness3 not the exact condition1 because in arriving at this result we have regarded the sails as square flat planes whereas in reality they are arched and of rectangular form4 ,at the most effective condition1 the resistance to propulsion is only about one-tenth the weight supported4 ,evidently the air is helping the motor4 ,resistance of ,dirigibles ,if the bow of a balloon were cut off square1 its head end resistance would be that given by the rule already cited 7page #ai73 one three-hundredth pound per square foot1 multiplied by the square of the velocity4 ,but by pointing the bow an enormous reduction of this pressure is possible4 ,if the head end is a hemisphere 7as in the ,english military dirigible71 the reduction is about one-third4 ,if it is a sharp cone1 the reduction may be as much as four-fifths4 ,unless the stern is also tapered1 however1 there will be a considerable eddy resistance at that point4 ,illustration3 ,,head ,,end ,,shapes ,if head end resistance were the only consideration1 then for a balloon of given diameter and end shape it would be independent of the length and capacity4 ,the longer the balloon1 the better4 ,again1 since the volume of any solid body increases more rapidly than its surface 7as the linear dimensions are increased71 large balloons would have a distinct advantage over small ones4 ,the smallest dirigible ever built was that of ,santos-,dumont1 of about #ejjj cubic feet4 ,large balloons1 however1 are structurally weak3 and more is lost by the extra bracing necessary than is gained by reduction of head end resistance4 ,it is probable that the ,zeppelin represents the limit of progress in this direction2 and even in that balloon1 if it had not been that the adoption of a rigid type necessitated great structural strength1 it is doubtful if as great a length would have been fixed upon1 in proportion to the diameter4 ,the frictional resistance of the air gliding along the surface of the envelope1 moreover1 invalidates any too arbitrary conclusions4 ,this1 as in the aeroplane1 varies nearly as the square of the velocity1 and is usually considerably greater than the direct head end resistance4 ,should the steering gear break1 however1 and the wind strike the side of the balloon1 the pressure of the wind against this greatly increased area would absolutely deprive it of dirigibility4 ,a stationary1 drifting1 or sailing balloon may as well have the spherical as well as any other shape3 it makes the wind a friend instead of a foe and requires nothing in the way of control other than regulation of altitude4 ,independent ,speed and ,time ,table ,the air pressure1 direct and frictional resistances1 and power depend upon the relative velocity of flying machine and air4 ,it is this relative velocity1 not the velocity of the balloon as compared with a point on the earth's surface1 that marks the limit of progression4 ,hence the speed of the wind is an overwhelming factor to be reckoned with in developing an aerial time table4 ,if we wish to travel east at an effective speed of thirty miles per hour1 while the wind is blowing due west at a speed of ten miles1 our machine must have an independent speed of forty miles4 ,on the other hand1 if we wish to travel west1 an independent speed of twenty miles per hour will answer4 ,illustration3 ,,the ,,santos-,,dumont ,,dirigible ,,no4 #b 7#aiji7 ,again1 if the wind is blowing north at thirty miles per hour1 and the minimum 7relative7 velocity at which an aeroplane will sustain its load is forty miles per hour1 we cannot progress northward any more slowly than at seventy miles' speed4 ,and we have this peculiar condition of things3 suppose the wind to be blowing north at fifty miles per hour4 ,the aeroplane designed for a forty mile speed may then face this wind and sustain itself while actually moving backward at an absolute speed 7as seen from the earth7 of ten miles per hour4 ,we are at the mercy of the wind1 and wind velocities may reach a hundred miles an hour4 ,the inherent disadvantage of aerial flight is in what engineers call its low load factor4 ,that is1 the ratio of normal performance required to possible abnormal performance necessary under adverse conditions is extremely low4 ,to make a balloon truly dirigible throughout the year involves1 at ,paris1 for example1 as we have seen1 a speed exceeding fifty-four miles per hour3 and even then1 during one-tenth the year1 the effective speed would not exceed twenty miles per hour4 ,a time table which required a schedule speed reduction of #fj on one day out of ten would be obviously unsatisfactory4 ,illustration3 ,,in ,,the ,,bay ,,of ,,monaco ,,santos-,,dumont',s ,,no4 #f ,the flights terminated with a fall into the sea1 happily without injury to the operator ,further1 if we aim at excessively high independent speeds for our dirigible balloons1 in order to become independent of wind conditions1 we soon reach velocities at which the gas bag is unnecessary3 that is1 a simple wing surface would at those speeds give ample support4 ,the increased difficulty of maintaining rigidity of the envelope1 and of steering1 at the great pressures which would accompany these high velocities would also operate against the dirigible type4 ,with the aeroplane1 higher speed means less sail area for a given weight and a stronger machine4 ,much higher speeds are probable4 ,we have already a safe margin as to weight per horse-power of motor1 and many aeroplane motors are for stanchness purposely made heavier than they absolutely need to be4 ,the ,cost of ,speed ,since the whole resistance1 in either type of flying machine1 is approximately proportional to the square of the velocity2 and since horse-power 7work7 is the product of resistance and velocity1 the horse-power of an air craft of any sort varies about as the cube of the speed4 ,to increase present speeds of dirigible balloons from thirty to sixty miles per hour would then mean eight times as much horse-power1 eight times as much motor weight1 eight times as rapid a rate of fuel consumption1 and 7since the speed has been doubled7 four times as rapid a consumption of fuel in proportion to the distance traveled4 ,either the radius of action must be decreased1 or the weight of fuel carried must be greatly increased1 if higher velocities are to be attained4 ,present 7independent7 aeroplane speeds are usually about fifty miles per hour1 and there is not the necessity for a great increase which exists with the lighter-than-air machines4 ,we have already succeeded in carrying and propelling fifty pounds of total load or fifteen pounds of passenger load per horse-power of motor1 with aeroplanes2 the ratio of net load to horse-power in the dirigible is considerably lower2 but the question of weight in relation to power is of relatively smaller importance in the latter machine1 where support is afforded by the gas and not by the engine4 ,the ,propeller ,very little effort has been made to utilize paddle wheels for aerial propulsion2 the screw is almost universally employed4 ,every one knows that when a bolt turns in a stationary nut1 it moves forward a distance equal to the pitch 7lengthwise distance between two adjacent threads7 at every revolution4 ,a screw propeller is a bolt partly cut away for lightness1 and the nut in which it works is water or air4 ,it does not move forward quite as much as its pitch1 at each revolution1 because any fluid is more or less slippery as compared with a nut of solid metal4 ,the difference between the pitch and the actual forward movement of the vessel at each revolution is called the slip1 or slip ratio4 ,it is never less than ten or twelve per cent in marine work1 and with aerial screws is much greater4 ,within certain limits1 the less the slip1 the greater the efficiency of the propeller4 ,small screws have relatively greater slips and less efficiency1 but are lighter4 ,the maximum efficiency of a screw propeller in water is under #hj4 ,according to ,langley's experiments1 the usual efficiency in air is only about #ej4 ,this means that only half the power of the motor will be actually available for producing forward movement--a conclusion already foreshadowed4 ,in common practice1 the pitch of aerial screws is not far from equal to the diameter4 ,the rate of forward movement1 if there were no slip1 would be proportional to the pitch and the number of revolutions per minute4 ,if the latter be increased1 the former may be decreased4 ,screws direct-connected to the motors and running at high speeds will therefore be of smaller pitch and diameter than those run at reduced speed by gearing1 as in the machine illustrated on page #acd4 ,the number of blades is usually two1 although this gives less perfect balance than would a larger number4 ,the propeller is in many monoplanes placed in front3 this interferes1 unfortunately1 with the air currents against the supporting surfaces4 ,there is always some loss of power in the bearings and power-transmitting devices between the motor and propeller4 ,this may decrease the power usefully exerted even to less than half that developed by the motor4 ,,getting ,,up ,,and ,,down3 ,,models ,,and ,,gliders3 ,,aeroplane ,,details ,launching ,the ,wright machines 7at least in their original form7 have usually been started by the impetus of a falling weight1 which propels them along skids until the velocity suffices to produce ascent4 ,the preferred designs among ,french machines have contemplated self-starting equipment4 ,this involves mounting the machine on pneumatic-tired bicycle wheels so that it can run along the ground4 ,if a fairly long stretch of good1 wide1 straight road is available1 it is usually possible to ascend4 ,the effect of altitude and atmospheric density on sustaining power is forcibly illustrated by the fact that at ,salt ,lake ,city one of the aviators was unable to rise from the ground4 ,illustration3 ,,wright ,,biplane ,,on ,,starting ,,rail1 ,,showing ,,pylon ,,and ,,weight ,to accelerate a machine from rest to a given velocity in a given time or distance involves the use of propulsive force additional to that necessary to maintain the velocity attained4 ,apparently1 therefore1 any self-starting machine must have not only the extra weight of framework and wheels but also extra motor power4 ,illustration3 ,,launching ,,system ,,for ,,wright ,,aeroplane 7,from ,brewer's ,art of ,aviation7 ,upon closer examination of the matter1 we may find a particularly fortunate condition of things in the aeroplane4 ,both sustaining power and resistance vary with the inclination of the planes1 as indicated by the chart on page #bd4 ,it is entirely possible to start with no such inclination1 so that the direct wind resistance is eliminated4 ,the motor must then overcome only air friction1 in addition to providing an accelerating force4 ,the machine runs along the ground1 its velocity rapidly increasing4 ,as soon as the necessary speed 7or one somewhat greater7 is attained1 the planes are tilted and the aeroplane rises from the ground4 ,illustration3 ,,the ,,nieuport ,,monoplane ,self-,starting with an #ah hp4 motor 7,from ,the ,air ,scout7 ,the velocity necessary to just sustain the load at a given angle of inclination is called the critical or soaring velocity4 ,for a given machine1 there is an angle of inclination 7about half a right angle7 at which the minimum speed is necessary4 ,this speed is called the least soaring velocity4 ,if the velocity is now increased1 the angle of inclination may be reduced and the planes will soar through the air almost edgewise1 apparently with diminished resistance and power consumption4 ,this decrease in power as the speed increases is called ,langley's ,paradox1 from its discoverer1 who1 however1 pointed out that the rule does not hold in practice when frictional resistances