lifornia 
 
 onal 
 
 lity
 
 UNIVERSITY OF CALIFORNIA 
 AT LOS ANGELES 
 
 GIFT OF CAPT. AND MRS. 
 PAUL MCBRIDE PERIGORD
 
 of 
 AT 
 
 LOS ANGELES 
 LIBRARY
 
 ARTIFICIAL AND NATURAL FLIGHT.
 
 A Pockct-Book of Aeronautics. By H. W. 
 
 L. MOEDEBECK. Translated from the German by 
 Dr. W. MANSERGH VARLEY. With 150 Illustrations, 
 los. 6d. net. 
 
 CONTENTS. Gases Physics of the Atmosphere Meteoro- 
 logical Observations Balloon Technics Kites and 
 Parachutes On Ballooning Balloon Photography 
 Photographic Surveying from Balloons Military Bal- 
 looning Animal Flight Artificial Flight Airships 
 Flying Machines Motors Air Screws Appendix 
 Index. 
 
 "Will be highly welcome to all aeronauts. It may be said to be the 
 only complete work practically dealing with such matters. We have no 
 hesitation in thoroughly recommending this as an absolutely indispensable 
 book. '" Knowledge. 
 
 "It is without a doubt the best book that has appeared 011 the subject." 
 Aeronautical Journal. 
 
 " The present volume ought certainly to be possessed by every student 
 of Aeronautics, as it contains a vast amount of information of the highest 
 value." Glasgow Herald. 
 
 WHITTAKER & CO., LONDON, E.G.
 
 ARTIFICIAL AND 
 NATURAL FLIGHT 
 
 SIR HIRAM S. MAXIM. 
 
 WITH 95 ILLUSTRATIONS. 
 
 THE MACMILLAN CO., 
 
 64-66 FIFTH AVENUE, NEW YORK. 
 
 WHITTAKER & CO., LONDON, E.G. 
 
 1908. 
 
 136510
 
 TU 
 
 PREFACE. 
 
 IT was in 1856 that I first had my attention called to 
 the subject of flying machines. My father, who was a 
 profound thinker and a clever mechanician, seems to have 
 given the subject a great deal of thought, and to have 
 matured a plan identical with what has been proposed by 
 hundreds since that time. I was then sixteen years of 
 age, and a fairly good mechanician, and any new thing in 
 the mechanical line interested me immensely. 
 
 My father's proposed machine, of which he made a 
 sketch, was of the Helicoptere type, having two screws 
 both on the same axis the lower one to be right hand 
 and mounted on a tubular shaft, and the top one to be left 
 hand and mounted on a solid shaft running through the 
 lower tubular shaft. These screws were to be rotated in 
 reverse directions by means of a small pinion engaging a 
 bevel gear attached to each of the shafts. His plan con- 
 templated large screws with very fine pitch, and he 
 proposed to obtain horizontal motion by inclining the axis 
 forward. He admitted that there was no motor in 
 existence light enough, but thought one might be invented, 
 and that an engine might be worked by a series of ex- 
 plosions in the cylinder, that is, what is known to-day as 
 internal combustion ; but he was not clear how such an 
 engine could be produced. He, however, said that a flying 
 machine would be so valuable in time of war, that it 
 mattered little how expensive the explosive might be, 
 even if fulminate of mercury had to be used. It is 
 interesting to note in this connection that the great Peter 
 Cooper of New York thought out an identical machine 
 about the same time, and actually commenced experiments. 
 It seems that this gentleman regarded fulminate of mercury 
 
 \L
 
 vi PREFACE. 
 
 as altogether too feeble and inert, because we find that 
 he selected chloride of nitrogen as his explosive agent. 
 However, his work was soon brought to an end by the 
 loss of the sight of one eye, after which time he had no 
 further dealings with this lively explosive. 
 
 The many early conversations that I had with my father 
 on the subject kept the matter constantly before me, and 
 I think it was in 1872, after having seen Roper's hot-air 
 engine and Brayton's petroleum engine, that I took the 
 matter up, and commenced to make drawings of a machine 
 of the Helicoptere type, but instead of having one screw 
 above the other, I saw at once that it would be much 
 better if the two screws were widely separated, so that 
 each would engage new air, the inertia of which had not 
 been disturbed. The designing of the machine itself was 
 a simple matter, but the engine gave me trouble. No 
 matter from what point I examined the subject, the engine 
 was always too heavy. It appears that the Brayton engine 
 was shown at the Centennial Exhibition at Philadelphia 
 in 1876, and that Otto visited this exhibition. Up to that 
 time, he had been making a species of rocket engine that is, 
 an engine in which an explosive mixture shot the piston 
 upward and then sucked it back, a rack and pinion 
 transmitting movement to the rotating shaft by means of a 
 pawl and ratchet. He appears to have been much interested 
 in the Brayton engine, as it was evidently very much 
 in advance of his own. It actually developed, even at that 
 time, one horse-power per hour for every pound of crude 
 petroleum consumed, but it was very heavy indeed, very 
 difficult to start, arid not always reliable. The shaft that 
 worked the valve gear was parallel to the cylinder, and 
 placed in the exact position occupied by a similar shaft in 
 the present Otto engine, but instead of revolving only 
 half as fast as the crank shaft, it made the same number of 
 revolutions. On Otto's return to Germany, he evidently 
 profited by what he had seen, and made a new engine, 
 which in reality was a cross between his own and the
 
 PREFACE. vii 
 
 Brayton ; the result was a very important invention, which 
 has been of incalculable value to mankind. It is this 
 engine which is now propelling our motor cars, and it 
 is the only engine suitable for employment on a flying 
 machine; but even this motor was not in a sufficiently 
 high state of development as far as lightness was concerned, 
 to be of any use to me. The drawings which I made in 
 1873, although of little or no value, kept my thoughts on 
 artificial flight, and while I was away from home attending 
 to business, especially when in foreign countries, I often 
 amused myself by making mathematical calculations. 
 Quite true, the formula which I used at the time 
 Has well's was not correct ; still, it was near enough 
 to the mark to be of considerable value. Moreover, the 
 error in this formula affected the Helicoptere quite as 
 much as the aeroplane system, and as I was working with 
 the view of ascertaining the relative merits of the two 
 systems, the error, although considerable, did not have any 
 influence at all in the decision which I arrived at namely, 
 that the aeroplane system was the best. The machine 
 that I thought out at that time contemplated superposed 
 aeroplanes of very great length from port to starboard. 
 The size in the other direction was more for the purpose 
 of preventing a rapid fall than for a lifting effect. I saw 
 that it would be necessary to have horizontal fore and aft 
 rudders placed a long distance apart, so as to prevent rapid 
 pitching, and it appeared to me that the further these 
 rudders were apart, the easier it would be to manoeuvre 
 the machine. As I never had any doubts regarding the 
 efficiency of screw propellers working in the air, I decided 
 to use two of these of a large size rotating in opposite 
 directions. Of course, all this speculation was theory only, 
 but I verified it later on by actual experiments before 
 I built my machine, 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 time, 
 and found to be the best. All have superposed aeroplanes
 
 Viii PREFACE. 
 
 of great length from port to starboard, all have fore and 
 aft horizontal rudders, and all are driven with screw 
 propellers. The change from my model is only a change 
 in the framework made possible by dispensing with the 
 boiler, water tank, and steam engine. Tn this little work, 
 I have dealt at considerable length with air currents, the 
 flight of birds, and the behaviour of kites, perhaps at the 
 expense of some repetitions ; as the resemblance between 
 kite flying and the soaring of birds is similar in many 
 respects, repetitions are necessary. To those who go to 
 sea in ships, it is necessary to know something of the 
 currents they are liable to encounter ; if it be a sailing ship, 
 certainly a knowledge of the air currents is of the greatest 
 importance, and so it is with flying machines. If flights 
 of any considerable distance are to be made, the machine is 
 liable at any time to encounter very erratic air currents, 
 and it has been my aim in discussing these three subjects 
 air currents, birds, and kites to bring them before the 
 would-be navigators of the air, in order that they may 
 anticipate the difficulties they have to deal with and 
 be ready to combat them. Then, again, there has been 
 almost an infinite amount of discussion regarding the 
 soaring of birds and the flying of kites. Many years 
 ago, after reading numerous works on the subject of 
 flight, I became a close observer myself, and always 
 sought in my travels to learn as much as possible. I 
 have attempted to discuss this subject in simple and 
 easily understood language, and to present sufficient 
 evidence to prevent the necessity of any further disputes. 
 I do not regard what I have said as a theory, but simply 
 as a plain statement of absolute and easily demonstrated 
 facts. During the last few years, a considerable number 
 of text-books and scientific treatises have been written 
 on the subject of artificial flight, the most elaborate and 
 by far the most reliable of these being the " Pocket-Book 
 of Aeronautics," by Herman W. L. Moedebeck, Major 
 und battaillons Kommandeur im Badischen Fussartillerie
 
 PREFACE. IX 
 
 Regiment No. 14 ; in collaboration with O. Chanute 
 and others. Translated by W. Mansergh Varley, B.A., 
 D.Sc., Ph.D., and published by Whittaker & Co. This 
 work does not, however, confine itself altogether to flying 
 machines, but has a great deal of information which is of 
 little or no value to the builder of true flying machines ; 
 moreover, it is not simple enough to be readily understood 
 by the majority of experimenters. In some other works 
 which I have recently examined, I find a confusing mass of 
 the most intricate mathematical calculations, abounding in 
 an almost infinite number of characters, and extending over 
 hundreds of pages, but on a close examination of some of 
 the deductions arrived at, I find that a good many of the 
 mathematical equations are based on a mistaken hypothesis, 
 and the results arrived at are very wide of the truth. I 
 have shown several diagrams which will explain what 
 I mean. What is required by experimenters in flying 
 machines and there will soon be a great number of them 
 is a treatise which they can understand, and which requires 
 no more delicate instruments than a carpenter's 2-foot rule 
 and a grocer's scales. The calculations relating to the lift, 
 drift, and the skin friction of an aeroplane are extremely 
 simple, and it is quite possible to so place this matter that 
 it can be understood by anyone who has the least smatter- 
 ing of mathematical knowledge. Mathematics of the 
 higher order expressed in elaborate formulae do very well 
 in communications between college professors that is, if 
 they happen to be agreed. When, however, these calcula- 
 tions are so intricate as to require a clever mathematician 
 a whole day to study out the meaning of a single page, 
 and if when the riddle is solved, we find that these 
 calculations are based on a fallacy, and the results in 
 conflict with facts, it becomes quite evident to the actual 
 experimenter that they are of little value. For many 
 years, Newton's law was implicitly relied upon. Chanute, 
 after going over my experimental work, wrote that Newton's 
 law was out as 20 is to 1 that is, that an aeroplane would
 
 lift twenty times as much in practice as could be shown by 
 the use of Newton's formula. Some recent experiments, 
 which I have made myself, at extremely high velocities 
 and at a very low angle, seem to demonstrate that the 
 error is nearer 100 to 1 than 20 to 1. It will, therefore, 
 be seen how little this subject was understood until quite 
 recently, and even now the mathematicians who write 
 books and use such an immense amount of formulae, do not 
 agree by any means, as will be witnessed by the mass of 
 conflicting controversy which has been appearing in 
 Engineering during the last four months. When,- an 
 aeroplane placed at a working angle of, say, 1 in 99 is 
 driven through the air at a high velocity, it, of course, 
 pushes the air beneath it downwards at one-tenth part of 
 its forward velocity that is, in moving 10 feet, it pushes 
 the air down 1 foot. 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 air, the value of this acceleration being in proportion to 
 the square of the velocity which is imparted to it. Suppose 
 now that the aeroplane is thin and well-made, that both 
 top and bottom sides are equally smooth and perfect ; not 
 only does the air engaged by the under side shoot down- 
 wards, but the air also follows the exact contour of 
 the top side, and is also shot downwards with the same 
 mean velocity as that passing on the underneath side, so if 
 we are going to consider the lifting effect of the aeroplane, 
 we must not leave out of the equation, the air above the 
 aeroplane, which has quite as much mass and the same 
 acceleration imparted to it, as the air below the aeroplane. 
 Even calculations made on this basis will not bring the 
 lifting effect of an aeroplane up to what it actually does lift 
 in practice ; in fact, 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 unaccountable. Only a few 
 mathematicians appear to have a proper grasp of the
 
 subject. However, three could be pointed out who under- 
 stand the subject thoroughly, but these are all mathe- 
 maticians of the very highest order Lord Kelvin, Lord 
 Rayleigh, and Professor Langley. In placing before the 
 public, the results of my experiments and the conclusions 
 arrived at, it is necessary to show the apparatus which I 
 employed, otherwise it might be inferred that my con- 
 clusions were guesswork, or mathematical calculations which 
 might or might not be founded on a mistaken hypothesis ; 
 this is my excuse for showing my boiler and engine, my 
 rotating arm, and my large machine. I do not anticipate 
 that anyone will ever use a steam engine again, because 
 any form of a boiler is heavy ; moreover, the amount of 
 fuel required is much greater than with an internal com- 
 bustion engine, and certainly seven times as much water 
 has to be dealt with. However, 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 work. In the Appendix will be 
 found a description of my machine, and some of my 
 apparatus. The conclusions which I arrived at were written 
 down at the time with a considerable degree of care, and 
 are of interest because they show that, at that date, I had 
 produced a machine that lifted considerably more than its 
 own weight and had all of the essential elements, as far as 
 superposed aeroplanes, fore and aft horizontal rudders, and 
 screw propellers were concerned, common to all of the 
 successful machines which have since been made. The 
 fact that practically no essential departure has been made 
 from my original lines, indicates to my mind that I had 
 reasoned out the best type of a machine even before I 
 commenced a stroke of the work. 
 
 I have to thank Mr. Albert T. Thurston for reading the 
 proofs of this work. 
 
 H. S. M.
 
 CONTENTS. 
 
 CHAPTER I. 
 
 PAGE 
 
 Introductory 1 
 
 CHAPTER II. 
 Air Currents and the Flight of Birds, .11 
 
 CHAPTER III. 
 Flying of Kites, 25 
 
 CHAPTER IV. 
 Principally Relating to Screws, 31 
 
 CHAPTER V. 
 
 Experiments with Apparatus Attached to a Rotating Arm Crystal 
 
 Palace Experiments 62 
 
 CHAPTER VI. 
 
 Hints as to the Building of Flying Machines Steering by Means of 
 
 a Gyroscope, 77 
 
 CHAPTER VII. 
 
 The Shape and Efficiency of Aeroplanes The Action of Aeroplanes 
 and the Power Required Expressed in the Simplest Terms Some 
 Recent Machines 99 
 
 CHAPTER VIII. 
 Balloons, .'' . . . . . .120 
 
 APPENDIX I . . . . . . . 126 
 
 APPENDIX II. 
 
 Recapitulation of Early Experiments Efficiency of Screw 
 Propellers, Steering, Stability, &c. The Comparative Value 
 of Different Motors Engines Experiments with Small 
 Machines Attached to a Rotating Arm, 130 
 
 INDEX, . . 163
 
 INDEX OF ILLUSTRATIONS. 
 
 FIG. PAGE 
 
 1. Diagram showing the reduction of the projected horizontal 
 
 area, . . . . . . t f 
 
 2. Professor Langley's experiments, .... 5 
 
 3. Eagles balancing themselves on an ascending current of air, . 14 
 
 4. Air currents observed in Mid- Atlantic, . . . .16 
 
 5. Glassy streaks in the Bay of Antibes, . . . .17 
 
 6. Air currents observed in the Mediterranean, . . .18 
 
 7. The circulation of air produced by a difference in temperature, 27 
 
 8. Kite flying, . . . . . .29 
 
 9. Group of screws and other objects used in my experiments, . 32 
 
 10. Some of the principal screws experimented with, . . 32 
 
 11. The three best screws, ...... 33 
 
 12. Apparatus for testing the thrust of screws, . . .34 
 
 13. Apparatus for testing the direction of air currents, . . 35 
 
 14. The ends of screw blades, . . . . .36 
 
 15. The manner of building up the large screws, . . .39 
 
 16. A fabric-covered screw, ...... 40 
 
 17. The hub and one of the blades of the screw on the Farman 
 
 machine, ....... 42 
 
 18. Section of screw blades having radial edges, . . .43 
 
 1 9. Form of the blade of a screw made of sheet metal, . . 44 
 
 20. New form of hub, ....... 45 
 
 21. Small apparatus for testing fabrics for aeroplanes, . . 50 
 
 22. Apparatus for testing the lifting effect of aeroplanes and 
 
 condensers, .... 51 
 
 23. Apparatus for testing aeroplanes, condensers, &c. , j .52 
 
 24. Cross-sections of bars of wood, . * . * .53 
 
 25. Sections of bars of wood, . . . l .54 
 
 26. A flat aeroplane placed at different angles, . 55 
 
 27. Group of aeroplanes used in experimental research, . . 56 
 
 28. An 8-inch aeroplane which did very well, . . .57 
 
 29. Resistance due to placing objects in close proximity to each 
 
 other, ........ 58 
 
 30. Cross-section of condenser tube made in the form of Philipps' 
 
 sustainers, ....... 60 
 
 31. The grouping of condenser tubes made in the form of Philipps' 
 
 sustainers, t . . . . . , 61 
 
 32. Machine with a rotating arm, ..... 63 
 
 33. A screw and fabric-covered aeroplane in position for testing, . 64 
 
 34. The rotating arm of the machine with a screw and aeroplane 
 
 attached, ....... 65 
 
 35. The little steam engine used by me in my rotating arm 
 
 experiments, ....... 66 
 
 36. The machine attached to the end of the rotating shaft, . 68 
 37- Marking off the dynamometer, ..... 69 
 37a. Right- and left-hand four-blade screws, . . . .70 
 38. Apparatus for indicating the force and velocity of the wind 
 
 direct,. ....... 71
 
 XIV INDEX OF ILLUSTRATIONS. 
 
