,transcriber's ,notes3 ,text printed in italics in the original work has been transcribed between underscores1 bold text has been transcribed between equals signs4 ,small ,capitals in the original work have been transformed to ,,all ,,capitals4 ,more ,transcriber's ,notes may be found at the end of this text4 ,,artificial ,,and ,,natural ,,flight4 ,a ,pocket-,book of ,aeronautics4--,by ,h4 ,w4 ,l4 ,,moedebeck4 ,translated from the ,german by ,dr4 ,w4 ,,mansergh ,,varley4 ,with #aej ,illustrations4 #ajs4 #f;d4 net4 ,,contents4--,gases--,physics of the ,atmosphere--,meteorological ,observations--,balloon ,technics--,kites and ,parachutes--,on ,ballooning--,balloon ,photography--,photographic ,surveying from ,balloons--,military ,ballooning--,animal ,flight--,artificial ,flight--,airships--,flying ,machines--,motors--,air ,screws--,appendix--,index4 8,will be highly welcome to all aeronauts4 ,it may be said to be the only complete work practically dealing with such matters4 ,we have no hesitation in thoroughly recommending this as an absolutely indispensable book40--,knowledge4 8,it is without a doubt the best book that has appeared on the subject40--,aeronautical ,journal4 8,the present volume ought certainly to be possessed by every student of ,aeronautics1 as it contains a vast amount of information of the highest value40--,glasgow ,herald4 ,,whittaker ,,co41 ,,london1 ,e4,c4 ,,artificial ,,and ,,natural ,,flight4 ,,by ,,sir ,,hiram ,s4 ,,maxim4 ,,with #ie ,,illustrations4 ,,whittaker ,,co41 #b ,,white ,,hart ,,street1 ,,paternoster ,,square1 ,,london1 ,e4,c41 ,,and #fd-ff ,,fifth ,,avenue1 ,,new ,,york4 #aijh4 ,,preface4 ,it was in #ahef that ,i first had my attention called to the subject of flying machines4 ,my father1 who was a profound thinker and a clever mechanician1 seems to have given the subject a great deal of thought1 and to have matured a plan identical with what has been proposed by hundreds since that time4 ,i was then sixteen years of age1 and a fairly good mechanician1 and any new thing in the mechanical line interested me immensely4 ,my father's proposed machine1 of which he made a sketch1 was of the ,hlicoptre type1 having two screws both on the same axis--the lower one to be right hand and mounted on a tubular shaft1 and the top one to be left hand and mounted on a solid shaft running through the lower tubular shaft4 ,these screws were to be rotated in reverse directions by means of a small pinion engaging a bevel gear attached to each of the shafts4 ,his plan contemplated large screws with very fine pitch1 and he proposed to obtain horizontal motion by inclining the axis forward4 ,he admitted that there was no motor in existence light enough1 but thought one might be invented1 and that an engine might be worked by a series of explosions in the cylinder1 that is1 what is known to-day as internal combustion2 but he was not clear how such an engine could be produced4 ,he1 however1 said that a flying machine would be so valuable in time of war1 that it mattered little how expensive the explosive might be1 even if fulminate of mercury had to be used4 ,it is interesting to note in this connection that the great ,peter ,cooper of ,new ,york thought out an identical machine about the same time1 and actually commenced experiments4 ,it seems that this gentleman regarded fulminate of mercury as altogether too feeble and inert1 because we find that he selected chloride of nitrogen as his explosive agent4 ,however1 his work was soon brought to an end by the loss of the sight of one eye1 after which time he had no further dealings with this lively explosive4 ,the many early conversations that ,i had with my father on the subject kept the matter constantly before me1 and ,i think it was in #ahgb1 after having seen ,roper's hot-air engine and ,brayton's petroleum engine1 that ,i took the matter up1 and commenced to make drawings of a machine of the ,hlicoptre type1 but instead of having one screw above the other1 ,i saw at once that it would be much better if the two screws were widely separated1 so that each would engage new air1 the inertia of which had not been disturbed4 ,the designing of the machine itself was a simple matter1 but the engine gave me trouble4 ,no matter from what point ,i examined the subject1 the engine was always too heavy4 ,it appears that the ,brayton engine was shown at the ,centennial ,exhibition at ,philadelphia in #ahgf1 and that ,otto visited this exhibition4 ,up to that time1 he had been making a species of rocket engine--that is1 an engine in which an explosive mixture shot the piston upward and then sucked it back1 a rack and pinion transmitting movement to the rotating shaft by means of a pawl and ratchet4 ,he appears to have been much interested in the ,brayton engine1 as it was evidently very much in advance of his own4 ,it actually developed1 even at that time1 one horse-power per hour for every pound of crude petroleum consumed1 but it was very heavy indeed1 very difficult to start1 and not always reliable4 ,the shaft that worked the valve gear was parallel to the cylinder1 and placed in the exact position occupied by a similar shaft in the present ,otto engine1 but instead of revolving only half as fast as the crank shaft1 it made the same number of revolutions4 ,on ,otto's return to ,germany1 he evidently profited by what he had seen1 and made a new engine1 which in reality was a cross between his own and the ,brayton2 the result was a very important invention1 which has been of incalculable value to mankind4 ,it is this engine which is now propelling our motor cars1 and it is the only engine suitable for employment on a flying machine2 but even this motor was not in a sufficiently high state of development as far as lightness was concerned1 to be of any use to me4 ,the drawings which ,i made in #ahgc1 although of little or no value1 kept my thoughts on artificial flight1 and while ,i was away from home attending to business1 especially when in foreign countries1 ,i often amused myself by making mathematical calculations4 ,quite true1 the formula which ,i used at the time--,haswell's--was not correct2 still1 it was near enough to the mark to be of considerable value4 ,moreover1 the error in this formula affected the ,hlicoptre quite as much as the aeroplane system1 and as ,i was working with the view of ascertaining the relative merits of the two systems1 the error1 although considerable1 did not have any influence at all in the decision which ,i arrived at--namely1 that the aeroplane system was the best4 ,the machine that ,i thought out at that time contemplated superposed aeroplanes of very great length from port to starboard4 ,the size in the other direction was more for the purpose of preventing a rapid fall than for a lifting effect4 ,i saw that it would be necessary to have horizontal fore and aft rudders placed a long distance apart1 so as to prevent rapid pitching1 and it appeared to me that the further these rudders were apart1 the easier it would be to manuvre the machine4 ,as ,i never had any doubts regarding the efficiency of screw propellers working in the air1 ,i decided to use two of these of a large size rotating in opposite directions4 ,of course1 all this speculation was theory only1 but ,i verified it later on by actual experiments before ,i built my machine1 and it is very gratifying to me to know that all the successful flying machines of to-day are built on the lines which ,i had thought out at that time1 and found to be the best4 ,all have superposed aeroplanes of great length from port to starboard1 all have fore and aft horizontal rudders1 and all are driven with screw propellers4 ,the change from my model is only a change in the framework made possible by dispensing with the boiler1 water tank1 and steam engine4 ,in this little work1 ,i have dealt at considerable length with air currents1 the flight of birds1 and the behaviour of kites1 perhaps at the expense of some repetitions2 as the resemblance between kite flying and the soaring of birds is similar in many respects1 repetitions are necessary4 ,to those who go to sea in ships1 it is necessary to know something of the currents they are liable to encounter2 if it be a sailing ship1 certainly a knowledge of the air currents is of the greatest importance1 and so it is with flying machines4 ,if flights of any considerable distance are to be made1 the machine is liable at any time to encounter very erratic air currents1 and it has been my aim in discussing these three subjects--air currents1 birds1 and kites--to bring them before the would-be navigators of the air1 in order that they may anticipate the difficulties they have to deal with and be ready to combat them4 ,then1 again1 there has been almost an infinite amount of discussion regarding the soaring of birds and the flying of kites4 ,many years ago1 after reading numerous works on the subject of flight1 ,i became a close observer myself1 and always sought in my travels to learn as much as possible4 ,i have attempted to discuss this subject in simple and easily understood language1 and to present sufficient evidence to prevent the necessity of any further disputes4 ,i do not regard what ,i have said as a theory1 but simply as a plain statement of absolute and easily demonstrated facts4 ,during the last few years1 a considerable number of text-books and scientific treatises have been written on the subject of artificial flight1 the most elaborate and by far the most reliable of these being the 8,pocket-,book of ,aeronautics10 by ,herman ,w4 ,l4 ,moedebeck1 ,major und ,battaillonskommandeur im ,badischen ,fussartillerie ,regiment ,no4 #ad2 in collaboration with ,o4 ,chanute and others4 ,translated by ,w4 ,mansergh ,varley1 ,b4,a41 ,d4,sc41 ,ph4,d41 and published by ,whittaker ,co4 ,this work does not1 however1 confine itself altogether to flying machines1 but has a great deal of information which is of little or no value to the builder of true flying machines2 moreover1 it is not simple enough to be readily understood by the majority of experimenters4 ,in some other works which ,i have recently examined1 ,i find a confusing mass of the most intricate mathematical calculations1 abounding in an almost infinite number of characters1 and extending over hundreds of pages1 but on a close examination of some of the deductions arrived at1 ,i find that a good many of the mathematical equations are based on a mistaken hypothesis1 and the results arrived at are very wide of the truth4 ,i have shown several diagrams which will explain what ,i mean4 ,what is required by experimenters in flying machines--and there will soon be a great number of them--is a treatise which they can understand1 and which requires no more delicate instruments than a carpenter's #b-;foot rule and a grocer's scales4 ,the calculations relating to the lift1 drift1 and the skin friction of an aeroplane are extremely simple1 and it is quite possible to so place this matter that it can be understood by anyone who has the least smattering of mathematical knowledge4 ,mathematics of the higher order expressed in elaborate formul do very well in communications between college professors--that is1 if they happen to be agreed4 ,when1 however1 these calculations are so intricate as to require a clever mathematician a whole day to study out the meaning of a single page1 and if when the riddle is solved1 we find that these calculations are based on a fallacy1 and the results in conflict with facts1 it becomes quite evident to the actual experimenter that they are of little value4 ,for many years1 ,newton's law was implicitly relied upon4 ,chanute1 after going over my experimental work1 wrote that ,newton's law was out as #bj is to #a--that is1 that an aeroplane would lift twenty times as much in practice as could be shown by the use of ,newton's formula4 ,some recent experiments1 which ,i have made myself1 at extremely high velocities and at a very low angle1 seem to demonstrate that the error is nearer #ajj to #a than #bj to #a4 ,it will1 therefore1 be seen how little this subject was understood until quite recently1 and even now the mathematicians who write books and use such an immense amount of formul1 do not agree by any means1 as will be witnessed by the mass of conflicting controversy which has been appearing in ,engineering during the last four months4 ,when an aeroplane placed at a working angle of1 say1 #a in #aj is driven through the air at a high velocity1 it1 of course1 pushes the air beneath it downwards at one-tenth part of its forward velocity--that is1 in moving #aj feet1 it pushes the air down #a foot4 ,a good many mathematicians rely altogether upon the acceleration of the mass of air beneath the aeroplane which is accelerated by its march through the air1 the value of this acceleration being in proportion to the square of the velocity which is imparted to it4 ,suppose now that the aeroplane is thin and well-made1 that both top and bottom sides are equally smooth and perfect2 not only does the air engaged by the under side shoot downwards1 but the air also follows the exact contour of the top side1 and is also shot downwards with the same mean velocity as that passing on the underneath side1 so if we are going to consider the lifting effect of the aeroplane1 we must not leave out of the equation1 the air above the aeroplane1 which has quite as much mass and the same acceleration imparted to it1 as the air below the aeroplane4 ,even calculations made on this basis will not bring the lifting effect of an aeroplane up to what it actually does lift in practice2 in fact1 the few mathematicians who have made experiments themselves have referred to the actual lifting effect of aeroplanes placed at a low angle and travelling at a high velocity as being unaccountable4 ,only a few mathematicians appear to have a proper grasp of the subject4 ,however1 three could be pointed out who understand the subject thoroughly1 but these are all mathematicians of the very highest order--,lord ,kelvin1 ,lord ,rayleigh1 and ,professor ,langley4 ,in placing before the public1 the results of my experiments and the conclusions arrived at1 it is necessary to show the apparatus which ,i employed1 otherwise it might be inferred that my conclusions were guesswork1 or mathematical calculations which might or might not be founded on a mistaken hypothesis2 this is my excuse for showing my boiler and engine1 my rotating arm1 and my large machine4 ,i do not anticipate that anyone will ever use a steam engine again1 because any form of a boiler is heavy2 moreover1 the amount of fuel required is much greater than with an internal combustion engine1 and certainly seven times as much water has to be dealt with4 ,however1 the description which ,i am giving of my apparatus will demonstrate that ,i had the instruments for doing the experimental work that ,i have described in this work4 ,in the ,appendix will be found a description of my machine1 and some of my apparatus4 ,the conclusions which ,i arrived at were written down at the time with a considerable degree of care1 and are of interest because they show that1 at that date1 ,i had produced a machine that lifted considerably more than its own weight and had all of the essential elements1 as far as superposed aeroplanes1 fore and aft horizontal rudders1 and screw propellers were concerned1 common to all of the successful machines which have since been made4 ,the fact that practically no essential departure has been made from my original lines1 indicates to my mind that ,i had reasoned out the best type of a machine even before ,i commenced a stroke of the work4 ,i have to thank ,mr4 ,albert ,t4 ,thurston for reading the proofs of this work4 ,h4 ,s4 ,m4 ,,contents4 ,,chapter ,i4 ,,page ,introductory1 #a ,,chapter ,,ii4 ,air ,currents and the ,flight of ,birds1 #aa ,,chapter ,,iii4 ,flying of ,kites1 #be ,,chapter ,,iv4 ,principally ,relating to ,screws1 #ca ,,chapter ,v4 ,experiments with ,apparatus ,attached to a ,rotating ,arm--,crystal ,palace ,experiments1 #fb ,,chapter ,,vi4 ,hints as to the ,building of ,flying ,machines--,steering by ,means of a ,gyroscope1 #gg ,,chapter ,,vii4 ,the ,shape and ,efficiency of ,aeroplanes--,the ,action of ,aeroplanes and the ,power ,required ,expressed in the ,simplest ,terms--,some ,recent ,machines1 #ii ,,chapter ,,viii4 ,balloons1 #abj ,,appendix ,i41 #abe ,,appendix ,,ii4-- ,recapitulation of ,early ,experiments--,efficiency of ,screw ,propellers1 ,steering1 ,stability1 c4--,the ,comparative ,value of ,different ,motors--,engines--,experiments with ,small ,machines ,attached to a ,rotating ,arm1 #acj ,,index1 #afc ,,index ,,of ,,illustrations4 ,,fig4 ,,page #a4 ,diagram showing the reduction of the projected horizontal area1 #b #b4 ,professor ,langley's experiments1 #e #c4 ,eagles balancing themselves on an ascending current of air1 #ad #d4 ,air currents observed in ,mid-,atlantic1 #af #e4 ,glassy streaks in the ,bay of ,antibes1 #ag #f4 ,air currents observed in the ,mediterranean1 #ah #g4 ,the circulation of air produced by a difference in temperature1 #bg #h4 ,kite flying1 #bi #i4 ,group of screws and other objects used in my experiments1 #cb #aj4 ,some of the principal screws experimented with1 #cb #aa4 ,the three best screws1 #cc #ab4 ,apparatus for testing the thrust of screws1 #cd #ac4 ,apparatus for testing the direction of air currents1 #ce #ad4 ,the ends of screw blades1 #cf #ae4 ,the manner of building up the large screws1 #ci #af4 ,a fabric-covered screw1 #dj #ag4 ,the hub and one of the blades of the screw on the ,farman machine1 #db #ah4 ,section of screw blades having radial edges1 #dc #ai4 ,form of the blade of a screw made of sheet metal1 #dd #bj4 ,new form of hub1 #de #ba4 ,small apparatus for testing fabrics for aeroplanes1 #ej #bb4 ,apparatus for testing the lifting effect of aeroplanes and condensers1 #ea #bc4 ,apparatus for testing aeroplanes1 condensers1 c41 #eb #bd4 ,cross-sections of bars of wood1 #ec #be4 ,sections of bars of wood1 #ed #bf4 ,a flat aeroplane placed at different angles1 #ee #bg4 ,group of aeroplanes used in experimental research1 #ef #bh4 ,an #h-;inch aeroplane which did very well1 #eg #bi4 ,resistance due to placing objects in close proximity to each other1 #eh #cj4 ,cross-section of condenser tube made in the form of ,philipps' sustainers1 #fj #ca4 ,the grouping of condenser tubes made in the form of ,philipps' sustainers1 #fa #cb4 ,machine with a rotating arm1 #fc #cc4 ,a screw and fabric-covered aeroplane in position for testing1 #fd #cd4 ,the rotating arm of the machine with a screw and aeroplane attached1 #fe #ce4 ,the little steam engine used by me in my rotating arm experiments1 #ff #cf4 ,the machine attached to the end of the rotating shaft1 #fh #cg4 ,marking off the dynamometer1 #fi #cg;a4 ,right- and left-hand four-blade screws1 #gj #ch4 ,apparatus for indicating the force and velocity of the wind direct1 #ga #ci4 ,apparatus for testing the lifting effect of aeroplanes1 #gc #dj4 ,front elevation of proposed aeroplane machine1 #gg #da4 ,side elevation of proposed aeroplane machine1 #gh #db4 ,plan of proposed aeroplane machine1 #gi #dc4 ,plan of a hlicoptre machine1 #hb #dd4 ,showing the position of the blades of a hlicoptre as they pass around a circle1 #hc #de4 ,system of splicing and building up wooden members1 #hf #df4 ,cross-section of struts1 #hf #dg4 ,truss suitable for use with flying machines1 #hg #dh4 ,the paradox aeroplane1 #hh #di4 ,the ,antoinette motor1 #hi #ej4 ,section showing the ,antoinette motor as used in the ,farman and ,de la ,grange machines1 #ij #ea4 ,pneumatic buffer1 #ia #eb4 ,gyroscope1 #id #ec4 ,adjusting the lifting effect1 #ie #ed4 ,showing that the machine could be tilted in either direction by changing the position of the rudder1 #if #ee4 ,adjusting the lifting effect1 #ig #ef4 ,adjustment of the rudders1 #ih #eg4 ,diagram showing the evolution of a wide aeroplane1 #ajb #eh4 ,in a recently published mathematical treatise on aerodynamics an illustration is shown1 representing the path that the air takes on encountering a rapidly moving curved aeroplane1 #ajd #ei4 ,an illustration from another scientific publication also on the dynamics of flight1 #ajd #fj4 ,another illustration from the same work1 #aje #fa4 ,the shape and the practical angle of an aeroplane1 #aje #fb4 ,an aeroplane of great thickness1 #ajf #fc4 ,section of a screw blade having a rib on the back1 #ajf #fd4 ,shows a flat aeroplane placed at an angle of #de1 #ajg #fe4 ,the aeroplane here shown is a mathematical paradox1 #ajg #ff4 ,this shows fig4 #fe with a section removed1 #ajg #fg4 ,diagram showing real path of a bird1 #ajh #fh4 ,the ,de la ,grange machine on the ground1 #aaa #fi4 ,the ,de la ,grange machine in full flight1 #aaa #gj4 ,farman's machine in flight1 #aab #ga4 ,bleriot's machine1 #aac #gb4 ,santos ,dumont's flying machine1 #aac #gb;a4 ,angles and degrees compared1 #aae #gb;b4 ,diagram showing direction of the air with a thick curved aeroplane1 #aah #gb;c4 ,aeroplanes experimented with by ,mr4 ,horatio ,philipps1 #aah #gc4 ,the enormous balloon 8,ville de ,paris10 #abc #gd4 ,photograph of a model of my machine1 #acj #ge4 ,the fabric-covered aeroplane experimented with1 #aca #gf4 ,the forward rudder of my large machine showing the fabric attached to the lower side1 #aca #gg4 ,view of the track used in my experiments1 #acd #gh4 ,the machine on the track tied up to the dynamometer1 #ace #gi4 ,two dynagraphs1 #acf #hj4 ,the outrigger wheel that gave out and caused an accident with the machine1 #acg #ha4 ,shows the broken planks and the wreck that they caused1 #ach #hb4 ,the condition of the machine after the accident1 #aci #hc4 ,this shows the screws damaged by the broken planks1 #adj #hd4 ,this shows a form of outrigger wheels which were ultimately used1 #ada #he4 ,one pair of my compound engines1 #adb #hf4 ,diagram showing the path that the air has to take in passing between superposed aeroplanes in close proximity to each other1 #add #hg4 ,position of narrow aeroplanes arranged so that the air has free passage between them1 #ade #hh4 ,the very narrow aeroplanes or sustainers employed by ,mr4 ,philipps1 #adf #hi4 ,one of the large screws being hoisted into position1 #adi #ij4 ,steam boiler employed in my experiments1 #aeg #ia4 ,the burner employed in my steam experiments1 #aeg #ib4 ,count ,zeppelin's aluminium-covered airship coming out of its shed on ,lake ,constance1 #afa #ic4 ,count ,zeppelin's airship in full flight1 #afa #id4 ,the new ,british war balloon 8,dirigible0 ,no4 #b1 #afb #ie4 ,the ,wright aeroplane in full flight1 #afb ,,artificial ,,and ,,natural ,,flight4 ,,chapter ,i4 ,,introductory4 ,it has been my aim in preparing this little work for publication to give a description of my own experimental work1 and explain the machinery and methods that have enabled me to arrive at certain conclusions regarding the problem of flight4 ,the results of my experiments did not agree with the accepted mathematical formul of that time4 ,i do not wish this little work to be considered as a mathematical text-book2 ,i leave that part of the problem to others1 confining myself altogether to data obtained by my own actual experiments and observations4 ,during the last few years1 a considerable number of text-books have been published4 ,these have for the most part been prepared by professional mathematicians1 who have led themselves to believe that all problems connected with mundane life are susceptible of solution by the use of mathematical formul1 providing1 of course1 that the number of characters employed are numerous enough4 ,when the ,arabic alphabet used in the ,english language is not sufficient1 they exhaust the ,greek also1 and it even appears that both of these have to be supplemented sometimes by the use of ,chinese characters4 ,as this latter supply is unlimited1 it is evidently a move in the right direction4 ,quite true1 many of the factors in the problems with which they have to deal are completely unknown and unknowable2 still they do not hesitate to work out a complete solution without the aid of any experimental data at all4 ,if the result of their calculations should not agree with facts1 8bad luck to the facts40 ,up to twenty years ago1 ,newton's erroneous law as relates to atmospheric resistance was implicitly relied upon1 and it was not the mathematician who detected its error1 in fact1 we have plenty of mathematicians to-day who can prove by formul that ,newton's law is absolutely correct and unassailable4 ,it was an experimenter that detected the fault in ,newton's law4 ,in one of the little mathematical treatises that ,i have before me1 ,i find drawings of aeroplanes set at a high and impracticable angle with dotted lines showing the manner in which the writer thinks the air is deflected on coming in contact with them4 ,the dotted lines show that the air which strikes the lower or front side of the aeroplane1 instead of following the surface and being discharged at the lower or trailing edge1 takes a totally different and opposite path1 moving forward and over the top or forward edge1 producing a large eddy of confused currents at the rear and top side of the aeroplane4 ,it is very evident that the air never takes the erratic path shown in these drawings2 moreover1 the angle of the aeroplane is much greater than one would ever think of employing on an actual flying machine4 ,fully two pages of closely written mathematical formul follow1 all based on this mistaken hypothesis4 ,it is only too evident that mathematics of this kind can be of little use to the serious experimenter4 ,the mathematical equation relating to the lift and drift of a well-made aeroplane is extremely simple2 at any practicable angle from #a in #bj to #a in #e1 the lifting effect will be just as much greater than the drift1 as the width of the plane is greater than the elevation of the front edge above the horizontal--that is1 if we set an aeroplane at an angle of #a in #aj1 and employ #a lb4 pressure for pushing this aeroplane forward1 the aeroplane will lift #aj lbs4 ,if we change the angle to #a in #af1 the lift will be #af times as great as the drift4 ,it is quite true that as the front edge of the aeroplane is raised1 its projected horizontal area is reduced--that is1 if we consider the width of the aeroplane as a radius1 the elevation of the front edge will reduce its projected horizontal area just in the proportion that the versed sine is increased4 ,for instance1 suppose the sine of the angle to be one-sixth of the radius1 giving1 of course1 to the aeroplane an inclination of #a in #f1 which is the sharpest practical angle1 this only reduces the projected area about #b per cent41 while the lower and more practical angles are reduced considerably less than #a per cent4 ,it will1 therefore1 be seen that this factor is so small that it may not be considered at all in practical flight4 ,illustration3 ,fig4 #a4--;,diagram showing the reduction of the projected horizontal area of aeroplanes due to raising the front edge above the horizontal--a1 b1 shows an angle of #a in #d1 which is the highest angle that will ever be used in a flying machine1 and this only reduces the projected area about #b per cent4 ,the line c b shows an angle of #a in #h1 and this only reduces the projected area an infinitesimal amount4 ,as the angle of inclination is increased1 the projected area becomes less as the versed sine f d becomes greater4 ,some of the mathematicians have demonstrated by formul1 unsupported by facts1 that there is a considerable amount of skin friction to be considered1 but as no two agree on this or any other subject1 some not agreeing to-day with what they wrote a year ago1 ,i think we might put down all of their results1 add them together1 and then divide by the number of mathematicians1 and thus find the average coefficient of error4 ,when we subject this question to experimental test1 we find that nearly all of the mathematicians are radically wrong1 ,professor ,langley1 of course1 excepted4 ,i made an aeroplane of hard rolled brass1 #bj gauge2 it was #a foot wide and dead smooth on both sides2 ,i gave it a curvature of about #a_/af inch and filed the edges1 thin and sharp4 ,i mounted this with a great deal of care in a perfectly horizontal blast of air of #dj miles an hour4 ,when this aeroplane was placed at any angle between #a in #h and #a in #bj1 the lifting effect was always just in proportion to its angle4 ,the distance that the front edge was raised above the horizontal1 as compared with the width of the aeroplane1 was always identical with the drift as compared with the lift4 ,on account of the jarring effect caused by the rotation of the screws that produced the air blast1 we might consider that all of the articulated joints about the weighing device were absolutely frictionless1 as the jar would cause them to settle into the proper position quite irrespective of friction4 ,i was1 therefore1 able to observe very carefully1 the lift and the drift4 ,as an example of how these experiments were conducted1 ,i would say that the engine employed was provided with a very sensitive and accurate governor2 the power transmission was also quite reliable4 ,before making these tests1 the apparatus was tested as regards the drift1 without any aeroplane in position1 and with weights applied that would just balance any effect that the wind might have on everything except the aeroplane4 ,the aeroplane was then put in position and the other system of weights applied until it exactly balanced1 all the levers being rapped in order to eliminate the friction in their joints4 ,the engine was then started and weights applied just sufficient to counterbalance the lifting effect of the aeroplane1 and other weights applied to exactly balance the drift or the tendency to travel with the wind4 ,in this way1 ,i was able to ascertain1 with a great degree of accuracy1 the relative difference between the lift and drift4 ,if there had been any skin friction1 even to the extent of #b per cent41 it would have been detected4 ,this brass aeroplane was tested at various angles1 and always gave the same results1 but of course ,i could not use thick brass aeroplanes on a flying machine2 it was necessary for me to seek something much lighter4 ,i therefore conducted experiments with other materials1 the results of which are given4 ,however1 with a well-made wooden aeroplane #a foot wide and with a thickness in the centre of #g_/af inch1 ,i obtained results almost identical with those of the very much thinner brass aeroplane1 but it must not be supposed that in practice an aeroplane is completely without friction4 ,if it is very rough1 irregular in shape1 and has any projections whatsoever on either the top or bottom side1 there will be a good deal of friction1 although it may not1 strictly speaking1 be skin friction2 still1 it will absorb the power1 and the coefficient of this friction may be anything from #je to #dj4 ,these experiments with the brass aeroplane demonstrated that the lifting effect was in direct proportion to the angle1 and that skin friction1 if it exists at all1 was extremely small1 but this does not agree with a certain kind of reasoning which can be made very plausible and is consequently generally accepted4 ,illustration3 ,fig4 #b4--,professor ,langley's experiments--a1 end of the rotating arm2 b1 brass plane weighing #a lb42 c c1 spiral springs4 ,when the arm was driven through the air1 in the direction shown1 the plane assumed approximately a horizontal position1 and the pull on the springs c c was reduced from #a lb4 to #a oz4 ,writers of books1 as a rule1 have always supposed that the lifting effect of an aeroplane was not in proportion to its inclination1 but in proportion to the square of the sine of the angle4 ,in order to make this matter clear1 ,i will explain4 ,suppose that an aeroplane is #bj inches wide and the front edge is raised #a inch above the horizontal4 ,in ordinary parlance this is1 of course1 called an inclination of #a in #bj1 but mathematicians approach it from a different standpoint4 ,they regard the width of the aeroplane as unity or the radius1 and the #a inch that the front edge is raised as a fraction of unity4 ,the geometrical name of this #a inch is the sine of the angle--that is1 it is the sine of the angle at which the aeroplane is raised above the horizontal4 ,suppose1 now1 that we have another identical aeroplane and we raise the front edge #b inches above the horizontal4 ,it is very evident that1 under these conditions1 the sine of the angle will be twice as much1 and that the square of the sine of the angle will be four times as great4 ,all the early mathematicians1 and some of those of the present day1 imagine that the lift must be in proportion to the square of the sine of the angle4 ,they reason it out as follows3--,if an aeroplane is forced through the air at a given velocity1 the aeroplane in which the sine of the angle is #b inches will push the air down with twice as great a velocity as the one in which the sine of the angle is only #a inch1 and as the force of the wind blowing against a normal plane increases as the square of the velocity1 the same law holds good in driving a normal plane through still air4 ,from this reasoning1 one is led to suppose that an aeroplane set at an angle of #a in #aj will lift four times as much as one in which the inclination is only #a in #bj1 but experiments have shown that this theory is very wide of the truth4 ,there are dozens of ways of showing1 by pure mathematics1 that ,newton's law is quite correct2 but in building a flying machine no theory is good that does not correspond with facts1 and it is a fact1 without any question1 that the lifting effect of an aeroplane1 instead of increasing as the square of the sine of the angle1 only increases as the angle4 ,lord ,kelvin1 when he visited my place1 was1 ,i think1 the first to mention this1 and point out that ,newton's law was at fault4 ,professor ,langley also pointed out the fallacy of ,newton's law1 and other experimenters have found that the lifting effect does not increase as the square of the sine of the angle4 ,in order to put this matter at rest1 ,lord ,rayleigh1 who1 ,i think we must all admit1 would not be likely to make a mistake1 made some very simple experiments1 in which he demonstrated that two aeroplanes1 in which we may consider the sine of the angle to be #a_/d inch1 lifted slightly more than a similar aeroplane in which the sine of the angle was only #a_/b inch4 ,of course1 ,lord ,rayleigh did not express it in inches1 but in term of the radius4 ,his aeroplanes were1 however1 very small4 ,we can rely upon it that the lifting effect of an aeroplane at any practical angle1 everything else being equal1 increases in direct proportion to the angle of the inclination4 ,in this little work1 ,i have attempted to make things as simple as possible2 it has not been written for mathematicians1 and ,i have1 therefore1 thought best to express myself in inches instead of in degrees4 ,if ,i write1 8an inclination of #a in #bj10 everyone will understand it1 and only a carpenter's #b-;foot rule is required to ascertain what the angle is4 ,then1 again1 simple measurements make calculations much simpler1 and the lifting effect is at once understood without any computations being necessary4 ,if the angles are expressed in degrees and minutes1 it is necessary to have a protractor or a text-book in order to find out what the inclination really is4 ,when ,i made my experiments1 ,i only had in mind the obtaining of correct data1 to enable me to build a flying machine that would lift itself from the ground4 ,at that time ,i was extremely busy1 and during the first two years of my experimental work1 ,i was out of ,england fourteen months4 ,after having made my apparatus1 ,i conducted my experiments rather quickly1 it is true1 but ,i intended later on to go over them systematically and deliberately1 make many more experiments1 write down results1 and prepare some account of them for publication4 ,however1 the property where ,i made these experiments was sold by the company owning it1 and