are included4 ,we cannot expect to actually save power by moving more rapidly than at present2 but we should have to provide much more power if we tried to move much more slowly4 ,illustration3 ,a ,,biplane 7,from ,aircraft7 ,illustration3 ,,ely ,,at ,,los ,,angeles 7,photo by ,american ,press ,association7 ,economical and practicable starting of an aeroplane thus requires a free launching space1 along which the machine may accelerate with nearly flat planes3 a downward slope would be an aid4 ,when the planes are tilted for ascent1 after attaining full speed1 quick control is necessary to avoid the possibility of a back-somersault4 ,a fairly wide launching platform of #bjj feet length would ordinarily suffice4 ,the flight made by ,ely in ,january of this year1 from ,san ,francisco to the deck of the cruiser ,pennsylvania and back1 demonstrated the possibility of starting from a limited area4 ,the wooden platform built over the after deck of the warship was #acj feet long1 and sloped4 ,on the return trip1 the aeroplane ran down this slope1 dropped somewhat1 and then ascended successfully4 ,if the effort is made to ascend at low velocities1 then the motor power must be sufficient to propel the machine at an extreme angle of inclination--perhaps the third of a right angle1 approximating to the angle of least velocity for a given load4 ,according to ,chatley1 this method of starting by ,farman at ,issy-les-,moulineaux involved the use of a motor of fifty horse-power3 while ,roe's machine at ,brooklands rose1 it is said1 with only a six horse-power motor4 ,descending ,illustration3 ,,trajectory ,,during ,,descent ,what happens when the motor stops8 ,the velocity of the machine gradually decreases3 the resistance to forward movement stops its forward movement and the excess of weight over upward pressure due to velocity causes it to descend4 ,it behaves like a projectile1 but the details of behavior are seriously complicated by the variation in head resistance and sustaining force due to changes in the angle of the planes4 ,the angle of inclination is now not the angle made by the planes with the horizontal1 but the angle which they make with the path of flight4 ,theory indicates that this should be about two-thirds the angle which the path itself makes with the horizontal3 that is1 the planes themselves are inclined downward toward the front4 ,the forces which determine the descent are fixed by the velocity and the angle between the planes and the path of flight4 ,manipulation of the rudders and main planes or even the motor may be practised to ensure lancing to best advantage2 but in spite of these 7or perhaps on account of these7 scarcely any part of aviation offers more dangers1 demands more genius on the part of the operator1 and has been less satisfactorily analyzed than the question of getting down4 ,it is easy to stay up and not very hard to get up1 weather conditions being favorable2 but it is an all-sufficient job to come down4 ,under the new rules of the ,international ,aeronautic ,federation1 a test flight for a pilot's license must terminate with a descent 7motor stopped7 in which the aviator is to land within fifty yards of the observers and come to a full stop inside of fifty yards therefrom4 ,the elevation at the beginning of descent must be at least #aej feet4 ,illustration3 ,,descending ,gliders ,if the motor and its appurtenances1 and some of the purely auxiliary planes1 be omitted1 we have a glider4 ,the glider is not a toy2 some of the most important problems of balancing may perhaps be some day solved by its aid4 ,any boy may build one and fly therewith1 although a large kite promises greater interest4 ,the cost is trifling1 if the framework is of bamboo and the surfaces are cotton4 ,areas of glider surfaces frequently exceed #ajj square feet4 ,this amount of surface is about right for a person of moderate weight if the machine itself does not weigh over fifty pounds4 ,by running down a slope1 sufficient velocity may be attained to cause ascent2 or in a favorable wind 7up the slope7 a considerable backward flight may be experienced4 ,excessive heights have led to fatal accidents in gliding experiments4 ,illustration3 ,,the ,,witteman ,,glider ,models ,the building of flying models has become of commercial importance4 ,it is not difficult to attain a high ratio of surface to weight1 but it is almost impossible to get motor power in the small units necessary without exceeding the permissible limit of motor weight4 ,no gasoline engine or electric motor can be made sufficiently light for a toy model4 ,clockwork springs1 if especially designed1 may give the necessary power for short flights1 but no better form of power is known just now than the twisted rubber band4 ,for the small boy1 a biplane with sails about eighteen inches by four feet1 eighteen inches apart1 anchored under his shoulders by six-foot cords while he rides his bicycle1 will give no small amount of experience in balancing and will support enough of a load to make the experiment interesting4 ,some ,details3 ,balancing ,illustration3 ,,french ,,monoplane 7,from ,aircraft7 ,it is easily possible to compute the areas1 angles1 and positions of auxiliary planes to give desired controlling or stabilizing effects2 but the computation involves the use of accurate data as to positions of the various weights1 and on the whole it is simpler to correct preliminary calculations by actually supporting the machine at suitable points and observing its balance4 ,stability is especially uncertain at very small angles of inclination1 and such angles are to be avoided whether in ordinary operation or in descent4 ,the necessity for rotating main planes in order to produce ascent is disadvantageous on this ground2 but the proposed use of sliding or jockey weights for supplementary balancing appears to be open to objections no less serious4 ,steering may be perceptibly assisted1 in as delicately a balanced device as the aeroplane1 by the inclination of the body of the operator1 just as in a bicycle4 ,the direction of the wind in relation to the required course may seriously influence the steering power4 ,suppose the course to be northeast1 the wind east1 the independent speed of the machine and that of the wind being the same4 ,the car will head due north4 ,by bringing the rudder in position 7a71 the course may be changed to north1 or nearly so1 the wind exerting a powerful pressure on the rudder2 but if a more easterly or east-northeast course be desired1 and the rudder be thrown into the usual position therefor 7b71 it will exert no influence whatever1 because it is moving before the wind and precisely at the speed of the wind4 ,illustration3 ,a ,,problem ,,in ,,steering ,it might be thought that1 following analogies of marine engineering1 the center of gravity of an aeroplane should be kept low4 ,the effect of any unbalanced pressure or force against the widely extended sails of the machine is to rotate the whole apparatus about its center of gravity4 ,the further the force from the center of gravity1 the more powerful is the force in producing rotation4 ,the defect in most aeroplanes 7especially biplanes7 is that the center of gravity is too low4 ,if it could be made to coincide with the center of disturbing pressure1 there would be no unbalancing effect from the latter4 ,it is claimed that the steadiest machines are those having a high center of gravity2 and the claim1 from these considerations1 appears reasonable4 ,illustration3 ,,lejeune ,,biplane 7#che ,,lbs41 #aj-ab ,,hp47 ,weights ,it has been found not difficult to keep down the weight of framework and supporting surfaces to about a pound per square foot4 ,the most common ratio of surface to total weight is about one to two3 so that the machinery and operator will require one square foot of surface for each pound of their weight4 ,on this basis1 the smallest possible man-carrying aeroplane would have a surface scarcely below #bej square feet4 ,most biplanes have twice this surface3 a thousand square feet seems to be the limit without structural weakness4 ,some recent ,french machines1 designed for high speeds1 show a greatly increased ratio of weight to surface4 ,the ,hanriot1 a monoplane with wings upwardly inclined toward the outer edge1 carries over #hjj pounds on less than #cjj square feet4 ,the ,farman monoplane of only #ahj square feet sustains over #fjj pounds4 ,the same aviator's racing biplane is stated to support nearly #ijj pounds on less than #djj square feet4 ,illustration3 ,,the ,,tellier ,,two-,,seat ,,six-,,cylinder ,,monoplane ,,at ,,the ,,paris ,,show ,one of this type has been sold to the ,russian ,government 7,from ,aircraft7 ,motor weights can be brought down to about two pounds per horse-power1 but such extreme lightness is not always needed and may lead to unreliability of operation4 ,the effect of an accumulation of ice1 sleet1 snow1 rain1 or dew might be serious in connection with flights in high altitudes or during bad weather4 ,after one of his last year's flights at tampes ,mr4 ,farman is said to have descended with an extra load of nearly #bjj pounds on this account4 ,with ample motor power1 great flexibility in weight sustention is made possible by varying the inclination of the planes4 ,in ,january of this year1 ,sommer at ,douzy carried six passengers in a large biplane on a cross-country flight3 and within the week afterward a monoplane operated by ,le ,martin flew for five minutes with the aeronaut and seven passengers1 at ,pau4 ,the total weight lifted was about half a ton1 and some of the passengers must have been rather light4 ,the two-passenger ,fort ,myer biplane of the ,wright brothers is understood to have carried about this total weight4 ,these records have1 however1 been surpassed since they were noted4 ,brguet1 at ,douai1 in a deeply-arched biplane of new design1 carried eleven passengers1 the total load being #bfjb pounds1 and that of aeronaut and passengers alone #acij pounds4 ,the flight was a short one1 at low altitude2 but the same aviator last year made a long flight with five passengers1 and carried a load of #abfb pounds at #fb miles per hour4 ,and as if in reply to this feat1 ,sommer carried a live load of #adcf pounds 7#ac passengers7 for nearly a mile1 a day or two later1 at ,mouzon4 ,one feels less certain than formerly1 now1 in the snap judgment that the heavier-than-air machine will never develop the capacity for heavy loads4 ,illustration3 ,a ,,monoplane 7,from ,aircraft7 ,miscellaneous ,french aviators are fond of employing a carefully designed car for the operator and control mechanism4 ,the ,wright designs practically ignore the car3 the aviator sits on the forward edge of the lower plane with his legs hanging over4 ,it has been found that auxiliary planes must not be too close to the main wings3 a gap of a distance about #ej greater than the width of the widest adjacent plane must be maintained if interference with the supporting air currents is to be avoided4 ,main planes are now always arched2 auxiliary planes1 not as universally4 ,the concave under surface of supporting wings has its analogy in the wing of the bird and had long years since been applied in the parachute4 ,illustration3 ,,cars ,,and ,,framework ,the car 7if used7 and all parts of the framework should be of wind splitter construction1 if useless resistance is to be avoided4 ,the ribs and braces of the frame are of course stronger1 weight for weight1 in this shape1 since a narrow deep beam is always relatively stronger than one of square or round section4 ,excessive frictional resistance is to be avoided by using a smoothly finished fabric for the wings1 and the method of attaching this fabric to the frame should be one that keeps it as flat as possible at all joints4 ,illustration3 ,,some ,,details ,the sketches give the novel details of some machines recently exhibited at the ,grand ,central ,palace in ,new ,york4 ,the stabilizing planes were invariably found in the rear1 in all machines exhibited4 ,the ,things to ,look ,after ,the operator of an aeroplane has to do the work of at least two men4 ,no vessel in water would be allowed to attain such speeds as are common with air craft1 unless provided with both pilot and engineer4 ,the aviator is his own pilot and his own engineer4 ,he must both manage his propelling machinery and steer4 ,separate control for vertical rudders1 elevating rudders and ailerons1 for starting the engine2 the adjustment of the carbureter1 the spark1 and the throttle to get the best results from the motor2 attention to lubrication and constant watchfulness of the water-circulating system3 these are a few of the things for him to consider2 to say nothing of the laying of his course and the necessary anticipation of wind and altitude conditions4 ,these things demand great resourcefulness1 but--for their best control--involve also no small amount of scientific knowledge4 ,for example1 certain adjustments at the motor may considerably increase its power1 a possibly necessary increase under critical conditions3 but if such adjustments also decrease the motor efficiency there must be a nice analysis of the two effects so that extra power may not be gained at too great a cost in radius of action4 ,illustration3 ,,some ,,recent ,,french ,,machines 7,from ,aircraft7 ,the whole matter of flight involves both sportsman's and engineers problems4 ,wind gusts produce the same effects as turning corners2 or worse--rapidly changing the whole balance of the machines and requiring immediate action at two or three points of control4 ,both ascent and descent are influenced by complicated laws and are scarcely rendered safe--under present conditions--by the most ample experience4 ,a lateral air current bewilders the steering and also demands special promptness and skill4 ,to avoid disturbing surface winds1 even over open country1 a minimum flying height of #cjj feet is considered necessary4 ,this height1 furthermore1 gives more choice in the matter of landing ground than a lower elevation4 ,when complete and automatic balance shall have been attained--as it must be attained--we may expect to see small amateur aeroplanes flying along country roads at low elevations--perhaps with a guiding wheel actually in contact with the ground4 ,they will cost far less than even a small automobile1 and the expense for upkeep will be infinitely less4 ,the grasshopper will have become a water-spider4 ,,some ,,aeroplanes--,,some ,,accomplishments ,illustration3 ,,orville ,,wright ,,at ,,fort ,,myer1 ,,va41 #aijh ,illustration3 ,,the ,,first ,,balloon ,,flight ,,across ,,the ,,british ,,channel ,more than a century before ,blriot's feat1 ,blanchard crossed from ,dover to ,calais ,the ,wright biplane has already been shown 7see pages #ca1 #cg1 #aba1 #abb74 ,it was distinguished by the absence of a wheel frame or car and by the wing-warping method of stabilizing4 ,later ,wright machines have the spring frame and wheels for self-starting4 ,the best known aeroplane of this design was built to meet specifications of the ,united ,states ,signal ,corps issued in #aijg4 ,it was tried out during #aijh at ,fort ,myer1 ,va41 while one of the ,wright brothers was breaking all records in ,europe3 making over a hundred flights in all1 first carrying a passenger and attaining the then highest altitude 7#cfj feet7 and greatest distance of flight 7seventy-seven miles74 ,illustration3 ,,wright ,,motor4 ,,dimensions ,,in ,,millimeters 7,from ,petit's ,how to ,build an ,aeroplane7 ,the ownership of the ,wrights in the wing-warping method of control is still the subject of litigation4 ,the ,french infringers1 it is stated1 concede priority of application to the ,wright firm1 but maintain that such publicity was given the device that it was in general use before it was patented4 ,the ,fort ,myer machine had sails of forty feet spread1 six and one-half feet deep1 with front elevating planes three by sixteen feet4 ,it made about forty miles per hour with two passengers4 ,the apparatus was specified to carry a passenger weight of #cej pounds1 with fuel for a #abe-mile flight4 ,the main planes were six feet apart4 ,the steering rudder 7double7 was of planes one foot deep and nearly six feet high4 ,the four-cylinder-four-cycle1 water-cooled motor developed twenty-five horse-power at #adjj revolutions4 ,the two propellers1 eight and one-half feet in diameter1 made #djj revolutions4 ,the flight by ,mr4 ,wilbur ,wright from the ,statue of ,liberty to the tomb of ,general ,grant1 in ,new ,york1 #aiji1 and the exploits of his brother in the same year1 when a new altitude record of #afjj feet was made and ,h4,r4,h4 the ,crown ,prince of ,germany was taken up as a passenger1 are only specimens of the later work done by these pioneers in aerial navigation4 ,like the ,wrights1 the ,voisin firm from the beginning adhered firmly to the biplane type of machine4 ,the sketch gives dimensions of one of the early cellular forms built for ,h4 ,farman 7see illustration1 page #adg74 ,the metal screw makes about a thousand revolutions4 ,the wings are of india rubber sheeting on an ash frame1 the whole frame and car body being of wood1 the latter covered with canvas and thirty inches wide by ten feet long4 ,the engine weighed #age pounds4 ,the whole weight of this machine was nearly #abjj pounds2 that built later for ,delagrange was brought under a thousand pounds4 ,the ratio of weight to main surface in the ,farman aeroplane was about #b-c_/d to #a4 ,a modified cellular biplane also built for ,farman had a main wing area of #efj square feet1 the planes being seventy-nine inches wide and only fifty-nine inches apart4 ,the tail was an open box1 seventy-nine inches wide and of about ten feet spread4 ,the cellular partitions in this tail were pivoted along the vertical front edges so as to serve as steering rudders4 ,the elevating rudder was in front4 ,the total weight was about the same as that of the first machine and the usual speed twenty-eight miles per hour4 ,illustration3 ,,voisin-,,farman ,,biplane ,henry ,farman has been flying publicly since #aijg4 ,he made the first circular flight of one kilometer1 and attained a speed of about a mile a minute1 in the year following4 ,in #aiji he accomplished a trip of nearly #aej miles1 remaining four hours in the air4 ,farman was probably the first man to ascend with two passengers4 ,illustration3 ,,the ,,champagne ,,grand ,,prize ,,won ,,by ,,henry ,,farman #hj ,kilometers in #c hours ,illustration3 ,,farman',s ,,first ,,biplane ,,at ,,issy-,,les-,,moulineaux ,returning to the ,hangar ,after a ,flight ,the ,june ,bug1 one of the first ,curtiss machines1 is shown below4 ,this was one of the lightest of biplanes1 having a wing spread of forty-two feet and an area of #cgj square feet4 ,the wings were transversely arched1 being furthest apart at the center3 an arrangement which has not been continued4 ,it had a box tail1 with a steering rudder of about six square feet area1 above the tail4 ,the horizontal rudder1 in front1 had a surface of twenty square feet4 ,four triangular ailerons were used for stability4 ,the machine had a landing frame and wheels1 made about forty miles per hour1 and weighed1 in operation1 #fej pounds4 ,illustration3 ,,the ,,june ,,bug ,mr4 ,curtiss first attained prominence in aviation circles by winning the ,scientific ,american cup by his flight at the speed of fifty-seven miles per hour1 in #aijh4 ,in the following year he exhibited intricate curved flights at ,mineola1 and circled ,governor's ,island in ,new ,york harbor4 ,in #aiaj he made his famous flight from ,albany to ,new ,york1 stopping en route1 as prearranged4 ,at ,atlantic ,city he flew fifty miles over salt water4 ,a flight of seventy miles over ,lake ,erie was accomplished in ,september of the same year1 the return trip being made the following day4 ,on ,january #bf1 #aiaa1 ,curtiss repeatedly ascended and descended1 with the aid of hydroplanes1 in ,san ,diego bay1 ,california3 perhaps one of the most important of recent achievements4 ,it is understood that ,mr4 ,curtiss is now attempting to duplicate some of these performances under the high-altitude conditions of ,great ,salt ,lake4 ,according to press reports1 he has been invited to give a similar demonstration before the ,german naval authorities at ,kiel4 ,illustration3 ,,curtis ,,biplane 7,photo by ,levick1 ,n4,y47 ,illustration3 ,,curtiss' ,,hydro-,,aeroplane ,,at ,,san ,,diego ,,getting ,,under ,,way 7,from the ,columbian ,magazine7 ,the aeroscaphe of ,ravard was a machine designed to move either on water or in air4 ,it was an aeroplane with pontoons or floaters4 ,the supporting surface aggregated #djj square feet1 and the gross weight was about #aajj pounds4 ,a fifty horse-power ,gnome seven-cylinder motor at #abjj revolutions drove two propellers of eight and ten and one-half feet diameter respectively3 the propellers being mounted one behind the other on the same shaft4 ,illustration3 ,,flying ,,over ,,the ,,water ,,at ,,fifty ,,miles ,,per ,,hour ,curtiss at ,san ,diego ,bay 7,from the ,columbian ,magazine7 ,ely's great shore-to-warship flight was made without the aid of the pontoons which he carried4 ,ropes were stretched across the landing platform1 running over sheaves and made fast to heavy sand bags4 ,as a further precaution1 a canvas barrier was stretched across the forward end of the platform4 ,the descent brought the machine to the platform at a distance of forty feet from the upper end3 grappling hooks hanging from the framework of the aeroplane then caught the weighted ropes1 and the speed was checked 7within about sixty feet7 so gradually that not a wire or bolt of the biplane was injured4 ,illustration3 ,,bl,,riot-,,voisin ,,cellular ,,biplane ,,with ,,pontoons ,hauled by a ,motor ,boat ,illustration3 ,,latham',s ,,antoinette ,illustration3 ,,james ,j4 ,,ward ,,at ,,lewiston ,,fair1 ,,idaho 7,photo copyright #aiaj by ,burns7 ,flying ,machine ,mfg4 ,co4 ,biplane 7#cj hp4 ,motor7 ,illustration3 ,,marcel ,,penot ,,in ,,the ,,mohawk ,,biplane1 ,mineola to ,hicksville1 ,l4 ,i4 #bf miles cross-country in #cj minutes 7#ej hp4 ,harriman ,engine7 ,recent combinations of aeroplane and automobile1 and aeroplane with motor boat1 have been exhibited4 ,one of the latter devices is like any monoplane1 except that the lower part is a water-tight aluminum boat body carrying three passengers4 ,it is expected to start of itself from the water and to fly at a low height like a flying fish at a speed of about seventy-five miles per hour4 ,should anything go wrong1 it is capable of floating on the water4 ,in the ,san ,diego ,curtiss flights1 the machine skimmed along the surface of the bay1 then rose to a height of a hundred feet1 moved about two miles through the air in a circular course1 and finally alighted close to its starting-point in the water4 ,turns were made in water as well as in air1 a speed of forty miles per hour being attained while skimming4 ,the hydroplanes used are rigid flat surfaces which utilize the pressure of the water for sustention1 just as the main wings utilize air pressure4 ,on account of the great density of water1 no great amount of surface is required3 but it must be so distributed as to balance the machine4 ,the use of pontoons makes it possible to rest upon the water and to start from rest4 ,a trip like ,ely's could be made without a landing platform1 with this type of machine2 the aeroplane could either remain alongside the war vessel or be hoisted aboard until ready to venture away again4 ,there are various other biplanes attracting public attention