 FIG. PAGE 
 
 39. Apparatus for testing the lifting effect of aeroplanes, . . 73 
 
 40. Front elevation of proposed aeroplane machine, . . 77 
 
 41. Side elevation of proposed aeroplane machine, . . .78 
 
 42. Plan of proposed aeroplane machine, . . . .79 
 
 43. Plan of a helicopt^re machine, ..... 82 
 
 44. Showing the position of the blades of a helicoptere as they pass 
 
 around a circle, . . . . . .83 
 
 45. System of splicing and building up wooden members, . . 86 
 
 46. Cross-section of struts, ...... 86 
 
 47. Truss suitable for use with flying machines, . . .87 
 
 48. The paradox aeroplane, ...... 88 
 
 49. The Antoinette motor, ...... 89 
 
 50. Section showing the Antoinette motor as used in the Farman 
 
 and De la Grange machines, . . . . .90 
 
 51. Pneumatic buffer, ...... 91 
 
 52. Gyroscope, ....... 94 
 
 53. Adjusting the lifting effect, . . . . .95 
 
 54. Showing that the machine could be tilted in either direction 
 
 by changing the position of the rudder, . . .96 
 
 55. Adjusting the lifting effect, . . . . .97 
 
 56. Adjustment of the rudders, ..... 98 
 
 57. Diagram showing the evolution of a wide aeroplane, . . 102 
 
 58. In a recently published mathematical treatise on aerodynamics 
 
 an illustration is shown, representing the path that the air 
 takes on encountering a rapidly moving curved aeroplane, 104 
 
 59. An illustration from another scientific publication also on the 
 
 dynamics of flight, ...... 104 
 
 60. Another illustration from the same work , . . . 105 
 
 61. The shape and the practical angle of an aeroplane, . . 105 
 
 62. An aeroplane of great thickness, .... 106 
 
 63. Section of a screw blade having a rib on the back, . . 106 
 
 64. Shows a flat aeroplane placed at an angle of 45, . . 107 
 
 65. The aeroplane here shown is a mathematical paradox, . 107 
 
 66. This shows fig. 65 with a section removed, . . 107 
 
 67. Diagram showing real path of a bird, . . 108 
 
 68. The De la Grange machine on the ground, . . .111 
 
 69. The De la Grange machine in full flight, . . .111 
 
 70. Farman's machine in flight, . . . . .112 
 
 71. Bleriot's machine, . . . . . .113 
 
 72. Santos Dumont's flying machine, . . . .113 
 72a. Angles and degrees compared, . . . . .115 
 726. Diagram showing direction of the air with a thick curved 
 
 aeroplane, ....... 118 
 
 72c. Aeroplanes experimented with by Mr. Horatio Philipps, . 118 
 
 73. The enormous balloon "Villede Paris," . . .123 
 
 74. Photograph of a model of my machine, .... 130 
 
 75. The faerie- covered aeroplane experimented with, . . 131 
 
 76. The forward rudder of my large machine showing the fabric 
 
 attached to the lower side, . . . -^ - . . 131 
 
 77. View of the track used in my experiments, . . . 134 
 
 78. The machine on the track tied up to the dynamometer, . 135 
 
 79. Two dynagraphs, ....... 136 
 
 80. The outrigger wheel that gave out and caused an accident 
 
 with the machine, ...... 137 
 
 81. Shows the broken planks and the wreck that they caused, . 138 
 
 82. The condition of the machine after the accident, . . 139 
 
 83. This shows the screws damaged by the broken planks, . 140 
 
 84. This shows a form of outrigger wheels which were ultimately used, 141
 
 INDEX OF ILLUSTRATIONS. XV 
 
 FIG. PAGE 
 
 85. One pair of my compound engines, .... 142 
 
 86. Diagram showing the path that the air has to take in passing 
 
 between superposed aeroplanes in close proximity to each 
 other, . . . . . . . .144 
 
 87. Position of narrow aeroplanes arranged so that the air has 
 
 free passage between them, ..... 145 
 
 88. The very narrow aeroplanes or sustainers employed by Mr. 
 
 Philipps, .146 
 
 89. One of the large screws being hoisted into position, . . 149 
 
 90. Steam boiler employed in my experiments, . . . 157 
 
 91. The burner employed in my steam experiments, . .157 
 
 92. Count Zeppelin's aluminium-covered airship coming out of its 
 
 shed on Lake Constance, . . . .161 
 
 93. Count Zeppelin's airship in full flight, . . 161 
 
 94. The new British war balloon " Dirigible " No. 2, . . 162 
 
 95. The Wright aeroplane in full flight, . . . .162
 
 ARTIFICIAL AND NATURAL FLIGHT. 
 
 CHAPTER I. 
 INTRODUCTORY. 
 
 IT has been my aim in preparing this little work for 
 publication to give a description of my own experimental 
 work, and explain the machinery and methods that have 
 enabled me to arrive at certain conclusions regarding 
 the problem of flight. The results of my experiments 
 did not agree with the accepted mathematical formulae of 
 that time. I do not wish this little work to be considered as 
 a mathematical text-book; I leave that part of the problem 
 to others, confining myself altogether to data obtained by 
 my own actual experiments and observations. During 
 the last few years, a considerable number of text-books 
 have been published. These have for the most part been 
 prepared by professional mathematicians, who have led 
 themselves to believe that all problems connected with 
 mundane life are susceptible of solution by the use of 
 mathematical formulae, providing, of course, that the 
 number of characters employed are numerous enough. 
 When the Arabic alphabet used in the English language 
 is not sufficient, they exhaust the Greek also, and it even 
 appears that both of these have to be supplemented some- 
 times by the use of Chinese characters. As this latter 
 supply is unlimited, it is evidently a move in the right 
 direction. Quite true, many of the factors in the problems 
 with which they have to deal are completely unknown 
 and unknowable ; still they do not hesitate to work out 
 a complete solution without the aid of any experimental 
 data at all. If the result of their calculations should not 
 agree with facts, "bad luck to the facts." Up to twenty 
 years ago, Newton's erroneous law as relates to atmo-
 
 2 ARTIFICIAL AND NATURAL FLIGHT. 
 
 spheric resistance was implicitly relied upon, and it was 
 not the mathematician who detected its error, in fact, we 
 have plenty of mathematicians to-day who can prove by 
 formulae that Newton's law is absolutely correct and 
 unassailable. It was an experimenter that detected the 
 fault in Newton's law. In one of the little mathematical 
 treatises that I have before me, I find drawings of aero- 
 planes 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 them. The 
 dotted lines show that the air which strikes the lower 
 or front side of the aeroplane, instead of following the 
 surface and being discharged at the lower or trailing edge, 
 takes a totally different and opposite path, moving forward 
 and over the top or forward edge, producing a large eddy 
 of confused currents at the rear and top side of the aero- 
 plane. It is very evident that the air never takes the 
 erratic path shown in these drawings ; moreover, the angle 
 of the aeroplane is much greater than one would ever 
 think of employing on an actual flying machine. Fully 
 two pages of closely written mathematical formulae follow, 
 all based on this mistaken hypothesis. It is only too 
 evident that mathematics of this kind can be of little use 
 to the serious experimenter. The mathematical equation 
 relating to the lift and drift of a well-made aeroplane is 
 extremely simple; at any practicable angle from I in 20 
 to 1 in 5, the lifting effect will be just as much greater 
 
 Fig. 1. Diagram showing the reduction of the projected horizontal area 
 of aeroplanes due to raising the front edge above the horizontal 
 tt, 6, shows an angle of 1 in 4, which is the highest angle that will 
 ever be used in a flying machine, and this only reduces the projected 
 area about 2 per cent. The line c b shows an angle of 1 in 8, and 
 this only reduces the projected area an infinitesimal amount. As the 
 angle of inclination is increased, the projected area becomes less as 
 the versed sineyrf becomes greater. 
 
 than the drift, as the width of the plane is greater than 
 the elevation of the front edge above the horizontal that
 
 INTRODUCTORY. 
 
 is, if we set an aeroplane at an angle of 1 in 10, and 
 employ 1 Ib. pressure for pushing this aeroplane forward, 
 the aeroplane will lift 10 Ibs. If we change the angle 
 to 1 in 16, the lift will be 16 times as great as the drift. 
 It is quite true that as the front edge of the aeroplane 
 is raised, its projected horizontal area is reduced that 
 is, if we consider the width of the aeroplane as a radius, 
 the elevation of the front edge will reduce its projected 
 horizontal area just in the proportion that the versed sine 
 is increased. For instance, suppose the sine of the angle 
 to be one-sixth of the radius, giving, of course, to the 
 aeroplane an inclination of 1 in 6, which is the sharpest 
 practical angle, this only reduces the projected area about 
 2 per cent., while the lower and more practical angles 
 are reduced considerably less than 1 per cent. It will, 
 therefore, be seen that this factor is so small that it may 
 not be considered at all in practical flight. 
 
 Some of the mathematicians have demonstrated by 
 formulae, unsupported by facts, that there is a consider- 
 able amount of skin friction to be considered, but as no 
 two agree on this or any other subject, some not agreeing 
 to-day with what they wrote a year ago, I think we 
 might put down all of their results, add them together, 
 and then divide by the number of mathematicians, and 
 thus find the average coefficient of error. When we 
 subject this question to experimental test, we find that 
 nearly all of the mathematicians are radically wrong, 
 Professor Langley, of course, excepted. I made an aero- 
 plane of hard rolled brass, 20 gauge ; it was 1 foot wide 
 and dead smooth on both sides; I gave it a curvature 
 of about T \ inch and filed the edges, thin and sharp. I 
 mounted this with a great deal of care in a perfectly 
 horizontal blast of air of 40 miles an hour. When this 
 aeroplane was placed at any angle between 1 in 8 and 
 1 in 20, the lifting effect was always just in proportion to 
 its angle. The distance that the front edge was raised 
 above the horizontal, as compared with the width of 
 the aeroplane, was always identical with the drift as 
 compared with the lift. On account of the jarring effect 
 caused by the rotation of the screws that produced the 
 air blast, we might consider that all of the articulated 
 joints about the weighing device were absolutely friction- 
 less, as the jar would cause them to settle into the proper 
 position quite irrespective of friction. I was, therefore,
 
 4 ARTIFICIAL AND NATURAL FLIGHT. 
 
 able to observe very carefully, the lift and the drift. As 
 an example of how these experiments were conducted, I 
 would say that the engine employed was provided with a 
 very sensitive and accurate governor; the power trans- 
 mission was also quite reliable. Before making these 
 tests, the apparatus was tested as regards the drift, with- 
 out any aeroplane in position, and with weights applied 
 that would just balance any effect that the wind might 
 have on everything except the aeroplane. The aeroplane 
 was then put in position and the other system of weights 
 applied until it exactly balanced, all the levers being 
 rapped in order to eliminate the friction in their joints. 
 The engine was then started and weights applied just 
 sufficient to counterbalance the lifting effect of the aero- 
 plane, and other weights applied to exactly balance the 
 drift or the tendency to travel with the wind. In this 
 way, I was able to ascertain, with a great degree of 
 accuracy, the relative difference between the lift and drift. 
 If there had been any skin friction, even to the extent of 
 2 per cent., it would have been detected. This brass 
 aeroplane was tested at various angles, and always gave 
 the same results, but of course I could not use thick brass 
 aeroplanes on a flying machine ; it was necessary for me 
 to seek something much lighter. I therefore conducted 
 experiments with other materials, the results of which 
 are given. However, with a well-made wooden aeroplane 
 1 foot wide and with a thickness in the centre of T V inch, 
 I obtained results almost identical with those of the very 
 much thinner brass aeroplane, but it must not be supposed 
 that in practice an aeroplane is completely without friction. 
 If it is very rough, irregular in shape, and has any pro- 
 jections whatsoever on either the top or bottom side, 
 there will be a good deal of friction, although it may not, 
 strictly speaking, be skin friction ; still, it will absorb the 
 power, and the coefficient of this friction may be anything 
 from '05 to '40. These experiments with the brass aero- 
 plane demonstrated that the lifting effect was in direct 
 proportion to the angle, and that skin friction, if it exists 
 at all, was extremely small, but this does not agree with 
 a certain kind of reasoning which can be made very 
 plausible and is consequently generally accepted. 
 
 Writers of books, as a rule, have always supposed that 
 the lifting effect of an aeroplane was not in proportion 
 to its inclination, but in proportion to the square of the
 
 INTRODUCTORY. 5 
 
 sine of the angle. In order to make this matter clear, I 
 will explain. Suppose that an aeroplane is 20 inches wide 
 and the front edge is raised 1 inch above the horizontal. 
 In ordinary parlance this is, of course, called an inclination 
 of 1 in 20, but mathematicians approach it from a different 
 standpoint. They regard the width of the aeroplane as 
 unity or the radius, and the 1 inch that the front edge 
 is raised as a fraction of unity. The geometrical name 
 of this 1 inch is the sine of the angle that is, it is the 
 sine of the angJe at which the aeroplane is raised above 
 the horizontal. Suppose, now, that we have another 
 identical aeroplane and we raise the front edge 2 inches 
 above the horizontal. It is very evident that, under 
 these conditions, the sine of the angle will be twice as 
 much, and that the square of the sine of the angle will 
 be four times as great. All the early mathematicians, 
 and some of those of the present day, imagine that the 
 lift must be in proportion to the square of the sine of 
 the angle. They reason it out as follows : If an aero- 
 plane is forced through the air at a given velocity, the 
 aeroplane in which the sine of the angle is 2 inches will 
 push the air down with twice as great a velocity as the 
 one in which the sine of the angle is only 1 inch, and 
 as the force of the wind blowing against a normal plane 
 increases as the square of the velocity, the same law holds 
 
 Fig. 2. Professor Langley's experiments a, end of the rotating arm; 
 6, brass plane weighing 1 lb. ; c c, spiral springs. When the arm was 
 driven through the air, in the direction shown, the plane assumed 
 approximately a horizontal position, and the pull on the springs c c 
 was reduced from 1 lb. to 1 oz. 
 
 good in driving a normal plane through still air. From 
 this reasoning, one is led to suppose that an aeroplane set
 
 b ARTIFICIAL AND NATURAL FLIGHT. 
 
 at an angle of 1 in 10 will lift four times as much as one 
 in which the inclination is only 1 in 20, but experiments 
 have shown that this theory is very wide of the truth. 
 There are dozens of ways of showing, by pure mathe- 
 matics, that Newton's law is quite correct ; but in building 
 a flying machine no theory is good that does not correspond 
 with facts, and it is a fact, without any question, that the 
 lifting effect of an aeroplane, instead of increasing as the 
 square of the sine of the angle, only increases as the angle. 
 Lord Kelvin, when he visited my place, was, I think, the 
 first to mention this, and point out that Newton's law was 
 at fault. Professor Langley also pointed out the fallacy 
 of Newton's law, and other experimenters have found that 
 the lifting effect does not increase as the square of the 
 sine of the angle. In order to put this matter at rest, 
 Lord Rayleigh, who, I think we must all admit, would 
 not be likely to make a mistake, made some very simple 
 experiments, in which he demonstrated that two aero- 
 planes, in which we may consider the sine of the angle 
 to be inch, lifted slightly more than a similar aeroplane 
 in which the sine of the angle was only | inch. Of course, 
 Lord Rayleigh did not express it in inches, but in term of 
 the radius. His aeroplanes were, however, very small. We 
 can rely upon it that the lifting effect of an aeroplane at 
 any practical angle, everything else being equal, increases in 
 direct proportion to the angle of the inclination. In this 
 little work, I have attempted to make things as simple 
 as possible ; it has not been written for mathematicians, 
 and I have, therefore, thought best to express myself in 
 inches instead of in degrees. If I write, " an inclination 
 of 1 in 20," everyone will understand it, and only a 
 carpenter's 2-foot rule is required to ascertain what the 
 angle is. Then, again, simple measurements make cal- 
 culations much simpler, and the lifting effect is at once 
 understood without any computations being necessary. 
 If the angles are expressed in degrees and minutes, it 
 is necessary to have a protractor or a text-book in . order 
 to find out what the inclination really is. When I made 
 my experiments, I only had in mind the obtaining of 
 correct data, to enable me to build a flying machine that 
 would lift itself from the ground. At that time I was 
 extremely busy, and during the first two years of my 
 experimental work, I was out of England fourteen months. 
 After having made my apparatus, I conducted my experi-
 
 INTRODUCTORY. 7 
 
 ments rather quickly, it is true, but I intended later on 
 to go over them systematically and deliberately, make 
 many more experiments, write down results, and prepare 
 some account of them for publication. However, the 
 property where I made these experiments was sold by 
 the company owning it, and my work was never finished, 
 so I am depending on the scraps of data that were written 
 down at the time. I am also publishing certain observa- 
 tions that I wrote down shortly after I had succeeded in 
 lifting more than the weight of my machine. I think 
 that the experiments which I made with an aeroplane 
 only 8 inches wide will be found the most reliable. All 
 the machinery was running 'smoothly, and the experiments 
 were conducted with a considerable degree of care. In 
 making any formula on the lifting effect of the aeroplane, 
 it should be based on what was accomplished with the 
 8-inch plane. Only a few experiments were made to 
 ascertain the relative value of planes of different widths. 
 However, I think we must all admit that a wide plane 
 is not as economical in power as a narrow one. In order 
 to make this matter plain, suppose that we have one 
 aeroplane placed at such an angle that it will lift 2 Ibs. 
 per square foot at a velocity of 40 miles an hour; 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 plane. If we 
 wish to obtain lifting effect on this air by another plane 
 of exactly the same width, we shall have to increase its 
 inclination in order to obtain the same lifting effect, and, 
 still further, it will be necessary to use more power in 
 proportion to the load lifted. If a third aeroplane is used, 
 it must be placed at an angle that will impart additional 
 acceleration to the air, and so on. Each plane that we 
 add will have to be placed at a sharper angle, and the 
 power required will be just in proportion to the average 
 angle of all the planes. As the action of a wide aeroplane 
 is identical with that of numerous narrow ones placed in 
 close proximity to each other, it is very evident that a 
 wide aeroplane cannot be as efficient in proportion to its 
 width as a narrow one. I have thought the matter over, 
 and I should say that the lifting effect of a flat aero- 
 plane increases rather faster than the square root of 
 its width. This will, at least, do for a working hypo- 
 thesis. Every flying machine must have what we will
 
 ARTIFICIAL AND NATURAL FLIGHT. 
 
 call " a length of entering edge " that is, the sum of 
 entering edges of all the aeroplanes must bear a fixed 
 relation to the load carried. If a machine is to have its 
 lifting effect doubled, it is necessary to have the length 
 of entering edge twice as long. This additional length 
 may, of course, be obtained by superposed planes, but as 
 we may assume that a large aeroplane will travel faster 
 than a small one, increased velocity will compensate in 
 some degree for the greater width of larger aeroplanes. 
 By careful study of the experiments which I have made, 
 
 1 think it is quite safe to state that the lifting effect of 
 well-made aeroplanes, if we do not take into consideration 
 the resistance due to the framework holding them in 
 position, increases as the square of their velocity. Double 
 their speed and they give four times the lifting effect. 
 The higher the speed, the smaller the angle of the plane, 
 and the greater the lifting effect in proportion to the 
 power employed. When we build a steamship, we know 
 that its weight increases as the cube of any one of its 
 dimensions that is, if the ship is twice as long, twice 
 as wide, and twice as deep it will carry eight times as 
 much ; but at the very best, with even higher speed, 
 the load carried by a flying machine will only increase 
 with the square of any one of its dimensions, or perhaps 
 still less. No matter whether it is a ship, a locomotive, 
 or a flying machine that we wish to build, we must first 
 of all consider the ideal, and then approximate it as closely 
 as possible with the material at hand. Suppose it were 
 possible to make a perfect screw, working without friction, 
 and that its weight should only be that of the surrounding 
 air ; if it should be 200 feet in diameter, the power of one 
 man, properly applied, would lift him into the air. This 
 is because the area of a circle 200 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 ladder. If the diameter should be 
 increased to 400 feet, then a man would be able to carry 
 a passenger as heavy as himself on his flying machine, and 
 if we should increase it still further, to 2,000 feet, the 
 weight of a horse could be sustained in still air by the 
 power which one man could put forth. On the other 
 hand, if we should reduce the diameter of the screw to 
 20 feet, then it would certainly require the power of one 
 horse to lift the weight of one man, and, if we made the
 
 INTRODUCTORY. 
 