my work was never finished1 so ,i am depending on the scraps of data that were written down at the time4 ,i am also publishing certain observations that ,i wrote down shortly after ,i had succeeded in lifting more than the weight of my machine4 ,i think that the experiments which ,i made with an aeroplane only #h inches wide will be found the most reliable4 ,all the machinery was running smoothly1 and the experiments were conducted with a considerable degree of care4 ,in making any formula on the lifting effect of the aeroplane1 it should be based on what was accomplished with the #h-;inch plane4 ,only a few experiments were made to ascertain the relative value of planes of different widths4 ,however1 ,i think we must all admit that a wide plane is not as economical in power as a narrow one4 ,in order to make this matter plain1 suppose that we have one aeroplane placed at such an angle that it will lift #b lbs4 per square foot at a velocity of #dj miles an hour2 it is very evident that the air just at the rear of this aeroplane would be moving downward at a velocity corresponding to the acceleration imparted to it by the plane4 ,if we wish to obtain lifting effect on this air by another plane of exactly the same width1 we shall have to increase its inclination in order to obtain the same lifting effect1 and1 still further1 it will be necessary to use more power in proportion to the load lifted4 ,if a third aeroplane is used1 it must be placed at an angle that will impart additional acceleration to the air1 and so on4 ,each plane that we add will have to be placed at a sharper angle1 and the power required will be just in proportion to the average angle of all the planes4 ,as the action of a wide aeroplane is identical with that of numerous narrow ones placed in close proximity to each other1 it is very evident that a wide aeroplane cannot be as efficient in proportion to its width as a narrow one4 ,i have thought the matter over1 and ,i should say that the lifting effect of a flat aeroplane increases rather faster than the square root of its width4 ,this will1 at least1 do for a working hypothesis4 ,every flying machine must have what we will call 8a length of entering edge0--that is1 the sum of entering edges of all the aeroplanes must bear a fixed relation to the load carried4 ,if a machine is to have its lifting effect doubled1 it is necessary to have the length of entering edge twice as long4 ,this additional length may1 of course1 be obtained by superposed planes1 but as we may assume that a large aeroplane will travel faster than a small one1 increased velocity will compensate in some degree for the greater width of larger aeroplanes4 ,by careful study of the experiments which ,i have made1 ,i think it is quite safe to state that the lifting effect of well-made aeroplanes1 if we do not take into consideration the resistance due to the framework holding them in position1 increases as the square of their velocity4 ,double their speed and they give four times the lifting effect4 ,the higher the speed1 the smaller the angle of the plane1 and the greater the lifting effect in proportion to the power employed4 ,when we build a steamship1 we know that its weight increases as the cube of any one of its dimensions--that is1 if the ship is twice as long1 twice as wide1 and twice as deep it will carry eight times as much2 but at the very best1 with even higher speed1 the load carried by a flying machine will only increase with the square of any one of its dimensions1 or perhaps still less4 ,no matter whether it is a ship1 a locomotive1 or a flying machine that we wish to build1 we must first of all consider the ideal1 and then approximate it as closely as possible with the material at hand4 ,suppose it were possible to make a perfect screw1 working without friction1 and that its weight should only be that of the surrounding air2 if it should be #bjj feet in diameter1 the power of one man1 properly applied1 would lift him into the air4 ,this is because the area of a circle #bjj feet in diameter is so great that the weight of a man would not cause it to fall through the air at a velocity greater than the man would be able to climb up a ladder4 ,if the diameter should be increased to #djj feet1 then a man would be able to carry a passenger as heavy as himself on his flying machine1 and if we should increase it still further1 to #b1jjj feet1 the weight of a horse could be sustained in still air by the power which one man could put forth4 ,on the other hand1 if we should reduce the diameter of the screw to #bj feet1 then it would certainly require the power of one horse to lift the weight of one man1 and1 if we made the screw small enough1 it might even require the power of #ajj horses to lift the same weight4 ,it will1 therefore1 be seen that everything depends upon the area of the air engaged1 and in designing a machine we should seek to engage as much air as possible1 so long as we can keep down the weight4 ,suppose that a flying machine should be equipped with a screw #aj feet in diameter1 with a pitch of #f feet1 and that the motor developed #dj horse-power and gave the screw #a1jjj turns a minute1 producing a screw thrust1 we will say1 of about #bbj lbs4 ,if we should increase the diameter of the screw to #bj feet1 and if it had the same pitch and revolved at the same rate1 it would require four times as much power and would give four times as much screw thrust1 because the area of the disc increases as the square of the diameter4 ,suppose1 now1 that we should reduce the pitch of the screw to #c feet1 we should in this case engage four times as much air1 and double the screw thrust without using any more power--that is1 assuming that the machine is stationary and that the full power of the engine is being used for accelerating the air4 ,the advantages of a large screw will1 therefore1 be obvious4 ,i have been unable to obtain correct data regarding the experiments which have taken place with the various machines on the ,continent4 ,i have1 however1 seen these machines1 and ,i should say when they are in flight1 providing that the engine develops #dj horse-power1 that fully #bh horse-power is lost in screw slip1 and the remainder in forcing the machine through the air4 ,these machines weigh #a1jjj lbs4 each1 and their engines are said to be #ej horse-power4 ,the lifting effect1 therefore1 per horse-power is #bj lbs4 ,if the aeroplanes were perfect in shape and set at a proper angle1 and the resistance of the framework reduced to a minimum1 the same lifting effect ought to be produced with an expenditure of less than half this amount of power1 providing1 of course1 that the screw be of proper dimensions4 ,it is said that ,professor ,langley and ,mr4 ,horatio ,philipps1 by eliminating the factor of friction altogether1 or by not considering it in their calculations1 have succeeded in lifting at the rate of #bjj lbs4 per horse-power4 ,the apparatus they employed was very small4 ,the best ,i ever did with my very much larger apparatus--and ,i only did it on one occasion--was to carry #acc lbs4 per horse-power4 ,in my large machine experiments1 ,i was amazed at the tremendous amount of power necessary to drive the framework and the numerous wires through the air4 ,it appeared to me1 from these experiments1 that the air resisted very strongly being cut up by wires4 ,i expected to raise my machine in the air by using only #ajj horse-power1 and my first condenser was made so that it did actually condense water enough to supply #ajj horse-power1 but the framework offered such a tremendous resistance that ,i was compelled to strengthen all of the parts1 make the machine heavier1 and increase the boiler pressure and piston speed until ,i actually ran it up to #cfb horse-power4 ,this1 however1 was not the indicated horse-power4 ,it was arrived at by multiplying the pitch of the screws1 in feet1 by the number of turns that they made in a minute1 and by the screw thrust in pounds1 and then dividing the product by the conventional unit #cc1jjj4 ,i have no doubt that the indicated horse-power would have been fully #djj4 ,on one occasion ,i ran my machine over the track with all the aeroplanes removed4 ,i knew what steam pressure was required to run my machine with the aeroplanes in position at a speed of #dj miles an hour4 ,with the planes removed1 it still required a rather high steam pressure to obtain this velocity1 but ,i made no note at the time of the exact difference4 ,it was not1 however1 by any means so great as one would have supposed4 ,from the foregoing1 it will be seen how necessary it is to consider atmospheric resistance4 ,although ,i do not expect that anyone will ever again attempt to make a flying machine driven by a steam engine1 still1 ,i have thought best to give a short and concise description of my engine and boiler1 in order that my readers may understand what sort of an apparatus ,i employed to obtain the data ,i am now1 for the first time1 placing before the public4 ,a full description of everything relating to the motor power was written down at the time1 and has been carefully preserved4 ,an abridgement of this will be found in the ,appendix4 ,,chapter ,,ii4 ,,air ,,currents ,,and ,,the ,,flight ,,of ,,birds4 ,in ,mr4 ,darwin's 8,voyage of the ,beagle0 ,i find3-- 8,when the condors are wheeling in a flock round and round any spot their flight is beautiful4 ,except when rising from the ground1 ,i do not remember ever having seen one of these birds flap its wings4 ,near ,lima ,i watched several for nearly half an hour1 without taking off my eyes2 they moved in large curves1 sweeping in circles1 descending and ascending without giving a single flap4 ,as they glided close over my head ,i intently watched from an oblique position1 the outlines of the separate and great terminal feathers of each wing1 and these separate feathers1 if there had been the least vibratory movement1 would have appeared as if blended together2 but they were seen distinct against the blue sky40 ,man is essentially a land animal1 and it is quite possible if ,nature had not placed before him numerous examples of birds and insects that are able to fly1 he would never have thought of attempting it himself4 ,but birds are very much in evidence1 and mankind from the very earliest times has not only admired the ease and rapidity with which they are able to move from place to place1 but has always aspired to imitate them4 ,the number of attempts that have been made to solve this problem has been very great2 but it was not until quite recently that science and mechanics had advanced far enough to put in the hands of experimenters suitable material to attack the problem4 ,perhaps nothing better has ever been written regarding our aspirations to imitate the flight of birds than what ,prof4 ,langley has said3-- 8,nature has made her flying machine in the bird1 which is nearly a thousand times as heavy as the air its bulk displaces1 and only those who have tried to rival it know how inimitable her work is1 for #8the way of a bird in the air' remains as wonderful to us as it was to ,solomon1 and the sight of the bird has constantly held this wonder before men's eyes1 and in some men's minds1 and kept the flame of hope from utter extinction1 in spite of long disappointment4 ,i well remember how1 as a child1 when lying in a ,new ,england pasture1 ,i watched a hawk soaring far up in the blue1 and sailing for a long time without any motion of its wings1 as though it needed no work to sustain it1 but was kept up there by some miracle4 ,but1 however sustained1 ,i saw it sweep1 in a few seconds of its leisurely flight1 over a distance that to me was encumbered with every sort of obstacle1 which did not exist for it4 ,the wall over which ,i had climbed when ,i left the road1 the ravine ,i had crossed1 the patch of undergrowth through which ,i had pushed my way--all these were nothing to the bird--and while the road had only taken me in one direction1 the bird's level highway led everywhere1 and opened the way into every nook and corner of the landscape4 ,how wonderfully easy1 too1 was its flight4 ,there was not a flutter of its pinions as it swept over the field1 in a motion which seemed as effortless as that of its shadow40 ,during the last #ej years a great deal has been said and written in regard to the flight of birds2 no other natural phenomenon has excited so much interest and been so imperfectly understood4 ,learned treatises have been written to prove that a bird is able to develop from ten to twenty times as much power for its weight as other animals1 while other equally learned works have shown most conclusively that no greater amount of energy is exerted by a bird in flying than by land animals in running or jumping4 ,prof4 ,langley1 who was certainly a very clever observer and a mathematician of the first order1 in discussing the subject relating to the power exerted by birds in flight and the old formula relating to the subject1 expresses himself as follows3-- 8,after many years and in mature life1 ,i was brought to think of these things again1 and to ask myself whether the problem of artificial flight was as hopeless and as absurd as it was then thought to be4 ,nature had solved it1 and why not man8 ,perhaps it was because he had begun at the wrong end1 and attempted to construct machines to fly before knowing the principles on which flight rested4 ,i turned for these principles to my books and got no help4 ,sir ,isaac ,newton had indicated a rule for finding the resistance to advance through the air1 which seemed1 if correct1 to call for enormous mechanical power1 and a distinguished ,french mathematician had given a formula showing how rapidly the power must increase with the velocity of flight1 and according to which a swallow1 to attain a speed it is known to reach1 must be possessed of the strength of a man4 8,remembering the effortless flight of the soaring bird1 it seemed that the first thing to do was to discard rules which led to such results1 and to commence new experiments1 not to build a flying machine at once1 but to find the principles upon which one should be built2 to find1 for instance1 with certainty by direct trial how much horse-power was needed to sustain a surface of given weight by means of its motion through the air40 ,there is no question but what a bird has a higher physical development1 as far as the generation of power is concerned1 than any other animal we know of4 ,nevertheless1 ,i think that everyone who has made a study of the question will agree that some animals1 such as hares and rabbits1 exert quite as much power in running1 in proportion to their weight1 as a sea-gull or an eagle does in flying4 ,the amount of power which a land animal has to exert is always a fixed and definite quantity4 ,if an animal weighing #ajj lbs4 has to ascend a hill #ajj feet high1 it always means the development of #aj1jjj foot-lbs4 ,with a bird1 however1 there is no such thing as a fixed quantity4 ,if a bird weighing #ajj lbs4 should raise itself into the air #ajj feet during a perfect calm1 the amount of energy developed would be #aj1jjj foot lbs4 plus the slip of the wings4 ,but1 as a matter of fact1 the air in which a bird flies is never stationary1 as ,i propose to show2 it is always moving either up or down1 and soaring birds1 by a very delicate sense of feeling1 always take advantage of a rising column4 ,if a bird finds itself in a column of air which is descending1 it is necessary for it to work its wings very rapidly in order to prevent a descent to the earth4 ,i have often observed the flight of hawks and eagles4 ,they seem to glide through the air with hardly any movement of their wings4 ,sometimes1 however1 they stop and hold themselves in a stationary position directly over a certain spot1 carefully watching something on the earth immediately below4 ,in such cases they often work their wings with great rapidity1 evidently expending an enormous amount of energy4 ,when1 however1 they cease to hover and commence to move again through the air1 they appear to keep themselves at the same height with an almost imperceptible expenditure of power4 ,illustration3 ,fig4 #c4--,while in the ,pyrenees ,i often observed eagles balancing themselves on an ascending current of air produced by the wind blowing over large masses of rock4 ,many unscientific observers of the flight of birds have imagined that a wind or a horizontal movement of the air is all that is necessary to sustain the weight of a bird in the air after the manner of a kite4 ,if1 however1 the wind1 which is only air in motion1 should be blowing everywhere at exactly the same velocity1 and in the same direction--horizontally--it would offer no more sustaining power to a bird than a dead calm1 because there is nothing to prevent the body of the bird from being blown along with the air1 and whenever it attained the same velocity as the air1 no possible arrangement of the wings could prevent it from falling to the earth4 ,it is well known that only a short distance above the earth's surface1 say #cj or #dj miles1 we find an extremely low temperature sometimes referred to as interstellar temperature or absolute zero4 ,in order to illustrate the extremely low temperature of space1 ,i would cite the following instance3-- ,one evening1 in the ,state of ,ohio1 a farmer saw a very brilliant meteor2 it struck in one of his fields not more than #ajj feet from his house4 ,he at once rushed to the spot1 and1 pushing his arm down the hole1 succeeded in touching it2 but he very quickly withdrew his hand1 as he found it extremely hot4 ,some of the neighbours rushed to the spot1 and he told them what had occurred1 whereupon one of them put his hand in the hole1 expecting to be burnt1 but1 much to his surprise1 the tips of his wet fingers were instantly frozen to the meteor4 ,the meteor had been travelling at such an exceedingly high velocity that the resistance of the intensely cold and highly attenuated outer atmosphere was sufficient to bring its temperature up to the melting point of iron2 but the heat did not have time to pass into the interior1 it only extended inwards perhaps #a_/h inch1 so that when the meteor came to a state of rest1 the heat of the exterior was soon absorbed by the intensely cold interior1 thus reducing the surface to a temperature much below any natural temperature that we find at the surface of the earth4 ,nothing can be more certain than that the temperature is extremely low a slight distance above the earth's surface4 ,as the air near the earth never falls in temperature to anything like the absolute zero1 it follows that there is a constant change going on1 the relatively warm air near the surface of the earth always ascending1 and1 in some cases1 doing sufficient work in expanding to render a portion of the water it contains visible1 forming clouds1 rain1 or snow1 while the very cold air is constantly descending to take the place of the rising column of warm air4 ,i have noticed a considerable degree of regularity in the movement of the air1 especially at a long distance from land1 where the regularity of the up and down currents is1 at times1 very marked4 ,on one occasion while crossing the ,atlantic in fine weather ,i noticed1 some miles directly ahead of the ship1 a long line of glassy water4 ,small waves indicated that the wind was blowing in the exact direction in which the ship was moving1 and as we approached the glassy line1 the waves became smaller and smaller until they completely disappeared in a mirror-like surface1 which was about #cjj or #djj feet wide1 and extended both to the port and starboard in approximately a straight line as far as the eye could reach4 ,after passing the centre of this zone1 ,i noticed that small waves began to show themselves1 but in the exact opposite direction to those through which we had already passed1 and these waves became larger and larger for nearly half an hour4 ,then they began to get gradually smaller1 when ,i observed another glassy line directly ahead of the ship4 ,as we approached it1 the waves again completely disappeared1 but after passing through it1 the wind was blowing in the opposite direction1 and the waves increased in size exactly in the same manner that they had diminished on the opposite side of the glassy streak 7,fig4 #d74 ,illustration3 ,fig4 #d4--;,air currents observed in mid ,atlantic1 warm air ascending at a1 a1 a1 and cold air descending at b1 b1 b4 c1 c1 c represent the lines where the waves were the largest4 ,this1 of course1 shows that directly over the centre of the first glassy streak1 the air was meeting from both sides and ascending in practically a straight line from the surface of the water1 and then spreading out high above the sea1 setting up a light wind in both directions4 ,i spent the winter of #ahij-ia on the ,riviera1 between ,hyres les ,palmiers and ,monte ,carlo4 ,the weather for the most part was very fine1 and ,i often had the opportunity of observing the peculiar phenomena which ,i had already noticed in the ,atlantic1 only on a much smaller scale4 ,whereas1 in the ,atlantic1 the glassy zones were from #h to #ae miles apart1 ,i often found them not more than #ejj feet apart in the bays of the ,mediterranean4 ,this was most noticeable at ,antibes 7,fig4 #e71 very good photographs of which ,i obtained4 ,it will be observed that the whole surface of the water is streaked like a block of marble4 ,illustration3 ,fig4 #e4--;,glassy streaks showing the centres of ascending and descending columns of air in the ,bay of ,antibes1 ,alpes ,maritimes4 ,at ,nice and ,monte ,carlo this phenomena was also very marked4 ,on one occasion1 while making observations from the highest part of the promontory of ,monaco on a perfectly calm day1 ,i noticed that the whole of the sea presented this peculiar effect as far as the eye could reach1 and that the lines which marked the descending air were never more than #a1jjj feet from those which marked the centre of the ascending column4 ,at about three o'clock one afternoon1 a large black steamer passed along the coast in a perfectly straight line1 and its wake was at once marked by a glassy line1 which indicated the centre of an ascending column4 ,this line remained almost straight for two hours1 when finally it became crooked and broken4 ,the heat of the steamer had been sufficient to determine this upward current of air4 ,illustration3 ,fig4 #f4--;,air currents observed in the ,mediterranean1 ascending currents at a1 a1 a1 and descending currents at b1 b1 b4 ,in #ahic ,i spent two weeks in the ,mediterranean1 going and returning by a slow steamer from ,marseilles to ,constantinople1 and ,i had many opportunities of observing the peculiar phenomena to which ,i have referred4 ,the steamer passed over thousands of square miles of calm sea1 the surface being only disturbed by large patches of small ripples 7,fig4 #f71 separated from each other by glassy streaks1 which1 however1 were not straight as on the ,atlantic1 and ,i found that in no case was the wind blowing in the same direction on both sides of these streaks1 every one of which indicated the centre of an ascending or a descending column of air4 ,if we should investigate these phenomena in what might be called a dead calm1 we should find that the air was rising very nearly straight up over the centres of some of these streaks and descending in a vertical line over the centres of others4 ,but1 as a matter of fact1 there is no such thing as a dead calm4 ,the movement of the air is the resultant of more than one force4 ,the air is not only rising in some places and descending in others1 but at the same time1 the whole mass is moving forward with more or less rapidity from one part of the earth to another1 so we must consider that1 instead of the air ascending directly from the relatively hot surface of the earth and descending vertically in other places1 in reality the whole mass of rotating air is moving horizontally at the same time4 ,suppose that the local influence which causes the up and down motion of the air should be sufficiently great to cause the air to rise at the rate of #b miles an hour1 and that the wind at the same time should be blowing at the rate of #aj miles an hour1 the motion of the air would then be the resultant of these two velocities4 ,in other words1 it would be blowing up an incline of #a in #e4 ,suppose1 now1 that a bird should be able to so adjust its wings that it advanced #e miles in falling #a mile through a perfectly calm atmosphere1 it would then be able to sustain itself in an inclined wind1 such as ,i have described1 without any movement at all of its wings4 ,if it were possible to adjust its wings in such a manner that it could advance #f miles by falling through #a mile of air1 it would then be able to rise as relates to the earth while in reality falling as relates to the surrounding air4 ,in conducting a series of experiments with artillery and small guns on a large and level plain just out of ,madrid1 ,i often observed the same phenomena1 as relates to the wind1 that ,i have already spoken of as having observed at sea1 except that the lines marking the centre of an ascending or a descending column of air were not so stationary as they were over the water4 ,it was not an uncommon thing1 when adjusting the sights of a gun to fire at a target at a very long range1 making due allowances for the wind1 to have the wind change and blow in the opposite direction before the word of command was given to fire4 ,while conducting these experiments1 ,i often noticed the flight of eagles4 ,on one occasion a pair of eagles came into sight on one side of the plain1 passed directly over our heads1 and disappeared on the opposite side4 ,they were apparently always at the same height from the earth1 and in soaring completely across the plain they never once moved their wings4 ,these phenomena1 ,i think1 can only be accounted for on the hypothesis that these birds were able to feel out with their wings an ascending column of air1 that the centre of this column of air was approximately a straight line running completely across the plain1 that they found upward movement more than sufficient to sustain their weight in the air1 and that whereas1 as relates to the earth1 they were not falling at all1 they were in reality falling some #d or #e miles an hour in the air which supported them4 ,again1 at ,cadiz in ,spain1 when the wind was blowing in strongly from the sea1 ,i observed that the sea-gulls always took advantage of an ascending column of air4 ,as the wind rose to pass over the fortifications1 the gulls selected a place where they would glide on the ascending current of air1 keeping themselves always approximately in the same place without any apparent exertion4 ,when1 however1 they left this ascending column1 it was necessary for them to work their wings with great vigour until they again found the proper place to encounter a favourable current4 ,i have often noticed that gulls are able to follow a ship without any apparent exertion2 they simply balance themselves on an ascending column of air1 where they seem to be quite as much at ease as they would have been roosting on a solid support4 ,if1 however1 they are driven out of this position1 they generally commence at once to work their passage4 ,if anything is thrown overboard which is too heavy for them to lift1 the ship soon leaves them behind1 and in order to catch up with it again they move their wings very much as other birds do2 but when once established in the ascending column of air1 they manage to keep up with the ship by doing little or no work4 ,in a calm or head wind we find them directly aft of the ship2 if the wind is from the port side they may always be found on the starboard quarter1 and vice vers4 ,one ,sunday morning1 while living at ,kensington1 ,i noticed some very curious atmospheric effects4 ,the weather had been intensely cold for about a week1 when suddenly the atmosphere became warm and very humid4 ,the earth being much colder than the atmosphere1 water was condensing on everything that it touched4 ,i went to the bridge over the ,serpentine in ,hyde ,park1 and was not disappointed in finding a large number of sea-gulls waiting about the bridge to be fed4 ,on all ordinary occasions these birds manage to move about with the expenditure of very little energy1 but on this occasion every one of them1 without a single exception1 no matter in what position he might be1 was working his passage like any other bird1 just as ,i had expected4 ,it is only on very rare occasions that the surface of the earth is sufficiently cold as relates to the atmosphere to prevent all upward currents of air4 ,everyone who has passed a winter on the northern shores of the ,mediterranean must have observed the cold wind which is generally called the mistral4 ,one may be out driving1 the sun may be shining brightly1 and the air warm and balmy1 when suddenly1 without any apparent cause1 one finds himself in a cold descending wind4 ,this is the much-dreaded mistral1 and if at sea it would be marked by a glassy line on the surface of the water4 ,on land1 however1 there is nothing to render its presence visible4 ,the ascending column of air is1 of course1 always very much warmer than the descending column1 and this is taking place in a greater or lesser degree everywhere and at all times4 ,a decided upward trend of air is often encountered by those who are experimenting with kites1 the kite often mounting higher than can be accounted for on the hypothesis that the wind is moving in a horizontal direction4 ,i have heard this discussed at considerable length4 ,when a kite is flown in an upward current1 it behaves in many respects like a soaring bird4 ,from the foregoing1 ,i think1 we may safely draw the following conclusions3-- ,first1 that there is a constant interchange of air taking place1 the cold air descending1 spreading itself out over the surface of the earth1 becoming warm1 and ascending in other places4 ,second1 that the centres of the two columns are generally separated from each other by a distance which may be from #ejj feet to #bj miles4 ,third1 that the centres of greatest action are not in spots1 but in lines which may be approximately straight1 but sometimes abound in many sinuosities4 ,fourth1 that this action is constantly taking place over both the sea and the land2 that the soaring of birds1 the phenomenon which has heretofore been so little understood1 may be accounted for on the hypothesis that the bird seeks out an ascending column of air1 and while sustaining itself at the same height in the air1 without any muscular exertion1 it is in reality falling at a considerable velocity through the air that surrounds it4 ,it has been supposed by some scientists that birds may take advantage of some vibratory or rolling action of the air4 ,i find1 however1 from careful observation and experiment1 that the motion of the wind is comparatively steady1 and that the short vibratory or rolling action is always very near to the earth and is produced by the air flowing over hills1 high buildings1 trees1 etc4 ,tools and instruments used by mechanicians are very often made of the material most used in their profession2 for instance1 a blacksmith's tools are generally of iron1 a carpenter's tools largely of wood1 and a glass-blower uses many things made of glass1 and so on4 ,mathematicians are no exception to this general rule1 and seem to imagine that everything can be accomplished by pure mathematical formul4 ,it appears that ,prof4 ,langley was at times considerably puzzled by the extraordinary behaviour of birds1 and was led to believe that they took advantage of some vibratory or oscillating movement of the air2 he called it 8the internal work of the air40 ,i have been very much amused in a recent mathematical work that ,i have read1 in which the writer seeks to solve all questions by pure mathematics4 ,in this case1 notwithstanding that all of the factors are unknown and unknowable1 still1 with the use of about two pages of closely written algebraic formul1 he appears to have solved the whole question4 ,just how he arrived at it1 however1 is more than ,i am able to understand4 ,if a kite is flown only a few feet above the ground1 it will be found that the current of air is very unsteady4 ,if it is allowed to mount to #ejj feet the unsteadiness nearly all disappears1 while if it is allowed to mount further to a height of #a1ejj or #b1jjj feet1 the pull on the cord is almost constant1 and1 if the kite is well made1 it remains practically stationary in the air4 ,i have often noticed in high winds that light and fleecy clouds come into view1 say1 about #b1jjj feet above the surface of the earth1 and pass rapidly and steadily by preserving their shape completely4 ,this would certainly indicate that there is no rapid local disturbance in the air in their immediate vicinity1 but that the whole mass of air in which these clouds are formed is practically travelling in the same direction and at the same velocity4 ,numerous aeronauts have also testified that1 no matter how hard the wind may be blowing1 the balloon is always practically in a dead calm1 and if a piece of gold-leaf is thrown overboard1 even in a gale1 the gold-leaf and the balloon never part company in a horizontal direction1 though they may in a vertical direction4 ,birds may be divided into two classes4 ,first1 the soaring birds1 which practically live upon the wing1 and1 by some very delicate sense of touch1 are able to feel the exact condition of the air4 ,many fish which live near the top of the water are greatly distressed by sinking too deeply1 while others which live at great depths are almost instantly killed by being raised to the surface4 ,the swim-bladder of a fish is in reality a delicate barometer provided with sensitive nerves which enable the fish to feel whether it is sinking or rising in the water4 ,with the surface fish1 if the pressure becomes too great1 it involuntarily exerts itself to rise nearer the surface and so diminish the pressure1 and ,i have no doubt that the air cells1 which are known to be very numerous and to abound throughout the bodies of birds1 are so sensitive as to enable soaring birds to know at once whether they are in an ascending or a descending column of air4 ,the other class of birds consists of those which only employ their wings occasionally for the purpose of taking them rapidly from one place to another4 ,such birds do not expend their power so economically as the soaring birds4 ,they do not pass much of their time in the air1 but what time they are on the wing they put forth an immense amount of power and fly very rapidly1 generally in a straight line1 taking no advantage of air currents4 ,partridges1 pheasants1 wild ducks1 geese1 and some birds of passage may be taken as types of this kind4 ,this class of birds has relatively small wings1 and carries about two and a half times as much weight per square foot of surface as soaring birds do4 ,we shall never be able to imitate the flight of the soaring birds4 ,we cannot hope to make a sensitive apparatus that will work quick enough to take advantage of the rising currents of air1 and he who seeks to fly has this problem to deal with4 ,a successful flying machine1 moving at a high velocity1 is likely at any time to encounter downward currents of air1 which will greatly interfere with its action4 ,therefore flying machines must1 in the very nature of things1 be provided with sufficient power to propel them through various currents of air1 after the manner of ducks1 partridges1 pheasants1 etc4 ---------------------------------------- ---------- ,corresponding ,common ,name4 ,sq4 ,ft4,lbs4 per,speed for a ,plane per ,lb4,sq4 ,ft4 at #c in ,miles per ,hour4 ---------------------------------------- ---------- ,bat1 #gfd #jaca #aei ,swallow1 #cfb #jbgf #bca ,lark1 #cjf #jcbg #bea ,sparrow hawk1 #cjj #jccc #bec ,sparrow1 #bdb #jdad #bhb ,gull1 #bce #jdbf #bhf ,owl1 #bbf #jddc #bib ,crane1 #bjb #jdie #cji ,rook1 #agd #jege #ccc ,plover1 #ach #jgbe #cgd ,balbuzzard1 #abf #jgie #cib ,egyptian