in this country4 ,in ,france the tendency is all toward the monoplane form1 and many of the records have1 during the past couple of years1 passed from the former to the latter type of machine4 ,the monoplane is simpler and usually cheaper4 ,the biplane may be designed for greater economy in weight and power4 ,farman has lately experimented with the monoplane type of machine3 the large number of ,french designs in this class discourages any attempt at complete description4 ,illustration3 ,,santos-,,dumont',s ,,demoiselle ,the smallest of aeroplanes is the ,santos-,dumont ,demoiselle4 ,the original machine is said to have supported #bfj pounds on #ajj square feet of area1 making a speed of sixty miles per hour4 ,its proprietor was the first aviator in ,europe of the heavier-than-air class4 ,after having done pioneer work with dirigible balloons1 he won the ,deutsch prize for a hundred meter aeroplane flight 7the first outside of the ,united ,states7 in #aijf2 the speed being twenty-three miles per hour4 ,his first flight1 of #djj feet1 in a monoplane was made in #aijg4 ,illustration3 ,,bl,,riot ,,monoplane ,the master of the monoplane has been ,louis ,blriot4 ,starting in #aijg with short flights in a ,langley type of machine1 he made his celebrated cross-country run1 and the first circling flights ever achieved in a monoplane1 the following year4 ,on ,july #be1 #aiji1 he crossed the ,british ,channel1 thirty-two miles1 in thirty-seven minutes4 ,illustration3 ,,latham',s ,,fall ,,into ,,the ,,channel ,the ,channel crossing has become a favorite feat4 ,mr4 ,latham1 only two days after ,blriot1 all but completed it in his ,antoinette monoplane4 ,de ,lesseps1 in a ,blriot machine1 was more fortunate4 ,sopwith1 last year1 won the de ,forest prize of #bj1jjj by a flight of #agd miles from ,england into ,belgium4 ,the ill-fated ,rolls made the round trip between ,england and ,france4 ,grace1 contesting for the same prize1 reached ,belgium1 was driven back to ,calais1 started on the return voyage1 and vanished--all save some few doubtful relics lately found4 ,moisant reached ,london from ,paris--the first trip on record between these cities without change of conveyance3 and one which has just been duplicated by ,pierre ,prier1 who1 on ,april #ab1 made the ,london to ,paris journey1 #bij miles1 in #bcf minutes1 without a stop4 ,this does not1 however1 make the record for a continuous flight3 which was attained by ,tabuteau1 who at ,buc1 on ,dec4 #cj1 #aiaj1 flew around the aerodrome for #dfe minutes at the speed of #dh-a_/b miles per hour4 ,other famous crossings include those of the ,irish ,sea1 #eb miles1 by ,loraine2 ,long ,island ,sound1 #be miles1 by ,harmon2 and ,lake ,geneva1 #dj miles1 by ,defaux4 ,it was just about a century ago that ,cayley first described a soaring machine1 heavier than air1 of a form remarkably similar to that of the modern aeroplane4 ,aside from ,henson's unsuccessful attempt to build such a machine1 in #ahdb1 and ,wenham's first gliding experiments with a triplane in #aheg1 soaring flight made no real progress until ,langley's experiments4 ,that investigator1 with ,maxim and others1 ascertained those laws of aerial sustention the application of which led to success in #aijc4 ,illustration3 ,,de ,,lesseps ,,in ,a ,,bl,,riot ,,crossing ,,the ,,channel 7,photo by ,levick1 ,n4,y47 ,the eight years since have held the crowded hours of aviation4 ,before this book is printed1 it may be rendered obsolete by new developments4 ,the exploits of ,paulhan1 of ,r4 ,e4 ,peltrie since #aijg1 ,bell's work with his tetrahedral kites--all have been either stimulating or directly fruitful4 ,delagrange began to break speed records in #aijh4 ,a year later he attained a speed of fifty miles4 ,the first woman to enjoy an aeroplane voyage was ,mme4 ,delagrange1 in ,turin1 in #aijh4 ,illustration3 ,,the ,,maxim ,,aeroplane ,illustration3 ,,langley',s ,,aeroplane 7#ahif7 ,steam driven ,the first flight in ,england by an ,english-built machine was made in ,january1 #aiji4 ,that year1 ,count de ,lambert flew over ,paris1 and in #aiaj ,grahame-,white circled his machine over the city of ,boston4 ,the year #aiaj surpassed all its predecessors in increasing the range and control of aeroplanes2 over #aejj ascents were made by ,wright machines alone2 but #aiaa promises to show even greater results4 ,three men made cross-country flights from ,belmont ,park to the ,statue of ,liberty and back1 in ,new ,york2,b at least five men attained altitudes exceeding #i1jjj feet4 ,hamilton made the run from ,new ,york to ,philadelphia and return1 in ,june4 ,the unfortunate ,chavez all but abolished the fames of ,hannibal and ,napoleon by crossing the icy barrier of the ,alps1 from ,switzerland to ,italy--in forty minutes6 ,illustration3 ,,robart ,,monoplane4 ,tabuteau1 almost on ,new ,year's eve1 broke all distance records by a flight of #cfc miles in less than eight hours2 while ,barrier at ,memphis probably reached a speed of eighty-eight miles per hour 7timing unofficial74 ,with the new year came reports of inconceivable speeds by a machine skidding along the ice of ,lake ,erie2 the successful receipt by ,willard and ,mc,curdy of wireless messages from the earth to their aeroplanes2 and the proposal by the ,united ,states ,signal ,corps for the use of flying machines for carrying ,alaskan mails4 ,illustration3 ,,vina ,,monoplane4 ,mc,curdy all but succeeded in his attempt to fly from ,key ,west to ,havana1 surpassing previous records by remaining aloft above salt water while traveling eighty miles4 ,lieutenant ,bague1 in ,march1 started from ,antibes1 near ,nice1 for ,corsica4 ,after a #abd-mile flight1 breaking all records for sea journeys by air1 he reached the islet of ,gorgona1 near ,leghorn1 ,italy1 landing on bad ground and badly damaging his machine4 ,the time of flight was #e-a_/b hours4 ,bellinger completed the #ejj-mile accommodation train flight from ,vincennes to ,pau2 ,vedrine1 on ,april #ab1 by making the same journey in #dae minutes of actual flying time1 won the ,barn prize of #djjj2 ,say attained a speed of #gd miles per hour in circular flights at ,issy-les-,moulineaux4 ,aeroplane flights have been made in ,japan1 ,india1 ,peru1 and ,china4 ,one of the most spectacular of recent achievements is that of ,renaux1 competing for the ,michelin ,grand ,prize4 ,a purse of #bj1jjj was offered in #aiji by ,m4 ,michelin1 the ,french tire manufacturer1 for the first successful flight from ,paris to ,clermont-,ferrand--#bfj miles--in less than six hours4 ,the prize was to stand for ten years4 ,it was prescribed that the aviator must1 at the end of the journey1 circle the tower of the ,cathedral and alight on the summit of the ,puy de ,dome--elevation #dejj feet--on a landing place measuring only #dj by #ajj yards1 surrounded by broken and rugged ground and usually obscured by fog4 ,the flight was attempted last year by ,weymann1 who fell short of the goal by only a few miles4 ,leon ,morane met with a serious accident1 a little later1 while attempting the trip with his brother as a passenger4 ,renaux completed the journey with ease in his ,farman biplane1 carrying a passenger1 his time being #cjh minutes4 ,this ,michelin ,grand ,prize is not to be confused with the ,michelin ,trophy of #djjj offered yearly for the longest flight in a closed circuit4 ,speeds have increased #ej during the past year2 even with passengers1 machines have moved more than a mile a minute3 average motor capacities have been doubled or tripled4 ,the ,french men and machines hold the records for speed1 duration1 distance1 and 7perhaps7 altitude4 ,the highest altitude claimed is probably that attained by ,garros at ,mexico ,city1 early this year--#ab1jeb feet above sea level4 ,the world's speed record for a two-man flight appears to be that of ,foulois and ,parmalee1 made at ,laredo1 ,texas1 ,march #c1 #aiaa3 #ajf miles1 cross-country1 in #abg minutes4 ,three-fourths of all flights made up to this time have been made in ,france--a fair proportion1 however1 in ,american machines4 ,,note ,the rapidity with which history is made in aeronautics is forcibly suggested by the revision of text made necessary by recent news4 ,the new ,deutschland has met the fate of its predecessors2 the ,paris-,rome-,turin flight is at this moment under way2 and ,lieutenant ,bayne1 attempting once more his ,france-to-,corsica flight1 has--for the time being at least--disappeared4 ,,the ,,possibilities ,,in ,,aviation ,men now fly and will probably keep on flying2 but aviation is still too hazardous to become the popular sport of the average man4 ,the overwhelmingly important problem with the aeroplane is that of stability4 ,these machines must have a better lateral balance when turning corners or when subjected to wind gusts3 and the balance must be automatically1 not manually1 produced4 ,illustration3 ,,blanc ,,monoplane ,other necessary improvements are of minor urgency and in some cases will be easy to accomplish4 ,better mechanical construction1 especially in the details of attachments1 needs only persistence and common sense4 ,structural strength will be increased2 the wide spread of wing presents difficulties here1 which may be solved either by increasing the number of superimposed surfaces1 as in triplanes1 or in some other manner4 ,greater carrying capacity--two men instead of one--may be insisted upon3 and this leads to the difficult question of motor weights4 ,the revolving air-cooled motor may offer further possibilities3 the two-cycle idea will help if a short radius of action is permissible3 but a weight of less than two pounds to the horse-power seems to imply1 almost essentially1 a lack of ruggedness and surety of operation4 ,a promising field for investigation is in the direction of increasing propeller efficiencies4 ,if such an increase can be effected1 the whole of the power difficulty will be greatly simplified4 ,illustration3 ,,melvin ,,vaniman ,,triplane ,illustration3 ,,jean ,,de ,,crawhez ,,triplane ,illustration3 ,a ,,triplane ,this same motor question controls the proposal for increased speed4 ,the use of a reserve motor would again increase weights2 though not necessarily in proportion to the aggregate engine capacity4 ,perhaps something may be accomplished with a gasoline turbine1 when one is developed4 ,in any case1 no sudden increase in speeds seems to be probable2 any further lightening of motors must be undertaken with deliberation and science4 ,if much higher maximum speeds are attained1 there will be an opportunity to vary the speed to suit the requirements4 ,then clutches1 gears1 brakes1 and speed-changing devices of various sorts will become necessary1 and the problem of weights of journal bearings--already no small matter--will be made still more serious4 ,and with variable speed must probably come variable sail area--in preference to tilting--so that the fabric must be reefed on its frame4 ,certainly two men1 it would seem1 will be needed6 ,better methods for starting are required4 ,the hydroplane idea promises much in this respect4 ,with a better understanding and control of the conditions associated with successful and safe descent--perhaps with improved appliances therefor--the problem of ascent will also be partly solved4 ,if such result can be achieved1 these measures of control must be made automatic4 ,the building of complete aeroplanes to standard designs would be extremely profitable at present prices1 which range from #bejj to #ejjj4 ,perhaps the most profitable part would be in the building of the motor4 ,the framing and fabric of an ordinary monoplane could easily be constructed at a cost below #cjj4 ,the propeller may cost #ej more4 ,the expense for wires1 ropes1 etc41 is trifling2 and unless special scientific instruments and accessories are