 screw small enough, it might even require the power of 
 100 horses to lift the same weight. It will, therefore, 
 be seen that everything depends upon the area of the 
 air engaged, and in designing a machine we should seek 
 to engage as much air as possible, so long as we can 
 keep down the weight. Suppose that a flying machine 
 should be equipped with a screw 10 feet in diameter, 
 with a pitch of 6 feet, and that the motor developed 
 40 horse-power and gave the screw 1,000 turns a minute, 
 producing a screw thrust, we will say, of about 220 Ibs. 
 If we should increase the diameter of the screw to 20 feet, 
 and if it had the same pitch and revolved at the same 
 rate, it would require four times as much power and 
 would give four times as much screw thrust, because the 
 area of the disc increases as the square of the diameter. 
 Suppose, now, that we should reduce the pitch of the 
 screw to 3 feet, we should in this case engage four times 
 as much air, and double the screw thrust without using 
 any more power that is, assuming that the machine is 
 stationary and that the full power of the engine is being 
 used for accelerating the air. The advantages of a large 
 screw will, therefore, be obvious. I have been unable to 
 obtain correct data regarding the experiments which have 
 taken place with the various machines on the Continent. 
 I have, however, seen these machines, and I should say 
 when they are in flight, providing that the engine develops 
 40 horse-power, that fully 28 horse-power is lost in screw 
 slip, and the remainder in forcing the machine through 
 the air. These machines weigh 1,000 Ibs. each, and their 
 engines are said to be 50 horse-power. The lifting effect, 
 therefore, per horse-power is 20 Ibs. If the aeroplanes 
 were perfect in shape and set at a proper angle, and the 
 resistance of the framework reduced to a minimum, the 
 same lifting effect ought to be produced with an expendi- 
 ture of less than half this amount of power, providing, 
 of course, that the screw be of proper dimensions. It is 
 said that Professor Langley and Mr. Horatio Philipps, by 
 eliminating the factor of friction altogether, or by not 
 considering it in their calculations, have succeeded in 
 lifting at the rate of 200 Ibs. per horse-power. The 
 apparatus they employed was very small. The best I 
 ever did with my very much larger apparatus and 
 I only did it on one occasion was to carry 133 Ibs. per 
 horse -power. In my large machine experiments, I was
 
 10 ARTIFICIAL AND NATURAL FLIGHT. 
 
 amazed at the tremendous amount of power necessary to 
 drive the framework and the numerous wires through the 
 air. It appeared to me, from these experiments, that 
 the air resisted very strongly being cut up by wires. I 
 expected to raise my machine in the air by using only 
 100 horse-power, and my first condenser was made so 
 that it did actually condense water enough to supply 
 100 horse-power, but the framework offered such a tre- 
 mendous resistance that I was compelled to strengthen 
 all of the parts, make the machine heavier, and increase 
 the boiler pressure and piston speed until I actually ran 
 it up to 362 horse-power. This, however, was not the 
 indicated horse-power. It was arrived at by multiplying 
 the pitch of the screws, in feet, by the number of turns 
 that they made in a minute, and by the screw thrust in 
 pounds, and then dividing the product by the conventional 
 unit 33,000. I have no doubt that the indicated horse- 
 power would have been fully 400. On one occasion I 
 ran my machine over the track with all the aeroplanes 
 removed. I knew what steam pressure was required to 
 run my machine with the aeroplanes in position at a speed 
 of 40 miles an hour. With the planes removed, it still 
 required a rather high steam pressure to obtain this 
 velocity, but I made no .note at the time of the exact 
 difference. It was not, however, by any means so great 
 as one would have supposed. From the foregoing, it will 
 be seen how necessary it is to consider atmospheric resist- 
 ance. Although I do not expect that anyone will ever 
 again attempt to make a flying machine driven by a steam 
 engine, still, I have thought best to give a short and concise 
 description of my engine and boiler, in order that my 
 readers may understand what sort of an apparatus I 
 employed to obtain the data I am now, for the first time, 
 placing before the public. A full description of everything 
 relating to the motor power was written down at the time, 
 and has been carefully preserved. An abridgement of this 
 will be found in the Appendix.
 
 11 
 
 CHAPTER II. 
 AIR CURRENTS AND THE FLIGHT OF BIRDS. 
 
 Ix Mr. Darwin's " Voyage of the Beagle " I find : 
 
 " When the condors are wheeling in a flock round and 
 round any spot their flight is beautiful. Except when 
 rising from the ground, I do not remember ever having 
 seen one of these birds flap its wings. Near Lima I 
 watched several for nearly half an hour, without taking 
 off my eyes ; they moved in large curves, sweeping in 
 circles, descending and ascending without giving a single 
 flap. As they glided close over my head I intently watched 
 from an oblique position, the outlines of the separate and 
 great terminal feathers of each wing, and these separate 
 feathers, if there had been the least vibratory movement, 
 would have appeared as if blended together; but they 
 were seen distinct against the blue sky." 
 
 Man is essentially a land animal, and it is quite possible 
 if Nature had not placed before him numerous examples 
 of birds and insects that are able to fly, he would never 
 have thought of attempting it himself. But birds are very 
 much in evidence, 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 place, but has 
 always aspired to imitate them. The number of attempts 
 that have been made to solve this problem has been very 
 great ; 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 problem. 
 Perhaps nothing better has ever been written regarding 
 our aspirations to imitate the flight of birds than what 
 Prof. Langley has said : 
 
 " Nature has made her flying machine in the bird, which 
 is nearly a thousand times as heavy as the air its bulk 
 displaces, and only those who have tried to rival it know 
 how inimitable her work is, for ' the way of a bird in the 
 air' remains as wonderful to us as it was to Solomon, 
 and the sight of the bird has constantly held this wonder 
 before men's eyes, and in some men's minds, and kept the
 
 12 ARTIFICIAL AND NATURAL FLIGHT. 
 
 flame of hope from utter extinction, in spite of long dis- 
 appointment. I well remember how, as a child, when lying 
 in a New England pasture, I watched a hawk soaring far 
 up in the blue, and sailing for a long time without any 
 motion of its wings, as though it needed no work to sustain 
 it, but was kept up there by some miracle. But, however 
 sustained, I saw it sweep, in a few seconds of its leisurely 
 flight, over a distance that to me was encumbered with 
 every sort of obstacle, which did not exist for it. The 
 wall over which I had climbed when I left the road, the 
 ravine I had crossed, 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 
 direction, the bird's level highway led everywhere, and 
 opened the way into every nook and corner of the land- 
 scape. How wonderfully easy, too, was its flight. There 
 was not a flutter of its pinions as it swept over the field, 
 in a motion which seemed as effortless as that of its 
 shadow." 
 
 During the last 50 years a great deal has been said and 
 written in regard to the flight of birds ; no other natural 
 phenomenon has excited so much interest and been so 
 imperfectly understood. 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 
 animals, 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 jumping. 
 
 Prof. Langley, who was certainly a very clever observer 
 and a mathematician of the first order, in discussing the 
 subject relating to the power exerted by birds in flight and 
 the old formula relating to the subject, expresses himself 
 as follows : 
 
 " After many years and in mature life, I was brought 
 to think of these things again, a,nd to ask myself whether 
 the problem of artificial flight was as hopeless and as 
 absurd as it was then thought to be. Nature had solved 
 it, and why not man? Perhaps it was because he had 
 begun at the wrong end, and attempted to construct 
 machines to fly before knowing the principles on which 
 flight rested. I turned for these principles to my books 
 and got no help. Sir Isaac Newton had indicated a rule 
 for finding the resistance to advance through the air,
 
 AIR CURRENTS AND THE FLIGHT OF BIRDS. 13 
 
 which seemed, if correct, to call for enormous mechanical 
 power, and a distinguished French mathematician had 
 given a formula showing how rapidly the power must 
 increase with the velocity of flight, and according to 
 which a swallow, to attain a speed it is known to reach, 
 must be possessed of the strength of a man. 
 
 " Remembering the effortless flight of the soaring bird, 
 it seemed that the first thing to do was to discard rules 
 which led to such results, and to commence new experi- 
 ments, not to build a flying machine at once, but to find 
 the principles upon which one should be built; to find, 
 for instance, 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 air." 
 
 There is no question but what a bird has a higher 
 physical development, as far as the generation of power 
 is concerned, than any other animal we know of. Never- 
 theless, I think that everyone who has made a study of 
 the question will agree that some animals, such as hares 
 and rabbits, exert quite as much power in running, in 
 proportion to their weight, as a sea-gull or an eagle does 
 in flying. 
 
 The amount of power which a land animal has to exert 
 is always a fixed and definite quantity. If an animal 
 weighing 100 Ibs. has to ascend a hill 100 feet high, it 
 always means the development of 10,000 foot-lbs. With 
 a bird, however, there is no such thing as a fixed quantity. 
 If a bird weighing 100 Ibs. should raise itself into the air 
 100 feet during a perfect calm, the amount of energy 
 developed would be 10,000 foot Ibs. plus the slip of the 
 wings. But, as a matter of fact, the air in which a bird 
 flies is never stationary, as I propose to show ; it is always 
 moving either up or down, and soaring birds, by a very 
 delicate sense of feeling, always take advantage of a rising 
 column. If a bird finds itself in a column of air which is 
 descending, it is necessary for it to work its wings very 
 rapidly in order to prevent a descent to the earth. 
 
 I have often observed the flight of hawks and eagles. 
 They seem to glide through the air with hardly any move- 
 ment of their wings. Sometimes, however, they stop and 
 hold themselves in a stationary position directly over a 
 certain spot, carefully watching something on the earth 
 immediately below. In such cases they often work their 
 wings with great rapidity, evidently expending an enormous
 
 14 
 
 ARTIFICIAL AND NATURAL FLIGHT. 
 
 amount of energy. When, however, they cease to hover 
 and commence to move again through the air, they appear 
 to keep themselves at the same height with an almost 
 imperceptible expenditure of power. 
 
 Many unscientific observers of the flight of birds have 
 
 Fig. 3. While in the Pyrenees I often observed eagles balancing them- 
 selves on an ascending current of air produced by the wind blowing 
 over large masses of rock. 
 
 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 kite. If, however, the wind, 
 which is only air in motion, should be blowing everywhere 
 at exactly the same velocity, and in the same direction
 
 AIR CURRENTS AND THE FLIGHT OF BIRDS. 15 
 
 horizontally it would offer no more sustaining power to a 
 bird than a dead calm, because there is nothing to prevent 
 the body of the bird from being blown along with the air, 
 and whenever it attained the same velocity as the air, no 
 possible arrangement of the wings could prevent it from 
 falling to the earth. 
 
 It is well known that only a short distance above- the 
 earth's surface, say 30 or 40 miles, we find an extremely 
 low temperature sometimes referred to as interstellar 
 temperature or absolute zero. In order to illustrate the 
 extremely low temperature of space, I would cite the 
 following instance : 
 
 One evening, in the State of Ohio, a farmer saw a very 
 brilliant meteor ; it struck in one of his fields not more 
 than 100 feet from his house. He at once rushed to the 
 spot, and, pushing his arm down the hole, succeeded in 
 touching it ; but he very quickly withdrew his hand, as he 
 found it extremely hot. Some of the neighbours rushed 
 to the spot, and he told them what had occurred, where- 
 upon one of them put his hand in the hole, expecting to be 
 burnt, but, much to his surprise, the tips of his wet fingers 
 were instantly frozen to the meteor. 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 iron ; but the heat did not have time 
 to pass into the interior, it only extended inwards perhaps 
 | inch, so that when the meteor came to a state of rest, 
 the heat of the exterior was soon absorbed by the intensely 
 cold interior, thus reducing the surface to a temperature 
 much below any natural temperature that we find at the 
 surface of the earth. 
 
 Nothing can be more certain than that the temperature 
 is extremely low a slight distance above the earth's surface. 
 As the air near the earth never falls in temperature to 
 anything like the absolute zero, it follows that there is a 
 constant change going on, the relatively warm air near the 
 surface of the earth always ascending, and, in some cases, 
 doing sufficient work in expanding to render a portion of 
 the water it contains visible, forming clouds, rain, or snow, 
 while the very cold air is constantly descending to take 
 the place of the rising column of warm air. I have noticed 
 a considerable degree of regularity in the movement of the 
 air, especially at a long distance from land, where the
 
 L6 
 
 ARTIFICIAL AND NATURAL FLIGHT. 
 
 regularity of the up and down currents is, at times, very 
 marked. 
 
 On one occasion while crossing the Atlantic in fine 
 weather I noticed, some miles directly ahead of the ship, 
 a long line of glassy water. Small waves indicated that 
 the wind was blowing in the exact direction in which the 
 ship was moving, and as we approached the glassy line, 
 the waves became smaller and smaller until they com- 
 pletely disappeared in a mirror-like surface, which was 
 about 300 or 400 feet wide, and extended both to the 
 port and starboard in approximately a straight line as 
 far as the eye could reach. After passing the centre of 
 
 Fig. 4. Air currents observed in mid Atlantic, warm air ascending at 
 a, a, a, and cold air descending at b, b, b. c, c, c represent the 
 lines where the waves were the largest. 
 
 this zone, I noticed that small waves began to show them- 
 selves, but in the exact opposite direction to those through 
 which we had already passed, and these waves became 
 larger and larger for nearly half an hour. Then they 
 began to get gradually smaller, when I observed another 
 glassy line directly ahead of the ship. As we approached 
 it, the waves again completely disappeared, but after passing 
 through it, the wind was blowing in the opposite direction, 
 and the waves increased in size exactly in the same manner 
 that they had diminished on the opposite side of the glassy 
 streak (Fig. 4). 
 
 This, of course, shows that directly over the centre of
 
 AIR CURRENTS AND THE FLIGHT OF BIRDS. 
 
 17 
 
 the first glassy streak, the air was meeting from both 
 sides and ascending in practically a straight line from the 
 surface of the water, and then spreading out high above 
 the sea, setting up a light wind in both directions. 
 
 I spent the winter of 1890-91 on the Riviera, between 
 Hyeres les Palmiers and Monte Carlo. The weather for 
 the most part was very fine, and I often had the oppor- 
 tunity of observing the peculiar phenomena which I had 
 already noticed in the Atlantic, only on a much smaller 
 scale. Whereas, in the Atlantic, the glassy zones were 
 
 Fig. 5. Glassy streaks showing the centres of ascending and descending 
 columns of air in the Bay of Antibes, Alpes Maritimes. 
 
 from 8 to 15 miles apart, I often found them not more 
 than 500 feet apart in the bays of the Mediterranean. 
 This was most noticeable at Antibes (Fig. 5), very good 
 photographs of which I obtained. It will be observed 
 that the whole surface of the water is streaked like a 
 block of marble. 
 
 At Nice and Monte Carlo this phenomena was also very 
 marked. On one occasion, while making observations 
 from the highest part of the promontory of Monaco on 
 a perfectly calm day, I noticed that the whole of the sea 
 presented this peculiar effect as far as the eye could reach, 
 
 2
 
 18 ARTIFICIAL AND NATURAL FLIGHT. 
 
 and that the lines which marked the descending air were 
 never more than 1,000 feet from those which marked the 
 centre of the ascending column. At about three o'clock 
 one afternoon, a large black steamer passed along the coast 
 in a perfectly straight line, and its wake was at once 
 marked by a glassy line, which indicated the centre of an 
 ascending column. This line remained almost straight for 
 two hours, when finally it became crooked and broken. 
 The heat of the steamer had been sufficient to determine 
 this upward current of air. 
 
 In 1893 I spent two weeks in the Mediterranean, going 
 and returning by a slow steamer from Marseilles to Con- 
 
 . \ 
 
 b c 
 
 
 Fig. 6. Air currents observed in the Mediterranean, ascending currents 
 at a, a, a, and descending currents at b, b, b. 
 
 stantinople, and I had many opportunities of observing 
 the peculiar phenomena to which I have referred. The 
 steamer passed over thousands of square miles of calm 
 sea, the surface being only disturbed by large patches of 
 small ripples (Fig. 6), sep irated from each other by glassy 
 streaks, which, however, were not straight as on the 
 Atlantic, and I found that in no case was the wind 
 blowing in the same direction on both sides of these 
 streaks, every one of which indicated the centre of an 
 ascending or a descending column of air. If we should 
 investigate these phenomena in what might be called a 
 dead calm, we should find that the air was rising very
 
 AIR CURRENTS AND THE FLIGHT OF BIRDS. 19 
 
 nearly straight up over the centres of some of these 
 streaks and descending in a vertical line over the centres 
 of others. But, as a matter of fact, there is no such thing 
 as a dead calm. The movement of the air is the resultant 
 of more than one force. The air is not only rising in some 
 places and descending in others, but at the same time, the 
 whole mass is moving forward with more or less rapidity 
 from one part of the earth to another, so we must consider 
 that, instead of the air ascending directly from the rela- 
 tively hot surface of the earth and descending vertically 
 in other places, in reality the whole mass of rotating air is 
 moving horizontally at the same time. 
 
 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 2 miles an hour, and 
 that the wind at the same time should be blowing at the 
 rate of 10 miles an hour, the motion of the air would then 
 be the resultant of these two velocities. In other words, 
 it would be blowing up an incline of 1 in 5. Suppose, 
 now, that a bird should be able to so adjust its wings 
 that it advanced 5 miles in falling 1 mile through a 
 perfectly calm atmosphere, it would then be able to 
 sustain itself in an inclined wind, such as I have 
 described, without any movement at all of its wings. 
 If it were possible to adjust its wings in such a manner 
 that it could advance 6 miles by falling through 1 mile 
 of air, it would then be able to rise as relates to the earth 
 while in reality falling as relates to the surrounding air. 
 
 In conducting a series of experiments with artillery and 
 small guns on a large and level plain just out of Madrid, 
 I often observed the same phenomena, as relates to the 
 wind, that I have already spoken of as having observed 
 at sea, 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 water. It was not an 
 uncommon thing, when adjusting the sights of a gun to 
 fire at a target at a very long range, making due allow- 
 ances for the wind, to have the wind change and blow in 
 the opposite direction before the word of command was 
 given to fire. While conducting these experiments, I often 
 noticed the flight of eagles. On one occasion a pair of 
 eagles came into sight on one side of the plain, passed 
 directly over our hea'is, and disappeared on the opposite 
 side. They were apparently always at the same height
 
 20 ARTIFICIAL AND NATURAL FLIGHT. 
 
 from the earth, and in soaring completely across the plain 
 they never once moved their wings. These phenomena, I 
 think, can only be accounted for on the hypothesis that these 
 birds were able to feel out with their wings an ascending 
 column of air, that the centre of this column of air was 
 approximately a straight line running completely across 
 the plain, that they found upward movement more than 
 sufficient to sustain their weight in the air, and that, 
 whereas, as relates to the earth, they were not falling at 
 all, they were in reality falling some 4 or 5 miles an hour 
 in the air which supported them. 
 
 Again, at Cadiz in Spain, when the wind was blowing 
 in strongly from the sea, I observed that the sea-gulls 
 always took advantage of an ascending column of air. 
 As the wind rose to pass over the fortifications, the gulls 
 selected a place where they would glide on the ascending 
 current of air, keeping themselves always approximately 
 in the same place without any apparent exertion. When, 
 however, they left this ascending column, it was necessary 
 for them to work their wings with great vigour until they 
 again found the proper place to encounter a favourable 
 current. 
 
 I have often noticed that gulls are able to follow a ship 
 without any apparent exertion ; they simply balance them- 
 selves on an ascending column of air, where they seem to 
 be quite as much at ease as they would have been roosting 
 on a solid support. If, however, they are driven out of 
 this position, they generally commence at once to work 
 their passage. If anything is thrown overboard which is 
 too heavy for them to lift, the ship soon leaves them 
 behind, and in order to catch up with it again they move 
 their wings very much as other birds do ; but when once 
 established in the ascending column of air, they manage 
 to keep up with the ship by doing little or no work. In 
 a calm or head wind we find them directly aft of the 
 ship; if the wind is from the port side they may always 
 be found on the starboard quarter, and vice versa. 
 