vulture1 #aah #jhdh #djd ,duck1 #jhfd #aaeh #ddb ,grey pelican1 #jgcb #acfe #eac ,wild goose1 #jehf #agjh #egd ,turkey1 #jebc #aiaj #fjf ,duck 7female71 #jdih #bjjh #fbb 7male71 #jdci #bbhj #ffb ---------------------------------------- ---------- ,,chapter ,,iii4 ,,flying ,,of ,,kites4 ,it was said of ,benjamin ,franklin that when he wished to fly a kite in order to ascertain if lightning could be drawn down from the clouds1 he managed to have a boy with him in order to avoid ridicule4 ,it was considered too frivolous in those days for grown-up men to amuse themselves with kites1 and a good many besides ,benjamin ,franklin have feared to face the ridicule that was inevitable if they took up or even discussed the question of artificial flight4 ,nineteen years ago1 when ,i commenced my own experiments1 ,i was told that my reputation would be greatly injured1 that mankind looked upon artificial flight as an ignis-fatuus1 and that anyone who experimented in that direction was placed in the same category as those who sought to make perpetual-motion machines or to find the philosopher's stone4 ,although ,i had little fear of ridicule1 still ,i kept things as quiet as ,i could for a considerable time1 and ,i had been working fully six months before anyone ascertained what ,i was doing4 ,when1 however1 it became known that ,i was experimenting with a view of building a flying machine1 the public seemed to think that ,i was making honest and praiseworthy scientific investigations2 true1 ,i might not succeed1 still it was said that ,i would accomplish something1 and find out some of the laws relating to the subject4 ,no one ridiculed my work except two individuals1 and both of these were men whom ,i had greatly benefited4 ,as is often the case1 those whom you find in difficulties and place on their feet seek to do you some injury as compensation for the benefits they have received4 ,at the present time it is not necessary for any man to take a small boy with him as a species of lightning-rod to ward off ridicule when he flies a kite4 ,i have been one of a committee on kite-flying at which some of the most learned and serious men in ,england were my colleagues in investigating the subject4 ,the behaviour of kites is certainly very puzzling to those who do not thoroughly understand the subject4 ,a kite may be made with the greatest degree of perfection1 and placed in the hands of one of considerable experience2 nevertheless1 it may behave very badly1 diving suddenly to the ground without any apparent cause4 ,then1 again1 this same kite will sometimes steadily mount in the air until it reaches a height difficult to account for4 ,if the surface of the earth should be perfectly smooth1 and the wind should always blow in a horizontal direction1 kites would not show these eccentric peculiarities1 but1 as a matter of fact1 the air seldom moves in a horizontal direction2 it is always influenced by the heat of the surface of the earth4 ,heated air is continually ascending in some places only to be cooled and to descend in other places4 ,if one is attempting to fly a kite where the air is moving downwards1 he will find it an extremely difficult matter1 whereas1 if he is fortunate enough to strike a current of air which is rising1 the kite will mount much higher in the air than can be accounted for1 except we admit of the existence of these upward draughts of air4 ,on one occasion many years ago1 ,i was present when a bonded warehouse in ,new ,york containing #aj1jjj barrels of alcohol was burnt4 ,it was nine o'clock at night1 and ,i walked completely around the fire1 and found things just as ,i had expected4 ,the wind was blowing a perfect hurricane through every street in the direction of the fire1 although it was a dead calm everywhere else2 the flames mounted straight in the air to an enormous height1 and took with them a large amount of burning wood4 ,when ,i was fully #ejj feet from the fire1 a piece of partly burnt #a-;inch board1 about #h inches wide and #d feet long1 fell through the air and landed very near me1 sending sparks in every direction4 ,this board had evidently been taken up to a great height by the tremendous uprush of air caused by the burning alcohol4 ,it is very evident that a kite made of boiler iron could have been successfully flown under these conditions providing that it could have been brought into the right position4 ,illustration3 ,fig4 #g4--,the circulation of air produced by a difference in temperature4 ,the sketch 7,fig4 #g7 shows a device consisting of a spirit lamp and a box of ice4 ,the lamp heats the metallic plate1 expands the air which rises and is cooled by convection on coming in contact with the top plate1 and descends as shown4 ,however1 a fire is not necessary to accomplish this result2 it is taking place all over the earth1 all the time4 ,a great number of plants depend upon a rising current of air to transport their seeds to distant places4 ,seeds of the thistle and dandelion variety are sometimes able to travel hundreds of miles1 to the great vexation of farmers2 and there is a certain class of small spider known as 8,balloon ,spiders0 which also depend upon a rising current of air to carry them from the place of their birth to some distant part where they1 of course1 hope to start a colony4 ,when ,i was a boy of eight1 ,i noticed small spiders webbing down from the sky4 ,i was greatly puzzled2 it appeared to me that they had attached their web to some stationary object high in the air and were spinning a web in order to lower themselves to the earth4 ,what could that stationary object be8 ,as the sky was clear1 ,i was quite unable to understand this phenomenon1 but afterwards ,i learned from scientific books that there was a class of spiders that managed to rise high in the air by the aid of the wind4 ,it appears that they climb a high tree until they have reached the uppermost extremity and then1 from a leaf or twig that projects into the air1 they wait for an ascending current of air4 ,although the spider is exceedingly small--the size of a pin's head--it has about #bjj spinnerets1 its ordinary web being formed of no less than that number of extremely fine threads4 ,these are spun out singly into the air until an almost invisible mass of fine webs interlacing each other in all directions and forming an approximately cylindrical network about half an inch in diameter and #ah inches long is produced4 ,whenever an upward draft of air approximately vertical occurs1 it takes this weightless tangle of fine webs with it1 and so soon as the spider finds there is sufficient pull to lift its weight1 it lets go and ascends with the air4 ,when the ,nulli ,secundus ascended at ,farnborough and landed at the ,crystal ,palace1 ,mr4 ,cody1 who was on board1 reported what he supposed to be a very curious and unaccountable phenomenon4 ,the balloon was covered with many thousands of minute spiders that it had picked up in the air on the voyage4 ,certainly this of itself is very strong evidence of the existence of these ascending currents of air4 ,illustration3 ,fig4 #h4--;a represents a kite in a horizontal wind1 e1 e1 e2 b1 the same kite in a rising column of air1 the wind blowing in the direction shown at f1 f4 ,if the kite is a good one1 it may pass over to the point c4 ,when in ,boston about fifteen years ago1 ,i went to ,blue ,hill to witness the remarkable kite flying which was taking place at that time4 ,the kites experimented with were of the ,hargrave type1 and of enormous dimensions4 ,a steel wire and windlass worked by a steam engine was employed4 ,i was told that on certain occasions the kites mounted extremely high1 much higher than they were able to account for2 but on this particular occasion1 although they let out a great amount of wire1 the kite did not mount very high4 ,i have heard much discussion first and last regarding the flight of kites1 and ,i think it is generally admitted that they do sometimes rise upwards and continue moving to the windward until they pass directly over the spot where they are attached to the earth4 ,it was not1 however1 till about three years ago that ,i witnessed this phenomenon myself4 ,mr4 ,cody1 who is the inventor of a very good kite1 had been flying kites at the ,crystal ,palace for some months1 and on one occasion ,i saw his kite rise1 pass to the windward and directly over our heads4 ,i took hold of the cord with both hands1 and was somewhat surprised to find what the lifting effect was4 ,the kite was1 however1 of large dimensions1 but by no means so large as ,mr4 ,cody's 8man-lifting kites40 ,in the drawing 7,fig4 #h7 ,i have shown1 at a1 the action of a kite in a horizontal wind1 lines e1 e1 showing the direction of the wind4 ,a good kite will easily mount #de1 the angle shown1 but on the occasion just mentioned1 the sun had been shining brightly into the valley where the experiments took place1 and an upward current of air had been determined4 ,the cooler air was1 of course1 rushing in from each side and mounting in about the centre of the valley1 and ,mr4 ,cody's kite1 instead of flying in a horizontal wind1 soon reached a point where the wind was ascending at an angle1 as shown at f1 f4 ,the kite would therefore mount until at b1 where it presented the same angle to the wind as with the horizontal wind at a1 and if it should be made to fly at a higher angle1 it might pass over to the position shown at c4 ,but it must not be imagined that this phenomenon can be witnessed every day in the year4 ,it is only on rare occasions that one is fortunate enough to find a wind which is blowing at a sufficiently sharp upward trend to cause a kite to pass to the windward over the point of support4 ,neither must it be supposed that this favourable condition of things is of long duration4 ,as the centre of the upward current is constantly moving1 it is certain that very soon it will move away from the point from which the kite is being flown4 ,what is true of kites is also true of flying machines4 ,it is very difficult indeed to make a kite mount providing that it is in a descending current of air1 and one is just as likely to find a descending current as any other4 ,flying machines will1 therefore1 have to be made with a considerable amount of reserve energy1 so as to be able to put on a spurt when they encounter an adverse current4 ,if a machine is made that is able to maintain itself in the air for any considerable length of time1 it will not be a very difficult task to know when a current of air of this kind is encountered1 because1 if the engine is working up to speed1 and everything is in perfect order1 and still the machine is falling1 it is very certain that an unfavourable current has been encountered1 and efforts should be made to get out of it as soon as possible4 ,then1 again1 if the machine has an abnormal tendency to rise without any increase in the number of rotations made by the screws1 the aeronaut may be certain that he has encountered an upward and favourable current of air which1 unfortunately1 will not last4 ,it should1 however1 be borne in mind that1 while the width of the upward current is not very great1 nevertheless1 it may extend in a practically straight line for many miles4 ,,chapter ,,iv4 ,,principally ,,relating ,,to ,,screws4 ,in #ahhg ,i was approached by several wealthy gentlemen who asked me if ,i thought it was possible to make a flying machine4 ,i said1 8certainly2 the domestic goose is able to fly and why should not man be able to do as well as a goose80 ,they then asked me what it would cost and how long it would take1 and1 without a moment's hesitation1 ,i said it would require my undivided attention for five years and might cost #ajj1jjj4 ,a great deal of experimenting would be necessary2 the first three years would be devoted to developing an internal combustion engine of the ,brayton or ,otto type1 and the next two years to experimenting with aeroplanes and screws and building a machine4 ,even at that time ,i had a clear idea of the system that would be the best4 ,however1 nothing was then done1 but in #ahhi ,i employed for the purpose two very skilful ,american mechanics1 and put them to work at ,baldwyn's ,park1 ,kent4 ,at that time the petroleum motor had not been reduced to its present degree of efficiency and lightness2 it was not suitable for a flying machine1 and ,i saw that it would require a lot of experimental work in order to develop it4 ,after taking into consideration all the facts of the case1 ,i decided to use a steam engine4 ,had ,i been able to obtain the light and efficient motors which have been recently developed1 thanks to the builders of racing cars1 ,i should not have had to experiment at all with engines and boilers1 as ,i could have obtained the necessary motors at once4 ,as it was1 ,i was obliged to content myself with the steam engine4 ,illustration3 ,fig4 #i4--;,group of screws and other objects used in my experiments4 ,illustration3 ,fig4 #aj4--,some of the principal screws experimented with--h1 a screw with very thick blades1 and g1 a screw made after a ,french model4 ,i found that there was a great deal of misunderstanding regarding the action of aeroplanes1 and also of screws working in the air4 ,i procured all the literature available on the subject1 both ,english and ,french1 and attempted to make a thorough study of the question2 but ,i was not satisfied1 on account of the wide difference in the views of the writers and the conflicting formul that were employed4 ,i therefore decided to make experiments myself1 and to ascertain what could be done without the use of anybody's formula4 ,although this was nearly twenty years ago1 ,i find that there is still a great deal of discussion regarding the action of aeroplanes and screws1 in which the majority taking part in the discussion are in the wrong4 ,however1 several good works on the subject have recently been published4 ,illustration3 ,fig4 #aa4--,the three best screws4 ,the screw on the right has a uniform pitch throughout1 the middle screw has increasing pitch1 and the left screw compound increasing pitch4 ,having designed and put my boiler and engine in hand1 ,i commenced a series of experiments for the purpose of ascertaining the efficiency of screw propellers working in the air1 and the form and size that would be best for my proposed machine4 ,the illustration ,fig4 #i shows a photographic group of the screws and other objects with which ,i experimented4 ,fig4 #aj shows some of the leading types which1 as will be seen1 have blades of different shape1 pitch1 and size4 ,fig4 #aa shows three of the best screws employed4 ,it will be observed that one has uniform pitch1 another increasing pitch1 and the third compound increasing pitch4 ,in order to test the efficiency of my screws ,i made the apparatus shown in ,fig4 #ab4 ,the power for running the screw was transmitted by means of a belt to the straight cylindrical pulley c1 c4 ,shaft b1 b was of steel1 rather small in diameter1 and ran smoothly1 and practically without friction1 through the two bearings d1 d4 ,when the first screw1 a1 a1 was run at a high velocity1 the axial thrust pushed the shaft b1 b back and elongated the spiral spring e4 ,the degree of screw thrust was indicated in pounds by the pointer g4 ,the power was transmitted through a very accurate and sensitive dynamometer1 so that the amount consumed could be easily observed by a pointer similar to the one employed for indicating the screw thrust4 ,a tachometer was also employed to observe the number of turns that the screw was making in a minute4 ,the whole apparatus was carefully and accurately made and worked exceedingly well4 ,i was thus enabled1 with my various forms of screws and other objects1 to make very accurate measurements1 some of which are exceedingly interesting4 ,illustration3 ,fig4 #ab4--;,apparatus for testing the thrust of screws--a1 a1 the screw2 b1 b1 shaft sliding freely in the bearing d1 d2 c1 cylindrical pulley2 e1 spiral spring2 f1 steel rod2 g1 pointer for indicating the thrust in pounds4 ,illustration3 ,fig4 #ac4--;,apparatus for testing the direction of air currents caused by a rapidly rotating screw4 ,silken threads were attached to the wire c1 c1 which indicated clearly the direction in which the air was moving4 ,in many of the treatises and books of that time it was stated that a screw propeller1 working in the air1 was exceedingly wasteful of energy on account of producing a fan-blower action4 ,some inventors suggested that the screw should work in a stationary cylinder1 or1 better still1 that the whole screw should be encased in a rotating cylinder1 to prevent this outward motion of the air4 ,in order to ascertain what the actual facts were1 ,i attached a large number of red silk threads to a brass wire1 which ,i placed completely around my screw 7see ,fig4 #ac74 ,upon starting up ,i found that1 instead of the air being blown out at the periphery of the screw1 it was in reality sucked in1 as will be seen in the illustration4 ,i was rather surprised to see how sharp a line of demarkation there was between the air that was moving in the direction of the screw and the air that was moving in the opposite direction4 ,the screw employed in these experiments was #ah inches in diameter and had a pitch of #bd inches4 ,it was evident1 however1 if the pitch of the screw was coarse enough that there would be a fan-blower action4 ,i therefore tried screws of various degrees of pitch1 and found when the pitch was a little more than three times the diameter1 giving to the outer end of the blade an angle of #de1 that a fan-blower action was produced--that is1 part of the time when the screw was running1 the air would alternate2 sometimes it would pass inwards at the periphery and sometimes outwards4 ,the change of direction1 however1 was always indicated by a difference in the pitch of the note given out1 and also by the thrust4 ,in ,fig4 #ad ,i have shown the extremities of the blades of some of the different forms of screws experimented with1 in which a shows a plain screw1 the front side being straight and of equal pitch from the periphery to the hub2 b is a screw of practically the same pitch1 but slightly curved so as to give what is known as an increasing pitch2 c shows the extremity of a screw in which the curve is not the same throughout--that is1 it is what is known as a compound increasing pitch2 d is the shape of the screw that gave the angle of #de above referred to4 ,illustration3 ,fig4 #ad4--,this drawing shows the ends of screw blades in which a is a plain screw2 b1 screw with increasing pitch2 c1 screw with compound increasing pitch2 d1 end of screw blade #de2 e1 screw with very thick blade2 f1 blade with no pitch at all2 g1 blade which gave a thrust in the direction of the convex side1 no matter in which direction it was revolved2 h1 screw said to have been used in the ,french ,government experiments4 ,the first screw experimented with was a4 ,this screw was run at a high velocity--about #b1ejj revolutions per minute--until a screw thrust of #ad lbs4 was obtained1 and then the governor of the engine was set so that all screws of the same diameter could be run at the same speed4 ,wishing to ascertain the efficiency of the screw and how much was lost in skin friction1 ,i multiplied the thrust in pounds by the pitch of the screw in feet and by the number of turns it was making in a minute4 ,this1 of course1 gave the exact number of foot-pounds in energy that was being imparted to the air4 ,i was somewhat surprised to find that it corresponded exactly with the readings of the dynamometer4 ,i thought at first that ,i must have made some mistake4 ,again ,i went very carefully over all the figures1 tested everything1 and made another experiment and found1 even if ,i changed the number of revolutions1 that the readings of the dynamometer were always exactly the same as the energy imparted to the air4 ,this seemed to indicate that the screw was working very well and that the skin friction must be very small indeed4 ,in order to test this1 ,i made what we will call1 for the moment1 a screw without any pitch at all--that is1 the blades were of wood and of the exact thickness and width of the blades of the screw a1 but without any pitch at all4 ,the extremity of the blade is shown at f4 ,i placed this screw on my machine in place of a1 and although my dynamometer was so sensitive that the pointer would move away from the zero pin by simply touching the tip of the finger to the shaft1 it failed to indicate1 and thus the screw appeared to consume no power at all4 ,these experiments were repeated a considerable number of times4 ,i then obtained a sheet of tin the same diameter as the screws1 #ah inches1 and upon running it at the same speed1 ,i found that it did consume a measurable amount of power1 certainly more than the two blades f4 ,this no doubt was due to the uneven surface of the tin4 ,had it been a well-made saw blade without teeth1 perfectly smooth and true on both sides1 it probably would not have required power enough to have shown on the dynamometer4 ,however1 it is quite possible that there is a little more skin friction with a polished metallic surface1 than with a piece of smooth evenly lacquered wood4 ,the screws which ,i employed were of ,american white pine such as used by patternmakers4 ,this wood was free from blemishes of all kind1 extremely light1 uniform1 and strong4 ,when the screw had been formed1 it was varnished on both sides with a solution of hot glue1 which greatly increased the strength of the wood crosswise of the grain4 ,when this glue was thoroughly dry1 the wood was sand-papered until it was as smooth as glass2 the whole thing was then carefully varnished with shellac1 rubbed down again and revarnished with very thin shellac something like lacquer4 ,in this way the surface of the screw was made very smooth4 ,the screws1 of course1 were made with a great degree of accuracy and as free as possible from any unevenness4 ,having tested screw a1 ,i next tested screw b4 ,i found with the same number of revolutions per minute that this screw produced more thrust1 but it required more power to run it1 and when the energy imparted to the air was compared with the readings of the dynamometer1 it was found that it did not do quite so well as a2 still as the thrust was greater and the efficiency only slightly less1 it appeared to be the better screw4 ,upon trying screw c1 under the same conditions1 the thrust was very much increased1 but the power required was also increased to a still greater degree1 showing that this form was not so favourable as either a or b4 ,all the screws experimented with had very thin blades1 and it occurred to me that the difference between a and b might arise from the fact that1 when a was running at a very high velocity1 the working side instead of being flat might have become convex to a slight extent1 whereas with b1 a slight bending back of the edges of the blade would still leave the working side concave4 ,i therefore made the screw shown at e1 which had the same pitch as the other three1 but the working side was of the same shape as a4 ,of course the additional thickness of the blades made it impossible to give an easy curve to the back4 ,curiously enough ,i found that e did nearly as well as a1 and quite as well as b4 ,the additional thickness did not interfere to any appreciable extent with its efficiency4 ,i then made another propeller1 shown at g1 which was of the same thickness in the middle as e4 ,upon running this1 ,i found that it required considerable power1 and no matter which way it was run1 the thrust was always in the direction of the convex side1 which was quite the reverse from what one would have naturally supposed4 ,illustration3 ,fig4 #ae4--,the manner of building up the large screws4 ,about the time that ,i was making these experiments1 my duties called me to ,paris1 and while there ,i called on my old friend ,gaston ,tissandier4 ,through his influence ,i was permitted to see some models of the screws that were alleged to have been used by ,captain ,renard in his experiments for the ,french ,government1 and ,i was somewhat surprised to find the form of the blades1 the same as shown at h1 ,fig4 #ad1 and completely without any twist4 ,on my return to ,england1 ,i made a screw of this description4 ,it is also shown in the photographic illustration1 ,fig4 #i4 ,upon testing this screw1 ,i found that its efficiency was only #dj per cent4 of that of a--that is1 the energy or acceleration imparted to the air was only #dj per cent4 of the readings of the dynamometer4 ,it then occurred to me that this particular form of screw was probably the one that the ,french had for exhibition purposes1 but not the one they intended to use4 ,having tried all the various forms of screws and other objects shown in ,fig4 #i1 ,i made some sheet metal screws2 also a screw which consisted of a steel frame covered with woven fabric1 and which was identical with screws that ,i had seen described in various works relating to aerial navigation4 ,it was found quite impossible to keep the fabric taut and smooth1 and the results were very bad indeed1 it being only #dj per cent4 as efficient as a well-made wooden screw4 ,illustration3 ,fig4 #af4--;,a fabric-covered screw with a very low efficiency4 ,having thus ascertained the best form of a screw1 ,i built up my first large screws1 which were #ag feet #aj inches in diameter1 after the well-known manner of making wooden patterns for casting steamship propellers4 ,fig4 #ae shows the form of the end of the blade1 the middle of the blade1 and the hub4 ,my first pair of large screws had a pitch of #bd feet1 but these were too great a drag on the engine4 ,i therefore made another pair with #af feet pitch which greatly increased the piston speed1 and permitted the engines to develop much more power2 the screw thrust was also increased just in an inverse ratio to the pitch of the screws4 ,another pair of screws was tried with #ad feet pitch and #ab feet in diameter1 but these did not do so well4 ,my large screws were made with a great degree of accuracy2 they were perfectly smooth and even on both sides1 the blades being thin and held in position by a strip of rigid wood on the back of the blade4 ,in order to prevent the thrust from collapsing the blades1 wires were extended backwards and attached to a prolongation of the shaft4 ,like the small screws1 they were made of the very best kind of seasoned ,american white pine1 and when finished were varnished on both sides with hot glue4 ,when this was thoroughly dry1 they were sand-papered again and made perfectly smooth and even4 ,the blades were then covered with strong ,irish linen fabric of the smoothest and best make4 ,glue was used for attaching the fabric1 and when dry another coat of glue was applied1 the surface rubbed down again and then painted with zinc white in the ordinary way and varnished4 ,these screws worked exceedingly well4 ,i had means of ascertaining1 with a great degree of accuracy1 the thrust of the screw1 the number of turns per minute1 the speed of the machine1 and1 in fact1 all the events that were taking place on the machine4 ,it was found that when the screw thrust in pounds was multiplied by the pitch in feet1 and by the number of revolutions made in a minute of time1 it exactly corresponded to the power that the engines were developing1 and that the amount of loss in skin friction was so small as to be practically negligible4 ,illustration3 ,fig4 #ag4--,the hub and one of the blades of the screw on the ,farman machine4 ,the blade c1 is a sheet of metal riveted to the rod b1 and forms a projection on the back of the blade which greatly reduces its efficiency4 ,the peculiar form of hub employed makes it possible to change the diameter and pitch of this screw at will4 ,in connection with this subject ,i would say that many experimenters claim to have shown that the skin friction on screws is considerable1 in fact1 so great as to be a very important factor in the equation of flight4 ,i am1 however1 of the opinion that these experimenters have not had well-made screws4 ,if the surface of the screw is uneven1 irregular1 or rough1 a considerable amount of energy is lost1 as shown in the ,french screw and the fabric covered screw4 ,it is simply a question of having a screw well-made4 ,in those recently employed in ,france 7see ,fig4 #ag71 the blades are of hammered sheet metal1 the twist is not uniform or true1 and what is worst of all1 the arm b projects on the back of the blade and offers a good deal of resistance to the air4 ,this form of screw1 however1 is very ingenious2 as will be seen by the drawing1 the pitch and diameter can be changed at will4 ,it is1 however1 heavy1 wasteful of power1 and altogether too small for the work it has to do4 ,the skin friction of screws in a steamship has led inventors to suppose that the same laws relate to screws running in air1 but such is by no means the case4 ,in designing a steamship1 we have to make a compromise in regard to the size of the screw4 ,if the screw is too small1 an increase in diameter is1 of course1 an advantage1 and it may also be an advantage1 not only to increase the diameter1 but also to reduce the pitch2 however1 a point is soon reached where the skin friction will more than neutralise the advantages of engaging a larger volume of water4 ,this is because the water adheres to the surface2 in fact1 the skin friction of a ship and its screw consumes fully #hj per cent4 of the total power of the engines1 but with an air propeller its surface is not wetted and the air does not stick to its surface4 ,if made of polished wood1 the friction is so extremely small as to be almost unmeasurable4 ,the diameter of a well-made screw running in air is therefore not limited in any degree by skin friction1 as is the case with a screw running in water2 in fact1 it is rather a question of its weight1 and its efficiency ought to increase in direct ratio with its diameter1 because the area of the disc increases with the square of the diameter4 ,the screw slip is therefore reduced by one-half by simply doubling the diameter of the screw4 ,it will be understood that by doubling the diameter of the screw1 four times as much air will be engaged4 ,if we push this back at half the speed1 we shall have the same screw thrust1 because the resistance of the air is in proportion to the square of the velocity that we impart to it1 so that one just balances the other1 and the diminution of wasteful slip is just in proportion to the increase in diameter4 ,in all cases1 the screw should be made as large as possible4 ,illustration3 ,fig4 #ah4--,section of screw blades having radial edges4 ,with screws of this form1 the blades1 of course1 become narrower as the hub is approached1 and if it is a true screw and the edges radial1 the sine of the angle will be the same at all points4 ,it is #b inches in this case4 ,illustration3 ,fig4 #ai4--,shows the form of the blade of a screw propeller made of sheet metal4 ,it is riveted at the edges and also to the arm of a screw with a stiffening piece at the extreme end4 ,however1 it is not necessary to rivet edges together4 ,they may be welded with a name of acetylene oxygen gases4 ,illustration3 ,fig4 #ai;a4--,shows the manner of welding and the finished edge4 ,illustration3 ,fig4 #bj4--;,a new form of hub1 of great strength and lightness1 for use on flying machines4 ,in the drawing 7,fig4 #ah7 ,i have shown screw blades of a proper shape to give the best results--that is1 providing a metallic screw is employed4 ,instead of having the arm of the screw on the back of the blade to offer resistance to the air1 the arm should be tubular1 flattened1 and covered on both sides with sheet metal4 ,this particular formation not only prevents the air from striking the arm1 but1 at the same time1 prevents the pressure of the air from deforming the blade1 so1 if a metallic screw is to be used1 the form of blade which ,i have shown will be found much superior to that employed at the present time on continental flying machines4 ,we should not lose sight of the fact that weight tells very seriously against the success of a flying machine1 and that no expense should be spared to reduce the weight1 providing that it is possible to do so without reducing the factor of safety4 ,suppose1 for example1 that we use an ordinary hub secured to a solid shaft by a common key4 ,all the parts have to be made heavy in order to be sufficiently strong to withstand the strain4 ,in the drawing 7,fig4 #bj7 ,i have shown a hub which ,i think is quite as light and strong as it is possible to make it4 ,the action of the motor is often spasmodic and puts very great strain upon the parts1 and there is a very strong tendency for the shaft to turn round in the hub4 ,if a key is used1 the hub has to be large and strong1 and the key of considerable size1 otherwise the parts would be deformed4 ,in my own experiments1 ,i have found considerable difficulty in securing a shaft to wooden screws4 ,however1 it will be seen in the drawings that a series of grooves is cut in the shaft and that the hub has internal projections1 so that the one fits the other4 ,this makes a very strong connection and is of extreme lightness4 ,both the hub and the shaft should be of tempered steel4 ,the spokes should be hard drawn steel tubes with long fine threads1 so as to withstand centrifugal force4 ,to prevent them from rotating in the hub1 the nuts d1 d are provided1 which compress the arms of the steel hub so as to grip the tube with any degree of force required4 ,it will be seen that with this system the pitch of the screw may be adjusted to some extent2 however1 it is better to have all parts of the screw1 from hub to centre1 of the same pitch4 ,a slight deviation from this is admissible in the experimental stage1 so long as the deviation from a true screw1 caused by rotating the arm1 is not greater than one half of the slip while in flight4 ,many experimenters have imagined that a screw is just as efficient placed in front of a machine as at the rear1 and it is quite probable that1 in the early days of steamships1 a similar state of things existed4 ,for several years there were steamboats running on the ,hudson ,river1 ,new ,york1 with screws at their bows instead of at their stern4 ,inventors of1 and experimenters with1 flying machines are not at all agreed by any means in regard to the best position for the screw4 ,it would appear that many1 having noticed that a horse-propelled carriage always has the horse attached to the front1 and that the carriage is drawn instead of pushed1 have come to the conclusion that1 in a flying machine1 the screw ought1 in the very nature of things1 to be attached to the front of the machine1 so as to draw it through the air4 ,railway trains have their propelling power in front1 and why should it not be the same with flying machines8 ,but this is very bad reasoning4 ,there is but one place for the screw1 and that is in the immediate wake1 and in the centre of the greatest atmospheric disturbance4 ,while a machine is running1 although there is a marked difference between water and air as far as skin friction is concerned1 still the conditions are the same as far as the position of the screw is concerned4 ,with a well-designed steamship1 the efficiency of the screw is so great as to be almost unbelievable2 in fact1 if a steamship had never been made1 and the design of one should be placed before the leading mathematicians of to-day1 with the request that they should compute the efficiency of the screw1 none of them would come anywhere near the mark4 ,they would make it altogether too small4 ,as before stated1 when a steamship is being driven through the water1 the water adheres to its sides and is moved forward by the ship--that is1 it has acceleration imparted to it which exactly corresponds to the power consumed in driving the ship through the water4 ,this1 of course1 retards it and we find in a well-designed ship1 not run above its natural speed1 that about #hj per cent4 of the power of the engine is consumed in skin friction1 or in