required1 all of the rest of the value lies in the motor and its accessories4 ,within reasonable limits1 present costs of motors vary about with the horse-power4 ,the amateur designer must therefore be careful to keep down weight and power unless he proposes to spend money quite freely4 ,the ,case of the ,dirigible ,not very much is being heard of performances of dirigible balloons just at present4 ,they have shown themselves to be lacking in stanchness and effectiveness under reasonable variations of weather4 ,we must have fabrics that are stronger for their weight and more impervious4 ,envelopes must be so built structurally as to resist deformation at high speeds1 without having any greatly increased weight4 ,a cheap way of preparing pure hydrogen gas is to be desired4 ,most important of all1 the balloon must have a higher speed1 to make it truly dirigible4 ,this1 with sufficient steering power1 will protect it against the destructive accidents that have terminated so many balloon careers4 ,here again arises the whole question of power in relation to motor weight1 though not as formidably as is the case with the aeroplane4 ,the required higher speeds are possible now1 at the cost merely of careful structural design1 reduced radius of action1 and reduced passenger carrying capacity4 ,better altitude control will be attained with better fabrics and the use of plane fin surfaces at high speeds4 ,the employment of a vertically-acting propeller as a somewhat wasteful but perhaps finally necessary measure of safety may also be regarded as probable4 ,illustration3 ,,giraudon',s ,,wheel ,,aeroplane ,the ,orthopter ,the aviplane1 ornithoptre or orthopter is a flying machine with bird-like flapping wings1 which has received occasional attention from time to time1 as the result of a too blind adherence to ,nature's analogies4 ,every mechanical principle is in favor of the screw as compared with any reciprocating method of propulsion4 ,there have been few actual examples of this type3 a model was exhibited at the ,grand ,central ,palace in ,new ,york in ,january of this year4 ,the mechanism of an orthopter would be relatively complex1 and the flapping wings would have to feather on their return stroke4 ,the flapping speed would have to be very high or the surface area very great4 ,this last requirement would lead to structural difficulties4 ,propulsion would not be uniform1 unless additional complications were introduced4 ,the machine would be the most difficult of any type to balance4 ,the motion of a bird's wing is extremely complicated in its details--one that it would be as difficult to imitate in a mechanical device as it would be for us to obtain the structural strength of an eagle's wing in fabric and metal1 with anything like the same extent of surface and limit of weight4 ,according to ,pettigrew1 the efficiency of bird and insect flight depends largely upon the elasticity of the wing4 ,chatley gives the ratio of area to weight as varying from fifty 7gnat7 to one-half 7,australian crane7 square feet per pound4 ,the usual ratio in aeroplanes is from one-third to one-half4 ,about the only advantages perceptible with the orthopter type of machine would be1 first1 the ability to start from rest without a preliminary surface glide2 and second1 more independence of irregularity in air currents1 since the propulsive force is exerted over a greater extent than is that of a screw propeller4 ,the ,helicopter ,the gyroplane or helicopter was the type of flying machine regarded by ,lord ,kelvin as alone likely to survive4 ,it lifts itself by screw propellers acting vertically4 ,this form was suggested in #aheb4 ,when only a single screw was used1 the whole machine rotated about its vertical axis4 ,it was attempted to offset this by the use of vertical fin-planes3 but these led to instability in the presence of irregular air currents4 ,one early form had two oppositely-pitched screws driven by a complete steam engine and boiler plant4 ,one of the ,cornu helicopters had adjustable inclined planes under the two large vertically propelling screws4 ,the air which slipped past the screws imposed a pressure on the inclined planes which was utilized to produce horizontal movement in any desired direction--if the wind was not too adverse4 ,a gasoline engine was carried in a sort of well between the screws4 ,illustration3 ,,br,,guet ,,gyroplane ,,during ,,construction 7,helicopter type7 ,the helicopter may be regarded as the limiting type of aeroplane1 the sail area being reduced nearly to zero2 the wings becoming mere fins1 the smaller the better4 ,it therefore requires maximum motor power and is particularly dependent upon the development of an excessively light motor4 ,it is launched and descends under perfect control1 without regard to horizontal velocity4 ,it has very little exposed surface and is therefore both easy to steer and independent of wind conditions4 ,by properly arranging the screws it can be amply balanced3 but it must have a particularly stout and strong frame4 ,the development of this machine hinges largely on the propeller4 ,it is not only necessary to develop power 7which means force multiplied by velocity7 but actual propulsive vertical force3 and this must exceed or at least equal the whole weight of the machine4 ,from ten to forty pounds of lifting force per horse-power have been actually attained3 and with motors weighing less than five pounds there is evidently some margin4 ,the propellers are of special design1 usually with very large blades4 ,four are commonly used3 one1 so to speak1 at each corner of the machine4 ,the helicopter is absolutely dependent upon its motors4 ,it cannot descend safely if the power fails4 ,if it is to do anything but ascend and descend it must have additional propulsive machinery for producing horizontal movement4 ,composite ,types ,the aeroplane is thus particularly weak as to stability1 launching1 and descending3 but it is economical in power because it uses the air to hold itself up4 ,the dirigible balloon is lacking in power and speed1 but can ascend and descend safely1 even if only by wasteful methods2 and it can carry heavy weights1 which are impossible with the structurally fragile aeroplane4 ,the helicopter is wasteful in power1 but is stable and sure in ascending and descending1 providing only that the motor power does not fail4 ,why1 then1 not combine the types8 ,an aeroplane-dirigible would be open to only one objection3 on the ground of stability4 ,the dirigible-helicopter would have as its only disadvantage a certain wastefulness of power1 while the aeroplane-helicopter would seem to have no drawback whatever4 ,all three combinations have been1 or are being1 tried4 ,an ,italian engineer officer has designed a balloon-aeroplane4 ,the balloon is greatly flattened1 or lens-shaped1 and floats on its side1 presenting its edge to the horizon--if inclination be disregarded4 ,with some inclination1 the machine acts like an aeroplane and is partially self-sustaining at any reasonable velocity4 ,the use of a vertically-acting screw on a dirigible combines the features of that type and the helicopter4 ,this arrangement has also been the subject of design 7as in ,captain ,miller's flexible balloon7 if not of construction4 ,the combination of helicopter and aeroplane seems especially promising3 the vertical propellers being employed for starting and descending1 as an emergency safety feature and perhaps for aid in stabilizing4 ,the fact that composite types of flying machine have been suggested is perhaps1 however1 an indication that the ultimate type has not yet been established4 ,what is ,promised ,the flying machine will probably become the vehicle of the explorer4 ,if ,stanley had been able to use a small high-powered dirigible in the search for ,livingstone1 the journey would have been one of hours as compared with months1 the food and general comfort of the party would have been equal in quality to those attainable at home1 and the expense in money and in human life would have been relatively trifling4 ,illustration3 ,,wellman',s ,,america 7,from ,wellman's ,aerial ,age7 ,most readers will remember the fate of ,andre1 and the projected polar expeditions of ,wellman in #aijg and #aiji4 ,misfortune accompanied both attempts2 but one has only to read ,peary's story of the dogged tramp over the ,greenland ice blink to realize that danger and misfortune in no less degree have accompanied other plans of ,arctic pioneering4 ,with proper design and the right men1 it does not seem unreasonable to expect that a hundred flying machines may soar above ,earth's invisible axial points during the next dozen years4,c ,the report of ,count ,zeppelin's ,spitzbergen expedition of last year has just been made public4 ,this was undertaken to ascertain the adaptability of flying machines for ,arctic navigation4 ,besides speed and radius of action1 the conclusive factors include that of freedom from such breakdowns as cannot be made good on the road4 ,for exploration in other regions1 the balloon or the aeroplane is sure to be employed4 ,rapidity of progress without fatigue or danger will replace the floundering through swamps1 shivering with ague1 and bickering with hostile natives now associated with tropical and other expeditions4 ,the stereoscopic camera with its scientific adjuncts will permit of almost automatic map-making1 more comprehensive and accurate than any now attempted in other than the most settled sections4 ,it is not too much to expect that arrangements will be perfected for conducting complete topographical surveys without more than occasional descents4 ,if extremely high altitudes must be attained--over a mile--the machines will be of special design2 but as far as can now be anticipated1 there will be no insurmountable difficulties4 ,the virgin peaks of ,ruwenzori and the ,himalayas may become easily accessible--even to women and children if they desire it4 ,we may obtain direct evidence as to the contested ascent of ,mt4 ,mc,kinley4 ,a report has been current that a ,blriot monoplane has been purchased for use in the inspection of construction work for an oil pipe line across the ,persian desert2 the aeroplane being regarded as more expeditious and effectual than an automobile4 ,the flying machine is the only land vehicle which requires no permanent way4 ,trains must have rails1 bicycles and automobiles must have good roads4 ,even the pedestrian gets along better on a path4 ,the ships of the air and the sea demand no improvement of the fluids in which they float4 ,to carry mails1 parcels1 persons1 and even light freight--these applications1 if made commercially practicable tomorrow1,d would surprise no one2 their possibility has already been amply demonstrated4 ,with the dirigible as the transatlantic liner and the aeroplane as the naphtha launch of the air1 the whole range of applications is commanded4 ,hangars and landing stages--the latter perhaps on the roofs of buildings1 revolutionizing our domestic architecture--may spring up as rapidly as garages have done4 ,and the aeroplane is potentially 7with the exception of the motorcycle7 the cheapest of self-propelled vehicles4 ,governments have already considered the possibilities of aerial smuggling4 ,perhaps our custom-house officers will soon have to watch a fence instead of a line3 to barricade in two dimensions instead of one4 ,they will need to be provided with ,united ,states ,revenue aeroplanes4 ,but how are aerial frontiers to be marked8 ,and does a nation own the air above it1 or is this1 like the high seas1 by natural right1 common to all8 ,can a flying-machine blockade-runner above the three-mile height claim extraterritoriality8 ,the flying machine is no longer the delusion of the crank1 because it has developed a great industry4 ,a