 One Sunday morning, while living at Kensington, I 
 noticed some very curious atmospheric effects. The 
 weather had been intensely cold for about a week, when 
 suddenly the atmosphere became warm and very humid. 
 The earth being much colder than the atmosphere, water 
 was condensing on everything that it touched. I went 
 to the bridge over the Serpentine in Hyde Park, and was
 
 AIR CURRENTS AND THE FLIGHT OF BIRDS. 21 
 
 not disappointed in finding a large number of sea-gulls 
 waiting about the bridge to be fed. On all ordinary 
 occasions these birds manage to move about with the 
 expenditure of very little energy, but on this occasion 
 every one of them, without a single exception, no matter 
 in what position he might be, was working his passage 
 like any other bird, just as I had expected. 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 air. 
 
 Everyone who has passed a winter on the northern 
 shores of the Mediterranean must have observed the cold 
 wind which is generally called the mistral. One may be 
 out driving, the sun may be shining brightly, and the air 
 warm and balmy, when suddenly, without any apparent 
 cause, one finds himself in a cold descending wind. This 
 is the much-dreaded mistral, and if at sea it would be 
 marked by a glassy line on the surface of the water. 
 On land, however, there is nothing to render its presence 
 visible. The ascending column of air is, of course, always 
 very much warmer than the descending column, and this 
 is taking place in a greater or lesser degree everywhere 
 and at all times. A decided upward trend of air is often 
 encountered by those who are experimenting with kites, 
 the kite often mounting higher than can be accounted for 
 on the hypothesis that the wind is moving in a horizontal 
 direction. I have heard this discussed at considerable 
 length. When a kite is flown in an upward current, it 
 behaves in many respects like a soaring bird. 
 
 From the foregoing, I think, we may safely draw the 
 following conclusions : 
 
 First, that there is a constant interchange of air taking 
 place, the cold air descending, spreading itself out over 
 the surface of the earth, becoming warm, and ascending 
 in other places. 
 
 Second, that the centres of the two columns are generally 
 separated from each other by a distance which may be from 
 500 feet to 20 miles. 
 
 Third, that the centres of greatest action are not in 
 spots, but in lines which may be approximately straight, 
 but sometimes abound in many sinuosities. 
 
 Fourth, that this action is constantly taking place over 
 both the sea and the land ; that the soaring of birds, the 
 phenomenon which has heretofore been so little under-
 
 22 ARTIFICIAL AND NATURAL FLIGHT. 
 
 stood, may be accounted for on the hypothesis that the 
 bird seeks out an ascending column of air, and while 
 sustaining itself at the same height in the air, without 
 any muscular exertion, it is in reality falling at a con- 
 siderable velocity through the air that surrounds it. 
 
 It has been supposed by some scientists that birds may 
 take advantage of some vibratory or rolling action of the 
 air. I find, however, from careful observation and experi- 
 ment, that the motion of the wind is comparatively steady, 
 and that the short vibratory or rolling action is alw r ays 
 very near to the earth and is produced by the air flowing 
 over hills, high buildings, trees, etc. 
 
 Tools and instruments used by mechanicians are very 
 often made of the material most used in their profession ; 
 for instance, a blacksmith's tools are generally of iron, a 
 carpenter's tools largely of wood, and a glass-blower uses 
 many things made of glass, and so on. Mathematicians 
 are no exception to this general rule, and seem to imagine 
 that everything can be accomplished by pure mathematical 
 formulae. 
 
 It appears that Prof. Langley was at times considerably 
 puzzled by the extraordinary behaviour of birds, and was 
 led to believe that they took advantage of some vibratory 
 or oscillating movement of the air ; he called it " the 
 internal work of the air." I have been very much 
 amused in a recent mathematical work that I have read, 
 in which the writer seeks to solve all questions by pure 
 mathematics. In this case, notwithstanding that all of 
 the factors are unknown and unknowable, still, with the 
 use of about two pages of closely written algebraic formulae, 
 he appears to have solved the whole question. Just how 
 he arrived at it, however, is more than I am able to under- 
 stand. 
 
 If a kite is flown only a few feet above the ground, it 
 will be found that the current of air is very unsteady. If 
 it is allowed to mount to 500 feet the unsteadiness nearly 
 all disappears, while if it is allowed to mount further to 
 a height of 1,500 or 2,000 feet, the pull on the cord is 
 almost constant, and, if the kite is well made, it remains 
 practically stationary in the air. 
 
 I have often noticed in high winds that light and fleecy 
 clouds come into view, say, about 2,000 feet above the 
 surface of the earth, and pass rapidly and steadily by 
 preserving their shape completely. This would certainly
 
 AIR CURRENTS AND THE FLIGHT OF BIRDS. 23 
 
 indicate that there is no rapid local disturbance in the 
 air in their immediate vicinity, but that the whole mass 
 of air in which these clouds are formed is practically 
 travelling in the same direction and at the same velocity. 
 Numerous aeronauts have also testified that, no matter 
 how hard the wind may be blowing, the balloon is always 
 practically in a dead calm, and if a piece of gold-leaf is 
 thrown overboard, even in a gale, the gold-leaf and the 
 balloon never part company in a horizontal direction, 
 though they may in a vertical direction. 
 
 Birds may be divided into two classes. First, the 
 soaring birds, which practically live upon the wing, and, 
 by some very delicate sense of touch, are able to feel 
 the exact condition of the air. Many fish which live 
 near the top of the water are greatly distressed by 
 sinking too deeply, while others which live at great 
 depths are almost instantly killed by being raised to 
 the surface. 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 water. With the surface fish, if the pressure becomes 
 too great, it involuntarily exerts itself to rise nearer the 
 surface and so diminish the pressure, and I have no doubt 
 that the air cells, which are known to be very numerous 
 and to abound throughout the bodies of birds, are so 
 sensitive as to enable soaring birds to know at once 
 whether they are in an ascending or a descending column 
 of air. 
 
 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 another. Such birds do 
 not expend their power so economically as the soaring 
 birds. They do not pass much of their time in the air, 
 but what time they are on the wing they put forth an 
 immense amount of power and fly very rapidly, generally 
 in a straight line, taking no advantage of air currents. 
 Partridges, pheasants, wild ducks, geese, and some birds of 
 passage may be taken as types of this kind. This class 
 of birds has relatively small wings, and carries about two 
 and a half times as much weight per square foot of surface 
 as soaring birds do. 
 
 We shall never be able to imitate the flight of the soaring 
 birds. We cannot hope to make a sensitive apparatus 
 that will work quick enough to take advantage of the
 
 24 
 
 ARTIFICIAL AND NATURAL FLIGHT. 
 
 rising currents of air, and he who seeks to fly has this 
 problem to deal with. A successful flying machine, moving 
 at a high velocity, is likely at any time to encounter down- 
 ward currents of air, which will greatly interfere with its 
 action. Therefore "flying machines must, in the very nature 
 of things, be provided with sufficient power to propel them 
 through various currents of air, after the manner of ducks, 
 partridges, pheasants, etc. 
 
 Common Name. 
 
 Sq. Ft. per Lb. 
 
 Lbs.perSq.Ft. 
 
 Corresponding 
 Speed for a Plane 
 at 3 in Miles 
 per Hour. 
 
 Bat 
 
 64 
 
 0-131 
 
 15-9 
 
 Swallow, . 
 
 3-62 
 
 0-276 
 
 23-1 
 
 Lark, 
 
 3-06 
 
 0-327 
 
 25-1 
 
 Sparrow hawk, 
 Sparrow, . 
 
 3-00 
 2-42 
 
 0-333 
 0-414 
 
 25-3 
 
 28-2 
 
 Gull, 
 
 2-35 
 
 0-426 
 
 28-6 
 
 Owl, 
 
 2-26 
 
 0-443 
 
 29-2 
 
 Crane, . 
 
 2-02 
 
 0-495 
 
 30-9 
 
 Rook, 
 
 1-74 
 
 0-575 
 
 33-3 
 
 Plover, . 
 
 1-38 
 
 0-725 
 
 37-4 
 
 Balbuzzard, 
 
 1-26 
 
 0-795 
 
 39-2 
 
 Egyptian vulture, . 
 
 1-18 
 
 0-848 
 
 40-4 
 
 Duck, 
 
 0-864 
 
 1-158 
 
 44-2 
 
 Grey pelican, . 
 
 0-732 
 
 1 -365 
 
 51-3 
 
 Wild goose, . 
 
 0-586 
 
 1-708 
 
 57-4 
 
 Turkey, . 
 
 0-523 
 
 1-910 
 
 60-6 
 
 Duck (female), . 
 
 0-498 
 
 2-008 
 
 62-2 
 
 ,, (male), . 
 
 0-439 
 
 2-280 
 
 66-2
 
 CHAPTER III. 
 FLYING OP KITES. 
 
 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 clouds, he managed to have a boy with him 
 in order to avoid ridicule. It was considered too frivolous 
 in those days for grown-up men to amuse themselves with 
 kites, 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 flight. 
 Nineteen years ago, when I commenced my own experi- 
 ments, I was told that my reputation would be greatly 
 injured, that mankind looked upon artificial flight as an 
 ignis-fatuus, 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 stone. Although I had little fear of ridicule, 
 still I kept things as quiet as I could for a considerable 
 time, and I had been working fully six months before 
 anyone ascertained what I was doing. When, however, 
 it became known that I was experimenting with a view 
 of building a flying machine, the public seemed to think 
 that I was making honest and praiseworthy scientific 
 investigations ; true, I might not succeed, still it was said 
 that I would accomplish something, and find out some of 
 the laws relating to the subject. No one ridiculed my 
 work except two individuals, and both of these were men 
 whom I had greatly benefited. As is often the case, those 
 whom you find in difficulties and place 'on their feet seek 
 to do you some injury as compensation for the benefits 
 they have received. 
 
 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 kite. 1 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 subject. The behaviour of kites is 
 certainly very puzzling to those who do not thoroughly
 
 26 ARTIFICIAL AND NATURAL FLIGHT. 
 
 understand the subject. A kite may be made with the 
 greatest degree of perfection, and placed in the hands of 
 one of considerable experience ; nevertheless, it may behave 
 very badly, diving suddenly to the ground without any 
 apparent cause. Then, again, this same kite will sometimes 
 steadily mount in the air until it reaches a height difficult 
 to account for. If the surface of the earth should be 
 perfectly smooth, and the wind should always blow in a 
 horizontal direction, kites would not show these eccentric 
 peculiarities, but, as a matter of fact, the air seldom moves 
 in a horizontal direction; it is always influenced by the 
 heat of the surface of the earth. Heated air is continually 
 ascending in some places only to be cooled and to descend 
 in other places. If one is attempting to fly a kite where 
 the air is moving downwards, he will find it an extremely 
 difficult matter, whereas, if he is fortunate enough to strike 
 a current of air which is rising, the kite will mount much 
 higher in the air than can be accounted for, except we 
 admit of the existence of these upward draughts of air. 
 On one occasion many years ago, I was present when a 
 bonded warehouse in New York containing 10,000 barrels 
 of alcohol was burnt. It was nine o'clock at night, and 
 1 walked completely around the fire, arid found things 
 just as I had expected. The wind was blowing a perfect 
 hurricane through every street in the direction of the fire, 
 although it was a dead calm everywhere else ; the flames 
 mounted straight in the air to an enormons height, and 
 took with them a large amount of burning wood. When 
 I was fully 500 feet from the fire, a piece of partly burnt 
 1-inch board, about 8 inches wide and 4 feet long, fell 
 through the air and landed very near me, sending sparks 
 in every direction. This board had evidently been taken 
 up to a great height by the tremendous uprush of air 
 caused by the burning alcohol. 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 position. 
 
 The sketch (Fig. 7) shows a device consisting of a spirit 
 lamp and a box of ice. The lamp heats the metallic plate, 
 expands the air which rises and is cooled by convection 
 on coming in contact with the top plate, and descends as 
 shown. However, a fire is not necessary to accomplish this 
 result ; it as taking place all over the earth, all the time. 
 A great number of plants depend upon a rising current of
 
 FLYING OF KITES. 
 
 27 
 
 air to transport their seeds to distant places. Seeds of the 
 thistle and dandelion variety are sometimes able to travel 
 hundreds of miles, to the great vexation of farmers ; and 
 there is a certain class of small spider known as "Balloon 
 Spiders " which also depend upon a rising current of air to 
 carry them from the place of their birth to some distant 
 
 Fig. 7. The circulation of air produced by a difference in temperature. 
 
 part where they, of course, hope to start a colony. When 
 I was a boy of eight, I noticed small spiders webbing down 
 from the sky. I was greatly puzzled ; 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 earth. What could that stationary object 
 be ? As the sky was clear, I was quite unable to understand
 
 28 ARTIFICIAL AND NATURAL FLIGHT. 
 
 this phenomenon, 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 wind. It appears 
 that they climb a high tree until they have reached the 
 uppermost extremity and then, from a leaf or twig that 
 projects into the air, they wait for an ascending current of 
 air. Although the spider is exceedingly small the size of 
 a pin's head it has about 200 spinnerets, its ordinary web 
 being formed of no less than that number of extremely fine 
 threads. 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 18 inches 
 long is produced. . Whenever an upward draft of air 
 approximately vertical occurs, it takes this weightless 
 tangle of fine webs with it, and so soon as the spider finds 
 there is sufficient pull to lift its weight, it lets go and 
 ascends with the air. When the Nulli Secundus ascended 
 at Farnborough and landed at the Crystal Palace, Mr. 
 Cody, who was on board, reported what he supposed to be 
 a very curious and unaccountable phenomenon. The 
 balloon was covered with many thousands of minute 
 spiders that it had picked up in the air on the voyage. 
 Certainly this of itself is very strong evidence of the 
 existence of these ascending currents of air. 
 
 When in Boston about fifteen years ago, I went to Blue 
 Hill to witness the remarkable kite flying which was 
 taking place at that time. The kites experimented with 
 were of the Hargrave type, and of enormous dimensions. 
 A steel wire and windlass worked by a steam engine was 
 employed. I was told that on certain occasions the kites 
 mounted extremely high, much higher than they were able 
 to account for ; but on this particular occasion, although 
 they let out a great amount of wire, the kite did not mount 
 very high. I have heard much discussion first and last 
 regarding the flight of kites, and I think it is generally 
 admitted that they do sometimes rise upwards and con- 
 tinue moving to the windward until they pass directly 
 over the spot where they are attached to the earth. It 
 was not, however, till about three years ago that I 
 witnessed this phenomenon myself. Mr. Cody, who is the 
 inventor of a very good kite, had been flying kites at the 
 Crystal Palace for some months, and on one occasion I saw 
 his kite rise, pass to the windward and directly over our
 
 FLYING OF KITES. 
 
 29 
 
 heads. I took hold of the cord with both hands, and was 
 somewhat surprised to find what the lifting effect was. 
 The kite was, however, of large dimensions, but by no 
 means so large as Mr. Cody's " man-lifting kites." In the 
 
 drawing (Fig. 8) I have shown, at a, the action of a kite in 
 a horizontal wind, lines e, e, showing the direction of the 
 wind. A good kite will easily mount 45, the angle shown, 
 but on the occasion just mentioned, the sun had been 
 shining brightly into the valley where the experiments
 
 30 ARTIFICIAL AND NATURAL FLIGHT. 
 
 took place, and an upward current of air had been deter- 
 mined. The cooler air was, of course, rushing in from each 
 side and mounting in about the centre of the valley, and 
 Mr. Cody's kite, instead of flying in a horizontal wind, 
 soon reached a point where the wind was ascending at 
 an angle, as shown at /, /. The kite would therefore 
 mount until at 6, where it presented the same angle 
 to the wind as with the horizontal wind at a, and 
 if it should be made to fly at a higher angle, it 
 might pass over to the position shown at c. But 
 it must not be imagined that this phenomenon can be 
 witnessed every day in the year. 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 
 support. Neither must it be supposed that this favourable 
 condition of things is of long duration. As the centre of 
 the upward current is constantly moving, it is certain that 
 very soon it will move away from the point from which 
 the kite is being flown. What is true of kites is also true 
 of flying machines. It is very difficult indeed to make a 
 kite mount providing that it is in a descending current of 
 air, and one is just as likely to find a descending current 
 as any other. Flying machines will, therefore, have to be 
 made with a considerable amount of reserve energy, so as 
 to be able to put on a spurt when they encounter an 
 adverse current. If a machine is made that is able to 
 maintain itself in the air for any considerable length of 
 time, it will not be a very difficult task to know when a 
 current of air of this kind is encountered, because, if the 
 engine is working up to speed, and everything is in perfect 
 order, and still the machine is falling, it is very certain 
 that an unfavourable current has been encountered, and 
 efforts should be made to get out of it as soon as possible. 
 Then, again, if the machine has an abnormal tendency to 
 rise without any increase in the number of rotations made 
 by the screws, the aeronaut may be certain that he has 
 encountered an upward and favourable current of air 
 which, unfortunately, will not last. It should, however, 
 be borne in mind that, while the width of the upward 
 current is not very great, nevertheless, it may extend in a 
 practically straight line for many miles.
 
 31 
 
 CHAPTER IV. 
 PRINCIPALLY RELATING TO SCREWS. 
 
 Iv 1887 I was approached by several wealthy gentlemen 
 who asked me if I thought it was possible to make a 
 flying machine. I said, " certainly ; the domestic goose 
 is able to fly and why should not man be able to do as 
 well as a goose?" They then asked me what it would 
 cost and how long it would take, and, without a moment's 
 hesitation, I said it would require my undivided attention 
 for five years and might cost 100,000. A great deal of 
 experimenting would be necessary ; the first three years 
 would be devoted to developing an internal combustion 
 engine of the Brayton or Otto type, and the next two 
 years to experimenting with aeroplanes and screws and 
 building a machine. Even at that time I had a clear idea 
 of the system that would be the best. However, nothing 
 was then done, but in 1889 I employed for the purpose 
 two very skilful American mechanics, and put them to 
 work at Baldwyn's Park, Kent. At that time the 
 petroleum motor had not been reduced to its present 
 degree of efficiency and lightness; it was not suitable 
 for a flying machine, and 1 saw that it would require 
 a lot of experimental work in order to develop it. After 
 taking into consideration all the facts of the case, I decided 
 to use a steam engine. Had I been able to obtain the 
 light and efficient motors which have been recently 
 developed, thanks to the builders of racing cars, I 
 should not have had to experiment at all with engines 
 and boilers, as I could have obtained the necessary motors 
 at once. As it was, I was obliged to content myself with 
 the steam engine. 
 
 I found that there was a great deal of misunderstanding 
 regarding the action of aeroplanes, and also of screws 
 working in the air. I procured all the literature avail- 
 able on the subject, both English and French, and 
 attempted to make a thorough study of the question; 
 but I was not satisfied, on account ot the wide difference 
 in the views of the writers and the conflicting formulae 
 that were employed. I therefore decided to make experi-
 
 32 ARTIFICIAL AND NATURAL FLIGHT. 
 
 ments myself, and to ascertain what could be done without 
 the use of anybody's formula. Although this was nearly 
 
 Fig. 9. Group of screws and other objects used in my experiments. 
 
 twenty years ago, I find that there is still a great deal of 
 discussion regarding the action of aeroplanes and screws, 
 
 Fig. 10. Some of the principal screws experimented with h, a screw 
 with very thick blades, and g, a screw made after a French model. 
 
 in which the majority taking part in the discussion are in 
 the wrong. However, several good works on the subject 
 have recently been published.
 