imparting a forward motion to the water4 ,suppose that we should take such a ship1 remove the screw1 and tow it through the water with a very long wire rope at a speed of1 say1 #bj miles an hour2 we should find that the water at the stern of the ship was moving forward at a velocity of fully #f miles an hour--that is1 travelling in the same direction as the ship4 ,by replacing the screw1 and applying engine power sufficient to give the ship the same speed of #bj miles an hour1 identical results would be produced4 ,the skin friction still impels the water forward1 so that the screw1 instead of running in stationary water1 is actually running in water moving in the same direction as the ship at a velocity of #f miles an hour4 ,if the slip of the screw should only be equal to this forward motion1 the apparent slip would be nothing2 in fact1 the ship would be moving just as fast as it would move if the screw were running in a solid nut instead of in the yielding water4 ,curiously enough there have been cases of negative slip in which the actual slip of the screw in the water was less than the forward movement of the water1 and in such cases a ship is said to have negative slip4 ,a very noticeable case of this kind occurred in the ,royal ,navy in the sixties4#a ,i was at the time engaged in a large shipbuilding establishment in ,new ,york1 and remember distinctly the interest that the case created amongst the draughtsmen and engineers of that establishment4 ,of course1 this apparently impossible phenomenon created a great deal of discussion on both sides of the ,atlantic4 ,it appears that this ship had been built under an ,admiralty ,specification which called for a screw of a certain diameter and pitch with a specified number of revolutions per minute1 and for a certain number of knots per hour1 also that the boiler pressure should not go above a certain number of pounds per square inch4 ,when the ship was finished and went on her trial trip1 it was found impossible to make the full number of turns called for in the specification with the boiler pressure allowable2 nevertheless1 the speed was greater than the specification called for1 and as speed was the desideratum1 and not the number of revolutions1 the contractors thought their ship should be accepted4 ,then arose a discussion as to the diameter and pitch of the screw4 ,it was claimed that a mistake must have occurred4 ,a careful measurement was made in the dry dock1 and all was found correct4 ,once more the ship was tried1 and again her speed was in excess of the specification1 notwithstanding that it was still impossible to get the specified number of revolutions per minute4 ,mathematicians then took the matter in hand1 and it was found that the ship actually travelled faster than she would have done if the screw had been running in a solid nut4 ,instead of a positive slip1 the screw had in reality a negative slip2 but this was not believed at the time1 and the discussion and controversy continued4 ,the ship was tried again and again1 and always with the same results4 ,this apparently inexplicable phenomenon was accounted for in the following manner3--,the hull of the ship was said to be rather imperfect and to cause a considerable drag in the water1 so that1 when the ship was moving at full speed1 the water at the stern had imparted to it a forward velocity greater than the actual slip4 #a ,the particulars relating to this event are taken from accounts published at the time in ,american papers4 ,what is true of ships is true of flying machines4 ,good results can never be obtained by placing the screw in front instead of in the rear of the machine4 ,if the screw is in front1 the backwash strikes the machine and certainly has a decidedly retarding action4 ,the framework1 motor1 etc41 offer a good deal of resistance to the passage of the air1 and if the air has already had imparted to it a backward motion1 the resistance is greatly increased4 ,the framework will always require a considerable amount of energy to drive it through the air1 and the whole of this energy is spent in imparting a forward motion to the air1 so if we place the propelling screw at the rear of the machine in the centre of the greatest atmospheric resistance1 it will recover a portion of the lost energy1 as in the steamship referred to4 ,it will1 therefore1 be seen that when the screw is at the rear1 it is running in air which is already moving forward with a considerable velocity1 which reduces the slip of the screw in a corresponding degree4 ,i have made experiments with a view of proving this1 which ,i shall mention further on1 and which ought to leave no chance for future discussion4 ,illustration3 ,fig4 #ba4--,small apparatus for testing fabrics for aeroplanes1 the material being subjected to an air blast in order to test its lifting effect as compared with its tendency to travel with the blast4 ,my first experiments had shown that wooden aeroplanes did much better than any of the fabric covered aeroplanes that ,i was able to make at that time1 but as wood was quite out of the question on my large machine on account of its weight1 it was necessary for me to conduct experiments with a view of ascertaining the relative values of different fabrics4 ,for this purposes1 ,i made the little apparatus shown 7,fig4 #ba74 ,this was connected to a fan blower driven by a steam engine having a governor that worked directly on the point of cut-off4 ,the speed was1 therefore1 quite uniform and the blast of air practically constant4 ,i had a considerable number of little frames cut out of sheet steel1 and to these ,i attached various kinds of fabric1 such as ordinary satin1 white silk1 closely woven silk1 linen1 various kinds of woollen fabrics1 including some very coarse tweeds1 also glass-paper1 tracing linen1 and the best quality of ,spencer's balloon fabric4 ,the blast of air was not large enough to cover the whole surface of the aeroplanes1 so that the character of the back of the frames was of no account4 ,the first object experimented with was a smooth piece of tin4 ,when this was placed at an angle of #a in #ad1 it was found that the drift or tendency to travel in the direction of the blast was just one-fourteenth part of the upward tendency1 or lift4 ,this was exactly as it should have been4 ,upon changing the angle to #a in #aj1 a similar thing occurred2 the lift was ten times the drift4 ,i1 therefore1 considered the results obtained with the sheet of tin as unity1 and gave to every other material experimented with1 a coefficient of the unity thus established4 ,upon testing a frame covered with tightly-drawn white silk1 a considerable amount of air passed through1 and with an angle of #a in #ad1 the lift was only about double the drift4 ,a piece of very open fabric1 a species of buckram1 was next tried1 and with this the lift and drift were about equal4 ,with closely-woven1 shiny satin the coefficient was about #hj2 with a piece of ordinary sheeting the coefficient was #ij2 with closely-woven1 rough tweeds1 #gj2 and with glass-paper about #ge4 ,with a piece of tracing linen very tightly drawn1 results were obtained identical with those of a sheet of tin1 and with ,spencer's balloon fabric the coefficient was about #ii4 ,i1 therefore1 decided to cover my aeroplanes with this material4 ,it will be observed that the apparatus is so arranged that both the lift and the drift can be easily measured4 ,illustration3 ,fig4 #bb4--;,apparatus for testing the lifting effect of aeroplanes and condensers in an air blast4 k1 k show two aeroplanes in position for being tested4 ,illustration3 ,fig4 #bc4--;,apparatus for testing aeroplanes1 condensers1 etc41 in an air blast4 ,the opening is #c feet square4 ,thin brass sustainers are shown in position for testing4 ,illustration3 ,fig4 #bd4--;,cross-sections of bars of wood employed for ascertaining the coefficient of different forms4 ,illustration3 ,fig4 #be4--,transverse sections of bars of wood experimented with for the purpose of ascertaining their coefficients as relates to a normal plane4 ,illustration3 ,fig4 #bf4--;,a flat aeroplane placed at different angles4 ,in order to ascertain the resistance encountered by various shaped bodies driven at various speeds through the air1 the best form of aeroplanes1 and the efficiency of atmospheric condensers1 ,i made the apparatus shown in ,figs4 #bb and #bc4 ,the smaller and straight portion of this apparatus was #ab feet long and exactly #c feet square inside1 and was connected as shown to a shorter box #d feet square4 ,two strongly made wooden screws b1 b and d1 were attached to the same shaft4 ,these screws had two blades each1 and while one pair of blades was in a vertical position1 the other was in a horizontal position4 ,i interposed between the screws1 slats of thin wood arranged in the manner shown at d1 d2 this was to prevent rotation of the air4 ,at e ,i placed vertical slats of thin wood1 and horizontal slats of the same size at f4 ,at g two wide and thin boards1 sharp at both edges and made in the form of the letter ,x1 were placed in the box as shown in section ,,xy4 ,an engine of #ajj ,h4,p4 with an automatic variable cut-off was employed which gave to the screws a uniform rate of rotation1 and as the engine had no other work to do1 the governor could be arranged to give varying speeds such as were required for the experiments4 ,the objects to be tested were attached to the movable bars4 ,in the drawing1 the aeroplane k1 k is shown in position for testing4 ,this apparatus was provided with a rather complicated set of levers1 which permitted not only the measurement of the lift of the objects experimented with1 but also that of the drift4 ,the principle employed in this apparatus was a modification of the ordinary weighing apparatus used by grocers1 etc4 ,the first object tested was a bar of wood exactly #b inches square shown in ,fig4 #bd4 ,this was placed in such a manner that the wind struck squarely against the side as shown in the drawing1 and with a wind of #di miles per hour1 it was found that the drift or tendency to move with the air was #eaf lbs42 at the same time1 the wind on my instrument gave a pressure of #b lbs4 on a normal plane #f inches square4 ,the velocity of the wind was ascertained by an anemometer of the best ,london make4 ,upon turning the same bar of wood in the position shown at b1 the drift mounted to #edg lbs4 ,a round bar of wood1 #b inches in diameter1 shown at c1 gave a drift of #big lbs4 ,these experiments were repeated with a wind velocity of #dj miles per hour1 when it was found that the drift of a was #def lbs41 and that of the round bar1 #bhj lbs4 ,it will be seen from these experiments that the power required for driving bars or rods through the air is considerably greater than one would have supposed4 ,the next object experimented with was a1 ,fig4 #be4 ,when this was subject to a wind of #dj miles an hour1 the drift was #jgh lb4 ,upon reversing this bar--that is1 putting the thin edge instead of the thick edge next to the wind--the drift mounted to #abb lbs42 b showed a drift of #jbh lb4 with the thick edge to the wind1 and #jdb lb4 with the thin edge to the wind2 c showed a drift of #jbc lb4 with the thick edge to the wind1 and #jei lb4 with the thin edge to the wind2 and d1 which was the same thickness as the others and #ab inches wide1 both edges being alike1 showed a drift of only #jai lb4 ,these experiments show in a most conclusive manner the shapes that are most advantageous to use in constructing the framework of flying machines4 ,aeroplane e1 ,fig4 #bf1 when placed on the machine in a horizontal position showed neither lift nor drift1 but upon placing it at an angle of #a in #bj1 as shown at f1 the lift was #cih lbs4 and the drift #jcj lb4 with a wind velocity of #dj miles per hour4 ,at this low angle the blade trembled slightly4 ,upon placing the same plane at an angle of #a in #af as shown at g1 the lift was #dei lbs4 and the drift #jec lb4 ,it will be observed that the underneath side of this plane is perfectly flat4 ,the next experiment was with planes slightly curved1 as shown in ,fig4 #bg4 ,the aeroplane a was #af inches wide1 very thin1 and only slightly curved4 ,when set at a very low angle1 it vibrated so as to make the readings very uncertain1 but when set at an angle of #a in #aj it lifted #iid lbs4 with a drift of #aab lbs4 ,by slightly changing the angle it was made to lift #ajcd lbs4 with a drift of #abc lbs41 the wind velocity being #da miles per hour4 ,aeroplane b1 #ab inches wide1 ,fig4 #bg1 when placed at an angle of #a in #ad with an air blast of #da miles per hour1 gave a lift of #ebh lbs4 with a drift of #jdd lb42 at an angle of #a in #ab the lift was #ehb lbs4 and the drift #je lb42 at an angle of #a in #aj the lift was #fge lbs4 and the drift #jgc lb42 with an angle of #a in #h the lift was #gge lbs4 and the drift #a lb42 with an angle of #a in #g the lift was #he lbs4 and the drift #abe lbs42 at an angle of #a in #f the lift was #ihg lbs4 and the drift #aga lbs4 ,aeroplane c1 ,fig4 #bg1 which had more curvature than b1 when run in a horizontal position1 gave a considerable lift1 and when raised to an angle of #a in #ab it gave a lift of #fab lbs4 with a drift of #jed lb4 ,in another experiment at the same angle1 it gave a lift of #fda lbs4 with a drift of #jef lb42 at an angle of #a in #af it gave a lift of #edg lbs4 with a drift of #jcg lb42 at an angle of #a in #aj it gave a lift of #fig lbs4 and a drift of #jgj lb42 at an angle of #a in #h it gave a lift of #hbb lbs4 with a drift of #ajh lbs42 at an angle of #a in #g it gave a lift of #iid lbs4 with a drift of #ade lbs42 at an angle of #a in #f it gave a lift of #ajcd lbs4 and a drift of #age lbs4 ,this plane was then carefully set so that both the forward and aft edges were exactly the same height1 and with a wind blast of #da miles per hour it gave a lift of #bji lbs4 with a drift of #jba lb4 ,it was then pitched #a in #ah in the wrong direction1 and at this point1 the lifting effect completely disappeared1 while the drift was practically nothing4 ,illustration3 ,fig4 #bg4--;,group of aeroplanes used in experimental research4 ,although shown the same size in the drawing1 aeroplane a was #af inches wide1 and b and c1 #ab inches wide4 ,illustration3 ,fig4 #bh4--;,an #h-;inch aeroplane which did very well4 ,this aeroplane gave decided lifting effect when the bottom side was placed dead level1 as shown at a4 ,when the aeroplane a 7,fig4 #bh7 was placed in a horizontal position1 and the apparatus carefully balanced1 it showed at a wind velocity of #dj miles an hour1 a lift of #aef lbs41 and a drift of #jjh lb42 at an angle of #a in #bj1 a lift of #cfb lbs4 and a drift of #jba lb42 at an angle of #a in #af1 a lift of #dji lbs4 with a drift of #jbf lb42 at an angle of #a in #ad1 a lift of #de lbs4 and a drift of #jcc lb42 at an angle of #a in #ab1 a lift of #e lbs4 and a drift of #jdc lb42 at an angle of #a in #aj1 a lift of #ege lbs4 and a drift of #jfj lb42 at an angle of #a in #h1 a lift of #fge lbs4 and a drift of #jhf lb4 ,the blast was then increased to a velocity of #dgcc miles an hour1 when it was found that the lift at an angle of #a in #af was #e lbs4 and the drift #jcc lb4 ,it will be observed that this aeroplane was only #h inches wide1 while the others were #ab inches or more4 ,they were all rather more than #c feet long1 but the width of the blast to which they were subjected was exactly #c feet1 and they were placed as near to the end of the trunk as possible4 ,illustration3 ,fig4 #bi4--,resistance due to placing objects in close proximity to each other4 ,the next experiments were made with the view of ascertaining what effect would be produced when objects were placed near to each other 7see ,fig4 #bi74 ,two bars of wood #b inches thick1 and shaped as shown in the drawing1 were placed on the machine and subjected to a blast of #da miles per hour2 the drift at various distances from center to center was as follows3-- #bd inches centers1 drift #f ozs4 #bb #f #bj #f #ah #f-a_/h #af #f-a_/h #ad #f-a_/d #ab #f-a_/b #aj #g #h #g-c_/d #f #h-a_/b #d #i-a_/d ,it will be seen by this that the various members constituting the frame of a flying machine should not be placed in close proximity to each other4 ,a bar of wood similar in shape to d 7,fig4 #be71 but being #i inches wide instead of #ab inches1 was mounted in a wind blast of #da miles an hour1 with the front edge #cca inches above the rear edge1 and this showed a lift of #gjh lbs4 and a drift of #cbc lbs4 ,when the angle was reduced to #bca inches1 it gave a lift of #dec lbs4 with a drift of #jgh lb41 and with the angle reduced to #aca inches1 the lift was #ccg lbs4 and the drift #je lb4 ,it will1 therefore1 be seen that even objects rounded on both sides give a very fair lift1 and in designing the framework of machines advantage should be taken of this knowledge4 ,the bar of wood c 7,fig4 #be7 was next experimented with4 ,with the sharp edge to the wind1 and with the front edge #b inches higher than the rear edge1 the lift was #bed lbs4 and the drift #jgf lb4 ,by turning it about so that the wind struck the thick edge1 the lift was #dde lbs4 and the drift #jdg lb4 ,this seemed rather remarkable1 but1 as it actually occurred1 ,i mention it for other people to speculate upon4 ,it1 however1 indicates that we should take advantage of all these peculiarities of the air in constructing the framework of a machine1 which in itself is extremely important1 as ,i find that a very large percentage of the energy derived from the engines is consumed in forcing the framework through the air4 ,it is quite true that a certain amount of this energy may be recovered by the screw1 provided that the screw runs in the path occupied by the framework4 ,still1 it is much better that the framework should be so constructed as to offer the least possible resistance to the air1 and1 as far as possible1 all should be made to give a lifting effect4 ,illustration3 ,fig4 #cj4--;,cross-section of condenser tube1 made in the form of ,philipps' sustainers1 in which c is the steam passage4 ,illustration3 ,fig4 #ca4--,the grouping of condenser tubes1 made in the form of ,philipps' sustainers4 ,this arrangement is very effective1 condenses the steam or cools the water1 and gives a lifting effect at the same time4 ,the shape and arrangement of tubes shown at b1 b1 although effective as a condenser1 produce no lifting effect1 but a rather heavy drift4 ,having ascertained the lifting effect of wooden aeroplanes of various forms and at varying velocities of the wind1 and1 also1 the resistance offered by various bodies driven through the air1 ,i next turned my attention to the question of condensation4 ,i wished to recover as much water as possible from my exhaust steam4 ,i had already experimented with ,mr4 ,horatio ,philipps' sustainers1 and ,i found that their lifting effect was remarkable4 ,a curious thing about these aeroplanes was that they gave an appreciable lift when the front edge was rather lower than the rear4 ,i therefore determined to take advantage of this peculiar phenomenon1 and to make my condenser tubes as far as possible in the shape of ,mr4 ,philipps' sustainers4 ,fig4 #cj shows a section of one of these tubes1 in which a1 a is the top surface1 b a soldered joint1 and c the steam space4 ,these were mounted on a frame as shown at a 7,fig4 #ca74 ,i had already found that bodies placed near to each other offered an increased resistance to the air1 but by placing these sustainers in the manner shown this was avoided1 as the air had sufficient space to pass through without being either driven forward or compressed4 ,it was found by experiment that the arrangement of tubes or sustainers1 shown at d1 d 7,fig4 #ca71 was very efficient as a condenser1 but it gave a very heavy drift and no lifting effect at all2 whereas1 on the other hand1 the arrangement shown at a was equally efficient1 and1 at the same time1 gave a decided lifting effect4 ,when twelve of these tubes or sustainers were placed at an angle of #a in #ab1 the lifting effect was #abfc lbs4 and the drift #bjf lbs4 ,it was found1 however1 that a good deal of the drift was due to the wind getting at the framework that was used for holding the sustainers in position4 ,with a wind velocity of #dj miles an hour and a temperature of #fb ,f41 #bbe lbs4 of water were condensed in five minutes1 and1 while running1 the back edge of the sustainers was quite cool4 ,at another trial of the same arrangement under the same conditions1 the lift was #aa lbs4 and the drift #bfc lbs4 ,it is quite possible on this occasion that the metal was so extremely thin that the angles were not always maintained2 consequently1 that no two readings would be alike4 ,it was found at this point that the belt was slipping1 and a larger pulley was put on the driving shaft of the screws2 and under these conditions1 with a wind of #di miles per hour and an angle of #a in #h1 the lifting effect ran up to #adhg lbs4 with a drift of #bdd lbs41 and the condenser delivered #bhg lbs4 of water from dry steam in five minutes4 ,the weight of metal in this condenser was extremely small1 the thickness being only about #a_/ejj of an inch4 ,this condenser delivered the weight of the sustainers in water every five minutes4 ,they should1 however1 have been twice as heavy4 ,cylinder oil was now introduced with the steam in order to ascertain what effect this would have4 ,after seven minutes' steaming1 #bbe lbs4 of water were condensed in five minutes4 ,it will be seen from these experiments that an atmospheric condenser1 if properly constructed1 is fairly efficient4 ,roughly speaking1 it requires #b1djj times as much air in volume as of water to use as a cooling agent4 ,with the steam engine condenser only a relatively small amount of water is admitted1 and this is found to be sufficient2 but in an atmospheric condenser working in the atmosphere1 it must be as open as possible1 so that no air which has struck one heated surface can ever come in contact with another4 ,,chapter ,v4 ,,experiments ,,with ,,apparatus ,,attached ,,to ,a ,,rotating ,,arm4 ,from what information ,i have at hand1 it appears that ,prof4 ,langley made his first experiments with a small apparatus1 using aeroplanes only a few inches in dimensions which travelled round a circle perhaps #ab feet in diameter4 ,with this little apparatus1 he was able to show that the lifting effect of aeroplanes was a great deal more than had previously been supposed4 ,after having made these first experiments1 he seems to have come to the conclusion that ,newton's law was erroneous4 ,shortly after ,langley had made these experiments on what he called a whirling table1 which1 however1 was not a very appropriate name1 ,i made an apparatus myself1 but very much larger than that employed by ,prof4 ,langley4 ,i reckoned the size of my aeroplanes in feet1 where he had reckoned his in inches4 ,the circumference of the circle around which my aeroplanes were driven was exactly #bjj feet1 and shortly after this ,langley constructed another apparatus1 the same dimensions as my own4 ,from an engraving which ,i have before me1 it appears that he constructed an extremely large wooden scale beam supported by numerous braces1 but free to be tilted in a vertical direction after the manner of all other scale beams4 ,as this apparatus was of great weight and offered enormous resistance to the air1 ,i do not understand how it was possible to obtain any very correct readings1 especially as it was in the open and subject to every varying current of air4 ,illustration3 ,fig4 #cb4--,machine with a rotating arm1 #cah feet long1 to which is attached the object to be experimented with4 ,professor ,langley had a similar machine and called it a 8whirling table40 ,illustration3 ,fig4 #cc4--;,a screw and fabric covered aeroplane in position for testing4 ,illustration3 ,fig4 #cd4--,the rotating arm of the machine with a screw and aeroplane attached4 ,in constructing my apparatus1 which is shown in the photographs1 and also in a side elevation 7,fig4 #cb71 ,i aimed at making the apparatus very light and strong1 avoiding as far as possible atmospheric resistance4 ,in the drawing1 a1 is a thick seamless steel pipe #f inches diameter2 b1 is a cast-iron pedestal firmly bolted to d1 and connected to a large cast-iron spider embedded in hydraulic cement2 by this means great rigidity and stiffness were obtained4 n1 n was formed of strong ,georgia pine planks #b inches thick1 and strongly bolted together4 ,the two members of the long radial arm h1 h1 were made of ,honduras mahogany1 an extremely strong wood1 and had their edges tapered off as shown at y1 y4 ,the power was transmitted from a small steam engine provided with a sensitive governor through the shaft f1 f4 ,in the base c1 of the casting b1 was placed a pair of tempered steel bevel gears1 giving to the vertical shaft a high velocity4 ,from a pulley on the top of this shaft1 the belt i1 was run through the arms h1 h1 as shown in section y1 y4 ,this gave a rapid rotation to the screw shaft in a very simple manner4 ,the operation of the machine was as follows3--the aeroplane g1 to be tested was secured to a sort of weighing apparatus which is shown in detail 7,fig4 #cf71 and the screw attached to the shaft4 ,upon starting the engine1 a very rapid rotation was given to the screw which caused the radial arm to travel at a high velocity1 the whole weight resting on a ball bearing at w4 ,the radial arms and all of their attachments were balanced by a cigar-shaped lead weight s1 which was secured to a sliding bar so as to make it easily adjustable4 ,the thrust of the screw caused the screw shaft to travel longitudinally1 and this was opposed by a spring connected by a very thin and light wire to the pointer of the index o4 ,as the apparatus rotated rather slowly on account of its great diameter1 it was quite possible to observe the lift while the machine was running at its highest speed4 ,the aeroplanes were mounted after the manner of the tray of a grocer's scales 7see ,fig4 #cf71 and the lift of the aeroplane was determined by what it would lift at r--that is1 while the machine was running at a given speed1 iron or lead weights were placed in the pail r1 until the lift of the aeroplane was exactly balanced1 and then1 in order to ascertain exactly what the lift was1 the aeroplane was placed under what might be called a small crane1 and a cord1 running over a pulley1 attached4 ,the amount of weight necessary to lift the plane into the same position that it occupied while running was taken as its true lift4 ,in order to facilitate experiments the gauge p1 was provided4 ,this gauge consisted of a large glass tube and the index p1 with a quantity of red water at q4 ,the centrifugal force of rotation caused the red water to rise in the tube4 ,this was easily seen1 so that if experiments were being tried1 we will say at #ej miles an hour1 it was always possible to turn on steam until the red liquid mounted to #ej4 ,this device was very simple and effective1 and saved a great deal of time4 ,in order to prevent the twisting of the radial arm1 a piece of stiff oval steel tube #ab feet long was secured between the arms at j1 and on each end of this tube were attached the wires u1 u4 ,this not only effectually supported the end of the arm1 but at the same time prevented twisting and made everything extremely stiff4 ,of course1 while the machine was running at a high velocity1 centrifugal force had to be dealt with1 and in order to prevent this from causing friction in the articulated joints of the weighing apparatus 7,fig4 #cf71 thin steel wires k1 k were provided4 ,as this apparatus was in the open1 it was found that the slightest movement of the air greatly interfered with its action4 ,on one occasion when a fabric covered aeroplane1 #d feet long by #c feet wide1 was placed in position1 the four corners being held down by the wires v1 v1 and the apparatus driven at a high velocity1 a sudden gust of wind snapped two of the wires1 broke the aeroplane1 and the flying fragments smashed the screw1 and this notwithstanding that each of the four wires was supposed to be strong enough to resist at least four times any possible lifting that the whole aeroplane might be subjected to4 ,illustration3 ,fig4 #ce4--,the little steam engine used by me in my rotating arm experiments2 the tachometer and dynamometer are distinctly shown4 ,in order to ascertain the force and direction of the wind1 ,i made an extremely simple and effective apparatus which is fully shown 7see ,fig4 #ch74 ,whilst conducting these experiments it occurred to me1 when a large aeroplane was used1 that after it had been travelling for a considerable time1 it would impart to the air in the path of its travel1 a downward motion1 and that the lifting effect would be greatly reduced on this account4 ,in order to test this1 ,i provided four light brass screws and mounted them1 as shown at x1 on a hardened polished steel point much above their centre of gravity1 so that they balanced themselves4 ,on account of the absence of friction1 they were easily rotated1 and responded to the least breath of air that might be moving4 ,one morning when there was a dead calm1 ,i placed four of these screws equidistant around the whole circle4 ,some of them rotated very slowly in one direction and some in another2 some alternated1 but all their motions were extremely slow4 ,however1 upon setting the machine going with a large aeroplane and a powerful screw1 ,i found after a few turns that the air was moving downwards around the whole circle at a velocity of about #b miles an hour1 but as the screw was a considerable distance below the aeroplane1 ,i estimated that the actual downward velocity of the air in which the aeroplane was travelling was about #d miles an hour4 ,the result of my experiments are clearly shown in an unpublished paper which ,i wrote at the time1 and as it is of considerable historical interest1 ,i have placed it in the appendix1 notwithstanding that there may be certain repetitions4 ,illustration3 ,fig4 #cf4--,the machine attached to the end of the rotating shaft--a1 a1 the body of the machine2 b1 b1 four-legged spider secured to a1 a2 c1 c1 parallel bars2 d1 d1 vertical member to which the aeroplane g1 g is attached2 h1 h1 the screw2 f1 f1 wires for preventing distortion of the aeroplane4 ,illustration3 ,fig4 #cg4--,marking off the dynamometer4 ,in order to ascertain the actual amount of power consumed in driving the propeller1 a brake was put on in place of the screw1 a weight applied1 and the engine run at full speed4 ,in this way all the uncertain and unknowable factors were eliminated4 ,in ,fig4 #cf1 a1 a is the body of the apparatus1 partly of gunmetal and partly of wood4 ,it is provided with a steel shaft to which the screw h1 is attached1 and also with a cylindrical pulley for taking the belt4 ,the thrust of the screw pushes the shaft inwards and records the lift at o 7,fig4 #cb74 ,the corners of the aeroplane g1 g1 are attached by wires to the steel plate e4 b1 b1 is a four-arm spider for holding the ends of the parallel bars c1 c1 and d1 d1 show vertical steel bars to which all devices to be tested are attached4 ,in testing aeroplanes1 weights may be placed at e1 sufficient to balance the lifting effect1 and then by adding the weight to the upward pull of the aeroplane1 the true lift of the aeroplane is obtained4 ,it is also possible to attach an aeroplane at e1 that is1 the machine was made to test superposed aeroplanes if required4 ,in these experiments1 ,i naturally assumed that the best position for a screw was at the rear and in the path of the greatest resistance1 but as some experimenters with navigable balloons placed the screw in front in order to pull the apparatus along instead of to push it1 ,i made experiments to see what the relative difference might be4 ,in order to do this1 ,i wound a large amount of rope one-half inch in diameter around the whole apparatus forward of the screw1 converting it into an irregular mass well calculated to offer atmospheric resistance4 ,upon starting the engine1 ,i was rather surprised to see how little retardation these ropes gave to the apparatus4 ,it appeared to me that nearly all of the energy consumed in driving the ropes through the air was recovered by the screw4 ,i then removed the right-hand screw and replaced it by a left-hand screw of the same pitch and dimensions 7,fig4 #cg;a74 ,i then found that the blast of the screw blowing against the tangle of ropes greatly retarded the travel2 in fact1 with the same number of revolutions per minute1 the velocity fell off #fj per cent4 ,i think that these experiments ought to show that there is but one place for the screw1 and that is at the stern1 and in the direct path of the greatest atmospheric resistance4 ,illustration3 ,fig4 #cg;a4--,right- and left-hand four-blade screws used in my experiments for ascertaining the comparative efficiency between screws placed in front and in the rear of the machine4 ,illustration3 ,fig4 #ch4--;,apparatus for indicating the force and velocity of the wind direct without any timing1 counting1 or mathematical calculations4 ,fig4 #ch shows an original apparatus which ,i designed and made for my own use2 with ordinary anemometers it is necessary to count the number of turns per minute in order to ascertain the velocity of the wind4 ,i wanted something that would indicate the velocity and the direction of the wind without any figures or formul4 ,i therefore made the apparatus shown in the drawing1 in which a1 a1 is a metallic disc #aced inches in diameter1 giving it an area of exactly #a square foot4 ,this is attached to the horizontal bar b1 and the whole mounted on two bell crank levers as shown4 ,when the wind is not blowing1 the long arms of these two levers assume a vertical position1 and the spiral spring h1 is in exact line with the pivots on which these levers are mounted1 and has no effect except to hold the levers in a vertical position4 ,as the spring has very little tension in this position1 and as it requires a considerable movement in order to give it tension1 the arms c1 c1 and the bar b1 b1 are very easily pushed backwards1 but as the distance through which they travel increases1 the angle of the lever changes and the tension of the spring increases at the same time1 so that when the disc is pushed backwards to any considerable distance1 a strong resistance is encountered4 ,had ,i made this apparatus so that the pressure acted directly on the spiral spring1 the spaces on the index indicating low velocities would have been very near together1 while those indicating high velocities would have been widely separated1 but with this device properly designed1 the spacing on the index became regular and even4 ,the index being very large enabled one to read it at a considerable distance1 and at the same time1 it acted as a tail and kept the apparatus face to the wind4 ,the spaces of the dial were not laid off with a pair of dividers1 but each particular division was marked by an actual pull on the bar b1 through the agency of a cord and easily running pulley and weight4 ,the markings1 however1 were not correct1 because ,haswell's formula was employed in which the pressure of the wind against the normal plane is considerably greater than with the more recent formula1 which is now known to be correct4 ,haswell's formula was ,v #jje ,p1 and the recent formula ,p #jjjc ,v1 where ,p pressure in lbs4 per square foot and ,v velocity in miles per hour4 ,in my experiments1 ,i also employed a very well made and delicate anemometer by ,negretti ,zambra4 ,illustration3 ,fig4 #ci4--;,apparatus for testing the lifting effect of aeroplanes at a low angle and extremely high velocity4 a1 a1 the aeroplane2 b1 lead weight2 c1 long and slender pine rod2 d1 tail for keeping the apparatus head on and ensuring its travelling straight through the air2 e1 the point of suspension1 also the centre of gravity4 ,when this apparatus was travelling at the rate of #hj miles an hour1 it gave a lifting effect of about #cf lbs41 which is about #g lbs4 