now antiquated statement put the capitalization of aeroplane manufactories in ,france at a million dollars1 and the development expenditure to date at six millions4 ,there are dozens of builders1 in ,new ,york ,city alone1 of monoplanes1 biplanes1 gliders1 and models4 ,a permanent exhibition of air craft is just being inaugurated4 ,we have now even an aeronautic trust1 since the million-dollar capitalization of the ,maxim1 ,blriot1 ,grahame-,white firm4 ,according to the ,new ,york ,sun1 over #ejj1jjj has been subscribed for aviation prizes in #aiaa4 ,the most valuable prizes are for new records in cross-country flights4 ,the ,paris ,journal has offered #gj1jjj for the best speed in a circling race from ,paris to ,berlin1 ,brussels1 ,london1 and back to ,paris--#aejj miles4 ,supplementary prizes from other sources have increased the total stake in this race to #ajj1jjj4 ,a purse of #ej1jjj is offered by the ,london ,daily ,mail for the ,circuit of ,britain race1 from ,london up the east coast to ,edinburgh1 across to ,glasgow1 and home by way of the west coast1 ,exeter1 and the ,isle of ,wight2 a thousand miles1 to be completed in two weeks1 beginning ,july #bb1 with descents only at predetermined points4 ,this contest will be open 7at an entrance fee of #ejj7 to any licensee of the ,international ,federation4 ,a ,german circuit1 from ,berlin to ,bremen1 ,magdeburg1 ,dsseldorf1 ,aix-la-,chapelle1 ,dresden1 and back to the starting point1 is proposed by the ,zeitung am ,mittag of ,berlin1 a prize of #be1jjj having been offered4 ,in this country1 a comparatively small prize has been established for a run from ,san ,francisco to ,new ,york1 via ,chicago4 ,besides a meet at ,bridgeport1 ,may #ah-bj1 together with those to be held by several of the colleges and the ones at ,bennings and ,chicago1 there will be1 it is still hoped1 a national tournament at ,belmont ,park at the end of the same month4 ,here probably a dozen aviators will contest in qualification for the international meet in ,england1 to which three ,american representatives should be sent as competitors for the championship trophy now held by ,mr4 ,grahame-,white4 ,it is anticipated that the chances in the international races favor the ,french aviators1 some of whom--in particular1 ,leblanc--have been making sensational records at ,pau4 ,flights between aviation fields in different cities are the leading feature in the ,american program for the year4 ,a trip is proposed from ,washington to ,belmont ,park1 via ,atlantic ,city1 the ,new ,jersey coast1 and lower ,new ,york bay4 ,the distance is #bej miles and the time will probably be less than that of the best passenger trains between ,washington and ,new ,york4 ,if held1 this race will probably take place late in ,may4 ,it is wisely concluded that the advancement of aviation depends upon cross-country runs under good control and at reasonable speeds and heights rather than upon exhibition flights in enclosures4 ,it is to be hoped that commercial interests will not be sufficiently powerful to hinder this development4 ,we shall of course have the usual international championship balloon race1 preceded by elimination contests4 ,from present indications ,omaha is likely to be chosen as the point of departure4 ,the need for scientific study of aerial problems is recognized4 ,the sum of #cej1jjj has been offered the ,university of ,paris to found an aeronautic institute4 ,in ,germany1 the university at ,gttingen has for years maintained an aerodynamic laboratory4 ,lord ,rayleigh1 in ,england1 is at the head of a committee of ten eminent scientists and engineers which has1 under the authority of ,parliament1 prepared a program of necessary theoretical and experimental investigations in aerostatics and aerodynamics4 ,our ,american colleges have organized student aviation societies and in some of them systematic instruction is given in the principles underlying the art4 ,a permanent aeronautic laboratory1 to be located at ,washington1 ,d4,c41 is being promoted4 ,aviation as a sport is under the control of the ,international ,aeronautic ,federation1 having its headquarters at ,paris4 ,bodies like the ,royal ,aero ,club of ,england and the ,aero ,club of ,america are subsidiaries to the ,federation4 ,in addition1 we have in this country other clubs1 like the ,aeronautic ,society1 the ,united ,states ,aeronautical ,reserve1 etc4 ,the ,national ,council of the ,aero ,clubs of ,america is a sort of supreme court for all of these1 having control of meets and contests2 but it has no affiliation with the ,international body1 which is represented here by the ,aero ,club of ,america4 ,the ,canadian ,auto and ,aero ,club supervises aviation in the ,dominion4 ,aviation has developed new legal problems3 problems of liability for accidents to others2 the matter of supervision of airship operators4 ,bills to license and regulate air craft have been introduced in at least two state legislatures4 ,schools for instruction in flying as an art or sport are being promoted4 ,it is understood that the ,wright firm is prepared to organize classes of about a dozen men1 supplying an aeroplane for their instruction4 ,each man pays a small fee1 which is remitted should he afterward purchase a machine4 ,mr4 ,grahame-,white1 at ,pau1 in the south of ,france1 conducts a school of aviation1 and the arrangements are now being duplicated in ,england4 ,instruction is given on ,blriot monoplanes and ,farman biplanes1 at a cost of a hundred guineas for either4 ,the pupil is coached until he can make a three-mile flight2 meanwhile1 he is held partially responsible for damage and is required to take out a third-party insurance policy4 ,there is no lack of aeronautic literature4 ,major ,squier's paper in the ,transactions of the ,american ,society of ,mechanical ,engineers1 #aijh1 gave an eighteen-page list of books and magazine articles of fair completeness up to its date2 ,professor ,chatley's book1 ,aeroplanes1 #aiaa1 discusses some recent publications2 the ,brooklyn ,public ,library in ,new ,york issued in #aiaj 7misdated #aiji7 a manual of fourteen pages critically referring to the then available literature1 and itself containing a list of some dozen bibliographies4 ,aerial ,warfare ,illustration3 ,,the ,,german ,,emperor ,,watching ,,the ,,progress ,,of ,,aviation ,the use of air craft as military auxiliaries is not new4 ,as early as #ahab the ,russians1 before retreating from ,moscow1 attempted to drop bombs from balloons3 an attempt carried to success by ,austrian engineers in #ahdi4 ,both contestants in our own ,war of ,secession employed captive and drifting balloons4 ,president ,lincoln organized a regular aeronautic auxiliary staff in which one ,lowe held the official rank of chief aeronaut4 ,this same gentleman 7who had accomplished a reconnaissance of #cej miles in eight hours in a #be1jjj cubic foot drifting balloon7 was subjected to adverse criticism on account of a weakness for making ascents while wearing the formal ,prince ,albert coat and silk hat6 ,a portable gas-generating plant was employed by the ,union army4 ,we are told that ,general ,stoneman1 in #ahfb1 directed artillery fire from a balloon1 which was repeatedly fired at by the enemy1 but not once hit4 ,the ,confederates were less amply equipped4 ,their balloon was a patchwork of silk skirts contributed 7one doubts not1 with patriotic alacrity7 by the daughters of the ,confederacy4 ,it is not forgotten that communication between besieged ,paris and the external world was kept up for some months during #ahgj-ga by balloons exclusively4 ,mail was carried on a truly commercial scale3 pet animals and--the anticlimax is unintended--#afd persons1 including ,m4 ,gambetta1 escaped in some sixty-five flights4 ,balloons were frequently employed in the ,franco-,prussian contest2 and they were seldom put hors de combat by the enemy4 ,during our war with ,spain1 aerial craft were employed in at least one instance1 namely1 at ,san ,juan1 ,porto ,rico1 for reconnoitering entrenchments4 ,frequent ascents were made from ,ladysmith1 during the ,boer war4 ,the balloons were often fired at1 but never badly damaged4 ,cronje's army was on one occasion located by the aid of a ,british scout-balloon4 ,artillery fire was frequently directed from aerial observations4 ,both sides employed balloons in the epic conflict between ,russia and ,japan4 ,a declaration introduced at the second international peace conference at the ,hague proposed to prohibit1 for a limited period1 the discharge of projectiles or explosives from flying machines of any sort4 ,the ,united ,states was the only first-class power which endorsed the declaration4 ,it does not appear likely1 therefore1 that international law will discountenance the employment of aerial craft in international disputes4 ,the building of airships goes on with increasing eagerness4 ,last year the ,italian chamber appropriated #e1jjj1jjj for the construction and maintenance of flying machines4 ,a press report dated ,february #d stated that a ,german aeronaut had been spending some weeks at ,panama1 studying the air currents of the ,canal ,zone4 ,no flying machine may in ,germany approach more closely than within six miles of a fort1 unless specially licensed4 ,at the ,krupp works in ,essen there are being tested two new guns for shooting at aeroplanes and dirigibles4 ,one is mounted on an armored motor truck4 ,the other is a swivel-mounted gun on a flat-topped four-wheeled carriage4 ,the ,united ,states battleship ,connecticut cost #i1jjj1jjj4 ,it displaces #ah1jjj tons1 uses #ag1jjj horse-power and #ajjj men1 and makes twenty miles an hour4 ,an aeroplane of unusual size with nearly three times this speed1 employing from one to three men with an engine of #ajj horse-power1 would weigh one ton and might cost #ejjj4 ,a ,dreadnought costs #af1jjj1jjj1 complete1 and may last--it is difficult to say1 but few claim more than ten years4 ,it depreciates1 perhaps1 at the rate of #b1jjj1jjj a year4 ,aeroplanes built to standard designs in large quantities would cost certainly not over #ajjj each4 ,the ratio of cost is #af1jjj to #a4 ,would the largest ,dreadnought1 exposed unaided to the attack of #af1jjj flying machines1 be in an entirely enviable situation8 ,an aeroplane is a fragile and costly thing to hazard at one blow3 but not more fragile or costly than a ,whitehead torpedo4 ,the aeroplane soldier takes tremendous risks2 but perhaps not greater risks than those taken by the crew of a submarine4 ,there is never any lack of daring men when daring is the thing needed4 ,all experience goes to show that an object in the air is hard to hit4 ,the flying machine is safer from attack where it works than it is on the ground4 ,the aim necessary to impart a crippling blow to an aeroplane must be one of unprecedented accuracy4 ,the dirigible balloon gives a larger mark1 but could not be immediately crippled by almost any projectile4 ,it could take a good pounding and still get away4 ,interesting speculations might be made as to the outcome of an aerial battle between the two types of craft4 ,the aeroplane might have a sharp cutting beak with which to ram its more cumbersome adversary1 but this would involve some risk to its own stability3 and the balloon could easily escape by a quick ascent4 ,it has been suggested that each dirigible would need an aeroplane escort force for its defense against ramming4 ,any collision between two opposing heavier-than-air machines could not1 it would seem1 be other than disastrous3 but perhaps the dirigible could rescue the wrecks4 ,possibly gas-inflated life buoys might be attached to the individual combatants4 ,in the ,french manoeuvers1 a small aeroplane circled the dirigible with ease1 flying not only around it1 but in vertical circles over and under