 PRINCIPALLY RELATING TO SCREWS. 33 
 
 Having designed and put my boiler and engine in hand, 
 I commenced a series of experiments for the purpose of 
 ascertaining the efficiency of screw propellers working 
 in the air, and the form and size that would be best for 
 my proposed machine. The illustration Fig. 9 shows a 
 photographic group of the screws and other objects with 
 which I experimented. Fig. 10 shows some of the leading 
 types which, as will be seen, have blades of different shape, 
 pitch, and size. Fig. 11 shows three of the best screws 
 employed. It will be observed that one has uniform pitch, 
 another increasing pitch, and the third compound increasing 
 pitch. In order to test the efficiency of my screws I made 
 the apparatus shown in Fig. 12. The power for running 
 the screw was transmitted by means of a belt to the 
 straight cylindrical pulley c, c. Shaft b, b was of steel, 
 rather small in diameter, and ran smoothly, and practically 
 
 Fig. 11. The three best screws. The screw on the right has a uniform 
 pitch throughout, the middle screw has increasing pitch, and the left 
 screw compound increasing pitch. 
 
 without friction, through the two bearings d, d. When 
 the first screw, a, a, was run at a high velocity, the axial 
 thrust pushed the shaft 6, b back and elongated the spiral 
 spring e. The degree of screw thrust was indicated in 
 pounds by the pointer g. The power was transmitted 
 through a very accurate and sensitive dynamometer, so 
 that the amount consumed could be easily observed by 
 a pointer similar to the one employed for indicating the 
 screw thrust. A tachometer was also employed to observe 
 the number of turns that the screw was making in a 
 minute. The whole apparatus was carefully and accurately 
 made and worked exceedingly well. I was thus enabled, 
 with my various forms of screws and other objects, to 
 make very accurate measurements, some of which are 
 exceedingly interesting. 
 
 In many of the treatises and books of that time it was 
 
 3
 
 PRINCIPALLY RELATING TO SCREWS. 35 
 
 stated that a screw propeller, working in the air, was 
 exceedingly wasteful of energy on account of producing 
 a fan-blower action. Some inventors suggested that the 
 screw should work in a stationary cylinder, or, better 
 still, that the whole screw should be encased in a rotating 
 cylinder, to prevent this outward motion of the air. In 
 
 Fig. 13. Apparatus for testing the direction of air currents caused by a 
 rapidly rotating screw. Silken threads were attached to the wire c, c 
 which indicated clearly the direction in which the air was moving. 
 
 order to ascertain what the actual facts were, I attached 
 a large number of red silk threads to a brass wire, which 
 I placed completely around my screw (see Fig. 13). Upon 
 starting up I found that, instead of the air being blown 
 out at the periphery of the screw, it was in reality sucked 
 in, as will be seen in the illustration. I was rather sur-
 
 36 ARTIFICIAL AND NATURAL FLIGHT. 
 
 prised 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 
 direction. The screw employed in these experiments' was 
 18 inches in diameter and had a pitch of 24 inches. It 
 was evident, however, if the pitch of the screw was coarse 
 enough that there would be a fan-blower action. I there- 
 fore tried screws of various degrees of pitch, and found 
 when the pitch was a little more than three times the 
 
 Fig. 14. This drawing shows the ends of screw blades in which a is a 
 plain screw; 6, screw with increasing pitch; c, screw with compound 
 increasing pitch ; d, end of screw blade 45 ; e, screw with very thick 
 blade; /, blade with no pitch at all; g, blade which gave a thrust in 
 the direction of the convex side, no matter in which direction it was 
 revolved ; h, screw said to have been used in the French Government 
 experiments. 
 
 diameter, giving to the outer end of the blade an angle 
 of 45, that a fan -blower action was produced that is, 
 part of the time when the screw was running, the air 
 would alternate; sometimes it would pass inwards at the 
 periphery and sometimes outwards. The change of direc- 
 tion, however, was always indicated by a difference in 
 the pitch of the note given out, and also by the thrust. 
 In Fig. 14 I have shown the extremities of the blades of 
 some of the different forms of screws experimented with.
 
 PRINCIPALLY RELATING TO SCREWS. 37 
 
 in which a shows a plain screw, the front side being 
 straight and of equal pitch from the periphery to the 
 hub; 6 is a screw of practically the same pitch, but 
 slightly curved so as to give what is known as an 
 increasing pitch; c shows the extremity of a screw in 
 which the curve is not the same throughout that is, it 
 is what is known as a compound increasing pitch ; d is 
 the shape of the screw that gave the angle of 45 above 
 referred to 
 
 The first screw experimented with was a. This screw 
 was run at a high velocity about 2,500 revolutions per 
 minute until a screw thrust of 14 Ibs. was obtained, and 
 then the governor of the engine was set so that all screws 
 of the same diameter could be run at the same speed. 
 Wishing to ascertain the efficiency of the screw and how 
 much was lost in skin friction, 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 minute. This, of 
 course, gave the exact number of foot-pounds in energy 
 that was being imparted to the air. I was somewhat 
 surprised to find that it corresponded exactly with the 
 readings of the dynamometer. I thought at first that 
 I must have made some mistake. Again I went very 
 carefully over all the figures, tested everything, and 
 made another experiment and found, even if I changed 
 the number of revolutions, that the readings of the 
 dynamometer were always exactly the same as the 
 energy imparted to the air. This seemed to indicate 
 that the screw was working very well and that the skin 
 friction must be very small indeed. In order to test this, 
 I made what we will call, for the moment, a screw without 
 any pitch at all that is, the blades were of wood and of 
 the exact thickness and width of the blades of the screw a, 
 but without any pitch at all. The extremity of the blade 
 is shown at /. I placed this screw on my machine in place 
 of a, 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 shaft, it failed to 
 indicate, and thus the screw appeared to consume no power 
 at all. These experiments were repeated a considerable 
 number of times. I then obtained a sheet of tin the same 
 diameter as the screws, 18 inches, and upon running it at 
 the same speed, I found that it did consume a measurable 
 amount of power, certainly more than the two blades /. 
 
 136510
 
 38 ARTIFICIAL AND NATURAL FLIGHT. 
 
 This no doubt was due to the uneven surface of the tin. 
 Had it been a well-made saw blade without teeth, perfectly 
 smooth and true on both sides, it probably would not have 
 required power enough to have shown on the dynamometer. 
 However, it is quite possible that there is a little more 
 skin friction with a polished metallic surface, than with a 
 piece of smooth evenly lacquered wood. The screws which 
 I employed were of American white pine such as used by 
 patternmakers. This wood was free from blemishes of all 
 kind, extremely light, uniform, and strong. When the 
 screw had been formed, it was varnished on both sides with 
 a solution of hot glue, which greatly increased the strength 
 of the wood crosswise of the grain. When this glue was 
 thoroughly dry, the wood was sand-papered until it was as 
 smooth as glass ; the whole thing was then carefully var- 
 nished with shellac, rubbed down again and revarnished 
 with very thin shellac something like lacquer. In this way 
 the surface of the screw was made very smooth. The screws, 
 of course, were made with a great degree of accuracy and 
 as free as possible from any unevenness. Having tested 
 screw a, I next tested screw b. I found with the same 
 number of revolutions per minute that this screw produced 
 more thrust, but it required more power to run it, and 
 when the energy imparted to the air was compared with 
 the readings of the dynamometer, it was found that it did 
 not do quite so well as a; still as the thrust was greater and 
 the efficiency only slightly less, it appeared to be the better 
 screw. Upon trying screw c, under the same conditions, 
 the thrust was very much increased, but the power 
 required was also increased to a still greater degree, show- 
 ing that this form was not so favourable as either a or b. 
 All the screws experimented with had very thin blades, 
 and it occurred to me that the difference between a and b 
 might arise from the fact that, when a was running at a 
 very high velocity, the working side instead of being flat 
 might have become convex to a slight extent, whereas with 
 b, a slight bending back of the edges of the blade would 
 still leave the working side concave. I therefore made 
 the screw shown at e, which had the same pitch as the 
 other three, but the working side was of the same shape as 
 a. Of course the additional thickness of the blades made 
 it impossible to give an easy curve to the back. Curiously 
 enough I found that e, did nearly as well as a, and quite as 
 well as b. The additional thickness did not interfere to
 
 PRINCIPALLY RELATING TO SCREWS. 
 
 39 
 
 any appreciable extent with its efficiency. I then made 
 another propeller, shown at g, which was of the same 
 thickness in the middle as e. Upon running this, I found 
 that it required considerable power, and no matter which 
 way it was run, the thrust was always in the direction of 
 the convex side, which was quite the reverse from what 
 one would have naturally supposed. 
 
 About the time that I was making these experiments, 
 my duties called me to Paris, and while there I called on 
 my old friend Gaston Tissandier. 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 Government, and I was some- 
 what surprised to find the form of the blades, the same as 
 
 Fig. 15. The manner of building up the large screws. 
 
 shown at h, Fig. 14, and completely without any twist. 
 On my return to England, I made a screw of this descrip- 
 tion. It is also shown in the photographic illustration, 
 Fig 9. Upon testing this screw, I found that its efficiency 
 was only 40 per cent, of that of a that is, the energy or 
 acceleration imparted to the air was only 40 per cent, of 
 the readings of the dynamometer. It then occurred to me 
 that this particular form of screw was probably the one 
 that the French had for exhibition purposes, but not the one 
 they intended to use. Having tried all the various forms 
 of screws and other objects shown in Fig. 9, I made some 
 sheet metal screws ; also a screw which consisted of a steel 
 frame covered with woven fabric, and which was identical 
 with screws that I had seen described in various works
 
 4U ARTIFICIAL AND NATURAL FLIGHT. 
 
 relating to aerial navigation. It was found quite impos- 
 sible to keep the fabric taut and smooth, and the results 
 were very bad indeed, it being only 40 per cent, as 
 efficient as a well-made wooden screw. 
 
 Having thus ascertained the best form of a screw, I 
 built up my first large screws, which were 17 feet 10 
 inches in diameter, after the well-known manner of making 
 wooden patterns for casting steamship propellers. Fig. 15 
 
 Fig. 16. A fabric-covered screw with a very low efficiency. 
 
 shows the form of the end of the blade, the middle of the 
 blade, and the hub. My first pair of large screws had 
 a pitch of 24 feet, but these were too great a drag 
 on the engine. I therefore made another pair with 16 feet 
 pitch which greatly increased the piston speed, and 
 permitted the engines to develop much more power; the 
 screw thrust was also increased just in an inverse ratio 
 to the pitch of the screws. Another pair of screws
 
 PRINCIPALLY RELATING TO SCREWS. 41 
 
 was tried with 14 feet pitch and 12 feet in diameter, 
 but these did not do so well. My large screws were 
 made with a great degree of accuracy ; they were perfectly 
 smooth and even on both sides, the blades being thin and 
 held in position by a strip of rigid wood on the back of 
 the blade. In order to prevent the thrust from collapsing 
 the blades, wires were extended backwards and attached 
 to a prolongation of the shaft. Like the small screws, 
 they were made of the very best kind of seasoned 
 American white pine, and when finished were varnished 
 on both sides with hot glue. When this was thoroughly 
 dry, they were sand-papered again and made perfectly 
 smooth and even. The blades were then covered with 
 strong Irish linen fabric of the smoothest and best make. 
 Glue was used for attaching the fabric, and when dry 
 another coat of glue was applied, the surface rubbed down 
 again and then painted with zinc white in the ordinary 
 way and varnished. These screws worked exceedingly 
 well. I had means of ascertaining, with a great degree of 
 accuracy, the thrust of the screw, the number of turns per 
 minute, the speed of the machine, and, in fact, all the events 
 that were taking place on the machine. It was found 
 that when the screw thrust in pounds was multiplied by 
 the pitch in feet, and by the number of revolutions made 
 in a minute of time, it exactly corresponded to the power 
 that the engines were developing, and that the amount of 
 loss in skin friction was so small as to be practically 
 negligible. 
 
 In connection with this subject I would say that many 
 experimenters claim to have shown that the skin friction 
 on screws is considerable, in fact, so great as to be a very 
 important factor in the equation of flight. I am, however, 
 of the opinion that these experimenters have not had well- 
 made screws. If the surface of the screw is uneven, 
 irregular, or rough, a considerable amount of energy is lost, 
 as shown in the French screw and the fabric covered 
 screw. It is simply a question of having a screw well- 
 made. In those recently employed' in France (see Fig. 17), 
 the blades are of hammered sheet metal, the twist is not 
 uniform or true, and what is worst of all, the arm b 
 projects on the back of the blade and offers a good deal of 
 resistance to the air. This form of screw, however, is very 
 ingenious ; as will be seen by the drawing, the pitch and 
 diameter can be changed at will. It is, however, heavy,
 
 42 ARTIFICIAL AND NATURAL FLIGHT. 
 
 wasteful of power, and altogether too small for the work 
 it has to do. The skin friction of screws in a steamship 
 has led inventors to suppose that the same laws relate to 
 screws running in air, but such is by no means the case. 
 
 Fig. 17. The hub and one of the blades of the screw on the Farman 
 machine. The blade c, is a sheet of metal riveted to the rod b, and 
 forms a projection on the back of the blade which greatly reduces 
 its efficiency. The peculiar form of hub employed makes it possible 
 to change the diameter and pitch of this screw at will. 
 
 In designing a steamship, we have to make a compromise 
 in regard to the size of the screw. If the screw is too 
 small, an increase in diameter is, of course, an advantage, 
 and it may also be an advantage, not only to increase the
 
 
 S 
 
 J 
 
 
 n
 
 14 
 
 ARTIFICIAL AND NATURAL PLIGHT. 
 
 diameter, but also to reduce the pitch ; however, a point 
 is soon reached where the skin friction will more than 
 neutralise the advantages of engaging a larger volume of 
 water. This is because the water adheres to the surface ; 
 in fact, the skin friction of a ship and its screw consumes 
 fully 80 per cent, of the total power of the engines, but 
 with an air propeller its surface is not wetted and the air 
 does not stick to its surface. If made of polished wood, 
 the friction is so extremely small as to be almost untneasur- 
 
 OOOOOOOOOOOOOOo 
 
 Fig. 19. Shows the form of the blade of a screw propeller made of sheet 
 metal. It is riveted at the edges and also to the arm of a screw with a 
 stiffening piece at the extreme end. However, it is not necessary to 
 rivet edges together. They may be welded with a flame of acetylene 
 oxygen gases. 
 
 Fig. 19a. Shows the manner of welding and the finished edge. 
 
 able. The diameter of a well-made screw running in air is 
 therefore not limited in any degree by skin friction, as is 
 the case with a screw running in water ; in fact, it is rather 
 a question of its weight, and its efficiency ought to increase 
 in direct ratio with its diameter, because the area of the 
 disc increases with the square of the diameter. The screw 
 slip is therefore reduced by one-half by simply doubling 
 the diameter of the screw. It will be understood that by 
 doubling the diameter of the screw, four times as much air
 
 d 
 
 b 
 
 Fig. 20. A new form of hub, of great strength and lightness, for use on 
 flying machines.
 
 46 ARTIFICIAL AND NATURAL FLIGHT. 
 
 will be engaged. If we push this back at half the speed, 
 we shall have the same screw thrust, because the resistance 
 of the air is in proportion to the square of the velocity 
 that we impart to it, so that one just balances the other, 
 and the diminution of wasteful slip is just in proportion to 
 the increase in diameter. In all cases, the screw should be 
 made as large as possible. 
 
 In the drawing (Fig. 18) I have shown screw blades of 
 a proper shape to give the best results that is, providing a 
 metallic screw is employed. Instead of having the arm of 
 the screw on the back of the blade to offer resistance to the 
 air, the arm should be tubular, flattened, and covered on 
 both sides with sheet metal. This particular formation not 
 only prevents the air from striking the arm, but, at the 
 same time, prevents the pressure of the air from deforming 
 the blade, so, if a metallic screw is to be used, the 
 form of blade which I have shown will be found much 
 superior to that employed at the present time on continental 
 flying machines. We should not lose sight of the fact that 
 weight tells very seriously against the success of a flying 
 machine, and that no expense should be spared to reduce 
 the weight, providing that it is possible to do so without 
 reducing the factor of safety. Suppose, for example, that 
 we use an ordinary hub secured to a solid shaft by a 
 common key. All the parts have to be made heavy in 
 order to be sufficiently strong to withstand the strain. In 
 the drawing (Fig. 20) I have shown a hub which I think is 
 quite as light and strong as it is possible to make it. The 
 action of the motor is often spasmodic and puts very great 
 strain upon the parts, and there is a very strong tendency 
 for the shaft to turn round in the hub. If a key is used, 
 the hub has to be large and strong, and the key of con- 
 siderable size, otherwise the parts would be deformed. In 
 my own experiments, I have found .considerable difficulty 
 in securing a shaft to wooden screws However, it will be 
 seen in the drawings that a series of grooves is cut in the 
 shaft and that the hub has internal projections, so that the 
 one fits the other. This makes a very strong connection 
 and is of extreme lightness. Both the hub and the shaft 
 should be of tempered steel. The spokes should be hard 
 drawn steel tubes with long fine threads, so as to with- 
 stand centrifugal force. To prevent them from rotating in 
 the hub, the nuts d, d are provided, which compress the 
 arms of the steel hub so as to grip the tube with any
 
 PRINCIPALLY RELATING TO SCREWS. 47 
 
 degree of force required. It will be seen that with this 
 system the pitch of the screw may be adjusted to some 
 extent ; however, it is better to have all parts of the screw, 
 from hub to centre, of the same pitch. A slight deviation 
 from this is admissible in the experimental stage, so long 
 as the deviation from a true screw, caused by rotating the 
 arm, is not greater than one half of the slip while in flight. 
 Many experimenters have imagined that a screw is just 
 as efficient placed in front of a machine as at the rear, and 
 it is quite probable that, in the early days of steamships, a 
 similar state of things existed. For several years there 
 were steamboats running on the Hudson River, New York, 
 with screws at their bows instead of at their stern. In- 
 ventors of, and experimenters with, flying machines are not 
 at all agreed by any means in regard to the best position 
 for the screw. It would appear that many, having noticed 
 that a horse -propelled carriage always has the horse 
 attached to the front, and that the carriage is drawn in- 
 stead of pushed, have come to the conclusion that, in a 
 flying machine, the screw ought, in the very nature of 
 things, to be attached to the front of the machine, so as to 
 draw it through the air. Railway trains have their 
 propelling power in front, and why should it not be the 
 same with flying machines ? But this is very bad reasoning. 
 There is but one place for the screw, and that is in the 
 immediate wake, and in the centre of the greatest atmos- 
 pheric disturbance. While a machine is running, although 
 there is a marked difference between water and air as far 
 as skin friction is concerned, still the conditions are the 
 same as far as the position of the screw is concerned. 
 With a well-designed steamship, the efficiency of the screw 
 is so great as to be almost unbelievable; in fact, if a 
 steamship had never been made, and the design of one 
 should be placed before the leading mathematicians of to- 
 day, with the request that they should compute the 
 efficiency of the screw, none of them would come anywhere 
 near the mark. They would make it altogether too small. 
 As before stated, when a steamship is being driven through 
 the water, the water adheres to its sides and is moved 
 forward by the ship that is, it has acceleration imparted to 
 it which exactly corresponds to the power consumed in 
 driving the ship through the water. This, of course, 
 retards it, and we find in a well-designed ship, not run 
 above its natural speed, that about 80 per cent, of the
 
 48 ARTIFICIAL AND NATURAL FLIGHT. 
 
 power of the engine is consumed in skin friction, or in 
 imparting a forward motion to the water. Suppose that 
 we should take such a ship, remove the screw, and tow it 
 through the water with a very long wire rope at a 
 speed of, say, 20 miles an hour ; we should find that the 
 water at the stern of the ship was moving forward at a 
 velocity of fully 6 miles an hour that is, travelling in the 
 same direction as the ship. By replacing the screw, and 
 applying engine power sufficient to give the ship the same 
 speed of 20 miles an hour, identical results would be 
 produced. The skin friction still impels the water forward, 
 so that the screw, instead of running in stationary water, 
 is actually running in water moving in the same direction 
 as the ship at a velocity of 6 miles an hour. If the slip 
 of the screw should only be equal to this forward motion, 
 the apparent slip would be nothing ; in fact, 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 water. 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 water, 
 and in such cases a ship is said to have negative slip. A 
 very noticeable case of this kind occurred in the Koyal 
 Navy in the sixties.* I was at the time engaged in a large 
 shipbuilding establishment in New York, and remember 
 distinctly the interest that the case created amongst the 
 draughtsmen and engineers of that establishment. Of 
 course, this apparently impossible phenomenon created a 
 great deal of discussion on both sides of the Atlantic. 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 
 minute, and for a certain number of knots per hour, also 
 that the boiler pressure should not go above a certain 
 number of pounds per square inch. When the ship was 
 finished and went on her trial trip, it was found impossible 
 to make the full number of turns called for in the specifi- 
 cation with the boiler pressure allowable ; nevertheless, 
 the speed was greater than the specification called for, and 
 as speed was the desideratum, and not the number of 
 revolutions, the contractors thought their ship should be 
 accepted. Then arose a discussion as to the diameter and 
 
 * The particulars relating to this event are taken from accounts 
 published at the time in American papers.
 