per square foot4 ,,crystal ,,palace ,,experiments4 ,having fully satisfied myself that aeroplanes flying around a circle #bjj feet in circumference had their lifting effect reduced to no insignificant degree by constantly engaging air which had already had imparted to it a downward movement by a previous revolution1 ,i determined to make some experiments where this trouble could not occur1 but the opportunity did not present itself until after the large roundabout1 erroneously described as 8a captive flying machine10 was put up at the ,crystal ,palace4 ,this presented a fine opportunity for making experiments at an extremely high velocity around a very large circle4 ,i will only refer to a few of these experiments4 ,to a prolongation of one of the long arms1 ,i attached a thin steel wire rope about #fj feet above the platform2 ,i then attached to this wire rope the little device shown 7,fig4 #ci71 in which a1 is an aeroplane1 #e feet long and #a foot wide1 placed at an inclination of #a in #bj4 ,great care was used in preparing this aeroplane to see that it was free from blemish1 smooth1 and without any irregularities4 ,both edges were sharp and the curvature was about one-eighth of an inch on the underneath side4 ,it was made relatively thick in the middle where it was attached to the bar c1 and thinner at the ends4 b1 shows a lump of lead just heavy enough to balance the bar c1 and the tail2 d1 was a light but strong wooden frame1 all the edges being thin and sharp1 and covered with a special silk that ,mr4 ,cody had found to be best for such purposes4 ,the wire rope e1 was attached to the long arm which ,i referred to4 ,the great length of the bar c1 and the accuracy with which the whole was made and balanced caused the aeroplane to travel straight through the air adjusting itself to all the shifting currents4 ,upon starting the machine on a very calm day1 this apparatus mounted as high as the point of support1 sometimes going #aj or more feet higher and sometimes #h or #aj feet lower4 ,however1 as a rule1 it carried its own weight at a velocity of #hj miles an hour around a circle #a1jjj feet in circumference4 ,under these conditions1 of course1 there could be no downward motion of the air as all the air affected would be removed long before it could be struck the second time by the aeroplane4 ,i had no means of ascertaining exactly how much this plane did actually lift1 because the air was always moving to some extent1 and it was not an easy matter to ascertain whether it was above or below the point of support4 ,i am sure1 however1 that it was as much as #cf lbs41 or rather more than #g lbs4 to the square foot1 and this is just what it should have lifted1 providing that we consider the results obtained by smaller planes placed in an air blast of #dj miles an hour and at the same angle4 ,when these experiments were finished1 ,i made a very small apparatus having only about #be square feet of lifting surface1 and this carried the weight of a man1 in fact several gentlemen came up from ,london and went round on it themselves4 ,i saw1 however1 that it was a dangerous practice1 because if the wind was blowing at all1 the apparatus would mount very much above the point of support while travelling against the wind1 only to drop much below the point of support on the other side of the circle where it was travelling with the wind2 in fact1 on one occasion the apparatus shown 7,fig4 #ci7 mounted in a high wind fully #bj feet above the point of support and came down with such a crash on the other side that it broke the wire rope4 ,in connection with this1 it is interesting to note that when ,i erected the first so-called 8captive flying machine0 on my own grounds at ,thurlow ,park1 ,i intended that instead of ordinary boats such as were ultimately employed1 each particular boat should be fitted with an aeroplane1 that the engine should be of #bjj ,h4,p41 and that the passengers should actually be running on the air1 each boat being provided with a powerful electric motor in addition to the motive power that drove the shaft4 ,had this been carried out as was originally designed1 it would have removed the apparatus altogether from the category of vulgar merry-go-rounds1 but such was not to be4 ,unforeseen circumstances were against me4 ,i had some of these boats fitted up with aeroplanes and running on my grounds1 and two of the engineers of the ,london ,county ,council came out to see the apparatus before it was put up for public use4 ,on that occasion the wind was blowing a perfect gale of #dj miles an hour1 and as the boats travelled at the rate of #ce miles an hour1 they1 of course1 encountered a wind of #ge miles an hour when passing against the wind1 and a minus velocity of #e miles an hour when travelling with the wind on the other side of the circle4 ,the aeroplanes1 although of considerable size1 were small in relation to weight4 ,i had neglected to put any weight in the boats1 and when three of us were studying the eccentric path through which the boats were travelling1 suddenly one of them in passing to the windward1 raised very much above the point of support and plunged down with great force on the other side2 in fact1 the shock was so great that it made everything rattle1 but nothing was broken4 ,nevertheless1 the engineers said at once1 it would not do to run the boats with those aeroplanes2 it was too dangerous4 ,this would not1 however1 have occurred if the boats had been loaded1 or the velocity of the wind had been less4 ,it1 however1 demonstrated what a tremendous lift may be obtained from a well-made aeroplane passing at a high velocity through the wind at a sharp angle4 ,these aeroplanes were only about #ab feet long and #e feet wide1 having1 therefore1 #fj square feet of surface4 ,they were1 however1 strong1 well-made1 and perfectly smooth1 both top and bottom4 ,i would say right here that ,i am not a success as a showman--previous long years of rubbing up against honest men have disqualified me altogether for such a profession4 ,i was extremely anxious to go on with my experiments4 ,i appreciated fully that ,i had made a machine that lifted #b1jjj lbs4 more than its own weight1 and ,i knew for a dead certainty if ,i took the matter up again1 got rid of my boiler and water tank1 and used an internal combustion engine1 such as ,i thought ,i could produce1 that mechanical flight would soon be a fait accompli4 ,i had already spent more than #bj1jjj1 and was looking about for some means of making the thing self-supporting4 ,i believed that the so-called 8captive flying machine0 would be very popular1 and bring in a lot of money1 and it would have done so1 if it had been put up as originally designed4 ,i proposed to use my share of the profits for experimental work on real flying machines4 ,that ,i was not far wrong in believing that such a machine would be a success1 is witnessed by the fact that just about the same time1 an ,american inventor thought of the same thing1 put up some three or four machines the first year1 and the next year about #ej4 ,they were highly profitable1 and there are fully #adj of them running at the present time in the ,u4,s4,a4 ,it is a fact that nothing in the way of side-shows at exhibitions or public resorts has ever had the success of this machine in the ,u4,s4,a41 and even the little machine at ,earl's ,court took #cbe #ajs4 in one day and #g1ejj in a season4 ,however1 this little attempt to make one hand wash the other cost me no less than #aj1djj1 not to mention more than a year of very hard work4 ,this sum would have been amply sufficient to have enabled me to continue my experiments until success was assured4 ,,chapter ,,vi4 ,,hints ,,as ,,to ,,the ,,building ,,of ,,flying ,,machines4 ,illustration3 ,fig4 #dj4--;,front elevation of proposed aeroplane machine--a1 a1 the aeroplanes2 g1 g1 condenser2 f1 the engine2 q1 guard for screw2 k1 k1 support for wheels4 ,illustration3 ,fig4 #da4--,side elevation of proposed superposed aeroplane machine--a1 a1 main aeroplanes2 b1 b1 rear aeroplanes2 c1 vertical rudder2 d1 horizontal front rudder2 e1 screw2 f1 motor2 g1 condenser2 h1 steering gear2 i and j1 pneumatic buffers2 k and l1 wheels2 m1 point at which k is pivoted to the main frame2 n1 handle of the steering gear4 ,illustration3 ,fig4 #db4--,plan of proposed aeroplane machine1 in which a1 a are the proposed superposed main aeroplanes2 b1 b1 the after superposed aeroplanes2 c1 c1 the forward horizontal rudder2 d1 platform2 e1 screw2 h1 h1 and i1 i1 pulleys used in communicating motion from the steering gear1 f1 to the rudder1 j2 g1 lever attached to the aeroplane or rudder1 c1 c1 and connected to the steering gear1 f4 ,for those who really wish to build a flying machine that will actually fly with very little experimental work1 ,i have given an outline sketch sufficiently explicit to enable a skilful draughtsman to make a working drawing in which ,fig4 #dj is a front elevation1 ,fig4 #da a side elevation1 and ,fig4 #db a plan4 ,fig4 #da1 a1 a1 shows the two forward or main aeroplanes2 b1 b1 the two after aeroplanes1 which are smaller and shorter2 c1 the rudder2 d1 the forward horizontal rudder2 e1 the screw2 f1 the motor2 g1 the condenser or cooler2 h1 the steering gear2 i1 and j1 atmospheric buffers2 k and l1 wheels attached to a lever pivoted to the body of the machine2 q1 a shield for protecting the screw4 ,it will be observed that the framework is extremely long1 and1 consequently1 the distance between the aeroplanes is very great2 but it should be borne in mind that the longer the machine1 the less any change of center of lifting effect1 as relates to the center of gravity1 will be felt4 ,moreover1 it is much easier to manuvre a machine of great length than one which is very short1 because it gives one more time to think and act4 ,if the length was infinitely great the tendency to pitch would be infinitely small4 ,i have shown a steering gear consisting of a lever with a handle n1 arranged in such a manner that it moves both the vertical rudder c1 and the horizontal rudder d1 so that the man who steers the machine has nothing to think of except to point the lever n1 p1 in the direction that he wishes the machine to go4 ,this lever is mounted on a universal joint at h1 and is connected with suitable wires to the two rudders4 ,in order to prevent shock when the machine alights1 it is necessary to provide something that is strong and1 at the same time1 yielding1 and able to travel through a considerable distance before the machine comes to a state of rest4 ,in the machines which ,i have seen on the ,continent1 a very elaborate apparatus is employed1 which is not only very heavy1 but also offers a considerable resistance to the forward motion of the machine through the air4 ,it consists of many tubes1 very long levers and heavy spiral springs1 etc4 ,in the device which ,i am recommending1 all this is dispensed with1 and something very much simpler1 cheaper1 and lighter is substituted4 ,moreover1 with my proposed apparatus a certain amount of lifting effect is produced4 ,the levers k1 k1 to which the wheels are attached1 should be of thin wood1 light and strong1 and say about a foot wide1 strongly pivoted to the frame and held in position by an atmospheric buffer made of strong and thin steel tubing1 shown in section 7,fig4 #ea74 ,these pneumatic cylinders may be pumped up to any degree1 so as to support the weight of the machine1 and then1 as it comes down1 the compression and escape of air arrest its motion4 ,the condenser g1 is placed in such a position that it will act even while the machine is on the ground and the propellers working4 ,in ,continental machines1 very small screw propellers are used4 ,these screws have probably been made small because the experimenters have found that they encounter a good deal of friction in the atmosphere1 but this is caused by imperfect shape and the rib of steel at the back of the blades4 ,in order to use a small screw1 experimenters have been forced to use a very quick-running engine which makes it necessary to have the cylinders very short1 so1 in order to get the necessary power1 they are obliged to use no less than eight cylinders4 ,however1 by increasing the diameter of the screw and making it of such a form that very little or no atmospheric skin friction is encountered1 a much better and cheaper engine of a totally different type may be employed4 ,there is no reason why more than four cylinders should be used1 but the stroke of the piston and diameter of the cylinder should be increased4 ,doubtless ,continental experimenters have an idea that1 as the engine cannot be provided with a flywheel1 it must have a very large number of cylinders in order to give a steady pull completely around the circle1 and thus avoid so-called 8dead centers02 but1 when we consider the enormously high velocity of the periphery of the screw1 and also take into consideration that the momentum is in proportion to the square of the velocity1 it is quite obvious that there can be no slowing up between strokes even if only one cylinder should be employed working on the four-cycle principle1 in which work is only done one stroke in four4 ,then1 again1 ,i find that the weight of these ,continental engines can be greatly reduced1 providing that they are made with the same degree of refinement that ,i employed in building my steam engines4 ,recently there has been a great deal of discussion in ,engineering and other journals regarding the comparative merits of the aeroplane system and the hlicoptre4 ,some condemn both systems and pin their faith to flapping wings4 ,it has been contended that the screw propeller is extremely wasteful in energy1 and that in all ,nature neither fish nor bird propels itself by means of a screw4 ,as we do not find a screw in ,nature1 why then should we employ it in a machine for performing artificial flight8 ,why not stick to ,nature8 ,in reply to this1 ,i would say that even ,nature has her limits1 beyond which she cannot go4 ,when a boy was told that everything was possible with ,god1 he asked2 8,could ,god make a two-year old calf in five minutes80 ,he was told that ,god certainly could4 8,but10 said the boy1 8would the calf be two years old80 ,it appears to me that there is nothing in ,nature which is more efficient1 or gets a better grip on the water than a well-made screw propeller1 and no doubt there would have been fish with screw propellers1 providing that ,dame ,nature could have made an animal in two pieces4 ,it is very evident that no living creature could be made in two pieces1 and two pieces are necessary if one part is stationary and the other revolves2 however1 the tails and fins very often approximate to the action of the propeller blades2 they turn first to the right and then to the left1 producing a sculling effect which is practically the same4 ,this argument might also be used against locomotives4 ,in all ,nature1 we do not find an animal travelling on wheels1 but it is quite possible that a locomotive might be made that would walk on legs at the rate of two or three miles an hour4 ,but locomotives with wheels are able to travel at least three times as fast as the fleetest animal with legs1 and to continue doing so for many hours at a time1 even when attached to a very heavy load4 ,in order to build a flying machine with flapping wings1 to exactly imitate birds1 a very complicated system of levers1 cams1 cranks1 etc41 would have to be employed1 and these of themselves would weigh more than the wings would be able to lift4 ,however1 it is quite possible to approach very closely to the motion of a bird's wings with no reciprocating or vibrating parts1 and without flapping at all4 ,illustration3 ,fig4 #dc4--,plan of a hlicoptre machine showing position of the screws4 ,owing to the tilting of the shaft forward1 the blades present no angle when at d1 d1 but #aj at c1 c1 while at f1 f their angle above the horizontal is #e4 ,the horizontal arrows show the direction of the wind against the machine4 ,illustration3 ,fig4 #dd4--,shows the position of the blades of a hlicoptre as they pass around a circle1 when the angle of the shaft and the angle of the blades are the same4 ,in ,fig4 #dc1 ,i have shown a plan of a hlicoptre machine in which two screws are employed rotating in opposite directions1 a1 a1 being the port screw2 b1 b1 the starboard screw2 and d1 d1 the platform for the machinery and operator4 ,the screws should be #bj feet in diameter and made of wood4 ,suppose now that the pitch of these screws is such that the extremities of the blades have an angle of #e2 if now we tilt the shaft forward in the direction of flight to the extent of #e1 we shall completely wipe out the angle of inclination of the blades when at b 7,fig4 #dd71 whereas it will be observed that the pitch as regards the horizontal will be increased to #aj at a1 on the outer side1 and remain unchanged at c1 and d4 ,if the peripheral velocity of the blades is1 say1 four times the velocity at which the machine is expected to travel1 the blades will get a good grip on the air at c1 d1 but when they travel forward and encounter air which is travelling at a high velocity in the opposite direction1 they assume the position shown at b4 ,if the pitch of the screw blades was a little more than the angle of the shaft1 the blades at b would also produce a lifting effect1 and as the velocity with which they pass through the air is extremely high1 a very strong lifting effect would be produced even if the angle was not more than #a in #dj4 ,by tracing the path and noting the position of the ends of the blades as they pass completely around the circle as shown 7,fig4 #dd71 it will be observed that they very closely resemble the motion of a bird's wing4 ,i have no doubt that a properly made machine on this plan would be highly satisfactory1 but one should not lose sight of the fact that even with a machine of this type1 well designed and sufficiently light to sustain itself in the air while flying1 it would still be necessary for it to move along rapidly when starting in order to get the necessary grip on the air4 ,upon starting the engine1 in a machine of this kind1 a very strong downward draught of air would be produced1 and the whole power of the engines would be used in maintaining this downward blast1 but if the machine should at the same time be given a rapid forward motion sufficiently great to bring the blades into contact with new air1 the inertia of which had not been disturbed1 and which was not moving downwards1 the lifting effect would be increased sufficiently to lift the machine off the ground4 ,it would1 therefore1 work very much like an aeroplane machine4 ,it would also be possible to provide a third screw of less dimensions and running at a less velocity1 to push the machine forward1 so as not to render it necessary to give such a decided tilt to the shafts4 ,as before stated1 great care should be taken in designing and making the framework of flying machines1 and no stone should be left unturned in order to arrive at the greatest degree of lightness without diminishing the strength too much2 then1 again1 elasticity should be considered4 ,if we use a thin tube all the material is at the surface1 far from the neutral centre1 and great stiffness is obtained1 but such a tube will not stand so much deflection as a piece of wood2 then1 again1 wood is cheaper than steel1 and in case of an accident1 repairs are very quickly and easily made4 ,wood1 however1 cannot be obtained in long lengths absolutely free from blemishes4 ,it therefore becomes necessary to find some way of making these long members of flying machines of such wood as may be found suitable in the following table4 ---------------------------------------- ----------------- ,strength ,weight of a per ,sq4 ,in4 ,cube ,foot ,relative in ,lbs4 in ,lbs4 ,value4 ---------------------------------------- ----------------- ,alder1 444 #ej 444 ,apple1 444 #diefb 444 ,ash1 ,english1 #af1jjj #ebhab #cjbi ,ash1 ,white1 #ad1jjj #dcabe #cbdf ,bamboo1 #f1cjj #be #beb ,beech1 ,english1 #aa1ejj #ecbe #baei ,birch1 #ae1jjj #de #cccc ,box1 ,african1 #bc1jjj 444 444 ,france1 444 #hc 444 ,cedar1 ,american1 #aa1fjj #cejfb #ccjh ,deal1 ,christiania1 #ab1djj 444 444 ,ebony1 #bg1jjj #hcahg #cbdf ,elm1 #f1jjj #cefbe #afhd ,rock1 #ac1jjj #ej #bfj ,fir1 ,norway ,spruce1 444 #cb 444 ,dantzic1 444 #cfcge 444 ,hackmatack1 #ab1jjj #cg #cbdc ,hickory1 #aa1jjj #die #bbbb ,ironwood1 444 #fahge 444 ,juniper1 444 #cfcge 444 ,lance1 #bc1jjj #de #eaaa ,lignum-,vit1 #aa1hjj #hccab #adaf ,lime1 444 #ejbe 444 ,locust1 #bj1ejj #dee #deje ,mahogany1 ,honduras1 #ba1jjj #ce #fjj ,spanish1 #ab1jjj #ecbe #bbec ,maple1 444 #dfhge 444 ,oak1 ,african1 #i1ejj #eadcg #ahdg ,canadian1 444 #ede 444 ,dantzic1 #d1bjj #dgdcg #hhe ,english1 #g1ega #ecfbe #adab ,live1 #af1chj #ffge #bded ,pa1 seasoned1 #bj1ccc 444 444 ,white1 #af1ejj #ecge #cjfi ,va1 #be1bbb 444 444 ,pine1 ,norway1 #ad1jjj #dfbe #cjbg ,pitch1 444 #dabe 444 ,red1 #ac1jjj #cfhge #cebe ,white1 #aa1hjj #cdfbe #cdjh ,yellow1 #ac1jjj #bhhab #deab ,va1 #ai1bjj 444 444 ,poplar1 #g1jjj #bcicg #bibd ,white1 444 #ccjfb 444 ,redwood1 ,cal1 #aj1hcc 444 444 ,spruce1 #ab1djj #cabe #cifh ,sycamore1 #ac1jjj #chicg #ccch ,tamarack1 444 #bcicg 444 ,teak1 ,african1 #ba1jjj #fabe #cdbh ,indian1 #ae1jjj #dajfb #cfec ,walnut1 444 #daicg 444 ,black1 #af1fcc #cabe #ecbb ,michigan1 #ag1ejj 444 444 ,willow1 #ac1jjj #cfefb #ceee ---------------------------------------- ----------------- ,the relative value of different kinds of wood is shown in this table1 and it will be observed that some are much more suitable for the purpose than others4 ,the true value of a wood to be used in flying machines is only ascertained by considering its strength in comparison with its own weight--that is1 the wood which is strongest in proportion to its weight is the best4 ,it will be seen that ,honduras mahogany stands at the head of the list1 but ,american white pine is very good for certain purposes1 as it is light1 strong1 easily obtained1 and takes the glue very well indeed4 ,in ,fig4 #de1 ,i have shown a good system of producing the long members necessary in flying machines4 ,i will admit that it costs something to fit up and produce the kind of joints which ,i have shown1 but when the members are once made1 they are exceedingly strong and stiff4 ,fig4 #df shows sections of the struts1 and these may be made of either straight-grained ,honduras mahogany or of lance wood2 either answers the purpose very well1 because being very strong and straight-grained1 permits the struts to be made of such a shape and size as to offer very little resistance in cutting their way through the air4 ,the framework of the aeroplane unless carefully designed will offer great resistance to being driven through the air4 ,suppose that the bottom member of the truss 7,fig4 #dg7 is straight1 and the top one curved in the direction shown2 no matter how taut the cloth may be drawn1 the pressure of the air will cause it to bag upwards between the different trusses1 so as to present very nearly the correct curve which is necessary to produce the maximum lifting effect1 and without offering too much resistance to the air2 however1 one must not forget for a single moment that the air flows over both sides of the aeroplane4 ,when the aeroplane is made very thick in the middle and sharp at the edges 7,fig4 #dh71 with the bottom side dead level1 it produces a decided lifting effect no matter which way it is being propelled through the air4 ,this is not because the bottom side produces any lifting effect of itself1 but because the air running over the top follows the surface4 ,the aeroplane encounters air which is not moving at all4 ,the air is first moved upwards slightly1 but it also has to run down the incline to the rear edge of the aeroplane1 so that1 when it is discharged1 it has a decided downward trend2 therefore1 the air passing over the top side instead of under the bottom side1 produces the lifting effect1 showing that the top side of an aeroplane as well as the lower side should be considered4 ,the top side should1 therefore1 be free from all obstructions4 ,illustration3 ,fig4 #de4--,system of splicing and building up wooden members4 ,when they have to be curved and to keep their shape1 they should be bent at the curve at the time of being glued together1 and joined in the middle as at d4 ,illustration3 ,fig4 #df4--;,cross-section of struts4 ,illustration3 ,fig4 #dg4--,truss suitable for use with flying machines1 having aeroplanes about #f feet to #h feet wide4 ,the top of the aeroplane as well as the bottom should be covered with some light material1 if the very best results are to be obtained4 ,in another chapter ,i have shown a form of fabric-covered aeroplane1 made by myself1 that was not distorted in the least by the air pressure1 and produced just as good effects as it would have done if it had been carefully carved out of a piece of wood4 ,on more than one occasion ,lord ,kelvin came to my place2 he said that my workshop was a perfect museum of invention4 ,at the ,oxford ,meeting of the ,british ,association for the ,advancement of ,science1 ,lord ,salisbury in the chair1 ,i was much gratified when ,lord ,kelvin said that he had examined my work1 and found that it was beautifully designed and splendidly executed4 ,he complimented me very highly indeed4 ,while at my place1 he said that the most ingenious thing that he had seen was the way ,i had prevented my aeroplanes from being distorted by the air4 ,he spoke of this several times with great admiration1 and1 ,i think1 if the fabric-covered aeroplane is to be used at all1 that my particular system will be found altogether the best4 ,illustration3 ,fig4 #dh4--,the paradox aeroplane that lifts no matter in which direction it is being driven4 ,illustration3 ,fig4 #di4--,the ,antoinette motor4 ,regarding the motors now being employed1 ,i think that there is still room for a great deal of improvement in the direction of greater lightness1 higher efficiency and reliability4 ,at the present time1 flying machine motors have such small cylinders1 the rotation is so rapid1 and the cooling appliances so imperfect1 that the engine soon becomes intensely heated1 and then its efficiency is said to fall off about #dj or #ej per cent41 some say even #fj per cent4 ,this is probably on account of the high temperature of the cylinder1 piston1 and air inlet4 ,the heat expands the air as it enters1 so that the actual weight of air in the cylinder is greatly reduced1 and the engine power reduced in a corresponding degree4 ,there is no trouble about cooling the motor1 and a condenser of high efficiency may be made that will cool the water perfectly1 and1 at the same time1 lift a good deal more than its own weight4 ,all the conditions are favourable for using a very effective atmospheric condenser 7see ,figs4 #cj and #ca74 ,water may be considered as #bdjj times as efficient as air1 volume for volume1 in condensing steam4 ,when a condenser is made for the purpose of using water as a cooling agent1 a large number of small tubes may be closely grouped together in a box1 and the water pumped in at one end of the box and discharged at the other end through relatively small openings2 but when air is employed1 the tubes or condensing surfaces must be widely distributed1 so that a very large amount of air is encountered1 and air which has struck one tube and become heated must never touch a second tube 7see ,figs4 #cj and #ca1 also ,appendix74 ,illustration3 ,fig4 #ej4--,section showing the ,antoinette motor1 such as used in the ,farman and ,de la ,grange machines4 ,fig4 #ea shows a pneumatic buffer which ,i have designed1 in which a1 a1 is a steel tube highly polished on the inside2 b1 a nozzle for connecting the air-pump1 which is of the bicycle variety2 c1 a nipple to which is attached a strong india-rubber bulb2 d1 a piston which is made air-tight by a leather cup2 and f1 the connection to the lever carrying the wheels on which the machine runs4 ,while the machine is at a state of rest on the ground1 the piston-rod d1 is run out to its full extent1 and supports the weight of the machine--the pressure being about #aej lbs4 to the square inch4 ,when1 however1 the machine comes violently down to the earth1 the piston is pushed inward1 compressing the air1 and by the time it has travelled1 say1 one-half the stroke1 the air pressure will have mounted to #cjj lbs4 to the square inch4 ,at this point1 the rubber bulb c1 ought to burst and allow the compressed air to escape under a high pressure4 ,air escaping through a relatively small hole absorbs the momentum of the descent and brings the machine to a state of rest without a destructive shock4 ,it is1 of course1 necessary for the navigator to select a broad and level field for descent1 and then to approach it from the leeward and slow up his machine as near the ground as possible1 tilting the forward end upwards in order to arrest its forward motion1 and touching the ground while still moving against the wind at a fairly high velocity4 ,if all these points are studied1 and well carried out1 very little danger will result2 then1 again1 the aeroplanes b1 b1 and the forward rudder d 7,fig4 #da71 should be so arranged that1 in case of an accident1 their outward sides may be instantly turned upwards1 in such a manner as to prevent the machine from plunging1 and keep it on an even keel while the engines are not running4 ,illustration3 ,fig4 #ea4--,pneumatic buffer--a1 a1 cylinder2 b1 attachment for pumping up2 c1 air outlet1 covered with a rubber thimble made to burst under about #cjj lbs4 pressure2 d1 the piston4 ,,steering ,,by ,,means ,,of ,a ,,gyroscope4 ,a ship at sea has only to be steered in a horizontal direction2 the water in which it is floated assures its stability in a vertical direction2 but when a flying machine is once launched in the air1 it has to be steered in two directions--that is1 the vertical and the horizontal4 ,moreover1 it is constantly encountering air currents that are moving with a much higher velocity than any water currents that have ever to be encountered4 ,it is1 therefore1 evident that1 as far as vertical steering is concerned1 it should be automatic4 ,some have suggested shifting weights1 flowing mercury1 and swinging pendulums2 but none of these is of the least value1 on account of the swaying action which always has to be encountered4 ,a pendulum could not be depended upon for working machinery on board a ship1 and the same laws apply to an airship4 ,we have but one means at our disposal1 and that is the gyroscope4 ,when a gyroscope is spun at a very high velocity on a vertical axis1 with the point of support very much above the center of gyration1 it has a tendency to maintain a vertical axis2 a horizontal or swinging motion of its support will not cause it to swing like a pendulum4 ,it therefore becomes possible by its use to maintain an airship on an even keel4 ,in a steam steering apparatus1 such as is used on shipboard1 it is not sufficient to apply steam-power to move the rudders1 unless some means are provided whereby the movement of the rudder closes off the steam1 otherwise the rudder might continue to travel after the effect had been produced1 and ultimately be broken2 and so it is with steering a flying machine in a vertical direction4 ,whenever the fore and aft rudders respond to the action of the gyroscope and are set in motion1 they must at once commence to shut off the power that works them1 otherwise they would continue to travel4 ,in the photograph 7,fig4 #eb7 ,i have shown an apparatus which ,i constructed at ,baldwyn's ,park4 ,it will be seen that the gyroscope is enclosed in a metal case2 a tangent screw1 just above the case1 rotates a pointer around a small disc1 which admits of the speed of the gyroscope being observed4 ,steam is admitted through a universal joint1 descends through the shaft and escapes through a series of small openings placed at a tangent1 so as to give rotation to the wheel after the manner of a ,barker's mill4 ,the casing about the rotating wheel is extremely light as relates to the wheel1 so that1 when the gyroscope is once spun on a vertical axis1 the rest of the apparatus may be tilted in any direction1 while the gyroscope and its attachments maintain a vertical axis4 ,the gyroscope and its attachments are suspended from a long steel tube1 which in reality is a steam cylinder4 ,the sleeve which supports the gyroscope moves freely in a longitudinal direction1 and the whole is held in position by a triple-threaded screw on the small tube above the cylinder4 ,the steam is admitted through a piston value operated by a species of link motion1 as shown4 ,the piston-rod extends to each end of the cylinder1 and regulates the rudders by pulling a small wire rope1 the travel of the piston being about #h feet4 ,at the end of the cylinder 7not shown7 the piston-rod is provided with an arm and a nut which engages the small top tube--this tube being provided with a long spiral--so that1 as the piston moves1 the top tube is rotated1 and thereby slides the gyroscope's support1 and changes its position as relates to the piston valve4 ,it will1 therefore1 be seen that the action is the same as with the common steam steering gear used on shipboard4 ,a little adjusting screw at the right hand of the print is shown4 ,the upward projecting arm of the bell crank lever is for the purpose of attaching the wooden handle1 making it possible to move the connecting-rod instantly into a position where the steam piston will move the rudders into the position shown 7,fig4 #ef74 ,i copy the following from a description which ,i wrote of this apparatus at the time3-- 8,,gyroscope ,,apparatus ,,for ,,automatically ,,steering ,,machine ,,in ,a ,,vertical ,,direction4 8,this apparatus consists of a long steam cylinder which is provided with a piston1 the piston-rod extending beyond the cylinder at each end2 the ropes working the fore and aft rudders are attached to the ends of this piston-rod1 and steam is supplied through an equilibrium valve4 ,the gyroscope is contained in a gunmetal case1 and is driven by a jet of steam entering through the trunnions4 ,when the gyroscope is spinning at a high velocity1 the casing holding it becomes very rigid and is not easily moved from its vertical position4 ,if the machine rears or pitches1 the cylinder and valve are moved with the machine while the gyroscope remains in a vertical position4 ,this causes the steam valve to be moved so as to admit steam into the cylinder and move the piston in the proper direction to instantly bring the machine back into its normal position4 ,as the fore and aft rudders are moved1 the long tubular shaft immediately over the steam cylinder is rotated in such a manner as to move the whole gyroscope in the proper direction to close off the steam4 ,the apparatus may be made to regulate at any angle by adjusting the screw which regulates the position of the tubular shaft4 ,the link that suspends the end of the steam valve connecting-rod is supported by a bell crank lever1 and while the machine is moving ahead1 the lever occupies the position shown in the photograph 7,fig4 #eb72 but if the machinery and engine stop1 the bell crank lever may be moved so as to throw the connecting-rod below the centre1 when the steam will move the piston in the proper direction to throw both the rudders into the falling position1 as shown in ,fig4 #ef40 ,illustration3 ,fig4 #eb4--;,gyroscope1 used for the control of the fore and aft horizontal rudders1 thus keeping the machine on an even keel while in the air4 ,illustration3 ,fig4 #ec4--;,in order to adjust the lifting effect so that it was directly over the centre of gravity1 and to test the action of my fore and aft horizontal rudders1 ,i ran the machine along the steel rail i1 i1 and adjusted my weights and aeroplanes in such a manner that1 when the machine was run at a speed of #cj miles an hour along the track1 with the rudders adjusted in the manner shown1 the front wheel j1 was raised from the steel track and the small wheel m1 brought into contact