it4 ,illustration3 #g4e ,,centimeter ,,german ,,automatic ,,gun ,,for ,,attacking ,,airships 7,from ,brewer's ,art of ,aviation7 ,the ,french war office has exploited both types of machine4 ,in ,germany1 the dirigible has until recently received nearly all the attention of strategists3 but the results of a recent aerial war game have apparently suggested a change in policy1 and the ,germans are now1 without neglecting the balloon1 actively developing its heavier-than-air competitor4 ,england seems to be muddled as to its aerial policy1 while the ,united ,states has been waiting and for the most part doing nothing4 ,now1 however1 the mobilizations in ,texas have been associated with a considerable amount of aeroplane enthusiasm4 ,a half-dozen machines1 it is expected1 will soon be housed in the aerodrome at ,san ,antonio4 ,experiments are anticipated in the carrying of light ammunition and emergency supplies1 and one of the promised manoeuvers is to be the locating of concealed bodies of troops by air scouts4 ,thirty army officers are to be detailed for aeroplane service this year2 five training schools are to be established4 ,if flying machines are relatively unsusceptible to attack1 there is also some question as to their effectiveness in attack4 ,rifles have been discharged from moving balloons with some degree of accuracy in aim2 but long-range marksmanship with any but hand weapons involves the mastery of several difficult factors additional to those present in gunnery at sea4 ,the recoil of guns might endanger stability2 and it is difficult to estimate the possible effects of a powerful concussion1 with its resulting surges of air1 in the immediate vicinity of a delicately balanced aerial vessel4 ,but aside from purely combative functions1 air craft may be superlatively useful as messengers4 ,to send despatches rapidly and without interference1 or to carry a general #ajj miles in as many minutes--these accomplishments would render impossible the romance of a ,sheridan's ,ride1 but might have a romance of their own4 ,with the new sense added to human equipment by wireless communication1 the results of observations may be signaled to friends over miles of distance without intervening permanent connections of however fragile a nature4 ,flying machines would seem to be the safest of scouts4 ,they could pass over the enemy's country with as little direct danger--perhaps as unobserved--as a spy in disguise2 yet their occupants would scarcely be subjected to the penalty accompanying discovery of a spy4 ,they could easily study the movements of an opposing armed force3 a study now frequently associated with great loss of life and hampering of effective handling of troops4 ,they could watch for hostile fleets with relatively high effectiveness 7under usual conditions71 commanding distant approaches to a long coast line at slight cost4 ,from their elevated position1 they could most readily detect hostile submarines threatening their own naval fleet4 ,maximum effective reconnaissance in minimum time would be their chief characteristic3 in fact1 the high speeds might actually constitute an objection1 if they interfered with thorough observation4 ,but if air craft had been available at ,santiago in #ahih1 ,lieutenant ,blue's expedition would have been unnecessary1 and there would have been for no moment any doubt that ,admiral ,cervera's fleet was actually bottled up behind the ,morro4 ,no besieged fortress need any longer be deprived of communication with--or even some medical or other supplies from--its friends4 ,suppose that ,napoleon had been provided with a flying machine at ,elba--or even at ,st4 ,helena6 ,the applications to rapid surveying of unknown ground that have been suggested as possible in civil life would be equally possible in time of war4 ,even if the scene of conflict were in an unmapped portion of the enemy's territory1 the map could be quickly made1 the location of temporary defenses and entrenchments ascertained1 and the advantage of superior knowledge of the ground completely overcome prior to an engagement4 ,the searchlight and the compass for true navigation on long flights over unknown country would be the indispensable aids in such applications4 ,during the current mobilization of the ,united ,states ,army at ,texas1 a dispatch was carried #ba miles on a map-and-compass flight1 the round trip occupying less than two hours and being made without incident4 ,the machine flew at a height of #aejj feet and was sighted several miles off4 ,a dirigible balloon1 it has been suggested1 is comparatively safe while moving in the air1 but is subjected to severe strains when anchored to the ground1 if exposed4 ,it must have either safe harbors of refuge or actual shelter buildings--dry docks1 so to speak4 ,in an enemy's country a ravine or even a deep railway cut might answer in an emergency1 but the greatest reliance would have to be placed on quick return trips from a suitable base4 ,the balloon would be1 perhaps1 a more effective weapon in defense than in attack4 ,major ,squier regards a flying height of one mile as giving reasonable security against hostile projectiles in the daytime4 ,a lower elevation would be sufficient at night4 ,given a suitable telephotographic apparatus1 all necessary observations could easily be made from this altitude4 ,even in the enemy's territory1 descent to the earth might be possible at night under reasonably favorable conditions4 ,two sizes of balloon would seem to be indicated3 the scouting work described would be done by a small machine having the greatest possible radius of action4 ,frontiers would be no barrier to it4 ,sent from ,england in the night it could hover over a ,kiel canal or an island of ,heligoland at sunrise1 there to observe in most leisurely fashion an enemy's mobilizations4 ,illustration3 ,,german ,,gun ,,for ,,shooting ,,at ,,aeroplanes 7,from ,brewer's ,art of ,aviation7 ,at the ,london meeting of the ,institute of ,naval ,architects1 in ,april1 #aiaa1 the opinion was expressed that the only effective way of meeting attack from a flying machine at sea would be by a counter-attack from the same type of craft4 ,the ship designers concluded that the aeroplane would no more limit the sizes of battleships than the torpedo has limited them4 ,for the more serious work of fighting1 larger balloons would be needed1 with net carrying capacities perhaps upward from one ton4 ,such a machine could launch explosives and combustibles against the enemy's forts1 dry docks1 arsenals1 magazines1 and battleships4 ,it could easily and completely destroy his railroads and bridges2 perhaps even his capital itself1 including the buildings housing his chief executive and war office staff4 ,nothing--it would seem--could effectually combat it save air craft of its own kind4 ,the battles of the future may be battles of the air4 ,there are of course difficulties in the way of dropping missiles of any great size from flying machines4 ,curtiss and others have shown that accuracy of aim is possible4 ,eight-pound shrapnel shells have been dropped from an aeroplane with measurably good effect1 without upsetting the vessel2 but at best the sudden liberation of a considerable weight will introduce stabilizing and controlling difficulties4 ,the passengers who made junketing trips about ,paris on the ,clment-,bayard complained that they were not allowed to throw even a chicken-bone overboard6 ,but it does not seem too much to expect that these purely mechanical difficulties will be overcome by purely mechanical remedies4 ,an automatic venting of a gas ballonet of just sufficient size to compensate for the weight of the dropped shell would answer in a balloon3 a similar automatic change in propeller speed and angle of planes would suffice with the aeroplane4 ,there is no doubt but that air craft may be made efficient agents of destruction on a colossal scale4 ,illustration3 ,,santos-,,dumont ,,circling ,,the ,,eiffel ,,tower 7,from ,walker's ,aerial ,navigation7 ,a ,swedish engineer officer has invented an aerial torpedo1 automatically propelled and balanced like an ordinary submarine torpedo4 ,it is stated to have an effective radius of three miles while carrying two and one-half pounds of explosive at the speed of a bullet4 ,one can see no reason why such torpedoes of the largest size are not entirely practicable3 though much lower speeds than that stated should be sufficient4 ,according to press reports1 the ,krupps have developed a non-recoiling torpedo1 having a range exceeding #ejjj yards4 ,the percussion device is locked at the start1 to prevent premature explosion3 unlocking occurs only after a certain velocity has been attained4 ,major ,squier apparently contends that the prohibition of offensive aerial operations is unfair1 unless with it there goes the reciprocal provision that a war balloon shall not be fired at from below4 ,again1 there seems to be no good reason why aerial mines dropped from above should be forbidden1 while submarine mines--the most dangerous naval weapons--are allowed4 ,modern strategy aims to capture rather than to destroy3 the manoeuvering of the enemy into untenable situations by the rapid mobilization of troops being the end of present-day highly organized staffs4 ,whether the dirigible 7certainly not the aeroplane7 will ever become an effective vehicle for transport of large bodies of troops cannot yet be foreseen4 ,differences in national temper and tradition1 and the conflict of commercial enterprise1 perhaps the very recentness of the growth of a spirit of national unity on the one hand1 are rapidly bringing the two foremost powers of ,europe into keen competition3 a competition which is resulting in a bloodless revolution in ,england1 necessitated by the financial requirements of its naval program4 ,germany1 by its strategic geographical position1 its dominating military organization1 and the enforced frugality1 resourcefulness1 and efficiency of its people1 possesses what must be regarded as the most invincible army in the world4 ,its avowed purpose is an equally invincible navy4 ,whether the ,gibraltar-,power can keep its ascendancy may well be doubted4 ,the one doubtful--and at the same time perhaps hopeful--factor lies in the possibilities of aerial navigation4 ,illustration3 ,,latham1 ,,farman1 ,,and ,,paulhan ,if one battleship1 in terms of dollars1 represents #af1jjj airships1 and if one or a dozen of the latter can destroy the former--a feat not perhaps beyond the bounds of possibility--if the fortress that represents the skill and labor of generations may be razed by twoscore men operating from aloft1 then the nations may beat their spears into pruning-hooks and their swords into plowshares3 then the battle ceases to hinge on the power of the purse4 ,let war be made so costly that nations can no more afford it than sane men can wrestle on the brink of a precipice4 ,let armed international strife be viewed as it really is--senseless as the now dying duello4 ,let the navy that represents the wealth1 the best engineering1 the highest courage and skill1 of our age1 be powerless at the attack of a swarm of trifling gnats like ,gulliver bound by ,lilliputians--what happens then8 ,it is a reductio ad absurdum4 ,destructive war becomes so superlatively destructive as to destroy itself4 ,there is only one other way4 ,let the two rival ,powers on whom the peace of the world depends settle their difficulties--surely the earth must be big enough for both6--and then as one would gently but firmly take away from a small boy his too destructive toy rifle1 spike the guns and scuttle the ships1 their own and all the rest1 leaving to some unambitious and neutral power the prosaic task of policing the world4 ,here is a work for red blood and national self-consciousness4 ,if war were ever needed for man's best development1 other things will answer now4 ,the torn bodies and desolated homes of millions of men have paid the price demanded4 ,no imaged hell can surpass the unnamed horrors that our fathers braved4 ,enforced disarmament6 ,why not8 ,force 7and public opinion7 have abolished private duels4 ,why not national duels as well8 ,civilization's control of savagery always begins with compulsion4 ,for a generation1 no first-class power has had home experience in a serious armed conflict4 ,we should not willingly contemplate such experience now4 ,we have too much to do in the world to fight4 99 99 99 99 99 ,the writer has felt some hesitancy in letting these words stand as the conclusion of a book on flying machines3 but as with the old ,roman who terminated every oration with a defiance of ,carthage1 the conviction prevails that no other question of the day is of comparable importance2 and on a matter of overwhelming consequence like this no word can ever be out of place4 ,the five chief powers spent for war purposes 7officially1 as ,professor ,johnson puts it1 for the preservation of peace7 about #a1jjj1jjj1jjj in the year #aijh4 ,in the worst period of the ,napoleonic operations the ,french military and naval budget was less than #ajj1jjj1jjj annually4 ,great ,britain1 on the present peace footing1 is spending for armament more rapidly than from #agic to #ahae4 ,the gigantic ,war of the ,spanish ,succession 7which changed the map of ,europe7 cost ,england less than a present year's military expenditure4 ,since the types for these pages have been set1 the promise of international peace has been distinctly strengthened4 ,president ,taft has suggested that as1 first1 questions of individual privilege1 and1 finally1 even those of individual honor1 have been by common consent submitted to adjudication1 so also may those so-called issues involving national honor be disposed of without dishonor by international arbitration4 ,sir ,edward ,grey1 who does not hesitate to say that increase of armaments may end in the destruction of civilization unless stopped by revolt of the masses against the increasing burdens of taxation1 has electrified ,europe by his reception of the ,taft pronouncement4 ,england and the ,united ,states rule one-third the inhabitants of the earth4 ,it is true that a defensive alliance might be more advantageous to the former and disagreeably entangling to the latter2 but a binding treaty of arbitration between these powers would nevertheless be a worthy climax to our present era4 ,and if it led to alliance against a third nation which had refused to arbitrate 7led--as ,sir ,edward ,grey suggests--by the logic of events and not by subterranean device7 would not such be the fitting and conclusive outcome8 ,the ,taft-,grey program--one would wish to call it that--has had all reputable endorsement2 in ,england1 no factional opposition may be expected4 ,our own jingoes are strangely silent4 ,mr4 ,dillon's fear that compulsory disarmament would militate against the weaker nations is offset by the hearty adherence of ,denmark4 ,a resolution in favor of the establishment of an international police force has passed the ,house of ,commons by a heavy majority4 ,it looks now as if we might hope before long to re-date our centuries4 ,we have had ,olympiads and ,years of ,rome1 ,b4,c4 and ,a4,d4 ,perhaps next the dream of thoughtful men may find its realization in the new 7and1 we may hope1 ,english7 prefix1 ,y4,p4--,year of ,peace4 ,,footnotes ,a ,according to press reports1 temporary water ballast will be taken on during the daytime1 to offset the ascensional effect of the hot sun on the envelope4 ,b ,the contestants for the ,ryan prize of #aj1jjj were ,moisant1 ,count de ,lesseps1 and ,grahame-,white4 ,owing to bad weather1 there was no general participation in the preliminary qualifying events1 and some question exists as to whether such qualification was not tacitly waived2 particularly in view of the fact that the prize was awarded to the technically unqualified competitor1 ,mr4 ,moisant1 who made the fastest time4 ,this award was challenged by ,mr4 ,grahame-,white1 and upon review by the ,international ,aeronautic ,federation the prize was given to de ,lesseps1 the slowest of the contestants1 ,grahame-,white being disqualified for having fouled a pylon at the start4 ,this gentleman has again appealed the case1 and a final decision cannot be expected before the meeting of the ,federation in ,october1 #aiaa4 ,c ,the high wind velocities of the southern circumpolar regions may be an insurmountable obstacle in the ,antarctic4 ,yet ,mawson expects to take with him a #b-passenger monoplane having a #ahj-mile radius of action on the expedition proposed for this year4 ,d ,it seems that tomorrow has come2 for an aeroplane is being regularly used 7according to a reported interview with ,dr4 ,alexander ,graham ,bell7 for carrying mails in ,india4 ,books on ,aeronautics ,,flying ,,machines ,,to-,,day4 ,by ,,william ,d4 ,,ennis1 ,m4 ,e41 ,professor of ,mechanical ,engineering1 ,polytechnic ,institute1 ,brooklyn4 #abmo41 cloth1 #bah pp41 #abc illustrations #a4ej net ,,contents3 ,,the ,,delights ,,and ,,dangers ,,of ,,flying--,dangers of ,aviation--,what it is ,like to ,fly4 ,,soaring ,,flight ,,by ,,man--,what ,holds it ,up4 ,lifting ,power4 ,why so ,many ,sails4 ,steering4 ,,turning ,,corners--,what ,happens ,when ,making a ,turn4 ,lateral ,stability4 ,wing ,warping4 ,automatic ,control4 ,the ,gyroscope4 ,wind ,gusts4 ,,air ,,and ,,the ,,wind--,sailing ,balloons4 ,field and ,speed4 ,,gas ,,and ,,ballast--,buoyancy in ,air4 ,ascending and ,descending4 ,the ,ballonet4 ,the ,equilibrator4 ,,dirigible ,,balloons ,,and ,,other ,,kinds--,shapes4 ,dimensions4 ,fabrics4 ,framing4 ,keeping the ,keel ,horizontal4 ,stability4 ,rudders and ,planes4 ,arrangement and ,accessories4 ,amateur ,dirigibles4 ,fort ,omaha ,plant4 ,balloon ,progress4 ,,question ,,of ,,power--,resistance of ,aeroplanes4 ,resistance of ,dirigibles4 ,independent ,speed and ,timetable4 ,cost of ,speed4 ,propeller4 ,,getting ,,up ,,and ,,down2 ,,models ,,and ,,gliders2 ,,aeroplane ,,details--,launching4 ,descending4 ,gliders4 ,models4 ,balancing4 ,weights4 ,miscellaneous4 ,things to ,look ,after4 ,,some ,,aeroplanes--,,some ,,accomplishments4 ,,the ,,possibilities ,,in ,,aviation--,case of the ,dirigible4 ,the ,orthopter4 ,the ,helicopter4 ,composite ,types4 ,what is ,promised4 ,,aerial ,,warfare4 ,,aerial ,,flight4 ,vol4 #a4 ,aerodynamics4 ,by ,f4 ,w4 ,,lanchester4 #hvo41 cloth1 #dch pp41 #afb illustrations #f4jj net ,,contents3 ,fluid ,resistance and ,its ,associated ,phenomena4 ,viscosity and ,skin ,friction4 ,the ,hydrodynamics of ,analytical ,theory4 ,wing ,form and ,motion in the ,periphery4 ,the ,aeroplane4 ,the ,normal ,plane4 ,the ,inclined ,aeroplane4 ,the ,economics of ,flight4 ,the ,aerofoil4 ,on ,propulsion1 the ,screw ,propeller1 and the ,power ,expended in ,flight4 ,experimental ,aerodynamics4 ,glossary4 ,appendices4 ,vol4 ,,ii4 ,aerodonetics4 ,by ,f4 ,w4 ,,lanchester4 #hvo41 cloth1 #dcc pp41 #bjh illustrations #f4jj net ,,contents3 ,free ,flight4 ,general ,principles and ,phenomena4 ,the ,phugoid ,theory--,the ,equations of the ,flight ,path4 ,the ,phugoid #aheb-ahgb4 ,dirigible ,balloons from #ahhc-ahig2 #ahih-aijf4 ,flying ,machine ,theory--,the ,flight ,path ,plotted4 ,elementary ,deductions from the ,phugoid ,theory4 ,stability of the ,flight ,path as ,affected by ,resistance and ,moment of ,inertia4 ,experimental ,evidence and ,verification of the ,phugoid ,theory4 ,lateral and ,directional ,stability4 ,review of ,chapters ,i to ,,vii and ,general ,conclusions4 ,soaring4 ,experimental4 ,aerodonetics4 ,,aerial ,,navigation4 ,a practical handbook on the construction of dirigible balloons1 aerostats1 aeroplanes and aeromotors1 by ,,frederick ,,walker4 #abmo41 cloth1 #aea pp41 #ajj illustrations #c4jj net4 ,,contents3 ,laws of ,flight4 ,aerostatics4 ,aerostats4 ,aerodynamics4 ,screw ,propulsion4 ,paddles and ,aeroplanes4 ,motive ,power4 ,structure of ,airships and ,materials4 ,airships4 ,appendix4 ,,aeroplane ,,patents4 ,by ,,robert ,m4 ,,neilson4 #hvo41 cloth1 #aja pp41 #gg illustrations #b4jj net ,,contents3 ,advice to ,inventors4 ,review of ,british ,patents4 ,british ,patents and ,applications for ,patents from #ahfj to #aiaj1 arranged in ,order of ,application4 ,british ,patentees1 arranged alphabetically4 ,united ,states ,patents from #ahif to #aiji1 arranged in order of issue4 ,united ,states ,patentees1 arranged alphabetically4 ,,the ,,principles ,,of ,,aeroplane ,,construction4 ,by ,,rankin ,,kennedy1 ,c4 ,e4 #hvo41 cloth1 #ade pp41 #ea diagrams #a4ej net ,,contents3 ,elementary ,mechanics and ,physics4 ,principles of ,inclined ,planes4 ,air and ,its ,properties4 ,principles of the ,aeroplane4 ,the ,curves of the ,aeroplane4 ,centers of ,gravity3 ,balancing2 ,steering4 ,the ,propeller4 ,the ,hlicoptre4 ,the ,wing ,propeller4 ,the ,engine4 ,the ,future of the ,aeroplane4 ,,how ,,to ,,design ,,an ,,aeroplane4 ,by ,,herbert ,,chatley4 #afmo41 boards1 #aji pp41 illustrated 7,van ,nostrand's ,science ,series7 #ej cents ,,contents3 ,the ,aeroplane4 ,air ,pressure4 ,weight4 ,propellers and ,motors4 ,balancing4 ,construction4 ,difficulties4 ,future ,developments4 ,cost4 ,other ,flying-,machines 7,gyroplane and ,orinthoptere74 ,,how ,,to ,,build ,,an ,,aeroplane4 ,by ,,robert ,,petit4 ,translated from the ,french by ,t4 ,o',b4 ,hubbard and ,j4 ,h4 ,ledeboer4 #hvo41 cloth1 #aca pp41 #ic illustrations #a4ej net ,,contents3 ,general ,principles of ,aeroplane ,design4 ,theory and ,calculation4 ,resistance1 ,lift1 ,power1 ,calculations for the ,design of an ,aeroplane1 ,application of ,power1 ,design of ,propeller1 ,arrangements of ,surfaces1 ,stability1 ,center of ,gravity1 etc4 ,materials4 ,construction of ,propellers4 ,arrangements for ,starting and ,landing4 ,controls4 ,placing ,motor4 ,the ,planes4 ,curvatures4 ,motors4 ,,airships1 ,,past ,,and ,,present4 ,together with chapters on the use of balloons in connection with meteorology1 photography1 and the carrier pigeon4 ,by ,a4 ,,hildebrandt1 ,captain and ,instructor in the ,prussian ,balloon ,corps4 ,translated by ,w4 ,h4 ,story4 #hvo41 cloth1 #cfa pp41 #bbb illustrations #c4ej net ,,contents3 ,early ,history of the ,art4 ,invention of the ,air ,balloon4 ,montgolfieres1 ,charlieres1 and ,rozieres4 ,theory of the ,balloon4 ,development of the ,dirigible ,balloon4 ,history of the ,dirigible ,balloon1 #aheb-ahgb4 ,dirigible ,balloons from #ahhc-ahig2 #ahih-aijf4 ,flying ,machines4 ,kites4 ,parachutes4 ,development of ,military ,ballooning4 ,ballooning in ,franco-,prussian ,war4 ,modern ,organization of ,military ,ballooning in ,france1 ,germany1 ,england and ,russia4 ,military ,ballooning in ,other ,countries4 ,balloon ,construction and the ,preparation of the ,gas4 ,instruments4 ,ballooning as a ,sport4 ,scientific ,ballooning4 ,balloon ,photography4 ,photographic ,outfit for ,balloon ,work4 ,interpretation of ,photographs4 ,hectography by ,means of ,kites and ,rockets4 ,carrier ,pigeons for ,balloons4 ,balloon ,law4 ,illustration3 ,,van ,,nostrand ,,logo ,d4 ,,van ,,nostrand ,,co41 ,publishers #bc ,,murray and #bg ,,warren ,,streets1 ,,new ,,york ,transcriber's ,note3 ,italics are delimited by underscores2 bold by equal signs4 ,four occurrences of the oe-ligature in the word manoeuver are left as oe4 ,the four footnotes have been moved to the end of the book4 ,a few words were judged to be printer errors and were changed4 ,these include two occurrences of horse-power in the unhyphenated form1 the spelling of ,tabuteau as ,tabuteaw on p4 #afb1 and the spelling of hlicoptre as helicoptr on p4#bjh4 ,on a few of the figure captions1 missing accents were added to some ,french names4