 PRINCIPALLY RELATING TO SCREWS. 49 
 
 pitch of the screw. It was claimed that a mistake must 
 have occurred. A careful measurement was made in the 
 dry dock, and all was found correct. Once more the ship 
 was tried, and again her speed was in excess of the specifi- 
 cation, notwithstanding that it was still impossible to get 
 the specified number of revolutions per minute. Mathe- 
 maticians then took the matter in hand, and it was found 
 that the ship actually travelled faster than she would have 
 done if the screw had been running in a solid nut. 
 Instead of a positive slip, the screw had in reality a 
 negative slip ; but this was not believed at the time, and 
 the discussion and controversy continued. The ship was 
 tried again and again, and always with the same results. 
 This apparently inexplicable phenomenon was accounted 
 for in the following manner : The hull of the ship was 
 said to be rather imperfect and to cause a considerable 
 drag in the water, so that, when the ship was moving at 
 full speed, the water at the stern had imparted to it a 
 forward velocity greater than the actual slip. 
 
 What is true of ships is true of flying machines. Good 
 results can never be obtained by placing the screw in front 
 instead of in the rear of the machine. If the screw is in 
 front, the backwash strikes the machine and certainly has 
 a decidedly retarding action. The framework, motor, etc., 
 offer a good deal of resistance to the passage of the air, 
 and if the air has already had imparted to it a backward 
 motion, the resistance is greatly increased. The framework 
 will always require a considerable amount of energy to 
 drive it through the air, and the whole of this energy is 
 spent in imparting a forward motion to the air, so if we 
 place the propelling screw at the rear of the machine 
 in the centre of the greatest atmospheric resistance, 
 it will recover a portion of the lost energy, as in the 
 steamship referred to. It will, therefore, be seen that 
 when the screw is at the rear, it is running in air which 
 is already moving forward with a considerable velocity, 
 which reduces the slip of the screw in a corresponding 
 degree. I have made experiments with a view of proving 
 this, which I shall mention further on, and which ought to 
 leave no chance for future discussion. 
 
 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 time, but as wood was 
 quite out of the question on my large machine on account
 
 50 ARTIFICIAL AND NATURAL FLIGHT. 
 
 of its weight, it was necessary for me to conduct experi- 
 ments with a view of ascertaining the relative values of 
 different fabrics. For this purposes, I made the little 
 apparatus shown (Fig. 21). This was connected to a tan 
 blower driven by a steam engine having a governor that 
 worked directly on the point of cut-off. The speed was, 
 therefore, quite uniform and the blast of air practically 
 constant. I had a considerable number of little frames cut 
 out of sheet steel, and to these I attached various kinds of 
 fabric, such as ordinary satin, white silk, closely woven 
 silk, linen, various kinds of woollen fabrics, including some 
 
 Fig. 21. Small apparatus for testing fabrics for aeroplanes, the material 
 being subjected to an air blast in order to test its lifting effect as 
 compared with its tendency to travel with the blast. 
 
 very coarse tweeds, also glass-paper, tracing linen, and the 
 best quality of Spencer's balloon fabric. The blast of air 
 was not large enough to cover the whole surface of the 
 aeroplanes, so that the character of the back of the frames 
 was of no account. The first object experimented with 
 was a smooth piece of tin. When this was placed at an 
 angle of 1 in 14, it was found that the drift or tendency to 
 travel in the direction of the blast was just one-fourteenth 
 part of the upward tendency, or lift. This was exactly 
 as it should have been. Upon changing the angle to 
 1 in 10, a similar thing occurred ; the lift was ten times
 
 52 ARTIFICIAL AND NATURAL FLIGHT. 
 
 the drift. I, therefore, considered the results obtained 
 with the sheet of tin as unity, and gave to every other 
 material experimented with/a coefficient of the unity thus 
 established. Upon testing a frame covered with tightly- 
 drawn white silk, a considerable amount of air passed 
 through, and with an angle of 1 in 14, the lift was only 
 about double the drift. A piece of very open fabric, 
 a species of buckram, was next tried, and with this the 
 lift and drift were about equal. With closely-woven, 
 shiny satin the coefficient was about '80; with a piece 
 of ordinary sheeting the coefficient was '90 ; with closely - 
 woven, rough tweeds, '70 ; and with glass-paper about '75. 
 
 Fig. 23. Apparatus for testing aeroplanes, condensers, etc., in an 
 blast. The opening is 3 feet 
 shown in position for testing. 
 
 blast. The opening is 3 feet square. Thin brass sustainers are 
 n fo 
 
 With a piece of tracing linen very tightly drawn, results 
 were obtained identical with those of a sheet of tin, and 
 with Spencer's balloon fabric the coefficient was about '99. 
 I, therefore, decided to cover my aeroplanes with this 
 material. It will be observed that the apparatus is so 
 arranged that both the lift and the drift can be easily 
 measured. 
 
 In order to ascertain the resistance encountered by 
 various shaped bodies driven at various speeds through 
 the air, the best form of aeroplanes, and the efficiency of 
 atmospheric condensers, I made the apparatus shown in 
 Figs. 22 and 23. The smaller and straight portion of this
 
 PRINCIPALLY RELATING TO SCREWS. 
 
 ct 
 
 apparatus was 12 feet long and exactly 3 feet square 
 inside, and was connected as shown to a shorter box 
 4 feet square. Two strongly made wooden screws 6, 6 
 and d, were attached to the same shaft. These screws 
 had two blades each, and while one pair of blades was in 
 a vertical position, the other was in a horizontal position. 
 I interposed between the screws, slats of thin wood 
 arranged in the manner shown at d, d; this was to 
 prevent rotation of the air. At e I placed vertical slats 
 of thin wood, and horizontal slats of the same size at /. 
 At g two wide and thin boards, 
 sharp at both edges and made in 
 the form of the letter X, were 
 placed in the box as shown in 
 section XY. An engine of 100 
 H.P. with an automatic variable 
 cut-off was employed which gave 
 to the screws a uniform rate of 
 rotation, and as the engine had 
 no other work to do, the governor 
 could be arranged to give varying 
 speeds such as were required for 
 the experiments. The objects to 
 be tested were attached to the 
 movable bars. In the drawing, 
 the aeroplane k, k is shown in 
 position for testing. This appar- 
 atus was provided with a rather 
 complicated set of levers, which 
 permitted not only the measure- 
 ment of the lift of the objects Fig. 24 - C ^-sect/io ns of 
 experimented with, but also that foTas^ertSning^he co- 
 
 of the drift. The principle em- efficient of different forms. 
 
 plo3 7 ed in this apparatus was a 
 
 modification of the ordinary weighing apparatus used by 
 grocers, etc. The first object tested was a bar of wood 
 exactly 2 inches square shown in Fig. 24. This was placed 
 in such a manner that the wind struck squarely against the 
 side as shown in the drawing, and with a wind of 49 miles 
 per hour, it was found that the drift or tendency to move 
 with the air was 516 Ibs.; at the same time, the wind 
 on my instrument gave a pressure of 2 Ibs. on a normal 
 plane 6 inches square. The velocity of the wind was 
 ascertained by an anemometer of the best London make.
 
 54 
 
 ARTIFICIAL AND NATURAL PLIGHT. 
 
 Upon turning the same bar of wood in the position shown 
 at b, the drift mounted to 5'47 Ibs. A round bar of wood, 
 2 inches in diameter, shown at c, gave a dritt ot 2W Ibs. 
 These experiments were repeated with a wind velocity ot 
 40 miles per hour, when it was found that the drift ot a 
 was 4-56 Ibs., and that of the round bar, 2'80 Ibs. It will 
 
 xperir 
 purpose of ascertaining their coefficients as relates to a normal plane. 
 
 be seen from these experiments that the power required 
 for driving bars or rods through the air is considerably 
 greater than one would have supposed. The next object 
 experimented with was a, Fig. 25. When this was subject 
 to a wind of 40 miles an hour, the drift was 0-78 Ib. 
 Upon reversing this bar that is, putting the thin edge
 
 PRINCIPALLY RELATING TO SCREWS. 
 
 55 
 
 instead of the thick edge next to the wind the drift 
 mounted to 1'22 Ibs.; 6 showed a drift of 0'28 Ib. with 
 the thick edge to the wind, and 0'42 Ib. with the thin 
 edge to the wind ; e showed a drift of 0'23 Ib with the 
 thick edge to the wind, and 0'59 Ib. with the thin edge to 
 the wind; and d, which was the same thickness as the 
 others and 1 2 inches wide, both edges being alike, showed 
 a drift of only 0'19 Ib. These experiments show in a 
 most conclusive manner the shapes that are most advan- 
 tageous to use in constructing the framework of flying 
 machines. Aeroplane e, Fig. 26, when placed on the 
 
 Angle One in Twenty. 
 
 Angle One in ^Sixteen,. 
 
 Fig. 26. A flat aeroplane placed at different angles. 
 
 machine in a horizontal position showed neither lift nor 
 drift, but upon placing it at an angle of 1 in 20, as shown 
 at /, the lift was 3'98 Ibs. and the drift 0'30 Ib. with 
 a wind velocity of 40 miles per hour. At this low angle 
 the blade trembled slightly. Upon placing the same plane 
 at an angle of 1 in 16 as shown at g, the lift was 4%59 Ibs. 
 and the drift 0'53 Ib. It will be observed that the 
 underneath side of this plane is perfectly flat. The next 
 experiment was with planes slightly curved, as shown in 
 Fig. 27. The aeroplane a was 16 inches wide, very thin, 
 and only slightly curved. When set at a very low angle,
 
 56 ARTIFICIAL AND NATURAL FLIGHT. 
 
 it vibrated so as to make the readings very uncertain, 
 but when set at an angle of 1 in 10 it lifted 9'94 Ibs. 
 with a drift of 1-12 Ibs. By slightly changing the angle 
 it was made to lift 10'34 Ibs. with a drift of T23 Ibs 
 the wind velocity being 41 miles per hour. Aeroplane b 
 12 inches wide, Fig. 27, when placed at an angle of 1m 14 
 with an air blast of 41 miles per hour, gave a hit ot 
 5-28 Ibs. with a drift of 0'44 lb.; at an angle of 1 in 12 
 the lift was 5'82 Ibs. and the drift 05 lb.; at an angle ot 
 1 in 10 the lift was 675 Ibs. and the drift 073 lb.; with an 
 angle of 1 in 8 the lift was 7 75 Ibs. and the drift 1 lb. ; 
 
 . 16" - - 
 
 Fig. 27. Group of aeroplanes used in experimental research. Although 
 shown the same size in the drawing, aeroplane a was 16 inches wide, 
 and b and c, 12 inches wide. 
 
 with an angle of 1 in 7 the lift was 8*5 Ibs. and the drift 
 1-25 Ibs. ; at an angle of 1 in 6 the lift was 9 '87 Ibs. and 
 the drift 171 Ibs. Aeroplane c, Fig. 27, which had more 
 curvature than 6, when run in a horizontal position, gave 
 a considerable lift, and when raised to an angle of 1 in 12 
 it gave a lift of 6'12 Ibs. with a drift of 0'54 lb. In 
 another experiment at the same angle, it gave a lift of 
 6-41 Ibs. with a drift of 0'56 lb.; at an angle of 1 in 16 it 
 gave a lift of 5*47 Ibs. with a drift of 0'37 lb. ; at an angle 
 of 1 in 10 it gave a lift of 6'97 Ibs. and a drift of 070 lb. ; 
 at an angle of 1 in 8 it gave a lift of 8'22 Ibs. with a drift
 
 PRINCIPALLY RELATING TO SCREWS. 57 
 
 of 1'08 Ibs. ; at an angle of 1 in 7 it gave a lift of 9'94 Ibs. 
 with a drift of T45 Ibs. ; at an angle of 1 in 6 it gave a lift 
 of 10-34 Ibs. and a drift of 175 Ibs. This plane was then 
 carefully set so that both the forward and aft edges were 
 exactly the same height, and with a wind blast of 41 miles 
 per hour it gave a lift of 2'09 Ibs. with a drift of 0-21 Ib. 
 It was then pitched 1 in 18 in the wrong direction, and at 
 this point, the lifting effect completely disappeared, while 
 the drift was practically nothing. 
 
 When the aeroplane a (Fig. 28) was placed in a hori- 
 zontal position, and the apparatus carefully balanced, it 
 showed at a wind velocity of 40 miles an hour, a lift of 
 1-56 Ibs., and a drift of 08 Ib. ; at an angle of 1 in 20, a 
 lift of 3'62 Ibs. and a drift of 0'21 Ib. ; at an angle of 1 in 
 16, a lift of 4-09 Ibs. with a drift of 0'26 Ib. ; at an angle 
 
 Fig. 28. An 8 -inch aeroplane which did very well. This aeroplane 
 gave decided lifting effect when the bottom side was placed dead 
 level, as shown at a. 
 
 of 1 in 14, a lift of 4'5 Ibs. and a drift of 0'33 Ib.; at an 
 angle of 1 in 12, a lift of 5 Ibs. and a drift of 043 Ib. ; 
 at an angle of 1 in 10, a lift of 575 Ibs. and a drift of 
 60 Ib. j at an angle of 1 in 8, a lift of 675 Ibs. and a drift 
 of 0-86 Ib. The blast was then increased to a velocity of 
 47-33 miles an hour, when it was found that the lift at 
 an angle of 1 in 16 was 5 Ibs. and the drift 0'33 Ib. It will 
 be observed that this aeroplane was only 8 inches wide, 
 while the others were 12 inches or more. They were 
 all rather more than 3 feet long, but the width of the 
 blast to which they were subjected was exactly 3 feet, 
 and they were placed as near to the end of the trunk as 
 possible. . 
 
 The next experiments were made with the view ot 
 ascertaining what effect would be produced when objects
 
 ;,S ARTIFICIAL AND NATURAL FLIGHT. 
 
 were placed near to each other (see Fig. 29). Two bars of 
 wood 2 inches thick, and shaped as shown in the drawing, 
 
 Fig. 29. Resistance dxie to placing objects in close proximity 
 to each other. 
 
 were placed on the machine and subjected to a blast of 41 
 miles per hour ; the drift at various distances from center 
 to center was as follows : 
 
 24 inches centers, 
 
 22 
 
 20 
 
 18 
 
 16 
 
 14 
 
 12 
 
 10 
 
 8 
 
 6 
 
 4 
 
 drift 6 ozs. 
 6 
 6 
 
 64 
 
 7 
 7f
 
 PRINCIPALLY RELATING TO SCREWS. 59 
 
 It will be seen by this that the various members con- 
 stituting the frame of a flying machine should not be 
 placed in close proximity to each other. 
 
 A bar of wood similar in shape to d (Fig. 25), but being 
 9 inches wide instead of 12 inches, was mounted in a wind 
 blast of 41 miles an hour, with the front edge 3'31 inches 
 above the rear edge, and this showed a lift of 7 08 Ibs. and 
 a drift of 3'23 Ibs. When the angle was reduced to -'31 
 inches, it gave a lift of 4'53 Ibs. with a drift of 0'78 -lb., 
 and with the angle reduced to 1*31 inches, the lift was 
 3-37 Ibs. and the drift 0'5 Ib. It will, therefore, be seen 
 that even objects rounded on both sides give a very fair 
 lift, and in designing the framework of machines advantage 
 should be taken of this knowledge. The bar of wood c 
 (Fig. 25) was next experimented with. With the sharp 
 edge to the wind, and with the front edge 2 inches higher 
 than the rear edge, the lift was 2*54 Ibs. and the drift 76 
 Ib. By turning it about so that the wind struck the thick 
 edge, the lift was 4-45 Ibs. and the drift 0'47 Ib. This 
 seemed rather remarkable, but, as it actually occurred, I 
 mention it for other people to speculate upon. It, how- 
 ever, indicates that we should take advantage of all these 
 peculiarities of the air in constructing the framework of a 
 machine, which in itself is extremely important, as I find 
 that a very large percentage of the energy derived from 
 the engines is consumed in forcing the framework through 
 the air. It is quite true that a certain amount of this 
 energy may be recovered by the screw, provided that the 
 screw runs in the path occupied by the framework. Still, 
 it is much better that the framework should be so con- 
 structed as to offer the least possible resistance to the air, 
 and, as far as possible, all should be made to give a lifting 
 effect. 
 
 Having ascertained the lifting effect of wooden aero- 
 planes of various forms and at varying velocities of the 
 wind, and, also, the resistance offered by various bodies 
 driven through the air, I next turned my attention to the 
 question of condensation. I wished to recover as much 
 water as possible from my exhaust steam. I had already 
 experimented with Mr. Horatio Philipps' sustainers, and I 
 found that their lifting enect was remarkable. A curious 
 thing about these aeroplanes was that they gave an 
 appreciable lift when the front edge was rather lower than 
 the rear. I therefore determined to take advantage of this
 
 flO ARTIFICIAL AND ^NATURAL FLIGHT. 
 
 peculiar phenomenon, and to make my condenser tubes as 
 far as possible in the shape of Mr. Philipps sustamers. 
 Ficr 30 shows a section of one of these tubes, in which a, a 
 is the top surface, b a soldered joint, and c the steam space. 
 
 Fig. 30. Cross-section of condenser tube, made in the form of Philipps' 
 sustainers, in which c is the steam passage. 
 