with the upper track h4 ,when the rudder b1 b1 is in this position1 it produces a strong lifting effect1 while the rudder c1 c1 does not lift at all4 ,illustration3 ,fig4 #ed4--,this shows the rudders placed in such a position that b1 b1 does not lift at all1 while c1 is placed at such an angle as to produce a strong lifting effect1 especially so as it is in the blast of the screws d1 d4 ,with the rudders in this position1 and at a speed of #cj miles an hour1 ,i was able to lift the rear wheels k1 k1 off the steel rails and to bring the small wheel l1 in contact with the upper track h4 ,these experiments showed that the machine could be tilted in either direction by changing the position of the rudder4 ,illustration3 ,fig4 #ee4--,when the rudders were placed in the position shown1 and the machine was run over the track at a rate of #dj miles an hour1 all the weight was lifted off the wheels1 j1 and k1 and both the small wheels m1 and l1 engaged the upper track4 ,illustration3 ,fig4 #ef4--;,in case of a breakdown or failure of the engines when the machine is in flight1 it is necessary to place the rudders in the position shown1 in order to prevent the machine from diving to the earth4 ,when the rudders are in this position1 a rapid and destructive descent is not possible1 as the machine will preserve an even keel while falling4 ,,chapter ,,vii4 ,,the ,,shape ,,and ,,efficiency ,,of ,,aeroplanes4 ,in ,prof4 ,langley's lifetime1 we had many discussions regarding the width and shape of aeroplanes4 ,the ,professor had made many experiments with very small and narrow planes1 and was extremely anxious to obtain some data regarding the effect that would be produced by making the planes of greater width4 ,he admitted that by putting some two or three aeroplanes tandem1 and all at the same angle1 the front aeroplane a 7,fig4 #eg71 would lift a great deal more than b1 and that c1 would lift still less4 ,he suggested the arrangement shown at a1 b1 c1 in which b is set at such an angle as to give as much additional acceleration to the air as it had received in the first instance by passing under a1 and that c1 should also increase the acceleration to the same extent4 ,with this arrangement1 the lifting effect of the three aeroplanes ought to be the same1 but ,i did not agree with this theory4 ,it seemed to me that it would only be true if it dealt with the volume of air represented between j1 and k1 and that he did not take into consideration the mass of air between k1 and l1 that had to be dealt with1 and which would certainly have some effect in buoying up the stream of air1 j1 k4 ,prof4 ,langley admitted the truth of this1 and said that nothing but experiment would demonstrate what the real facts were4 ,but it was a matter which ,i had to deal with4 ,i did not like the arrangement a1 b1 c1 as the angle was so sharp1 especially at c1 that a very large screw thrust would be necessary4 ,i therefore made a compromise on this system which is shown at a1 b1 c4 ,in this case a1 has an inclination of #a in #aj1 b an inclination of #a in #f1 and c an inclination of #a in #e4 ,it will be seen that this form1 which is shown as one aeroplane at a1 b1 c1 is a very good shape4 ,it is laid out by first drawing the line c1 d1 dropping the perpendicular equal to one-tenth of the distance between c and d1 and then drawing a straight line from c1 through e1 to f1 where another perpendicular is dropped1 and half the distance between d and e laid off1 and another straight line drawn from e1 through g1 to h1 and the perpendicular h1 i1 laid off the same as f1 g4 ,we then have four points1 and by drawing a curve through these1 we obtain the shape of the aeroplane shown above1 which is an exceedingly good one4 ,this shape1 however1 is only suitable for velocities1 up to #dj miles per hour2 at higher velocities1 the curvature would be correspondingly reduced4 ,illustration3 ,fig4 #eg4--;,diagram showing the evolution of a wide aeroplane4 ,,the ,,action ,,of ,,aeroplanes ,,and ,,the ,,power ,,required ,,expressed ,,in ,,the ,,simplest ,,terms4 ,in designing aeroplanes for flying machines1 we should not lose sight of the fact that area alone is not sufficient4 ,our planes must have a certain length of entering edge--that is1 the length of the front edge must bear a certain relation to the load lifted4 ,an aeroplane #aj feet square will not lift half as much for the energy consumed as one #b feet wide and #ej feet long2 therefore1 we must have our planes as long as possible from port to starboard4 ,at all speeds of #dj miles per hour or less1 there should be at least #a foot of entering edge for every #d lbs4 carried4 ,however1 at higher speeds1 the length may be reduced as the square of the speed increases4 ,an aeroplane #a foot square will not lift one-tenth as much as one that is #a foot wide and #aj feet long4 ,this is because the air slips off at the ends1 but this can be prevented by a thin flange1 or la ,hargrave's kites4 ,an aeroplane #b feet wide and #ajj feet long placed at an angle of #a in #aj1 and driven edgewise through the air at a velocity of #dj miles per hour1 will lift #be lbs4 per square foot4 ,but as we find a plane #ajj feet in length too long to deal with1 we may cut it into two or more pieces and place them one above the other--superposed4 ,this enables us to reduce the width of our machine without reducing its lifting effect2 we still have #ajj feet of entering edge1 we still have #bjj feet of lifting surface1 and we know that each foot will lift #be lbs4 at the speed we propose to travel4 #bjj #be #ejj2 therefore our total lifting effect is #ejj lbs41 and the screw thrust required to push our aeroplane through the air is one-tenth of this1 because the angle above the horizontal is #a in #aj4 ,we1 therefore1 divide what ,prof4 ,langley has so aptly called the 8lift0 by #aj2 #ejj_/aj #ej4 ,it will be understood that the vertical component is the lift1 and the horizontal component the drift1 the expression 8drift0 also being a term first applied by ,prof4 ,langley4 ,our proposed speed is #dj miles per hour1 or #c1ebj feet in a minute of time4 ,if we multiply the drift in pounds by the number of feet travelled in a minute of time1 and divide the product thus obtained by #cc1jjj1 we ascertain the ,h4,p4 required-- #ej #c1ebj ---------- #ecc4 #cc1jjj ,it therefore takes #ecc ,h4,p4 to carry a load of #ejj lbs4 at a rate of #dj miles per hour1 allowing nothing for screw slip or atmospheric resistance due to framework and wires4 ,but we find we must lift more than #ejj lbs41 and as we do not wish to make our aeroplanes any longer1 we add to their width in a fore and aft direction--that is1 we place another similar aeroplane1 also #b feet wide1 just aft of our first aeroplane4 ,this will1 of course1 have to engage the air discharged from the first1 and which is already moving downwards4 ,it is1 therefore1 only too evident that if we place it at the same angle as our first one--viz41 #a in #aj--;it will not lift as much as the first aeroplane1 and we find that if we wish to obtain a fairly good lifting effect1 it must be placed at an angle of #a in #f4 ,under these conditions1 the screw thrust for this plane will be #a_/fth part of the lift1 or #hhh ,h4,p4 against #ecc ,h4,p4 with our first aeroplane4 ,in order to avoid confusion1 we will call our first plane a1 our second plane b1 and the third c1 the same as in ,fig4 #eg4 ,still we are not satisfied1 we want more lift1 we therefore add still another aeroplane as shown 7c1 ,fig4 #eg74 ,this one has to take the air which has already been set in motion by the two preceding planes a and b1 so in order to get a fair lifting effect1 we have to place our third plane at the high angle of #a in #e4 ,at this angle1 our thrust has to be #a_/eth of the lifting effect1 and the ,h4,p4 required is twice as much per pound carried as with the plane a1 where the angle was #a in #aj2 therefore1 it will take #ajff ,h4,p4 to carry #ejj lbs4 ,as there is no reason why we should have three aeroplanes placed tandem where one would answer the purpose much better1 we convert the whole of them into one1 as shown 7a1 b1 c1 ,fig4 #eg71 and by making the top side smooth and uniform1 we get the advantage of the lifting effect due to the air above the aeroplane as well as below it4 ,the average ,h4,p4 is therefore #ecc #hhh #ajff #c #hbi ,h4,p4 for each plane1 or #be ,h4,p4 for the whole1 which is at the rate of #fj lbs4 to the ,h4,p41 all of which is used to overcome the resistance due to the weight and the inclination of the aeroplanes1 and which is about half the total power required4 ,we should allow as much more for loss in screw slip and atmospheric resistance due to the motor1 the framework1 and the wires of the machine4 ,if1 however1 the screw is placed in the path of the greatest resistance1 it will recover a portion of the energy imparted to the air4 ,we shall1 however1 require a #ej ,h4,p4 motor1 and thus have #cj lbs4 to the ,h4,p4 ,from the foregoing it will be seen that at a speed of #dj miles an hour1 the weight per ,h4,p4 is not very great4 ,if we wish to make a machine more efficient1 we must resort to a multitude of very narrow superposed planes1 or sustainers1 as ,mr4 ,philipps calls them1 or we must increase the speed4 ,if an aeroplane will lift #be lbs4 per square foot placed at an angle of #a in #aj1 and driven at a velocity of #dj miles an hour1 the same aeroplane will lift #abe lbs4 if placed at an angle of #a in #bj1 and as the lifting effect varies as the square of the velocity1 the same plane will lift as much more at #fj miles per hour1 as #fj is greater than #dj--that is1 #bha lbs4 per square foot instead of #abe lbs4 ,at this high speed1 providing that the width of the plane is not more than #c feet1 it need be only slightly curved and have a mean angle of #a in #bj4 ,an aeroplane #ajj feet long and #c feet wide would have #cjj square feet of lifting surface1 each of which would lift #bha lbs41 making the total lifting effect #hdc lbs4 #hdc #bj #dbae1 which is the screw thrust that would be necessary to propel such a plane through the air at a velocity of #fj miles per hour4 #fj miles per hour is #e1bhj feet in a minute1 therefore the ,h4,p4 required is #dbae #e1bhj #cc1jjj #fg ,h4,p4 ,dividing the total lifting effect #hdc by #fg1 we have #hdc #fg #abeh1 the lift per ,h4,p4 ,if we allow one-half for loss in friction1 screw slip1 etc41 we shall be carrying a load of #hdc lbs4 with #acd ,h4,p4 ,it will1 therefore1 be seen that a velocity of #fj miles an hour is much more economical in power than the comparatively low velocity of #dj miles an hour2 moreover1 it permits of a considerable reduction in the size and weight of the machine1 and this diminishes the atmospheric resistance4 ,illustration3 ,fig4 #eh4--;,in a recently published mathematical treatise on ,aerodynamics1 an illustration is shown1 representing the path that the air takes on encountering a rapidly moving curved aeroplane4 ,it will be observed that the air appears to be attracted upwards before the aeroplane reaches it1 exactly as iron filings would be attracted by a magnet1 and that the air over the top of the aeroplane is thrown off at a tangent1 producing a strong eddying effect at the top and rear4 ,just why the air rises up before the aeroplane reaches it is not plain1 and as nothing could be further from the facts1 mathematical formulas founded on such a mistaken hypothesis can be of but little value to the serious experimenter on flying machines4 ,illustration3 ,fig4 #ei4--;,an illustration from another scientific publication also on the ,dynamics of ,flight4 ,it will be observed that the air in striking the underneath side of the aeroplane is divided into two streams1 a portion of it flowing backwards and over the top of the edge of the aeroplane where it becomes compressed4 ,an eddy is formed on the back and top of the aeroplane1 and the air immediately aft the aeroplane is neither rising nor falling4 ,just how these mathematicians reason out that the air in striking the front of the aeroplane would jump backwards and climb up over the top and leading edge against the wind pressure is not clear4 ,illustration3 ,fig4 #fj4--,this shows another illustration from the same mathematical work1 and represents the direction which the air is supposed to take on striking a flat aeroplane4 ,with this1 the air is also divided1 a portion moving forward and over the top of the aeroplane where it is compressed1 leaving a large eddy in the rear1 and1 as the dotted lines at the back of the aeroplane are horizontal1 it appears that the air is not forced downwards by its passage4 ,here1 again1 formula founded on such hypothesis is misleading in the extreme4 ,illustration3 ,fig4 #fa4--,this shows the shape and the practical angle of an aeroplane4 ,this angle is #a in #aj1 and it will be observed that the air follows both the upper and the lower surface1 and that it leaves the plane in a direction which is the resultant of the top and bottom angle4 ,illustration3 ,fig4 #fb4--,this shows an aeroplane of great thickness1 placed at the highest angle that will ever be used--#a in #d--;and even with this the air follows the upper and lower surfaces4 ,no eddies are formed1 and the direction that the air takes after leaving the aeroplane is the resultant of the top and bottom angles4 ,illustration3 ,fig4 #fc4--,section of a screw blade having a rib on the back4 ,the resistance caused by this rib is erroneously supposed to be skin friction4 ,illustration3 ,fig4 #fd4--,shows a flat aeroplane placed at an angle of #de1 an angle which will never be used in practical flight1 but at this angle the momentum of the approaching air and the energy necessary to give it an acceleration sufficiently great to make it follow the back of the aeroplane are equal1 and at this point1 the wind may either follow the surface or not4 ,sometimes it does and sometimes it does not4 ,see experiments with screws4 ,illustration3 ,fig4 #fe4--,the aeroplane here shown is a mathematical paradox4 ,this aeroplane lifts1 no matter in which direction it is driven4 ,it encounters air which is stationary and leaves it with a downward trend2 therefore it must lift4 ,however1 if we remove the section b1 and only subject a to the blast1 as shown at ,fig4 #ff1 no lifting effect is produced4 ,on the contrary1 the air has a tendency to press a1 downwards4 ,the path which the air takes is clearly shown2 this is most important1 as it shows that the shape of the top side is a factor which has to be considered4 ,all the lifting effect in this case is produced by the top side4 ,illustration3 ,fig4 #ff4 ,illustration3 ,fig4 #fg4--;,in this drawing a represents an aeroplane1 or a bird's wing4 ,suppose that the wind is blowing in the direction of the arrows2 the real path of the bird as relates to the air is from i to j1--that is1 the bird is falling as relates to the air although moving on the line c1 d1 against the wind4 ,in some cases1 a bird is able to travel along the line g1 h1 instead of in a horizontal direction1 thus rising and apparently flying into the teeth of the wind at the same time4 ,,some ,,recent ,,machines4 ,professor ,s4 ,p4 ,langley1 of the ,smithsonian ,institute1 ,washington1 ,d4,c41 made a small flying model in #ahif4 ,this1 however1 only weighed a few pounds2 but as it did actually fly and balance itself in the air1 the experiment was of great importance1 as it demonstrated that it was possible to make a machine with aeroplanes so adjusted as to steer itself automatically in a horizontal direction4 ,in order to arrive at this result1 an innumerable number of trials were made1 and it was only after months of careful and patient work that the ,professor and his assistants succeeded in making the model fly in a horizontal direction without rearing up in front1 and then pitching backwards1 or plunging while moving forward4 ,the ,wright ,brothers of ,dayton1 ,ohio1 ,u4,s4,a41 often referred to as 8the mysterious ,wrights10 commenced experimental work many years ago4 ,the first few years were devoted to making gliding machines1 and it appears that they attained about the same degree of success as many others who were experimenting on the same lines at the same time2 but they were not satisfied with mere gliding machines1 and so turned their attention in the direction of motors4 ,after some years of experimental work1 they applied their motor to one of their large gliding machines1 and it is said that with this first machine they actually succeeded in flying short distances4 ,later on1 however1 with a more perfect machine1 they claim to have made many flights1 amongst which ,i will mention three3 #ab miles in #bj minutes1 on ,september #bith1 #aije2 #bjge miles in #cc minutes1 on ,october #dth2 and #bdb miles in #ch minutes1 on ,october #eth of the same year4 ,as there seems to be much doubt regarding these alleged flights1 we cannot refer to them as facts until the ,wright ,brothers condescend to show their machine and make a flight in the presence of others2 nevertheless1 ,i think we are justified in assuming that they have met with a certain degree of success which may or may not be equal to the achievements of ,messrs ,farman and ,de la ,grange4 ,it is interesting to note in this connection that all flying machines that have met with any success have been made on the same lines2 all have superposed aeroplanes1 all have fore and aft horizontal rudders1 and all are propelled with screws2 and in this respect they do not differ from the large machine that ,i made at ,baldwyn's ,park many years ago4 ,i have seen both the ,farman and the ,de la ,grange machines2 they seem to be about the same in size and design1 and what is true of one is equally true of the other2 ,i will1 therefore1 only describe the one that seems to have done the best--the ,de la ,grange4 ,the general design of this machine is clearly shown in the illustrations 7,figs4 #fh and #fi74 ,the dimensions are as follows3 ,the two main aeroplanes are #cbh feet long and #di feet wide2 the tail or after rudder is made in the form of a ,hargrave's box kite1 the top and bottom sides of the box being curved and covered with balloon fabric1 thus forming aeroplanes4 ,this box is #ihd feet long from port to starboard1 and #fef feet wide in a fore and aft direction4 ,the diameter of the screw is #gb feet and it has a mean pitch of #eg feet4 ,the screw blades are two in number and are extremely small1 being only #fc inches wide at the outer end and #cae inches at the inner end1 their length being #ba feet4 ,the space between the fore and aft aeroplanes is #di feet4 ,the total weight is about #a1jjj lbs4 with one man on board4 ,the speed of this machine through the air is not known with any degree of certainty2 it is1 however1 estimated to be #cb to #dj miles per hour4 ,when the screw is making #a1ajj revolutions per minute1 the motor is said to develop #ej ,h4,p4 ,illustration3 ,fig4 #fh4--,the ,de la ,grange machine on the ground and about to make a flight4 ,illustration3 ,fig4 #fi4--,the ,de la ,grange machine in full flight and very near the ground4 ,in the following calculations1 ,i have assumed that the machine has the higher speed--#dj miles per hour4 ,i have been quite unable to obtain any reliable data regarding the angle at which the aeroplanes are set1 but it would appear that the angle is about #a in #aj4 ,the total area of the two main aeroplanes is #cbad square feet4 ,a certain portion of the lower main aeroplane is cut away1 but this is compensated for by the forward horizontal rudder placed in the gap thus formed4 ,the two rear aeroplanes forming the tail of the machine have an area of #abheg square feet4 ,the area of all the aeroplanes is1 therefore1 #dej square feet4 ,as the weight of the machine is #a1jjj lbs41 the lift per square foot is #bb lbs4 ,assuming that the angle of the aeroplanes is #a in #aj1 the screw thrust would be #ajj lbs41 providing1 however1 that the aeroplanes were perfect and no friction of any kind was encountered4 ,forty miles per hour is at the rate of #c1ebj feet in a minute of time1 therefore1 7#c1ebj #ajj7_/cc1jjj #ajff ,h4,p4 ,if we allow another #aj ,h4,p4 for atmospheric resistance due to the motor1 the man1 and the framework of the machine1 it would require #bjff ,h4,p4 to propel the machine through the air at the rate of #dj miles per hour4 ,if the motor actually develops #ej ,h4,p41 #bi ,h4,p4 will be consumed in screw slip and overcoming the resistance due to the imperfect shape of the screw4 ,the blades of the ,de la ,grange screw propeller are extremely small1 and the waste of energy is1 therefore1 correspondingly great--their projected area being only #af square feet for both blades4 ,allowing #bjj lbs4 for screw thrust1 we have the following3 #bjj_/afj #abe lbs4 pressure per square foot on the blades4 ,if we multiply the pitch of the screw in feet by the number of revolutions per minute1 we find that if it were travelling in a solid nut it would advance over #gj miles an hour4 ,by the ,eiffel tower formula ,p #jjjc ,v1 a wind blowing at a velocity of #gj miles per hour produces a pressure of #adg lbs4 per square foot on a normal plane2 therefore1 assuming that the projected area of the screw blades is #af1 we have #af #adg #bceb lbs41 which is only one-fifth part of what the pressure really is when the screws are making #a1ajj turns a minute4 ,it is interesting to note that the ends of the screw blades travel at a velocity of #dad feet per second1 which is about one-half the velocity of a cannon ball fired from an old-fashioned smooth bore4 ,illustration3 ,fig4 #gj4--;,farman's machine in flight4 ,a flying machine has1 of course1 to be steered in two directions at the same time--the vertical and the horizontal4 ,in the ,farman and ,de la ,grange machines1 the horizontal steering is effected by a small windlass provided with a hand wheel1 the same as on a steam launch1 and the vertical steering is effected by a longitudinal motion of the shaft of the same windlass4 ,as the length of the machine is not very great1 it requires very close attention on the part of the man at the helm to keep it on an even keel2 if one is not able to think and act quickly1 disaster is certain4 ,on one occasion1 the man at the wheel pushed the shaft of the windlass forward when he should have pulled it back1 and the result was a plunge and serious damage to the machine2 happily no one was injured1 though some of the bystanders were said to have had very narrow escapes4 ,the remedy for this is to make all hand-steered machines of great length1 which gives more time to think and act2 or1 still better1 to make them automatic by the use of a gyroscope4 ,illustration3 ,fig4 #ga4--;,bleriot's machine4 ,this machine raised itself from the ground1 but as the centre of gravity was very little1 if any1 above the centre of lifting effect1 it turned completely over in the air4 ,illustration3 ,fig4 #gb4--,santos ,dumont's flying machine4 ,,velocity ,,and ,,pressure ,,of ,,the ,,wind4 ,the pressure varies as the square of the velocity or ,p ,v4 ,the old formula for wind blowing against a normal plane was ,p #jjje ,v4 ,the latest or ,eiffel ,tower formula gives a much smaller value1 being ,p #jjjc ,v1 where ,v represents the velocity in miles per hour1 and ,p the pressure in pounds per square foot4 ---------------------------------------- ------------------------ ,,velocity4 ,pressure on a ,character of the ,wind4 -------------------------------,sq4 ,foot4 ,per ,hour4,per ,minute4,per ,second4 ---------------------------------------- ---------------------- ,miles4 ,feet4 ,feet4 ,lbs4 #a #hh #ae #jjc ,barely observable4 #b #agf #bi #jab ,just #c #bfd #dd #jbg perceptible4 #d #ceb #ei #jdh ,light breeze4 #e #ddj #gc #jge ,gentle1 #f #ebh #hh #ajh pleasant #h #gjd #aag #aib wind4 #aj #hhj #adg #c ,fresh breeze4 #ae #a1cbj #bb #fge ,brisk breeze4 #bj #a1gfj #bid #ab ,stiff breeze4 #be #b1bjj #cfg #ahge ,very brisk breeze4 #cj #b1fdj #dd #bg ,high #ce #c1jhj #eac #cfge wind4 #dj #c1ebj #ehg #dh ,very high wind4 #de #c1ifj #ff #fjge ,gale4 #ej #d1djj #gcd #ge ,storm4 #fj #e1bhj #hh #ajh ,great #gj #f1afj #ajbg #adg storm4 #hj #g1jdj #aagb #aib ,hurricane4 #ij #g1ibj #acb #bdc #ajj #h1hjj #adfg #cj ,tornado4 #aaj #i1fhj #afab #cfc #abj #aj1efj #agf #dcb 8,washoe #acj #aa1ddj #aia #ejg zephyrs40#b #adj #ab1cbj #bjec #ehh #aej #ac1bjj #bbj #fge ---------------------------------------- ---------------------- #b ,with apologies to ,mark ,twain4 ,illustration3 ,fig4 #gb;a4--,angles and degrees compared4 ,it will be observed that an angle of #a in #d is practically #ad4 ,,table ,,of ,,equivalent ,,inclinations4 ---------------------------------------- ------- ,rise4 ,sine of ,angle4 ,angle in ,degrees4 ---------------------------------------- ------- #a in #cj1 #jccc #aia #a #be1 #jd #bbi #a #bj1 #je #bhg #a #ah1 #jeee #cah #a #af1 #jfbe #ceh #a #ad1 #jgad #dji #a #ab1 #jhcc #dgh #a #aj1 #a #egc #a #i1 #aaaa #fch #a #h1 #abe #gah #a #g1 #adc #hbb #a #f1 #affg #if #a #e1 #b #aaec #a #d1 #be #addh #a #c1 #cccc #aide ---------------------------------------- ------- ,,table ,,of ,,equivalent ,,velocities4 ---------------------------------------- ----------------------- ,miles ,feet ,feet ,metres ,metres per ,hour4 per ,second4 per ,minute4 per ,minute4 per ,second4 ---------------------------------------- ----------------------- #a1 #ae #hh #bfh #ddg #b1 #bi #agf #ecf #hid #c1 #dd #bfd #hje #acda #d1 #ei #ceb #ajgc #aghh #e1 #gc #ddj #acda #bbce #f1 #hh #ebh #afji #bfhb #h1 #aag #gjd #badf #cegf #aj1 #adg #hhj #bfhb #ddgj #ae1 #bb #a1cbj #djbc #fgje #bj1 #bid #a1gfj #ecfd #hidj #be1 #cfg #b1bjj #fgje #aaagf #cj1 #dd #b1fdj #hjdf #acdaa #ce1 #eac #c1jhj #ichh #aefdf #dj1 #ehg #c1ebj #a1jgbi #aghha #de1 #ff #c1ifj #a1bjg #bjaaf #ej1 #gcd #d1djj #a1cdaa #bbceb #fj1 #hh #e1bhj #a1fjib #bfhbb #gj1 #ajbg #f1afj #a1hgge #cabib #hj1 #aagb #g1jdj #b1adeh #cegfc #ij1 #acb #g1ibj #b1dad #djbcc #ajj1 #adfg #h1hjj #b1fhbb #ddgjd #aaj1 #afab #i1fhj #b1iejb #diagd #abj1 #agf #aj1efj #c1bahd #ecfdd #acj1 #aia #aa1ddj #c1dhff #ehaae #adj1 #bjec #ab1cbj #c1geea #fbehe #aej1 #bbj #ac1bjj #d1jbcc #fgjef ---------------------------------------- ----------------------- ,to convert feet per minute into metres per second1 multiply by #jjejh4 ,,table ,,showing ,,velocity ,,and ,,thrust ,,corresponding ,,with ,,various ,,horse-,,powers4 ---------------------------------------- ------------------ ,velocity ,horse-,power4 in ,miles ---------------------------------------- ---- per ,hour4 #a #aj #bj #cj #dj #ej ---------------------------------------- ---- ,thrust in ,pounds4 ---------------------------------------- ------------- #a1 #cge #c1gej #g1ejj #aa1bej #ae1jjj #ah1gej #e1 #ge #gej #a1ejj #b1bej #c1jjj #c1gej #aj1 #cge #cge #gej #a1abe #a1ejj #a1hge #ae1 #be #bej #ejj #gej #a1jjj #a1bej #bj1 #ahh #ahge #cge #efbe #gej #icge #be1 #ae #aej #cjj #dej #fjj #gej #cj1 #abe #abe #bej #cge #ejj #fbe #ce1 #ajg #ajga #badc #cbad #dbhf #eceg #dj1 #id #ich #ahge #bhac #cge #dfhh #de1 #hc #hcc #affg #bej #cccc #dafg #ej1 #ge #ge #aej #bbe #cjj #cge #fj1 #fc #fbe #abe #ahge #bej #cabe #gj1 #ed #ecf #ajga #afjg #badc #bfgi #hj1 #dg #dfi #ich #adjf #ahge #bcdd #ij1 #db #dag #hcc #abe #affg #bjhc #ajj1 #cge #cge #ge #aabe #aej #ahge ---------------------------------------- ------------- ---------------------------------------- ------------- ,velocity ,horse-,power4 in ,miles ---------------------------------------- per ,hour4 #fj #gj #hj #ij #ajj ---------------------------------------- ,thrust in ,pounds4 ---------------------------------------- --------- #a1 #bb1ejj #bf1bej #cj1jjj #cc1gej #cg1ejj #e1 #d1ejj #e1bej #f1jjj #f1gej #g1ejj #aj1 #b1bej #b1fbe #c1jjj #c1cge #c1gej #ae1 #a1ejj #a1gej #b1jjj #b1bej #b1ejj #bj1 #a1abe #a1cabe #a1ejj #a1fhge #a1hge #be1 #ijj #a1jej #a1bjj #a1cej #a1ejj #cj1 #gej #hge #a1jjj #a1abe #a1bej #ce1 #fdbh #gej #hega #ifdc #a1jgad #dj1 #efbe #fefc #gej #hdch #icge #de1 #ejj #ehcc #fffg #gej #hccc #ej1 #dej #ebe #fjj #fge #gej #fj1 #cge #dcge #ejj #efbe #fbe #gj1 #cbad #cge #dbhf #dhba #eceg #hj1 #bhac #cbhb #cge #dbai #dfhh #ij1 #bej #biag #cccc #cge #dafg #ajj1 #bbe #bfbe #cjj #ccge #cge ---------------------------------------- --------- ,illustration3 ,fig4 #gb;b4--,when an aeroplane is driven through the air1 it encounters stationary air and leaves it with a downward trend4 ,with a thick curved aeroplane1 as shown1 the air follows both the top and the bottom surfaces1 and the direction that the air takes is the resultant of these two streams of air4 ,it will be seen that the air takes the same direction that it would take if the plane were flat1 and raised from a to c1 which would be substantially the same as shown at f1 h1 g4 ,it has1 however1 been found by actual experiment that the curved plane is preferable1 because the lifting effect is more evenly distributed1 and the drift is less in proportion to the lift4 ,illustration3 ,fig4 #gb;c4--,aeroplanes experimented with by ,mr4 ,horatio ,philipps4 ,in the published account which is before me1 the angles at which these planes were placed are not given1 but1 by comparing the lift with the drift1 we may assume that it was about #a in #aj4 ,fig4 #e seems to have been the best shape1 and ,i find that this plane would have given a lifting effect of #bb lbs4 per square foot at a velocity of #dj miles per hour4 ,,philipps' ,,experiments4 ---------------------------------------- ---------------------- ,,descrip- ,,speed ,,of ,,dimensions ,,lift4 ,,drift4 ,,tion ,,air ,,of ,,lift ,,of ,,current4 ,,aeroplanes4 ,,di- ,,form4 --------- ---------------------- ,,vided ,feet,miles ,whole ,lbs4,whole ,lbs4 ,,by per per ,plane4 per ,plane4 per ,,drift4 sec4hour4 ,ozs4 sq4 ,ozs4 sq4 ft4 ft4 ---------------------------------------- ------------------- ,plane sur- faces1 #ci #bfei #af #e #i #ajac #b #jbbe #de ,fig4 #a1 #fj #djia #af #abe #i #dje #jhg #jcib #ajc #b1 #dh #cbgc #af #c #i #afhh #jhg #jafc #ajc #c1 #dd #cj #af #c #i #afhh #jhg #jafc #ajc #d1 #dd #cj #af #e #i #ajac #jhg #jjih #ajc #e1 #ci #bfei #af #e #i #ajac #jhg #jjih #ajc #f1 #bg #ahda #af #e #i #ajac #bbe #jbec #d ,area sq4 ft4 ,rook's wing1 #ci #bfei #je #h #aj #aj #jabe #h ---------------------------------------- ------------------- ,,chapter ,,viii4 ,,balloons4 ,as far as the actual navigation of the air is concerned1 balloonists have had everything to themselves until quite recently1 but we find that at the present moment1 experimenters are dividing their attention about equally between balloons or machines lighter than the air1 and true flying machines or machines heavier than the air4 ,in all ,nature1 we do not find any bird or insect that does not fly by dynamic energy alone1 and ,i do not believe that the time is far distant when those now advocating machines lighter than the air1 will join the party advocating machines heavier than the air1 and1 eventually1 balloons will be abandoned altogether4 ,no matter from what standpoint we examine the subject1 the balloon is unsuitable for the service1 and it is not susceptible of much improvement4 ,on the other hand1 the flying machine is susceptible of a good deal of improvement2 there is plenty of scope for the employment of a great deal of skill1 both mechanical and scientific1 for a good many years to come4 ,i do not know that ,i can express myself better now than ,i did when ,i wrote an article for the ,engineering ,supplement of the ,times1 from which ,i quote the following3-- 8,the result of recent experiments must have convinced every thinking man that the day of the balloon is past4 ,a balloon1 from the very nature of things1 must be extremely bulky and fragile4 8,it has always appeared to the writer that it would be absolutely impossible to make a dirigible balloon that would be of any use1 even in a comparatively light wind4 ,experiments have shown that only a few hundred feet above the surface of the earth1 the air is nearly always moving at a velocity of at least #ae miles an hour1 and more than two-thirds of the time at a velocity considerably greater than this4 ,in order to give a balloon sufficient lifting power to carry two men and a powerful engine1 it is necessary that it should be of enormous bulk4 ,considered as a whole1 including men and engine1 it must have a mean density less than the surrounding air1 otherwise it will not rise4 ,therefore1 not only is a very large surface exposed to the wind1 but the whole thing is so extremely light and fragile as to be completely at the mercy of wind and weather4 ,take that triumph of engineering skill1 the #8,nulli ,secundus1' for example4 ,the gas-bag1 which was sausage-shaped and #cj feet in diameter1 was a beautiful piece of workmanship1 the whole thing being built up of goldbeater's skin4 ,the cost of this wonderful gas-bag must have been enormous4 ,the whole construction1 including the car1 the system of suspension1 the engine and propellers1 had been well thought out and the work beautifully executed2 still1 under these most favourable conditions1 only a slight shower of rain was sufficient to neutralise its lifting effect completely--that is1 the gas-bag and the cordage about this so-called airship absorbed about #djj lbs4 of water1 and this was found to be more than sufficient to neutralise completely the lifting effect4 ,a slight squall which followed entirely wrecked the whole thing1 and it was ignominiously carted back to the point of departure4 8,we now learn that the ,war ,office is soon to produce another airship similar to the #8,nulli ,secundus1' but with a much greater capacity and a stronger engine4 ,in the newspaper accounts it is said that the gas-bag of this new balloon would be sausage-shaped and #db feet in diameter1 that it is to be provided with an engine of #ajj horse-power1 which it is claimed will give to this new production a speed of #dj miles an hour through the air1 so that1 with a wind of #bj miles an hour1 it will still be able to travel by land #bj miles an hour against the wind4 ,probably the writer of the article did not consider the subject from a mathematical point of view4 ,as the mathematical equation is an extremely simple one1 it is easily presented so as to be understood by any one having the least smattering of mathematical or engineering knowledge4 ,the cylindrical portion of the gas-bag is to be #db feet in diameter2 the area of the cross-section would therefore be #a1che feet4 ,if we take a disc #db feet in diameter and erect it high in the air above a level plain1 and allow a wind of #dj miles an hour1 which is the proposed speed of the balloon1 to blow against it1 we should find that the air pressure would be #aa1jhc lbs4--that is1 a wind blowing at a velocity of #dj miles an hour would produce a pressure of #h lbs4 to every square foot of the disc4#c ,conversely1 if the air were stationary1 it would require a push of #aa1jhc lbs4 to drive this disc through the air at the rate of #dj miles an hour4 #c ,haswell gives the pressure of the wind at #dj miles an hour as #h lbs4 per square foot1 and this is said to have been verified by the ,united ,states ,coast ,survey4 ,molesworth makes it slightly less2 but the new formula1 according to most recent experiments 7,dr4 ,stanton's experiments at the ,national ,physical ,laboratory and ,m4 ,eiffel's at ,eiffel ,tower71 is ,p #jjjc ,v1 which would make the pressure only #dh lbs4 per square foot1 and which would reduce the total ,h4,p4 required from #dgb to #bhc1 where ,p represents pounds per square foot and ,v miles per hour4 8,a speed of #dj miles an hour is at the rate of #c1ebj feet in a minute of time4 ,we therefore have two factors--the pounds of resistance encountered1 and the distance through which the disc travels in one minute of time4 ,by multiplying the total pounds of pressure on the complete disc by the number of feet it has to travel in one minute of time1 we have the total number of foot-pounds required in a minute of time to drive a disc #db feet in diameter through the air at a speed of #dj miles an hour4 ,dividing the product by the conventional horse-power #cc1jjj1 we shall have #a1aha horse-power as the energy required to propel the disc through the air4 ,however1 the end of the gas-bag is not a flat disc1 but a hemisphere1 and the resistance to drive a hemisphere through the air is much less than it would be with a normal plane or flat disc4 ,in the #8,nulli ,secundus' we may take the coefficient of resistance of the machine1 considered as a whole1 as #jbj--that is1 that the resistance will be one-fifth as much as that of a flat disc4 ,this1 of course1 includes not only the resistance of the balloon itself1 but also that of the cordage1 the car1 the engine1 and the men4 8,multiplying #a1aha by the coefficient #bj1 we shall have #bcf2 therefore1 if the new balloon were attached to a long steel wire and drawn by a locomotive through the air1 the amount of work or energy required would be #bcf horse-power--that is1 if the gas-bag would stand being driven through the air at the rate of #dj miles an hour1 which is extremely doubtful4 ,under these conditions1 the driving wheels of the locomotive would not slip1 and therefore no waste of power would result1 but in the dirigible balloon we have a totally different state of affairs4 ,the propelling screws are very small in proportion to the airship1 and their slip is fully #ej per cent4--that is1 in order to drive the ship at the rate of #dj miles an hour1 the screws would have to travel at least #hj miles an hour4 ,therefore1 while #bcf horse-power was imparted to the ship in driving it forward1 an equal amount would have to be lost in slip1 or1 in other words1 in driving the air rearwards4 ,it would1 therefore1 require #dgb horse-power instead of #ajj to drive the proposed new balloon through the air at the rate of #dj miles an hour4 8,it will be seen from this calculation that the new airship will still be at the mercy of the wind and weather4 ,those who pin their faith on the balloon as the only means of navigating the air may dispute my figures4 ,however1 all the factors in the equation are extremely simple and well known1 and no one can dispute any of them except the assumed coefficient of resistance1 which is given here as #bj4 ,the writer feels quite sure that1 after careful experiments are made1 it will be found that this coefficient is nearer #dj than #bj1 especially so at high speeds when the air pressure deforms the gas-bag4 ,only a slight bagging in the front end of the balloon would run the coefficient up to fully #ej1 and perhaps even more40--,times1 ,feb4 #bf1 #aijh4 ,illustration3 ,fig4 #gc4--,the enormous balloon1 8,ville de ,paris10 of the ,french ,government4 ,this balloon is a beautiful piece of workmanship1 and is said to be the most practical balloon ever invented1 not excepting the balloon of ,count ,zeppelin4 ,some idea of its size may be obtained by comparing it with the size of the men who are standing immediately underneath4 ,since writing the ,times article1 a considerable degree of success has been attained by ,count ,zeppelin4 ,according to newspaper accounts1 his machine has a diameter of about #dj feet1 and a length of no less than #djj feet4 ,it appears that this balloon consists of a very light aluminium envelope1 which is used in order to produce a smooth and even surface1 give rigidity1 and take the place of the network employed in ordinary balloons4 ,it seems that the gas is carried in a large number of bags fitted in the interior of this aluminium envelope4 ,however1 by getting a firm and smooth exterior and by making his apparatus of very great length as relates to its diameter1 he has obtained a lower coefficient of resistance than has ever been obtained before1 and as his balloon is of great volume1 he is able to carry powerful motors and use screw propellers of large diameter4 ,it appears that he has made a circuit of considerable distance1 and returned to the point of departure without any accident4 ,a great deal of credit is1 therefore1 due to him4 ,his two first balloons came to grief very quickly2 he was not discouraged1 but stuck to the job with true ,teutonic grit1 and has perhaps attained a higher degree of success than has ever been attained with a balloon4 ,however1 some claim that the ,french ,government balloon1 8,la ,patrie0 is superior to the ,zeppelin balloon at all points4 ,when we take into consideration the fact that the ,zeppelin machine is #djj feet long and lighter than the same volume of air1 it becomes only too obvious that such a bulky and extremely delicate and fragile affair will easily be destroyed4 ,of course ascensions will only be made in very favourable weather1 but squalls and sudden gusts of wind are liable to occur4 ,it is always possible to start out in fine weather if one waits long enough1 but if a flight of #bd hours or even #ab hours is to be attempted1 the wind may be blowing very briskly when we return1 and an ordinary wind will not only prevent the housing of ,count ,zeppelin's balloon1 but will be extremely liable to reduce it to a complete wreck in a few minutes4#d #d ,shortly after this was written1 the ,zeppelin machine was completely demolished by a gust of wind4 ,i am still strongly of the opinion that the ultimate mastery of the air must be accomplished by machines heavier than the air4 ,,appendix ,i4 ,,major ,,baden-,,powell',s ,,demand4 7,from our own ,correspondent47 ,,berlin1 ,friday4 ,germany's fleet of 8air cruisers10 or dirigible airships1 will1 it is proudly announced to-day1 presently number six3-- ,count ,zeppelin's ,,iii41 rigid type4 ,count ,zeppelin's ,,iv41 rigid type1 which has done a twelve-hour flight and will be taken over by the ,government1 with ,no4 ,,iii41 for #ajj1jjj1 after a twenty-four-hour test4 ,major ,gross's ,army airship1 half rigid4 ,motor ,airship ,study ,society's old airship1 non-rigid4 ,major von ,parseval's non-rigid ship building for the above society4 ,new airship1 of which details are kept secret1 nearly ready at the works of the ,siemens-,schuckert ,electric ,company4 ,the first announcement of the last-named airship was given in ,the ,daily ,mail several months ago4 ,the company has engaged a celebrated military aeronaut1 ,captain von ,krogh1 as commander of the vessel4 ,the ,study ,society's new non-rigid ship will be sold to the ,war ,office as soon as she has completed her trial trips4 ,the ,army will then possess three dirigibles1 each representing one of the three opposed types of construction--rigid1 half-rigid1 and non-rigid--with a view to arriving at a conclusion on their merits4 99 99 99 99 99 8,only a year or so ago1 our authorities were talking of aerial navigation in its relation to war as #8an interesting and instructive study4' ,now we must reckon it as the gravest problem of the moment4 ,the cleverest aeronauts in ,england should be called upon at once to design an airship1 not only as efficient as that of ,count ,zeppelin's1 but possessed of even greater speed4 7,his average was said to be about #cd miles an hour47 ,in speed will lie the supremacy of the air when it comes to actual warfare4 ,of two opposing airships1 the faster will be able to outmanuvre its adversary and hold it at its mercy40--,daily ,mail1 ,july #aa1 #aijh4 ,,command ,,of ,,the ,,air4 ,,germany ,,as ,,the ,,aerial ,,power4 ,,teutonic ,,vision4 ,a ,,landing ,,of #cej1jjj ,,men4 ,herr ,rudolph ,martin1 author of books on war in the air and 8,is a ,world-,war ,imminent80 points out how ,england is losing her insular character by the development of airships and aeroplanes4 8,in a world-war10 he said to me1 8,germany would have to spend two hundred millions sterling in motor airships1 and a similar amount in aeroplanes1 to transport #cej1jjj men in half an hour during the night from ,calais to ,dover4 ,even to-day the landing of a large ,german army in ,england is a mere matter of money4 ,i am opposed to a war between ,germany and ,england1 but should it break out to-day1 it would last at least two years1 for we would conclude no peace until a ,german army had occupied ,london4 8,in my judgment it would take two years for us to build motor airships enough simultaneously to throw #cej1jjj men into ,dover via ,calais4 ,during the same night1 of course1 a second transport of #cej1jjj men could follow4 ,the newest ,zeppelin airship can comfortably carry fifty persons from ,calais to ,dover4 ,the ships which the ,zeppelin works in ,friedrichshafen will build during the next few months are likely to be considerably larger than ,,iv41 and will carry one hundred persons4 ,there is no technical reason against the construction of ,zeppelin airships of #a1ajj1jjj or even #a1gjj1jjj cubic feet capacity1 or twice or three times the capacity of ,,iv4 7#ejj1jjj cubic feet74 8,i am at present organising a ,german #8,air ,navy ,league1' to establish air-traffic routes in ,germany4 ,aluminium airships could carry on regular traffic between ,berlin and ,london1 ,paris1 ,cologne1 ,munich1 ,vienna1 ,moscow1 ,copenhagen1 and ,stockholm4 ,in war time these ships would be at the disposal of the ,german ,empire4 8,the development of motor airship navigation will lead to a perpetual alliance between ,england and ,germany4 ,the ,british fleet will continue to rule the waves1 while ,germany's airships and land armies will represent the mightiest ,power on the ,continent of ,europe40--,daily ,mail1 ,july #aa1 #aijh4 ,it is needless to say that the above was written before the wreck of ,zeppelin's machine4 99 99 99 99 99 ,for many years scientific mechanicians and mathematicians have told us that the navigation of the air was quite possible4 ,they have said it is only a question of motive power2 8,give us a motor that is sufficiently light and strong1 and we will very soon give you a practical flying machine40 ,a domestic goose weighs about #ab lbs41 and it has been estimated that it only exerts about one-twelfth part of a horse-power in flying--that is1 it is able to exert one man-power with a weight of only #ab lbs41 which seems to be a very good showing for the goose4 ,however1 at the present moment1 we are able to make motors which develop the power of ten men--that is1 one horse-power--with less than the weight of a common barnyard fowl4 ,under these conditions it is quite evident that if a machine can be so designed that it will not be too wasteful in power1 it must be a success4 ,it is admitted by scientific men that all animals1 such as horses1 deer1 dogs1 and also birds1 are able to develop much more dynamic energy for the carbon consumed than is possible with any thermodynamic machine that we are able to make4 ,it may be said that many animals are able to develop the full dynamic energy of the carbon they consume1 whereas the best of our motors do not develop more than #aj per cent4 of the energy contained in the combustibles that they consume2 but1 as against this1 it must be remembered that birds feed on grass1 fruit1 fish1 etc41 heavy and bulky materials containing only a small percentage of carbon1 whereas with a motor we are able to use a pure hydrocarbon that has locked up in its atoms more than twenty times as much energy per pound as in the ordinary food consumed by birds4 ,i think1 in fact ,i assert1 that the time has now arrived1 having regard to the advanced state of the art in building motors1 when it will be quite a simple and safe affair to erect works and turn out successful flying machines at less cost than motor cars2 in fact1 there is nothing that stands in the way of success to-day4 ,the value of a successful flying machine1 when considered from a purely military standpoint1 cannot be over-estimated4 ,the flying machine has come1 and come to stay1 and whether we like it or not1 it is a problem that must be taken into serious consideration4 ,if we are laggards we shall1 unquestionably1 be left behind1 with a strong probability that before many years have passed over our heads1 we shall have to change the colouring of our school maps4 99 99 99 99 99 ,as the newspaper accounts that we receive from the ,continent give all weights and measures in the metric system1 it is convenient to have some simple means at hand to convert their values into ,english weights and measures4 ,i therefore give the following1 which will greatly simplify matters both for ,french and ,english measurements3-- ,one metre #cicg inches4 decimetre #cicg centimetre #cicg inch4 millimetre #jcicg ,in order to convert ,metres into inches1 multiply by #cicg4 feet1 #cbh4 yards1 #aji4 miles1 #jjjfbach4 ,cubic metres into cubic yards1 multiply by #acjhjb4 feet1 #cecafeh4 ,miles per hour into feet per minute1 multiply by #hh4 second1 #adfffc4 kilometres per hour1 #afjic4 metres per second1 #ddgjb4 ,miles per minute into feet per second1 #hh4 ,pounds into grammes1 multiply by #deceibf4 kilogrammes1 #decei4 ,pounds pressure per sq4 inch into atmospheres1 multiply by #jfhjd4 ,british thermal units into ,pounds of water1 #a ,c41 multiply by #eeeef4 ,kilogramme-calories1 #beb ,joules 7mechanical equivalent71 multiply by #ajdgif4 ,foot-pounds1 multiply by #ggh4 ,pounds of water into pints1 multiply by #h4 cubic feet1 #jafjdf4 litres1 #dedehg4 cubic centimetres1 multiply by #dedfef4 ,gallons of water into pounds1 multiply by #aj4 cubic feet1 #afjeg4 kilogrammes1 #decei4 litres1 #dedehf4 ,litres of water into cubic inches1 multiply by #fajcfd4 pounds1 #bbjbbf4 gallons1 #baiih4 ,air1 #a cubic foot weighs at #fb #ecbe grains4 ,air1 cubic feet into pounds1 #cb ,f41 multiply by #jhjgc4 ,pounds of dry air into cubic feet1 #acade4 ,kilogramme-calories into ,british thermal units1 multiply by #cifhc4 gramme-calories1 #ajjj4 mechanic equivalent in foot-lbs41 multiply by #cjfeg4 ,,appendix ,,ii4 ,,recapitulation ,,of ,,early ,,experiments4 ,illustration3 ,fig4 #gd4--,photograph of a model of my machine1 showing the fore and aft horizontal rudders and the superposed aeroplanes4 ,in my early 8whirling table0#e experiments1 the aeroplanes used were from #f inches to #d feet in width4 ,they were for the most part made of thin pine1 being slightly concave on the underneath side and convex on the top1 both the fore and aft edges being very sharp4 ,i generally mounted them at an angle of #a in #adf--that is1 in such a position that in advancing #ad feet they pressed the air down #a foot4 ,with this arrangement1 ,i found that with a screw thrust of #e lbs4 the aeroplane would lift #e #ad1 or #gj lbs41 while if the same plane was mounted at an angle of #a in #aj1 the lifting effect was almost #ej lbs4 7#e #aj74 ,this demonstrated that the skin friction on these very sharp1 smooth and well-made aeroplanes was so small a factor as not to be considered4 ,when1 however1 there was the least irregularity in the shape of the aeroplane1 the lifting effect1 when considered in terms of screw thrust1 was greatly diminished4 ,with a well-made wooden plane placed at an angle of #a in #ad1 ,i was able to carry as much as #aac lbs4 to the ,h4,p41 whereas with an aeroplane consisting of a wooden frame covered with a cotton fabric 7,fig4 #ge71 ,i was only able to carry #dj lbs4 to the ,h4,p4#g #e ,a name given by ,professor ,langley to an apparatus consisting of a long rotating arm to which objects to be tested are attached4 #f ,i found it more convenient to express the angle in this manner than in degrees4 #g ,the actual power consumed by the aeroplane itself was arrived at as follows3--,the testing machine was run at the desired speed without the aeroplane1 and the screw thrust and the power consumed carefully noted4 ,the aeroplane was then attached and the machine again run at the same speed4 ,the difference between the two readings gave the power consumed by the aeroplane4 ,illustration3 ,fig4 #ge4--,the fabric-covered aeroplane experimented with4 ,the efficiency of this aeroplane was only #dj per cent4 of that of a well-made wooden aeroplane4 ,illustration3 ,fig4 #gf4--,the forward rudder of my large machine1 showing the fabric attached to the lower side4 ,the top was also covered with fabric4 ,this rudder considered as an aeroplane had a very high efficiency and worked very well indeed4 ,these facts taken into consideration with my other experiments with large aeroplanes1 demonstrated to my mind that it would not be a very easy matter to make a large and efficient aeroplane4 ,if ,i obtained the necessary rigidity by making it of boards1 it would be vastly too heavy for the purpose1 while if ,i obtained the necessary lightness by making the framework of steel and covering it with a silk or cotton fabric in the usual way1 the distortion would be so great that it would require altogether too much power to propel it through the air4 ,i therefore decided on making a completely new form of aeroplane4 ,i constructed a large steel framework arranged in such a manner that the fore and aft edges consisted of tightly drawn steel wires4 ,this framework was provided with a number of light wooden longitudinal trusses1 similar to those shown in ,fig4 #gf4 ,the bottom side was then covered with balloon fabric secured at the edges1 and also by two longitudinal lines of lacing through the centre4 ,it was stretched very tightly and slightly varnished1 but not sufficiently to make it absolutely air-tight4 ,the top of this framework was covered with the same kind of material1 but varnished so as to make it absolutely airtight4 ,the top and bottom were then laced together forming very sharp fore and aft edges1 and the top side was firmly secured to the light wooden trusses before referred to4 ,upon running this aeroplane1 ,i found that a certain quantity of air passed through the lower side and set up a pressure between the upper and lower coverings4 ,the imprisoned air pressed the top covering upward1 forming longitudinal corrugations which did not offer any perceptible resistance to the air1 whereas the bottom fabric1 having practically the same pressure on both sides1 was not distorted in the least4 ,this aeroplane was found to be nearly as efficient as it would have been had it been carved out of a solid piece of wood4 ,it will be seen by the illustration that this large or main aeroplane is practically octagonal in shape1 its greatest width being #ej feet1 and the total area #a1ejj square feet4 ,,experiments ,,with ,a ,,large ,,machine4 ,upon running my large machine over the track 7,fig4 #gg7 with only the main aeroplane in position1 ,i found that a lifting effect of #c1jjj to #d1jjj lbs4 could be obtained with a speed of #cg to #db miles an hour4 ,it was not always an easy matter to ascertain exactly what the lifting effect was at a given speed on account of the wind that was generally blowing4 ,early in my experiments1 ,i found if ,i ran my machine fast enough to produce a lifting effect within #a1jjj lbs4 of the total weight of the machine1 that it was almost sure to leave the rails if the least wind was blowing4 ,it was1 therefore1 necessary for me to devise some means of keeping the machine on the track4 ,the first plan tried was to attach some very heavy cast-iron wheels weighing with their axle-trees and connections about #a-a_/b tons4 ,these were constructed in such a manner that the light flanged wheels supporting the machine on the steel rails could be lifted #f inches above the track1 leaving the heavy wheels still on the rails for guiding the machine4 ,this arrangement was tried on several occasions1 the machine being run fast enough to lift the forward end off the track4 ,however1 ,i found considerable difficulty in starting and stopping quickly on account of the great weight1 and the amount of energy necessary to set such heavy wheels spinning at a high velocity4 ,the last experiment with these wheels was made when a head wind was blowing at the rate of about #aj miles an hour4 ,it was rather unsteady1 and when the machine was running at its greatest velocity1 a sudden gust lifted not only the front end1 but also the heavy front wheels completely off the track1 and the machine falling on soft ground was soon blown over by the wind4 ,i then provided a safety track of #c #i ,georgia pine placed about #b feet above the steel rails1 the wooden track being #cj feet gauge and the steel rails #i feet gauge 7,fig4 #gg74 ,the machine was next furnished with four extra wheels placed on strong outriggers and adjusted in such a manner that when it had been lifted #a inch clear of the steel rails1 these extra wheels would engage the upper wooden track4#h #h ,springs were interposed between the machine and the axle-trees4 ,the travel of these springs was about #d inches2 therefore1 when the machine was standing still1 the wheels on the outriggers were about #e inches below the upper track4 ,illustration3 ,fig4 #gg4--,view of the track used in my experiments4 ,the machine was run along the steel railway which was #i feet gauge1 and was prevented from rising by the wooden track which was #ce feet gauge4 ,illustration3 ,fig4 #gh4--,the machine on the track tied up to the dynamometer4 ,illustration3 ,fig4 #gi4--,two dynagraphs1 one for making a diagram of the lifting effect off the main axle-tree1 and the other for making a diagram of the lift off the front axle-tree4 ,by this arrangement1 ,i was able to ascertain the exact lifting effect at all speeds1 and to arrange my aeroplanes in such a manner that the center of lifting effect was directly over the center of gravity4 ,the paper-covered cylinders made one rotation in #b1jjj feet4 ,when fully equipped1 my large machine had five long and narrow aeroplanes projecting from each side4 ,those that are attached to the sides of the main aeroplanes are #bg feet long1 thus bringing the total width of the machine up to #ajd feet4 ,the machine is also provided with a fore and an aft rudder made on the same general plan as the main aeroplane4 ,when all the aeroplanes are in position1 the total lifting surface is brought up to about #f1jjj square feet4 ,i have1 however1 never run the machine with all the planes in position4 ,my late experiments were conducted with the main aeroplane1 the fore and aft rudders1 and the top and bottom side planes in position1 the total area then being #d1jjj square feet4 ,with the machine thus equipped1 with #fjj lbs4 of water in the tank and boiler and with the naphtha and three men on board1 the total weight was a little less than #h1jjj lbs4 ,the first run under these conditions was made with a steam pressure of #aej lbs4 to the square inch1 in a dead calm1 and all four of the lower wheels remained constantly on the rails1 none of the wheels on the outriggers touching the upper track4 ,the second run was made with #bdj lbs4 steam pressure to the square inch4 ,on this occasion1 the machine seemed to vibrate between the upper and lower tracks4 ,about three of the top wheels were engaged at the same time1 the weight on the lower steel rails being practically nil4 ,preparations were then made for a third run with nearly the full power of the engines4 ,the machine was tied up to a dynamometer 7,fig4 #gh71 and the engines were started with a pressure of about #bjj lbs4 to the square inch4 ,the gas supply was then gradually turned on with the throttle valves wide open2 the pressure soon increased1 and when #caj lbs4 was reached1 the dynamometer showed a screw thrust of #b1ajj lbs41#i but to this must be added the incline of the track which amounts to about #fd lbs4 ,the actual thrust was therefore #b1afd lbs4 ,in order to keep the thrust of the screws as nearly constant as possible1 ,i had placed a small safety valve--#c_/d-;inch--in the steam pipe leading to one of the engines4 ,this valve was adjusted in such a manner that it gave a slight puff of steam at each stroke of the engine with a pressure of #caj lbs4 to the square inch1 and a steady blast at #cbj lbs4 to the square inch4 ,as the valves and steam passages of these engines were made very large1 and as the piston speed was not excessive1 ,i believed if the steam pressure was kept constant that the screw thrust would also remain nearly constant1 because as the machine advances and the screws commence to run slightly faster1 an additional quantity of steam will be called for and this could be supplied by turning on more gas4 ,when everything was ready1 with careful observers stationed on each side of the track1 the order was given to let go4 ,the enormous screw thrust started the machine so quickly that it nearly threw the engineers off their feet1 and the machine bounded over the track at a great rate4 ,upon noticing a slight diminution in the steam pressure1 ,i turned on more gas1 when almost instantly the steam commenced to blow a steady blast from the small safety valve1 showing that the pressure was at least #cbj lbs4 in the pipes supplying the engines with steam4 ,before starting on this run1 the wheels that were to engage the upper track were painted1 and it was the duty of one of my assistants to observe these wheels during the run1 while another assistant watched the pressure gauges and dynagraphs 7,fig4 #gi74 ,the first part of the track was up a slight incline1 but the machine was lifted clear of the lower rails and all of the top wheels were fully engaged on the upper track when about #fjj feet had been covered4 ,the speed rapidly increased1 and when #ijj feet had been covered1 one of the rear axle-trees1 which were of #b-;inch steel tubing1 doubled up 7,fig4 #hj71 and set the rear end of the machine completely free4 ,the pencils ran completely across the cylinders of the dynagraphs and caught on the underneath end4 ,the rear end of the machine being set free1 raised considerably above the track and swayed4 ,at about #a1jjj feet1 the left forward wheel also got clear of the upper track and shortly afterwards1 the right forward wheel tore up about #ajj feet of the upper track4 ,steam was at once shut off and the machine sank directly to the earth imbedding the wheels in the soft turf 7,figs4 #ha and #hb7 without leaving any other marks1 showing most conclusively that the machine was completely suspended in the air before it settled to the earth4 ,in this accident1 one of the pine timbers forming the upper track went completely through the lower framework of the machine and broke a number of the tubes1 but no damage was done to the machinery except a slight injury to one of the screws 7,fig4 #hc74 #i ,the quantity of water entering the boiler at this time was so great as to be beyond the range of the feed-water indicator4 ,illustration3 ,fig4 #hj4--,the outrigger wheel that gave out and caused an accident with the machine4 ,illustration3 ,fig4 #ha4--,shows the broken planks and the wreck that they caused4 ,it will be observed that the wheels sank directly into the ground without leaving any track4 ,illustration3 ,fig4 #hb4--,the condition of the machine after the accident4 ,one of the broken planks that formed the upper track is shown4 ,it will be observed that the wheels have sunk directly into the ground without leaving any tracks1 showing that the machine did not run along the ground1 but came directly down when it stopped4 ,in my experiments with the small apparatus for ascertaining the power required to perform artificial flight1 ,i found that the most advantageous angle for my aeroplane was #a in #ad1 but when ,i came to make my large machine1 ,i placed my aeroplanes at an angle of #a in #h so as to be able to get a great lifting effect at a moderate speed with a short run4 ,in the experiments which led to the accident above referred to1 the total lifting effect upon the machine must have been at least #aj1jjj lbs4 ,all the wheels which had been previously painted and which engaged the upper track were completely cleaned of their paint and had made an impression on the wood1 which clearly indicated that the load which they had been lifting was considerable4#aj ,moreover1 the strain necessary to double up the axle-trees was fully #a1jjj lbs4 each1 without considering the lift on the forward axle-trees which did not give way but broke the upper track4 #aj ,the latest form of outrigger wheels for engaging the upper track is shown in ,fig4 #hd4 ,illustration3 ,fig4 #hc4--,this shows the screw damaged by the broken planks2 also a hole in the main aeroplane caused by the flying splinters4 ,the advantages arising from driving the aeroplanes on to new air1 the inertia of which has not been disturbed1 are clearly shown in these experiments4 ,the lifting effect of the planes was #be lbs4 per square foot4 ,a plane loaded at this rate will fall through the air with a velocity of #bbcf miles per hour1 according to the formula 7#bjj ,p7 ,v4 ,but as the planes were set at an angle of #a in #h1 and as the machine travelled at the rate of #dj miles an hour1 the planes only pressed the air downwards #e miles an hour 7#dj #h #e74 ,a fall of #e miles an hour without advancing would only exert a pressure of #abe lb4 per square foot1 according to the formula 7,v #jje ,p74#aa #aa ,this is the old formula used by ,haswell4 ,the account of this experimental work was written in the autumn of #ahid and ,haswell's formula was used4 ,i have thought best to make no changes4 ,illustration3 ,fig4 #hd4--,this shows a form of outrigger wheels which were ultimately used4 ,engineers and mathematicians who have written to prove that flying machines were impossible have generally computed the efficiency of aeroplanes moving through the air1 on the basis that the lifting effect would be equal to a wind blowing against the plane at the rate at which the air was pressed down by the plane while being driven through the air4 ,according to this system of reasoning1 my #d1jjj square feet of aeroplanes would have lifted only #abe lb4 per square foot1 and in order to have lifted #aj1jjj lbs4 they would have to have had an area twenty times as great4 ,this corresponds exactly with the discrepancy which ,professor ,langley has found in the formula of ,newton4 ,with aeroplanes of one-half the width of those ,i employed1 and with a velocity twice as great1 the angle could be much less1 and the advantages of continually running on to fresh air would be still more manifest4 ,with a screw thrust of #b1jjj lbs41 the air pressure on each square foot of the projected area of the screw blades is #bac lbs41 while the pressure on the entire discs of the screws is #d lbs4 per square foot1 which would seem to show with screws of this size1 that four blades would be more efficient than two4 ,illustration3 ,fig4 #he4--,one pair of my compound engines4 ,this engine weighed #caj lbs4 and developed #ahj ,h4,p41 with #cbj lbs4 of steam per square inch4 ,the engines1 as before stated1 are compound 7,fig4 #he74 ,the area of the high-pressure piston is #bj square inches1 and that of the low-pressure piston is #ejbf square inches4 ,both have a stroke of #ab inches4 ,with a boiler pressure of #cbj lbs41 the pressure on the low-pressure piston is #abe lbs4 to the square inch4 ,this abnormally high pressure in the low-pressure cylinder is due to the fact that there is a very large amount of clearance in the high-pressure cylinder to prevent shock in case water should go over when the machine pitches2 moreover1 the steam in the high-pressure cylinder is cut off at three-quarters stroke1 while the steam in the low-pressure cylinder is cut off at five-eighths stroke4 ,if we should compute the power of these engines with the steam entering at full stroke1 without any friction1 and with no back pressure on the low-pressure cylinder1 the total horse-power would foot up to #dfacf horse-power at the speed at which the engines were run--namely1 #cge turns per minute4 ,if we compute the actual power consumed by the screws1 by multiplying their thrust1 which is probably #b1jjj lbs4 while they are travelling1 by their pitch1 #af feet1 and this by the number of turns which they make in a minute1 and then divide the product by #cc1jjj1 #b1jjj #af #cge ---------------- #cfcfc1 #cc1jjj we find that we have #cfcfc horse-power in actual effect delivered on the screws of the machine1 which shows that there is rather less than #bb per cent4 loss in the engines1 due to cutting off before the end of the stroke1 to back pressure1 and to friction4 ,the actual power applied to the machine being #cfcfc horse-power1 it is interesting to know what becomes of it4 ,when the machine has advanced #dj miles 7which it would do in an hour71 the screws have travelled #fha miles 7#cge #af #fj_/e1bhj7 #fha2 therefore1 #aej horse-power is wasted in slip1 and #bacfc horse-power consumed in driving the machine through the air4 ,now1 as the planes are set at an angle of #a in #h1 the power actually used in lifting the machine is #acccc1 and the loss in driving the body of the machine1 its framework and wires through the air is #ijcj horse-power4 ,power lost in screw slip1 #aej ,h4,p4 driving machinery and framework1 #hjcj actually consumed in lifting the machine1 #acccc ------ ,total power delivered by the engines1 #cfcfc ,,the ,,advantages ,,and ,,disadvantages ,,of ,,very ,,narrow ,,planes4 ,illustration3 ,fig4 #hf4--,the path that the air has to take in passing between superposed aeroplanes in close proximity to each other4 ,by this arrangement the drift is considerably increased4 ,my experiments have demonstrated that relatively narrow aeroplanes lift more per square foot than very wide ones2 but as an aeroplane1 no matter how narrow it may be1 must of necessity have some thickness1 it is not advantageous to place them too near together4 ,suppose that aeroplanes should be made #a_/d-;inch thick1 and be superposed #c inches apart--that is1 at a pitch of #c inches--one-twelfth part of the whole space through which these planes would have to be driven would be occupied by the planes themselves1 and eleven-twelfths would be air space 7,fig4 #hf74 ,if a group of planes thus mounted should be driven through the air at the rate of #cf miles an hour1#ab the air would have to be driven forward at the rate of #c miles an hour1 or else it would have to be compressed1 or spun out1 and pass between the spaces at a speed of #ci miles an hour4 ,as a matter of fact1 however1 the difference in pressure is so very small that practically no atmospheric compression takes place4 ,the air1 therefore1 is driven forward at the rate of #c miles an hour1 and this consumes a great deal of power2 in fact1 so much that there is a decided disadvantage in using narrow planes thus arranged4 #ab ,the arrows in the accompanying drawings show the direction of the air currents1 the experiments having been made with stationary planes in a moving current of air4 ,in regard to the curvature of narrow aeroplanes1 ,i have found that if one only desires to lift a large load in proportion to the area1 the planes may be made very hollow on the underneath side2 but when one considers the lift in terms of the screw thrust1 ,i find it advisable that the planes should be as thin as possible1 and the underneath side nearly flat4 ,i have also found that it is a great advantage to arrange the planes after the manner shown in ,fig4 #hg4 ,in this manner the sum of all the spaces between the planes is equal to the whole area occupied by the planes2 consequently1 the air neither has to be compressed1 spun out1 nor driven forward4 ,i am1 therefore1 able by this arrangement to produce a large lifting effect per square foot1 and1 at the same time1 to keep the screw thrust within reasonable limits4 ,illustration3 ,fig4 #hg4--,the position of narrow aeroplanes arranged in such a manner that the air has free passage between them1 and this arrangement has been found superior to arranging one above the other after the manner of a ,venetian blind4 ,a large number of experiments with very narrow aeroplanes have been conducted by ,mr4 ,horatio ,philipps at ,harrow1 in ,england4 ,fig4 #hh shows a cross-section of one of ,mr4 ,philipps' planes4 ,mr4 ,philipps is of the opinion that the air1 in striking the top side of the plane1 is thrown upwards in the manner shown1 and a partial vacuum is thereby formed over the central part of the plane1 and that the lifting effect of planes made in this form is therefore very much greater than with ordinary narrow planes4 ,i have experimented with these 8sustainers0 7as ,mr4 ,philipps calls them7 myself1 and ,i find it is quite true that they lift in some cases as much as #h lbs4 per square