 These were mounted on a frame as shown at a (Fig. 31). 
 I had already found that bodies placed near to each other 
 offered an increased resistance to the air, but by placing 
 
 Fig. 31. The grouping of condenser tubes, made in the form of Philipps' 
 sustainers. This arrangement is very effective, condenses the steam 
 or cools the water, and gives a lifting effect at the same time. The 
 shape and arrangement of tubes shown at b, I), although effective as 
 a condenser, produce no lifting effect, but a rather heavy drift. 
 
 these sustainers in the manner shown this was avoided, as 
 the air had sufficient space to pass through without being 
 either driven forward or compressed. It was found by 
 experiment that the arrangement of tubes or sustainers,
 
 PRINCIPALLY RELATING TO SCREWS. 61 
 
 shown at d, d (Fig. 31), was very efficient as a condenser, 
 but it gave a very heavy drift and no lifting effect at 
 all ; whereas, on the other hand, the arrangement shown 
 at a was equally efficient, and, at the same time, gave a 
 decided lifting effect. When twelve of these tubes or 
 sustainers were placed at an angle of 1 in 12, the lifting 
 effect was 12 -63 Ibs. and the drift 2 -06 Ibs. It was found, 
 however, that a good deal of the drift was due to the wind 
 getting at the framework that was used for holding .the 
 sustainers in position. With a wind velocity of 40 miles 
 an hour and a temperature of 62 F., 2'25 Ibs. of water 
 were condensed in five minutes, and, while running, the 
 back edge of the sustainers was quite cool. At another 
 trial of the same arrangement under the same conditions, 
 the lift was 11 Ibs. and the drift 2'63 Ibs. It is quite 
 possible on this occasion that the metal was so extremely 
 thin that the angles were not always maintained ; conse- 
 quently, that no two readings would be alike. It was 
 found at this point that the belt was slipping, and a larger 
 pulley was put on the driving shaft of the screws; and 
 under these conditions, with a wind of 49 miles per hour 
 and an angle of 1 in 8, the lifting effect ran up to 14'87 Ibs. 
 with a drift of 2*44 Ibs., and the condenser delivered 2*87 
 Ibs. of water from dry steam in five minutes. The weight 
 of metal in this condenser was extremely small, the thick- 
 ness being only about -tb- of an i ncn - This condenser 
 delivered the weight of the sustainers in water every five 
 minutes. They should, however, have been twice as heavy. 
 Cylinder oil was now introduced with the steam in order 
 to ascertain what effect this would have. After seven 
 minutes' steaming, 2'25 Ibs. of water were condensed in 
 five minutes. It will be seen from these experiments that 
 an atmospheric condenser, if properly constructed, is fairly 
 efficient. Koughly speaking, it requires 2,400 times as 
 much air in volume as of water to use as a cooling agent. 
 With the steam engine condenser only a relatively small 
 amount of water is admitted, and this is found to be 
 sufficient ; but in an atmospheric condenser working in the 
 atmosphere, it must be as open as possible, so that no air 
 which has struck one heated surface can ever come in 
 contact with another.
 
 CHAPTER V. 
 
 EXPERIMENTS WITH APPARATUS ATTACHED 
 TO A ROTATING ARM. 
 
 FROM what information I have at hand, it appears that 
 Prof. Langley made his first experiments with a small 
 apparatus, using aeroplanes only a few inches in dimensions 
 which travelled round a circle perhaps 12 feet in diameter. 
 With this little apparatus, he was able to show that the 
 lifting effect of aeroplanes was a great deal more than had 
 previously been supposed After having made these first 
 experiments, he seems to have come to the conclusion that 
 Newton's law was erroneous. Shortly after Langley had 
 made these experiments on what he called a whirling 
 table, which, however, was not a very appropriate name, I 
 made an apparatus myself, but very much larger than that 
 employed by Prof. Langley. I reckoned the size of my 
 aeroplanes in feet, where he had reckoned his in inches. 
 The circumference of the circle around which my aeroplanes 
 were driven was exactly 200 feet, and shortly after this 
 Langley constructed another apparatus, the same dimen- 
 sions as my own. From an engraving which I have before 
 me, it appears that he constructed an extremely large 
 wooden scale beam supported by numerous braces, but free 
 to be tilted in a vertical direction after the manner of all 
 other scale beams. As this apparatus was of great weight 
 and offered enormous resistance to the air, I do not under- 
 stand how it was possible to obtain any very correct 
 readings, especially as it was in the open and subject to 
 every varying current of air. 
 
 In constructing my apparatus, which is shown in the 
 photographs, and also in a side elevation (Fig. 32), I aimed 
 at making the apparatus very light and strong, avoiding as 
 far as possible atmospheric resistance. In the drawing, a, 
 is a thick seamless steel pipe 6 inches diameter; 6, is a cast- 
 iron pedestal firmly bolted to d, and connected to a large 
 cast-iron spider embedded in hydraulic cement; by this 
 means great rigidity and stiffness were obtained, n, n was 
 formed of strong Georgia pine planks 2 inches thick, and
 
 11} 
 
 ARTIFICIAL AND NATURAL FLIGHT. 
 
 strongly bolted together. The two members of the long 
 radial arm h, h, were made of Honduras mahogany, an 
 extremely strong wood, and had their edges tapered off as 
 shown at y, y. The power was transmitted from a small 
 steam engine provided with a sensitive governor through 
 the shaft/,/. In the base c, of the casting b, was placed a 
 pair of tempered steel bevel gears, giving to the vertical 
 shaft a high velocity. From a pulley on the top of this 
 shaft, the belt i, was run through the arms h, h, as shown in 
 section y, y. This gave a rapid rotation to the screw shaft 
 in a very simple manner. The operation of the machine 
 
 Fig. 33. A screw and fabric covered aeroplane in position for testing. 
 
 was as follows : the aeroplane g, to be tested was secured 
 to a sort of weighing apparatus which is shown in detail 
 (Fig. 36), and the screw attached to the shaft. Upon 
 starting the engine, a very rapid rotation was given to the 
 screw which caused the radial arm to travel at a high 
 velocity, the whole weight resting on a ball bearing at w. 
 The radial arms and all of their attachments were balanced 
 by a cigar-shaped lead weight 8, which was secured to a 
 sliding bar so as to make it easily adjustable. The thrust 
 of the screw caused the screw shaft to travel longitudinally, 
 and this was opposed by a spring connected by a very
 
 EXPERIMENTS WITH APPARATUS. 65 
 
 thin and light wire to the pointer of the index o. As the 
 apparatus rotated rather slowly on account of its great 
 diameter, it was quite possible to observe the lift while the 
 machine was running at its highest speed. The aeroplanes 
 were mounted after the manner of the tray of a grocer's 
 scales (see Fig. 36), and the lift of the aeroplane was 
 determined by what it would lift at r that is, while 
 the machine was running at a given speed, iron or lead 
 weights were placed in the pail r, until the lift of 'the 
 aeroplane was exactly balanced, and then, in order to 
 
 Fig. 34. The rotating arm of the machine with a screw and 
 aeroplane attached. 
 
 ascertain exactly what the lift was, the aeroplane was 
 placed under what might be called a small crane, and 
 a cord, running over a pulley, attached. The amount of 
 weight necessary to lift the plane into the same position 
 that it occupied while running was taken as its true 
 lift. In order to facilitate experiments the gauge p, 
 was provided. This gauge consisted of a large glass tube 
 and the index p, with a quantity of red water at q. The
 
 66 ARTIFICIAL AND NATURAL FLIGHT. 
 
 centrifugal force of rotation caused the red water to rise 
 in the tube. This was easily seen, so that if experiments 
 were being tried, we will say at 50 miles an hour, it 
 was always possible to turn on steam until the red 
 liquid mounted to 50. This device was very simple 
 and effective, and saved a great deal of time. In order to 
 prevent the twisting of the radial arm, a piece of stiff 
 oval steel tube 12 feet long was secured between the arms 
 at j, and on each end of this tube were attached the wires 
 
 Fig. 35. The little steam engine used by me in my rotating arm experi- 
 ments ; the tachometer and dynamometer are distinctly shown. 
 
 u, u. This not only effectually supported the end of 
 the arm, but at the same time prevented twisting and 
 made everything extremely stiff. Of course, while the 
 machine was running at a high velocity, centrifugal force 
 had to be dealt with, and in order to prevent this from 
 causing friction in the articulated joints of the weighing 
 apparatus (Fig. 36), thin steel wires k, k were provided. 
 As this apparatus was in the open, it was found that 
 the slightest movement of the air greatly interfered with 
 its action. On one occasion when a fabric covered aero-
 
 EXPERIMENTS WITH APPARATUS. 67 
 
 plane, 4 feet long by 3 feet wide, was placed in position, 
 the four corners being held down by the wires v, v, and 
 the apparatus driven at a high velocity, a sudden gust of 
 wind snapped two of the wires, broke the aeroplane, and 
 the flying fragments smashed the screw, and this notwith- 
 standing 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 to. 
 
 In order to ascertain the force and direction of the 
 wind, I made an extremely simple and effective apparatus 
 which is fully shown (see Fig. 38). Whilst conducting 
 these experiments it occurred to me, when a large aeroplane 
 was used, that after it had been travelling for a consider- 
 able time, it would impart to the air in the path of its 
 travel, a downward motion, and that the lifting effect 
 would be greatly reduced on this account. In order to 
 test this, I provided four light brass screws and mounted 
 them, as shown at x, on a hardened polished steel point 
 much above their centre of gravity, so that they balanced 
 themselves. On account of the absence of friction, they 
 were easily rotated, and responded to the least breath of 
 air that might be moving. One morning when there was 
 a dead calm, I placed four of these screws equidistant 
 around the whole circle. Some of them rotated very 
 slowly in one direction and some in another ; some alter- 
 nated, but all their motions were extremely slow. However, 
 upon setting the machine going with a large aeroplane and 
 a powerful screw, I found after a few turns that the air 
 was moving downwards around the whole circle at a 
 velocity of about 2 miles an hour, but as the screw was 
 a considerable distance below the aeroplane, I estimated 
 that the actual downward velocity of the air in which the 
 aeroplane was travelling was about 4 miles an hour. 
 The result of my experiments are clearly shown in an 
 unpublished paper which I wrote at the time, and as it is 
 of considerable historical interest, I have placed it in the 
 appendix, notwithstanding that there may be certain 
 repetitions. 
 
 In Fig. 36, a, a is the body of the apparatus, partly of 
 gunmetal and partly of wood. It is provided with a steel 
 shaft to which the screw h, is attached, and also with a 
 cylindrical pulley for taking the belt. The thrust of the 
 screw pushes the shaft inwards and records the lift at o 
 (Fig. 32). The corners of the aeroplane g, g, are attached
 
 68 ARTIFICIAL AND NATURAL PLIGHT. 
 
 by wires to the steel plate e. b, b, is a four-arm spider for 
 holding the ends of the parallel bars c, c, and d, d, 
 show vertical steel bars to which all devices to be tested 
 are attached. In testing aeroplanes, weights may be 
 placed at e, sufficient to balance the lifting effect, and then 
 by adding the weight to the upward pull of the aeroplane, 
 the true lift of the aeroplane is obtained. It is also 
 possible to attach an aeroplane at e, that is, the machine 
 was made to test superposed aeroplanes if required. In 
 
 Fig. 36. The machine attached to the end of the rotating shaft a, a, the 
 body of the machine ; 6, b, four-legged spider secured to a, a ; c, c, 
 parallel bars ; d, d, vertical member to which the aeroplane g, </ is 
 attached ; h, h, the screw ; /,/, wires for preventing distortion of the 
 aeroplane. 
 
 these experiments, I naturally assumed that the best 
 position for a screw was at the rear and in the path of 
 the greatest resistance, but as some experimenters with 
 navigable balloons placed the screw in front in order 
 to pull the apparatus along instead of to push it, I made 
 experiments to see what the relative difference might be. 
 In order to do this, I wound a large amount of rope one-
 
 EXPERIMENTS WITH APPARATUS. 69 
 
 half inch in diameter around the whole apparatus 
 forward of the screw, converting it into an irregular mass 
 well calculated to offer atmospheric resistance. Upon 
 starting the engine, I was rather surprised to see how 
 little retardation these ropes gave to the apparatus. It 
 appeared to me that nearly all of the energy consumed in 
 driving the ropes through the air was recovered by the 
 screw. I then removed the right-hand screw and replaced 
 
 Fig. 37. Marking off the dynamometer. In order to ascertain the actual 
 amount of power consumed in driving the propeller, a brake was put 
 on in place of the screw, a weight applied, and the engine run at full 
 speed. In this way all the uncertain and unknowable factors were 
 eliminated. 
 
 it by a left-hand screw of the same pitch and dimensions 
 (Fig. 37a). I then found that the blast of the screw blowing 
 against the tangle of ropes greatly retarded the travel ; in 
 fact, with the same number of revolutions per minute, the 
 velocity fell off 60 per cent. I think that these experi- 
 ments ought to show that there is but one place for the 
 screw, and that is at the stern, and in the direct path 
 of the greatest atmospheric resistance.
 
 70 ARTIFICIAL AND NATURAL FLIGHT. 
 
 Fig. 38 shows an original apparatus which I designed 
 and made for my own use ; with ordinary anemometers it 
 is necessary to count the number of turns per minute in 
 order to ascertain the velocity of the wind. I wanted 
 something that would indicate the velocity and the 
 direction of the wind without any figures or formulae. 
 I therefore made the apparatus shown in the drawing, 
 in which a, a, is a metallic disc 13*54 inches in diameter, 
 giving it an area of exactly 1 square foot. This is 
 attached to the horizontal bar b, and the whole mounted 
 on two bell crank levers as shown. When the wind is 
 not blowing, the long arms of these two levers assume 
 a vertical position, and the spiral spring h, is in exact 
 
 Fig. 37a. 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 machine. 
 
 line with the pivots on which these levers are mounted, 
 and has no effect except to hold the levers in a vertical 
 position. As the spring has very little tension in this 
 position, and as it requires a considerable movement in 
 order to give it tension, the arms c, c, and the bar b, b, are 
 very easily pushed backwards, but as the distance through 
 which they travel increases, the angle of the lever changes 
 and the tension of the spring increases at the same time, 
 so that when the disc is pushed backwards to any consider- 
 able distance, a strong resistance is encountered. Had 
 I made this apparatus so that the pressure acted directly 
 on the spiral spring, the spaces on the index indicating- 
 low velocities would have been very near together, while
 
 EXPERIMENTS WITH APPARATUS. 
 
 71 
 
 t '
 
 72 ARTIFICIAL AND NATURAL FLIGHT. 
 
 those indicating high velocities would have been widely 
 separated, but with this device properly designed, the 
 spacing on the index became regular and even. The index 
 being very large enabled one to read it at a considerable 
 distance, and at the same time, it acted as a tail and kept 
 the apparatus face to the wind. The spaces of the dial 
 were not laid off' with a pair of dividers, but each par- 
 ticular division was marked by an actual pull on the bar 6, 
 through the agency of a cord and easily running pulley 
 and weight. The markings, however, were not correct, 
 because Haswell's formula was employed in which the 
 pressure of the wind against the normal plane is consider- 
 ably greater than with the more recent formula, which 
 is now known to be correct. Haswell's formula was 
 V 2 x -005 = P, and the recent formula P = O'OOSV 2 , where 
 P = pressure in Ibs. per square foot and V = velocity in 
 miles per hour. In my experiments, I also employed a very 
 well made and delicate anemometer by Negretti & Zambra. 
 
 CRYSTAL PALACE EXPERIMENTS. 
 
 Having fully satisfied myself that aeroplanes flying 
 around a circle 200 feet in circumference had their lifting 
 effect reduced to no insignificant degree by constantly 
 engaging air which had already had imparted to it a down- 
 ward movement by a previous revolution, I determined to 
 make some experiments where this trouble could not occur, 
 but the opportunity did not present itself until after the 
 large roundabout, erroneously described as "a captive 
 flying machine," was put up at the Crystal Palace. This 
 presented a fine opportunity for making experiments at an 
 extremely high velocity around a very large circle. I will 
 only refer to a few of these experiments. To a prolonga- 
 tion of one of the long arms, I attached a thin steel wire 
 rope about 60 feet above the platform ; I then attached to 
 this wire rope the little device shown (Fig. 39), in which a, 
 is an aeroplane, 5 feet long and 1 foot wide, placed at an 
 inclination of 1 in 20. Great care was used in preparing 
 this aeroplane to see that it was free from blemish, smooth, 
 and without any irregularities. Both edges were sharp 
 and the curvature was about one-eighth of an inch on 
 the underneath side. It was made relatively thick in the 
 middle where it was attached to the bar c, and thinner at
 
 CRYSTAL PALACE EXPERIMENTS. 
 
 73 
 
 the ends. 6, shows a lump of lead just heavy enough to 
 balance the bar c, and the tail ; d, was a light but strong 
 wooden frame, all the edges being thin and sharp and 
 covered with a special silk that Mr. Cody had found 
 to be best for such purposes. The wire rope e, was attached 
 to the long arm which I referred to. The great length 
 of the bar c, 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 currents. 
 Upon starting the machine on a very calm day, this 
 
 Fig. 39. Apparatus for testing the lifting effect of aeroplanes at a low 
 angle and extremely high velocity, a, a, the aeroplane ; b, lead 
 weight ; c, long and slender pine rod ; d, tail for keeping the 
 apparatus head on and ensuring its travelling straight through the 
 air ; e, the point of suspension, also the centre of gravity. When this 
 apparatus was travelling at the rate of 80 miles an hour, it gave 
 a lifting effect of about 36 Ibs. , which is about 7 Ibs. per square foot. 
 
 apparatus mounted as high as the point of support, some- 
 times going 10 or more feet higher and sometimes 8 or 
 10 feet lower. However, as a rule, it carried its own 
 weight at a velocity of 80 miles an hour around a circle 
 1,000 feet in circumference. Under these conditions, of 
 course, there could be no downward motion of the air 
 as all the air effected would be removed long before it 
 could be struck the second time by the aeroplane. I had 
 no means of ascertaining exactly how much this plane did
 
 74 ARTIFICIAL AND NATURAL FLIGHT. 
 
 actually lift, because the air was always moving to some 
 extent, and it was not an easy matter to ascertain whether 
 it was above or below the point of support. I am sure, 
 however, that it was as much as 36 Ibs., or rather more 
 than 7 Ibs. to the square foot, and this is just what it 
 should have lifted, providing that we consider the results 
 obtained by smaller planes placed in an air blast of 
 40 miles an hour and at the same angle. When these 
 experiments were finished, I made a very small apparatus 
 having only about 25 square feet of lifting surface, and 
 this carried the weight of a man, in fact several gentlemen 
 came up from London and went round on it themselves. 
 I saw, however, that.it was a dangerous practice, because 
 if the wind was blowing at all, the apparatus would mount 
 very much above the point of support while travelling 
 against the wind, only to drop much below the point 
 of support on the other side of the circle where it was 
 travelling with the wind; in fact, on one occasion the 
 apparatus shown (Fig. 39) mounted in a high wind fully 
 20 feet above the point of support and came down with 
 such a crash on the other side that it T}roke the wire rope. 
 In connection with this, it is interesting to note that when 
 I erected the first so-called " captive flying machine " on 
 my own grounds at Thurlow Park, I intended that instead 
 of ordinary boats such as were ultimately employed, each 
 particular boat should be fitted with an aeroplane, that the 
 engine should be of 200 H.P., and that the passengers 
 should actually be running on the air, each boat being 
 provided with a powerful electric motor in addition to the 
 motive power that drove the shaft. Had this been carried 
 out as was originally designed, it would have removed the 
 apparatus altogether from the category of vulgar merry-go- 
 rounds, but such was not to be. Unforeseen circumstances 
 were against me. I had some of these boats fitted up with 
 aeroplanes and running on my grounds, and two of the 
 engineers of the London County Council came out to see 
 the apparatus before it was put up for public use. On 
 that occasion the wind was blowing a perfect gale |of 
 40 miles an hour, and as the boats travelled at the rate 
 of 35 miles an hour, they, of course, encountered a wind 
 of 75 miles an hour when passing against the wind, and 
 a minus velocity of 5 miles an hour when travelling with 
 the wind on the other side of the circle. The aeroplanes, 
 although of considerable size, were small in relation to
 
 CRYSTAL PALACE EXPERIMENTS. 75 
 
 weight. I had neglected to put any weight in the boats, 
 and when three of us were studying the eccentric path' 
 through which the boats were travelling, suddenly one 
 of them in passing to the windward, raised very much 
 above the point of support and plunged down with great 
 force on the other side; in fact, the shock was so great 
 that it made everything rattle, but nothing was broken. 
 Nevertheless, the engineers said at once, it would not do to 
 run the boats with those aeroplanes ; it was too dangerous. 
 This would not, however, have occurred if the boats had 
 been loaded, or the velocity of the wind had been less. It, 
 however, demonstrated what a tremendous lift may be 
 obtained from a well-made aeroplane passing at a high 
 velocity through the wind at a sharp angle. These 
 aeroplanes were only about 12 feet long and 5 feet wide, 
 having, therefore, 60 square feet of surface. They were, 
 however, strong, well-made, and perfectly smooth, both 
 top and bottom. 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 profession. I was extremely anxious to go on with 
 my experiments. I appreciated fully that I had made 
 a machine that lifted 2,000 Ibs. more than its own weight, 
 and I knew for a dead certainty if I took the matter up 
 again, got rid of my boiler and water tank, and used an 
 internal combustion engine, such as I thought I could 
 produce, that mechanical flight would soon be a fait 
 accompli. I had already spent more than 20,000, and 
 was looking about for some means of making the thing 
 self-supporting. I believed that the so-called " captive 
 flying machine" would be very popular, and bring in a 
 lot of money, and it would have done so, if it had been 
 put up as originally designed. I proposed to use my 
 share of the profits for experimental work on real flying 
 machines. That I was not far wrong in believing that 
 such a machine would be a success, is witnessed by the 
 fact that just about the same time, an American inventor 
 thought of the same thing, put up some three or four 
 machines the first year, and the next year about 50. They 
 were highly profitable, and there are fully 140 of them 
 running at the present time in the U.S.A. It is a fact 
 that nothing in the way of side-shows at exhibitions pi- 
 public resorts has ever had the success of this machine in 
 the U.S.A., and even the little machine at Earl's Court
 
 76 ARTIFICIAL AND NATURAL FLIGHT. 
 
 took 325 10s. in one day and 7,500 in -a season. How- 
 ever, this little attempt to make one hand wash the other 
 cost me no less than 10,400, not to mention more than 
 a year of very hard work. This sum would have been 
 amply sufficient to have enabled me to continue my ex- 
 periments until success was assured.
 