foot1#ac but the lifting effect is not produced in the exact manner that ,mr4 ,philipps seems to suppose4 ,the air does not glance off in the manner shown4 ,as the 8sustainer0 strikes the air two currents are formed1 one following the exact contour of the top1 and the other that of the bottom4 ,these two currents join and are thrown downwards1 as relates to the 8sustainer10 at an angle which is the resultant of the angles at which the two currents meet4 ,these 8sustainers0 may be made to lift when the front edge is lower than the rear edge1 because they encounter still air1 and leave it with a downward motion4 #ac ,in my early experiments ,i lifted as much as #h lbs4 per square foot with aeroplanes which were only slightly curved1 but very thin and sharp4 ,illustration3 ,fig4 #hh4--,the very narrow aeroplanes1 or sustainers1 employed by ,mr4 ,philipps4 ,it has been supposed that the air in striking at ,a was deflected in the manner shown1 but such is not the case4 ,the air in reality follows the surface1 as shown in the dotted line in the second illustration4 ,in my experiments with narrow superposed planes1 ,i have always found that with strips of thin metal made sharp at both edges and only slightly curved1 the lifting effect1 when considered in terms of screw thrust1 was always greater than with any arrangement of the wooden aeroplanes used in ,philipps' experiments4 ,it would1 therefore1 appear that there is no advantage in the peculiar form of 8sustainer0 employed by this inventor4 ,if an aeroplane be made perfectly flat on the bottom side and convex on the top1 and be mounted in the air so that the bottom side is exactly horizontal1 it produces a lifting effect no matter in which direction it is run1 because1 as it advances1 it encounters stationary air which is divided into two streams4 ,the top stream being unable to fly off at a tangent when turning over the top curve1 flows down the incline and joins the current which is flowing over the lower horizontal surface4 ,the angle at which the combined stream of air leaves the plane is the resultant of these two angles2 consequently1 as the plane finds the air in a stationary condition1 and leaves it with a downward motion1 the plane itself must be lifted4 ,it is true that small and narrow aeroplanes may be made to lift considerably more per square foot of surface than very large ones1 but they do not offer the same safeguard against a rapid descent to the earth in case of a stoppage or breakdown of the machinery4 ,with a large aeroplane properly adjusted1 a rapid and destructive fall to the earth is quite impossible4 ,,the ,,efficiency ,,of ,,screw ,,propellers1 ,,steering1 ,,stability1 c4 ,before ,i commenced my experiments at ,baldwyn's ,park1 ,i attempted to obtain some information in regard to the action of screw propellers working in the air4 ,i went to ,paris and saw the apparatus which the ,french ,government employed for testing the efficiency of screw propellers1 but the propellers were so very badly made that the experiments were of no value4 ,upon consulting an ,english experimenter1 who had made a 8life-long study0 of the question1 he assured me that ,i should find the screw propeller very inefficient and very wasteful of power1 and that all screw propellers had a powerful fan-blower action1 drawing in air at the centre and discharging it with great force at the periphery4 ,i found that no two men were agreed as to the action of screw propellers4 ,all the data or formul available were so confusing and contradictory as to be of no value whatsoever4 ,some experimenters were of the opinion that1 in computing the thrust of a screw1 we should only consider the projected area of the blades1 and that the thrust would be equal to a wind blowing against a normal plane of equal area at a velocity equal to the slip4 ,others were of the opinion that the whole screw disc would have to be considered2 that is1 that the thrust would be equal to a wind blowing against a normal plane having an area equal to the whole disc1 and at the velocity of the slip4 ,the projected area of the two screw blades of my machine is #id square feet1 and the area of the two screw discs is #ejj square feet4 ,according to the first system of reasoning1 therefore1 the screw thrust of my large machine1 when running at #dj miles an hour with a slip of #ah miles per hour1 would have been1 according to the well-known formula1 ,v #jje ,p #ah #jje #id #aebbh lbs4 ,if1 however1 we should have considered the whole screw disc1 it would have been #ah #jje #ejj #haj lbs4 ,however1 when the machine was run over the track at this rate1 the thrust was found to be rather more than #b1jjj lbs4 ,when the machine was secured to the track and the screws revolved until the pitch in feet1 multiplied by the turns per minute1 was equal to #fh miles an hour1 it was found that the screw thrust was #b1afd lbs4 ,in this case1 it was of course1 all slip1 and when the screws had been making a few turns they had established a well-defined air-current1 and the power exerted by the engine was simply to maintain this air current4 ,it is interesting to note that1 if we compute the projected area of these blades by the foregoing formula1 the thrust would be--#fh #jje #id #b1agcbh lbs41 which is almost exactly the observed screw thrust4 ,when ,i first commenced my experiments with a large machine1 ,i did not know exactly what sort of boiler1 gas generator1 or burner ,i should finally adopt2 ,i did not know the exact size that it would be necessary to make my engines2 ,i did not know the size1 the pitch1 or the diameter of the screws which would be the most advantageous2 neither did ,i know the form of aeroplane which ,i should finally adopt4 ,it was1 therefore1 necessary for me to make the foundation or platform of my machine of such a character that it would allow me to make the modifications necessary to arrive at the best results4 ,the platform of the machine is1 therefore1 rather larger than is necessary1 and ,i find if ,i were to design a completely new machine1 that it would be possible to greatly reduce the weight of the framework1 and1 what is still more1 to greatly reduce the force necessary to drive it through the air4 ,illustration3 ,fig4 #hi4--,one of the large screws being hoisted into position4 ,its size may be judged by comparison with the man4 ,at the present time1 the body of my machine is a large platform1 about #h feet wide and #dj feet long4 ,each side is formed of very long trusses of steel tubes1 braced in every direction by strong steel wires4 ,the trusses which give stiffness are all below the platform4 ,in designing a new machine1 ,i should make the trusses much deeper and at the same time very much lighter1 and1 instead of having them below the platform on which the boiler is situated1 ,i should have them constructed in such a manner as to completely enclose the boiler and the greater part of the machinery4#ad ,i should make the cross-section of the framework rectangular and pointed at each end4 ,i should cover the outside very carefully with balloon material1 giving it a perfectly smooth and even surface throughout1 so that it might be easily driven through the air4 #ad ,this arrangement of the framework is now common to all successful machines4 ,in regard to the screws1 ,i am at the present time able to mount screws #ag feet #aj inches in diameter 7,fig4 #hi74 ,i find1 however1 that my machine would be much more efficient if the screws were #bd feet in diameter and ,i believe with such very large screws1 four blades would be much more efficient than two4 ,my machine may be steered to the right or to the left by running one of the propellers faster than the other4 ,very convenient throttle valves have been provided to facilitate this system of steering4 ,an ordinary vertical rudder placed just after the screws may1 however1 prove more convenient if not more efficient4 ,the machine is provided with fore and aft horizontal rudders1 both of which are connected with the same windlass4 ,in regard to the stability of the machine1 the centre of weight is much below the centre of lifting effect2 moreover1 the upper wings are set at such an angle that whenever the machine tilts to the right or to the left the lifting effect is increased on the lower side and diminished on the higher side4 ,this simple arrangement makes it automatic as far as rolling is concerned4 ,i am of the opinion that whenever flying machines come into use1 it will be necessary to steer in a vertical direction by means of an automatic steering gear controlled by a gyroscope4 ,it will certainly not be more difficult to manuvre and steer such machines than it is to control completely submerged torpedoes4 ,when the machine is once perfected1 it will not require a railway track to enable it to get the necessary velocity to rise4 ,a short run over a moderately level field will suffice4 ,as far as landing is concerned1 the aerial navigator will touch the ground when moving forward1 and the machine will be brought to a state of rest by sliding on the ground for a short distance4 ,in this manner very little shock will result1 whereas if the machine is stopped in the air and allowed to fall directly to the earth without advancing1 the shock1 although not strong enough to be dangerous to life or limb1 might be sufficient to disarrange or injure the machinery4 ,,the ,,comparative ,,value ,,of ,,different ,,motors4 ,so far ,i have only discussed the navigation of the air by the use of propellers driven by a steam engine4 ,the engines that ,i employ are what is known as compound engines--that is1 they have a large and a small cylinder4 ,steam at a very high pressure enters the high-pressure cylinder1 expands and escapes at a lower pressure into a larger cylinder where it again expands and does more work4 ,a compound engine is more economical in steam than a simple engine1 and therefore requires a smaller boiler to develop the same horse-power1 so that when we consider the weight of water and fuel for a given time1 together with the weight of the boiler and the engine1 the engine motor with a compound engine is lighter than a simple engine4 ,however1 if only the weight of the engine is to be considered then the simple engine will develop more power per unit of weight than the compound engine4 ,for instance1 if1 instead of allowing the steam to enter the small cylinder1 and the exhaust from this cylinder to enter the large or low-pressure cylinder--which necessitates that the high-pressure piston has to work against a back pressure equal to the full pressure on the low-pressure cylinder--,i should connect both cylinders direct with the live steam1 and allow both to discharge their exhaust directly into the air1 ,i should then have a pair of simple engines1 and instead of developing #cfc ,h4,p4 they would develop fully #ejj ,h4,p41 or nearly #a ,h4,p4 for every pound of their weight4 ,i mention this fact to show that the engines are exceedingly light1 and that when compared with simple engines their power should be computed on the same basis4 ,it will1 therefore1 be seen that if we do not take into consideration the steam supply or the amount of fuel and water necessary1 the simple steam engine is an exceedingly light motor4 ,but1 as before stated1 great improvements have recently been made in oil engines4 ,i have thought much on this subject1 and am of the opinion that if one had an unlimited supply of money1 a series of experiments could be very profitably conducted with a view of adapting the oil engine for use on flying machines4 ,if we use a steam engine1 it is necessary to have a boiler1 and at best a boiler is rather a large and heavy object to drive through the air4 ,if we use an oil engine1 no boiler is necessary1 and the amount of heat carried over in the cooling water will only be one-seventh part of what is carried over in the exhaust from a steam engine of the same power4 ,therefore1 the condenser only need be one-seventh part the size1 and consequently should be made lighter with the tubes placed at a greater distance apart1 and thus reduce the amount of power necessary to drive the machine through the air4 ,moreover1 the supply of water necessary will be greatly reduced1 and a cheaper and heavier oil may be employed1 which is not so liable to take fire in case of an accident4 ,it is then only a question as to whether an oil engine can be made so light as to keep its weight within that of a steam motor2 that is1 an oil engine in order to be available for the purpose must be as light1 including its water supply1 as a complete steam motor1 which includes not only the engine1 but also the boiler1 the feed pumps1 the water supply1 the burner1 the gas generator1 and six-sevenths of the condenser4 ,it requires a very perfect steam engine and boiler1 not using a vacuum1 to develop a horse-power with a consumption of #a-a_/b lbs4 of petroleum per hour2 but there are many oil engines which develop a horse-power with rather less than #a lb4 of oil per hour4 ,it will1 therefore1 be seen that1 as far as fuel is concerned1 the oil engine has a decided advantage over the more complicated steam motor4 ,moreover1 with an oil engine1 the cooling water is not under pressure1 so that the waste of water would be much less than with a steam engine1 where the pressure is so high as to cause a considerable amount of waste through joints and numerous stuffing-boxes4 ,the great advances that have been made of late years in electrical science and engineering have led many to believe that almost any knotty scientific question may be solved by the employment of electrical engineering1 and a great deal has been written and said in regard to navigating the air by flying machines driven by electric motors4 ,before ,i commenced my experiments1 ,i made enquiries of all the prominent electrical engineering establishments where there was any likelihood of obtaining light and efficient electric motors1 and found that it was impossible to obtain one that would develop a horse-power for any considerable time that would weigh less than #aej lbs4 ,since that time1 notwithstanding that a great deal has appeared in the public prints about the efficiency and lightness of electric motors1 ,i am unable to learn of any concern that is ready to furnish a complete motor1 including a primary battery1 which would supply the necessary current for two hours at a time1 at a weight of less than #aej lbs4 per horse-power1 and as far as ,i have been able to ascertain from what ,i have myself seen1 ,i cannot learn that there are any motors in practical use which do not weigh1 including their storage batteries1 at least #cjj lbs4 per horse-power4 ,the last electric motor which ,i examined was in a boat2 it was driven by a primary battery which weighed over #a1jjj lbs4 to the horse-power4 ,from this ,i am of the opinion that we cannot at present look to electricity with any hope of finding a motor which is suitable for the purpose of aerial navigation4 ,,engines4 ,there is no question but what birds1 and for that matter all animals1 when considered as thermo-dynamic machines1 are very perfect motors2 they develop the full theoretical amount of energy of the carbon consumed4 ,this we are quite unable to do with any artificial machine1 but birds1 for the most part1 have to content themselves with food which is not very rich in carbon4 ,it is quite true that a bird may develop from ten to fifteen times as much power from the carbon consumed as can be developed by the best steam engine1 but1 as an off-set against this1 a steam engine is able to consume petroleum1 which has at least twenty times as many thermal units per pound as the ordinary food of birds4 ,the movement of a bird's wings1 from long years of development1 has without doubt attained a great degree of perfection4 ,birds are able to scull themselves through the air with very little loss of energy4 ,to imitate by mechanical means1 the exact and delicate motion of their wings would certainly be a very difficult task1 and ,i do not believe that we should attempt it in constructing an artificial flying machine4 ,in ,nature it is necessary that an animal should be made all in one piece4 ,it is1 therefore1 quite out of the question that any part or parts should revolve4 ,for land animals there is no question but what legs are the most perfect system possible1 but in terrestrial locomotion by machinery1 not necessarily in one piece1 wheels are found to be much more effective and efficient4 ,the swiftest animal can only travel for a minute of time at half the speed of a locomotive1 while the locomotive is able to maintain its much greater speed for many hours at a time4 ,the largest land animals only weigh about #e tons1 while the largest locomotives weigh from #fj to #hj tons4 ,in the sea1 the largest animal weighs about #ge tons1 while the ordinary ,atlantic liner weighs from #d1jjj to #ad1jjj tons4 ,the whale1 no doubt1 is able to maintain a high speed for several hours at a time1 but the modern steamer is able to maintain a still higher speed for many consecutive days4 ,as artificial machines for terrestrial and aquatic locomotion have been made immensely stronger and larger than land or water animals1 so with flying machines1 it will be necessary to construct them much heavier and stronger than the largest bird4 ,if one should attempt to propel such a machine with wings1 it would be quite as difficult a problem to solve as it would be to make a locomotive that would walk on legs4 ,what is required in a flying machine is something to which a very large amount of power can be directly and continuously applied without any intervening levers or joints1 and this we find in the screw propeller4 99 99 99 99 99 ,when the ,brayton gas engine first made its appearance1 ,i commenced drawings of a flying machine1 using a modification of the ,brayton motor which ,i designed expressly for the purpose2 but even this was found to be too heavy1 and it was not until after ,i had abandoned the vertical screw system that it was possible for me to design a machine which1 in theory1 ought to fly4 ,the next machine which ,i considered was on the kite or aeroplane system4 ,this was also to be driven by an oil engine4 ,oil engines at that time were not so simple as now1 and1 moreover1 the system of ignition was very heavy1 cumbersome1 and uncertain4 ,since that time1 however1 gas and oil engines have been very much improved1 and the ignition tube which is almost universally used has greatly simplified the ignition1 so that at the present time1 ,i am of the opinion that an oil engine might be designed which would be suitable for the purpose4 ,in #ahhi ,i had my attention drawn to some very thin1 strong1 and comparatively cheap tubes which were being made in ,france1 and it was only after ,i had seen these tubes that ,i seriously considered the question of making a flying machine4 ,i obtained a large quantity of them and found that they were very light1 that they would stand enormously high pressures1 and generate a very large quantity of steam4 ,upon going into a mathematical calculation of the whole subject1 ,i found that it would be possible to make a machine on the aeroplane system1 driven by a steam engine1 which would be sufficiently strong to lift itself into the air4 ,i first made drawings of a steam engine1 and a pair of these engines was afterwards made4 ,these engines are constructed1 for the most part1 of a very high grade of cast steel1 the cylinders being only #c_/cb of an inch thick1 the crank shafts hollow1 and every part as strong and light as possible4 ,they are compound1 each having a high-pressure piston with an area of #bj square inches1 a low-pressure piston of #ejbf square inches1 and a common stroke of #a foot4 ,when first finished1 they were found to weigh #cjj lbs4 each2 but after putting on the oil cups1 felting1 painting1 and making some slight alterations1 the weight was brought up to #cbj lbs4 each1 or a total of #fdj lbs4 for the two engines1 which have since developed #cfb horse-power with a steam pressure of #cbj lbs4 per square inch4 ,a photograph of one of these engines is shown in ,fig4 #he4 99 99 99 99 99 ,when first designing this engine1 ,i did not know how much power ,i might require from it4 ,i thought that in some cases it might be necessary to allow the high-pressure steam to enter the low-pressure cylinder direct1 but as this would involve a considerable loss1 ,i constructed a species of an injector4 ,this injector may be so adjusted that when the steam in the boiler rises above a certain predetermined point1 say #cjj lbs4 to the square inch1 it opens a valve and escapes past the high-pressure cylinder instead of blowing off at the safety valve4 ,in escaping through this valve1 a fall of about #bjj lbs4 pressure per square inch is made to do work on the surrounding steam and to drive it forward in the pipe1 producing a pressure on the low-pressure piston considerably higher than the back pressure on the high-pressure piston4 ,in this way a portion of the work which would otherwise be lost is utilised1 and it is possible1 with an unlimited supply of steam1 to cause the engines to develop an enormous amount of power4 99 99 99 99 99 ,boiler ,experiments4--,the first boiler which ,i made was constructed something on the ,herreshoff principle1 but instead of having one simple pipe in one very long coil1 ,i used a series of very small and light pipes1 connected in such a manner that there was a rapid circulation through the whole--the tubes increasing in size and number as the steam was generated4 ,i intended that there should be a pressure of about #ajj lbs4 more on the feed water end of the series than on the steam end1 and ,i believed that this difference in pressure would be sufficient to ensure a direct and positive circulation through every tube in the series4 ,this first boiler was exceedingly light1 but the workmanship1 as far as putting the tubes together was concerned1 was very bad1 and it was found impossible to so adjust the supply of water as to make dry steam without overheating and destroying the tubes4 ,illustration3 ,fig4 #ij4--,steam boiler employed in my experiments4 ,with this boiler1 ,i had no trouble in producing all the steam that ,i could possibly use1 and at any pressure up to #djj lbs4 to the square inch4 ,illustration3 ,fig4 #ia4--,the burner employed in my steam experiments4 ,this produced a dense and uniform blue purple flame #bj inch deep4 ,before making another boiler ,i obtained a quantity of copper tubes1 about #h feet long1 #c_/h inch external diameter1 and #a_/ej of an inch thick4 ,i subjected about #ajj of these tubes to an internal pressure of #a ton per square inch of cold kerosine oil1 and as none of them leaked ,i did not test any more1 but commenced my experiments by placing some of them in a white-hot petroleum fire4 ,i found that ,i could evaporate as much as #bf-a_/b lbs4 of water per square foot of heating surface per hour1 and that with a forced circulation1 although the quantity of water passing was very small but positive1 there was no danger of over-heating4 ,i conducted many experiments with a pressure of over #djj lbs4 per square inch1 but none of the tubes failed4 ,i then mounted a single tube in a white-hot furnace1 also with a water circulation1 and found that it only burst under steam at a pressure of #a1fej lbs4 per square inch4 ,a large boiler1 having about #hjj square feet of heating surface including the feed-water heater1 was then constructed4 ,it is shown in ,fig4 #ij4 ,this boiler is about #d-a_/b feet wide at the bottom1 #h feet long and #f feet high4 ,it weighs with the casing1 the dome1 the smoke stack and connections1 a little less than #a1jjj lbs4 ,the water first passes through a system of small tubes--#a_/d inch in diameter and #a_/fj inch thick--which were placed at the top of the boiler and immediately over the larger tubes--not shown in the cut4 ,this feed-water heater is found to be very effective4 ,it utilises the heat of the products of combustion after they have passed through the boiler proper and greatly reduces their temperature1 while the feed-water enters the boiler at a temperature of #bej ,f4 ,a forced circulation is maintained in the boiler1 the feed-water entering through a spring valve1 the spring valve being adjusted in such a manner that the pressure on the water is always #cj lbs4 per square inch in excess of the boiler pressure4 ,this fall of #cj lbs4 in pressure acts upon the surrounding hot water which has already passed through the tubes1 and drives it down through a vertical outside tube1 thus ensuring a positive and rapid circulation through all the tubes4 ,this apparatus is found to work extremely well4 ,a little glass tube at the top provided with a moving button1 indicates exactly how many pounds of water per hour are passing into the boiler4 ,by this means1 the engineer is not only enabled to ascertain at a glance whether or not the pumps are working1 but also to what degree they are working4 ,water may be considered as #b1djj times as efficient as air1 volume for volume1 in condensing steam4 ,when a condenser is made for the purpose of using water as a cooling agent1 a large number of small tubes may be grouped together in a box1 and the water may be pumped in at one end of the box and discharged at the other end through relatively small openings2 but when air is employed1 the tubes or condensing surface must be widely distributed1 so that a very large amount of air is encountered1 and the air which has struck one tube and become heated must never strike a second tube4 ,in order to accomplish this1 ,i make my condenser something in the form of a ,venetian blind1 the tubes being made of very thin copper and each tube in the form of a small aeroplane4 ,these were driven edgewise through the air1 so that the actual volume of air passing between them is several thousand times greater than the volume of water passing through a marine condenser4 ,i find that with such a condenser ,i can recover the full weight of the copper tubes in water every five minutes1 and if ,i use aluminium1 in half that time4 ,moreover1 experiments have shown that a condenser may be made to sustain considerably more than its own weight and the weight of its contents in the air1 and that all the steam may be condensed into water sufficiently cool to be pumped with certainty4 ,i find that the most advantageous position for the condenser is immediately after the screw propellers4 ,in this case1 if the machine is moving through the air at the rate of #ej miles an hour1 and the slip of the screws is #ae miles an hour1 it follows that the air will be passing through the condenser at the rate of #fe miles an hour4 ,at this velocity1 the lifting effect on the narrow aeroplanes forming the condenser is very great1 and at the same time the steam is very rapidly condensed4 ,the tubes are placed at such an angle as to keep them completely drained and prevent the accumulation of oil1 the steam entering the higher end and the water being discharged at the lower end4 4 4 4 4 4 4 4 4 4 ,,experiments ,,with ,,small ,,machines ,,attached ,,to ,a ,,rotating ,,arm4 ,these experiments demonstrated most conclusively that as much as #acc lbs4 could be sustained and carried by the expenditure of one horse-power1 and that a screw was a fairly efficient air propeller4 ,they also demonstrated that a well made aeroplane1 placed at an angle of #a in #ad1 would lift practically fourteen times the thrust required to drive it through the air1 and that the skin friction on a smooth and well finished aeroplane or screw was so small as not to be considered4 ,a large number of aeroplanes were experimented with1 and it was found that those which were slightly concave on the underneath side and convex on the top1 both edges being very sharp and the surface very smooth and regular1 were the most efficient2 also that with small screw propellers1 two blades having slightly increasing pitch were the most efficient4 99 99 99 99 99 ,since writing the foregoing1 great progress has been made with flying machines1 and great disasters have happened to airships or balloons4 ,count ,zeppelin's gigantic airship encountered a squall or thunder shower1 and the work of years1 which had cost over #ajj1jjj1 was reduced to scrap metal in a few minutes4 ,similar disasters have happened to other balloons4 ,the ,british ,dirigible ,no4 #b has not attempted a long flight1 but the ,wright ,brothers1 ,farman1 and ,de la ,grange have all met with a certain degree of success4 ,a few months ago1 the remarkable feats of the ,wright ,brothers in the ,states were discredited in ,europe4 ,it was claimed that 8the accounts were not authentic10 8too good to be true10 etc41 but recent events have shown that the ,wright ,brothers are able to outdo anything that was reported in the ,american ,press4 ,on many occasions they have remained in the air for more than an hour1 and have travelled at the rate of #cj to #dj miles an hour2 in fact1 the remarkable success of the ,wright ,brothers has placed the true flying machine in a new category4 ,it can no longer be ranked with the philosopher's stone or with perpetual motion4 ,success is assured1 and great and startling events may take place within the next few years4 ,illustration3 ,fig4 #ib4--;,count ,zeppelin's aluminium-covered airship coming out of its shed on ,lake ,constance4 ,illustration3 ,fig4 #ic4--;,count ,zeppelin's airship in full flight4 ,illustration3 ,fig4 #id4--,the new ,british war balloon 8,dirigible0 ,no #b4 ,illustration3 ,fig4 #ie4--,the ,wright aeroplane in full flight4 ,,general ,,index4 ,,page ,accident to my large machine1 #ach ,action of aeroplanes and power required1 #ajj ,adjustment of birds' wings1 #ai ,admiralty specification for a steamship1 #dh ,advantages of driving aeroplanes on to new air1 #adj ,advantages and disadvantages of very narrow planes1 #adc ,aeroplanes3-- ,action of1 #ca1 #cb1 #ajj ,advantageous angle of1 #aci ,advantages and disadvantages of very narrow1 #adc arising from driving aeroplanes on to new air1 #adj ,curvature of1 #ade ,evolution of a wide aeroplane1 #ajb ,experiments with1 #di-ei ,fabric covered1 #aca ,lifting effect of1 #ada ,lifting surface of1 #ajc ,philipps' sustainers1 #adf ,reduction of projected horizontal area1 #c1 #d ,shape and efficiency of1 #ii ,superposed1 #add1 #adf ,testing fabrics for1 #ej ,the paradox aeroplane1 #hh ,air currents and the flight of birds1 #aa ,conclusions regarding1 #ba ,alpes ,maritimes1 #ag ,mediterranean1 #ah ,mid-,atlantic1 #af #b1jjj feet above the earth's surface1 #bb witnessed at ,cadiz1 #bj ,angles and degrees compared1 #aae ,antoinette motor1 ,the1 #hi ,balloons1 #abj spiders1 #bg ,birds as thermo-dynamic machines1 #aec ,two classes of1 #bc ,bleriot's machine1 #aac ,boiler experiments1 #aef ,brayton's gas engine1 #aed ,british war balloon1 #aei1 #afb ,building up of my large screws1 #da ,burner employed in my experiments1 #aeg ,character of text-books recently published1 #a ,circulation of air produced by differences in temperature1 #bg ,cody's kite1 #bh1 #cj ,comparative value of different motors1 #aea ,conclusions regarding air currents1 #ba ,condensers1 ,testing of1 #eb ,condenser tubes1 #fj ,continental flying machines1 #i ,crystal ,palace experiments1 #gb-gf ,darwin on the flight of condors1 #aa ,deflection of air coming in contact with aeroplanes1 #b ,de la ,grange machine1 ,the1 #aaj 8,dirigible0 ,no #b1 #aei1 #afb ,drift at various distances from center to center1 ,table of1 #eh ,dynagraphs1 #acf ,dynamic energy of animals1 #abg ,eagles1 ,flight of1 #ai ,efficiency of screw propellers1 #adg screws in steamships1 #dg ,energy developed by a bird1 #ac ,engines1 #aec ,equivalent inclinations1 #aae velocities1 #aaf ,experiments of ,count ,zeppelin1 #abd ,horatio ,philipps1 #i1 #aah1 #aai1 #ade ,lord ,rayleigh in reference to ,newton's ,law1 #f ,professor ,langley1 #i1 #fb1 #ii1 #aji ,wright ,bros41 #aji ,experiments to show efficiency of ,screw propellers1 #cc with apparatus attached to rotating arm1 #fb boiler1 #aef hard rolled brass aeroplane1 #c my large machine1 #aj1 #acc rotating arm1 #fd-gb small machines attached to rotating arm1 #aei ,fabric covered screw1 #dj ,farman's machine1 #aaj ,flying of kites1 #be1 #bh1 #bi ,forced circulation used by me1 #aeh ,formul unsupported by facts1 #c ,french and ,english measurements1 #abh1 #abi ,gulls1 #bj1 #ba ,gyroscope apparatus1 #ic ,steering by means of1 #ib ,hawks and ,eagles1 #ac ,hlicoptre machine1 #hb ,hints as to the building of flying machines1 #gg-ia ,horizontal movement of the air1 #ad ,hub for flying machine1 ,new form of1 #de ,interstellar temperature1 #ae ,introductory1 #a ,kites1 #ba1 #bb1 #be1 #bf1 #bh1 #bi ,behaviour of1 #bf ,flying of1 #be1 #bh1 #bi ,langley1 ,experiments of1 #i1 #fb1 #ii1 #aji on the flight of birds1 #aa1 #bb on the power exercised by birds1 #ab 8,la ,patrie10 #abd ,lifting effect of aeroplanes1 #e surface of aeroplanes1 #ajc ,low temperature of space1 #ae ,major ,baden ,powell's demand1 #abe ,mistral1 ,the1 #ba ,motors1 ,development of1 #ca ,motor1 ,the ,antoinette1 #hi ,my compound engines1 #adb experiments with aeroplanes1 #g large machine1 #aj1 #acc steam engines1 #aee ,newton's ,law1 #b1 #f 8,nulli ,secundus10 #bh1 #aba ,oil engines1 #aed ,philipps' experiments1 #i1 #aah1 #aai1 #ade sustainers1 #ade ,pneumatic buffer1 #ij ,position of screw1 #di ,power exerted by a land animal1 #ac required1 #ajj ,principally relating to screws1 #ca ,rayleigh's experiments in reference to ,newton's law1 #f ,recapitulation of early experiments1 #acj ,recent machines1 #aji ,relative value of woods for flying machines1 #he ,reserve energy necessary in flying machines1 #cj ,resistance encountered by various shaped bodies1 #eb ,rotating arm experiments1 #fd-gb ,santos ,dumont's flying machine1 #aac ,screw blade on ,farman's machine1 #da blades1 ,testing of1 #cf used by the ,french ,government1 #ci with radial edges1 #dc ,fabric-covered1 #dj ,position of1 #di propeller made of sheet metal1 #da propellers1 ,efficiency of1 #cc1 #adg ,screws1 #h1 #ca1 #ce1 #cf1 #dj1 #da1 #df1 #dg1 #di ,building up of my large1 #dj their efficiency in steamships1 #dg ,shape and efficiency of aeroplanes1 #ii ,skin friction1 #da1 #dh ,spider's webbing down from the sky1 #bg ,spirit lamp and ice box1 #fb ,stability of flying machines1 #adg1 #aej ,steam engines used by me1 #aee ,steering1 #adg1 #adi ,superposed aeroplanes1 #add ,system of splicing and building up wooden members1 #hf ,tables3-- ,equivalent inclinations1 #aae velocities1 #aaf ,french and ,english measurements1 #abh1 #abi ,philipps' experiments1 #aai ,relative value of different woods1 #he ,showing the relative power exerted by different birds1 #bd ,velocity and pressure of the wind1 #aad thrust corresponding with various horse-powers1 #aag ,testing aeroplanes1 condensers1 etc41 #eb ,teutonic vision of aerial power1 #abf ,velocity and pressure of wind1 #aad thrust corresponding with various horse-powers1 #aag 8,ville de ,paris10 #abc ,wright ,bros4' experiments1 #aji1 #aei1 #afb ,zeppelin's experiments1 #abd1 #aei1 #afa ,,bell ,,and ,,bain1 ,,limited1 ,,printers1 ,,glasgow4 ,transcriber's ,notes3 ,inconsistent spelling and hyphenation in the original work have been retained4 ,depending on the hard- and software used to read this text and their settings1 not all characters and symbols may display as intended4 ,changes made to the text3 ,illustrations and tables have been moved out of the text1 and footnotes have been moved to directly under the paragraph or table they refer to4 ,obvious punctuation and typographical errors have been corrected silently4 ,in some formulas has been inserted for consistency2 brackets have been added for clarity where necessary4 ,page vii3 battaillons ,kommandeur changed to ,bataillonskommandeur ,page x3 #a in #bj changed to #a in #aj 7as discussed in the remainder of the paragraph7 ,page #bd1 table3 #fd changed to #gfd ,page #gc3 all the air effected changed to all the air affected ,page #aaj3 ,hargraves' changed to ,hargrave's ,page #abh3 over estimated changed to over-estimated4