 77 
 
 CHAPTER VI. 
 
 HINTS AS TO THE BUILDING OP FLYING 
 MACHINES. 
 
 FOR those who really wish to build a flying machine that 
 will actually fly with very little experimental work, I have 
 given an outline sketch sufficiently explicit to enable a 
 skilful draughtsman to make a working drawing in which 
 Fig. 40 is a front elevation, Fig. 41 a side elevation, and 
 Fig. 42 a plan. Fig. 41, a, a, shows the two forward or 
 
 Fig. 40. Front elevation of proposed aeroplane machine a, a, the aero- 
 planes ; g, g, condenser ; /, the engine ; q, guard for screw ; 
 k, k, support for wheels. 
 
 main aeroplanes ; 6, 6, the two after aeroplanes, which are 
 smaller and shorter ; c, the rudder ; d, the forward hori- 
 zontal rudder ; e, the screw ; /, the motor ; g, the condenser 
 or cooler ; h, the steering gear ; i, and j, atmospheric 
 buffers ; k and I, wheels attached to a lever pivoted to the 
 body of the machine ; q, a shield for protecting the screw. 
 It will be observed that the framework is extremely long, 
 and, consequently, the distance between the aeroplanes is 
 very great ; but it should be borne in mind that the longer 
 the machine, the less any change of center of lifting effect, 
 as relates to the center of gravity, will be felt. Moreover,
 
 78 
 
 ARTIFICIAL AND NATURAL FLIGHT.
 
 HINTS AS TO THE BUILDING OF PLYING MACHINES. 
 
 7!) 
 
 it is much easier to manoeuvre a machine of great length 
 than one which is very short, because it gives one more 
 time to think and act. If the length was infinitely great 
 the tendency to pitch would be infinitely small I have 
 shown a steering gear consisting of a lever with a handle 
 n, arranged in such a manner that it moves both the 
 vertical rudder c, and the horizontal rudder d, so that the 
 man who steers the machine has nothing to think of except 
 
 j_ 
 
 Fig. 42. Plan of proposed aeroplane machine, in which a, a are the 
 proposed superposed main aeroplanes ; b, b, the after superposed 
 aeroplanes ; c, c, the forward horizontal rudder ; d, platform ; e, screw ; 
 h, k, and i, i, pulleys used in communicating motion from the steering 
 gear, /, to the rudder, j ; g, lever attached to the aeroplane or 
 rudder, c, c, and connected to the steering gear, /. 
 
 to point the lever n, p, in the direction that he wishes the 
 machine to go. This lever is mounted on a universal joint 
 at h, and is connected with suitable wires to the two 
 rudders. In order to prevent shock when the machine 
 alights, it is necessary to provide something that is strong 
 and, at the same time, yielding, and able to travel through 
 a considerable distance before the machine comes to a state
 
 80 ARTIFICIAL AND NATURAL FLIGHT. 
 
 of rest. In the machines which I have seen on the Con- 
 tinent, a very elaborate apparatus is employed, which is 
 not only very heavy, but also offers a considerable resist- 
 ance to the forward motion of the machine through the air. 
 It consists of many tubes, very long levers and heavy spiral 
 springs, etc. In the device which I am recommending, 
 all this is dispensed with, and something very much 
 simpler, cheaper, and lighter is substituted. Moreover, 
 with my proposed apparatus a certain amount of lifting 
 effect is produced. The levers k, k, to which the wheels are 
 attached, should be of thin wood, light and strong, and 
 say about a foot wide, strongly pivoted to the frame and 
 held in position by an atmospheric buffer made of strong 
 and thin steel tubing, shown in section (Fig 51). These 
 pneumatic cylinders may be pumped up to any degree, so 
 as to support the weight of the machine, and then, as it 
 comes down, the compression and escape of air arrest its 
 motion. The condenser g, is placed in such a position that 
 it will act even while the machine is on the ground and the 
 propellers working. In Continental machines, very small 
 screw propellers are used. These screws have probably 
 been made small because the experimenters have found 
 that they encounter a good deal of friction in the atmo- 
 sphere, but this is caused by imperfect shape and the rib of 
 steel at the back of the blades. In order to use a small 
 screw, experimenters have been forced to use a very quick - 
 running engine which makes it necessary to have the 
 cylinders very short, so, in order to get the necessary 
 power, they are obliged to use no less than eight cylinders. 
 However, by increasing the diameter of the screw and 
 making it of such a form that very little or no atmospheric 
 skin friction is encountered, a much better and cheaper 
 engine of a totally different type may be employed. There 
 is no reason why more than four cylinders should be used, 
 but the stroke of the piston and diameter of the cylinder 
 should be increased. Doubtless Continental experimenters 
 have an idea that, as the engine cannot be provided with a 
 flywheel, it must have a very large number of cylinders in 
 order to give a steady pull completely around the circle, and 
 thus avoid so-called "dead centers"; but, when we consider 
 the enormously high velocity of the periphery of the screw, 
 and also take into consideration that the momentum is in 
 proportion to the square of the velocity, it is quite obvious 
 that there can be no slowing up between strokes even if
 
 HINTS AS TO THE BUILDING OF FLYING MACHINES. 81 
 
 only one cylinder should be employed working on the 
 four-cycle principle, in which work is only done one stroke 
 in four. Then, again, I find that the weight of these 
 Continental engines can be greatly reduced, providing that 
 they are made with the same degree of refinement that 
 I employed in building my steam engines. 
 
 Recently there has been a great deal of discussion in 
 Engineering and other journals regarding the compara- 
 tive merits of the aeroplane system and the helicoptere. 
 Some condemn both systems and pin their faith to flapping 
 wings. It has been contended that the screw propeller 
 is extremely wasteful in energy, and that in all Nature 
 neither fish nor bird propels itself by means of a screw. 
 As we do not find a screw in Nature, why then should we 
 employ it in a machine for performing artificial flight ? 
 
 Why not stick to Nature ? . In reply to this, I would 
 say that even Nature has her limits, beyond which she 
 cannot go. When a boy was told that everything was 
 possible with God, he asked; " Could God make a two-year 
 old calf in five minutes ?" He was told that God certainly 
 could. " But," said the boy, " would the calf be two years 
 old ?" It appears to me that there is nothing in Nature 
 which is more efficient, or gets a better grip on the water 
 than a well-made screw propeller, and no doubt there 
 would have been fish with screw propellers, providing that 
 Dame Nature could have made an animal in two pieces. It 
 is very evident that no living creature could be made in two 
 pieces, and two pieces are necessary if one part is 
 stationary and the other revolves ; however, the tails and 
 fins very often approximate to the action of the propeller 
 blades ; they turn first to the right and then to the left, 
 producing a sculling effect which is practically the same. 
 This argument might also be used against locomotives. In 
 all Nature, we do not find an animal travelling on wheels, 
 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 hour. But locomotives with wheels are able to travel 
 at least three times as fast as the fleetest animal with legs, 
 and to continue doing so for many hours at a time, even 
 when attached to a very heavy load. In order to build a 
 flying machine with flapping wings, to exactly imitate 
 birds, a very complicated system of levers, cams, cranks, 
 etc., would have to be employed, and these of themselves 
 would wejgh more than the wings would be able to lift.
 
 82 ARTIFICIAL AND NATURAL FLIGHT. 
 
 However, it is quite possible to approach very closely to 
 the motion of a bird's wings with no reciprocating or 
 vibrating parts, and without napping at all. 
 
 In Fig. 43, I have shown a plan of a helicoptere machine 
 c 
 
 Fig. 43. Plan of a helicoptere machine showing position of the screws. 
 Uwing to the tilting of the shaft forward, the blades present no angle 
 when at d,d, but 10 at c, c, while at/,/ their angle above the hori- 
 zontal is 5 . The horizontal arrows show the direction of the wind 
 against the machine. 
 
 in which two screws are employed rotating in opposite 
 directions, a, a, being the port screw ; b, 6, the starboard 
 screw; and d, d, the platform for the machinery and 
 operator. The screws should be 20 feet in diameter and 
 made of wood. Suppose now that the pitch of these 
 screws is such that the extremities of the blades have
 
 HINTS AS TO THE BUILDING OF FLYING MACHINES. 83 
 
 an angle of 5 ; if now we tilt the shaft forward in the 
 direction of flight to the extent of 5, we shall completely 
 wipe out the angle of inclination of the blades when at 6 
 (Fig. 44), whereas it will be observed that the pitch as 
 regards the horizontal will be increased to 10 at a, on the 
 outer side, and remain unchanged at c, and d. If the 
 peripheral velocity of the blades is, say, four times the 
 velocity at which the machine is expected to travel 
 the blades will get a good grip on the air at c, d, but when 
 they travel forward and encounter air which is travelling 
 at a high velocity in the opposite direction, they assume 
 the position shown at b. If the pitch of the screw blades 
 
 Fig. 44. Shows the position of the blades of a helicoptere as they pass 
 around a circle, when the angle of the shaft and the angle of the 
 blades are the same. 
 
 was a little more than the angle of the shaft, the blades at 
 b would also produce a lifting effect, and as the velocity 
 with which they pass through the air is extremely high, a 
 very strong lifting effect would be produced even if the 
 angle was not more than 1 in 40. By tracing the path and 
 noting the position of the ends of the blades as they pass 
 completely around the circle as shown (Fig. 44), it will be 
 observed that they very closely resemble the motion of a 
 bird's wing. I have no doubt that a properly made 
 machine on this plan would be highly satisfactory, but one 
 should not lose sight of the fact that even with a machine 
 of this type, well designed and sufficiently light to sustain 
 itself in the air while flying, it would still be necessary for
 
 84 ARTIFICIAL AND NATURAL PLIGHT. 
 
 it to move along rapidly when starting in order to get the 
 necessary grip on the air. Upon starting the engine, in a 
 machine of this kind, a very strong downward draught of 
 air would be produced, and the whole power of the engines 
 would be used in maintaining this downward blast, 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 air, the inertia of which had not been 
 disturbed, and which was not moving downwards, the 
 lifting effect would be increased sufficiently to lift the 
 machine off the ground. It would, therefore, work very 
 much like an aeroplane machine. It would also be possible 
 to provide a third screw of less dimensions and running at 
 a less velocity, to push the machine forward, so as not to 
 render it necessary to give such a decided tilt to the shafts. 
 
 As before stated, great care should be taken in designing 
 and making the framework of flying machines, and no 
 stone should be left unturned in order to arrive at the 
 greatest degree of lightness without diminishing the 
 strength too much ; then, again, elasticity should be con- 
 sidered. If we use a thin tube all the material is at the 
 surface, far from the neutral centre, and great stiffness is 
 obtained, but such a tube will not stand so much deflection 
 as a piece of wood ; then, again, wood is cheaper than steel, 
 and in case of an accident, repairs are very quickly and 
 easily made. Wood, however, cannot be obtained in long 
 lengths absolutely free from blemishes. 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 table. 
 
 The relative value of different kinds of wood is shown in 
 this table, and it will be observed that some are much more 
 suitable for the purpose than others. 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 is, the wood which is strongest in proportion 
 to its weight is the best. It will be seen that Honduras 
 mahogany stands at the head of the list, but American 
 white pine is very good for certain purposes, as it is light, 
 strong, easily obtained, and takes the glue very well 
 indeed. In Fig. 45, I have shown a good system of 
 producing the long members necessary in flying machines. 
 I will admit that it costs something to fit up and produce 
 the kind of joints which I have shown, but when the
 
 HINTS AS TO THE BUILDING OP PLYING MACHINES. 
 
 
 Strength 
 per Sq. In. 
 in Lbs. 
 
 Weight of a 
 Cube Foot 
 in Lbs. 
 
 Relative 
 Value. 
 
 Alder, 
 
 
 50 
 
 
 Apple, 
 
 
 49-562 
 
 
 Ash, English 
 
 16,000 
 
 52-812 
 
 302-9 
 
 Ash, White, 
 
 14,000 
 
 43-125 
 
 324-6 
 
 Bamboo, .... 
 
 6,300 
 
 25 
 
 252 
 
 Beech, English, . 
 
 11,500 
 
 53-25 
 
 215-9 
 
 Birch, 
 
 15,000 
 
 45 
 
 333-3 
 
 Box, African, 
 
 23,000 
 
 ... 
 
 
 ,, France, 
 
 
 83 
 
 
 Cedar, American, 
 
 11,600 
 
 35-062 
 
 330-8 
 
 Deal, Christiania, 
 
 12,400 
 
 ... 
 
 
 Ebony, .... 
 
 27,000 
 
 83-187 
 
 324-6 
 
 Elm, 
 
 6,000 
 
 35-625 
 
 168-4 
 
 ,, Eock, . 
 
 13,000 
 
 50 
 
 260 
 
 Fir, Norway Spruce, . 
 
 
 32 
 
 ... 
 
 ,, Dantzic, 
 
 
 36-375 
 
 
 Hackmatack, 
 
 12,000 
 
 37 
 
 324-3 
 
 Hickory, .... 
 
 11,000 
 
 49-5 
 
 222-2 
 
 Ironwood, .... 
 
 
 61-875 
 
 
 
 
 36-375 
 
 
 Lance, . . . . 
 
 23,000 
 
 45 
 
 riri 
 
 Lignum-Vitae, 
 
 11,800 
 
 83-312 
 
 141-6 
 
 Lime, ..... 
 
 
 50-25 
 
 
 
 20,500 
 
 45-5 
 
 450-5 
 
 Mahogany, Honduras, 
 ,, Spanish, . 
 
 21,000 
 12,000 
 
 35 
 53-25 
 
 600 
 225-3 
 
 Maple, .... 
 
 
 46-875 
 
 
 Oak, African, 
 
 9,500 
 
 51-437 
 
 184-7 
 
 Canadian, 
 
 
 54-5 
 
 
 Dantzic, 
 
 4,200 
 
 47-437 
 
 88-5 
 
 English, 
 Live, .... 
 
 7,571 
 16,380 
 
 53-625 
 66-75 
 
 141-2 
 245-4 
 
 Pa, seasoned, 
 
 20,333 
 
 
 
 White, 
 
 16,500 
 
 53 : 75 
 
 306-9 
 
 Va, 
 
 25,222 
 
 
 
 Pine, Norway, 
 
 14,000 
 
 46 : 25 
 
 302-7 
 
 Pitch, .... 
 
 
 41-25 
 
 
 Red, .... 
 
 13,000 
 
 36-875 
 
 352-5 
 
 White, 
 
 11,800 
 
 34-625 
 
 340-8 
 
 Yellow, 
 
 13,000 
 
 28-812 
 
 451-2 
 
 Va, .... 
 
 19,200 
 
 
 
 Poplar, .... 
 
 7,000 
 
 23-937 
 
 292-4 
 
 White, . 
 
 
 33-062 
 
 
 Redwood, Cal, . 
 
 10,833 
 
 
 
 Spruce, .... 
 Sycamore, .... 
 Tamarack, .... 
 
 12,400 
 13,000 
 
 31-25 
 38-937 
 23-937 
 
 396-8 
 333-8 
 
 Teak, African, . 
 
 2l',000 
 
 61-25 
 
 342-8 
 
 Indian, 
 
 15,000 
 
 41-062 
 
 365-3 
 
 Walnut, .... 
 
 
 41 -937 
 
 
 Black, . 
 
 16,633 
 
 31-25 
 
 532-2 
 
 ,, Michigan, 
 Willow, .... 
 
 17,500 
 
 13,000 
 
 36 : 562 
 
 355-5
 
 ARTIFICIAL AND NATURAL FLIGHT. 
 
 members are once made, they are exceedingly strong and 
 stiff. Fig. 46 shows sections of the struts, and these may 
 
 Fig. 45. System of splicing and building up wooden members. When 
 they have to be curved and to keep their shape, they should be bent 
 at the curve at the time of being glued together, and joined in the 
 middle as at d. 
 
 be made of either straight-grained Honduras mahogany or 
 of lance wood ; either answers the purpose very well, 
 
 Section of Middle of Strut. 
 
 Section, of Ends of Strut. 
 
 Fig. 46. Cross-section of struts.
 
 HINTS AS TO THE BUILDING OF FLYING MACHINES. 
 
 because being very strong and straight- 
 grained, permits the struts to be made 
 of such a shape and size as to offer 
 very little resistance in cutting their 
 way through the air. The framework 
 of the aeroplane unless carefully de- 
 signed will offer great resistance to 
 being driven through the air. Suppose 
 that the bottom member of the truss 
 (Fig. 47) is straight, and the top one 
 curved in the direction shown ; no 
 matter how taut the cloth may be 
 drawn, the pressure of the air will 
 cause it to bag upwards between the 
 different trusses, so as to present very 
 nearly the correct curve which is 
 necessary to produce the maximum 
 lifting effect, and without offering too 
 much resistance to the air ; however, 
 one must not forget for a single moment 
 that the air flows over both sides of 
 the aeroplane. When the aeroplane is 
 made very thick in the middle and 
 sharp at the edges (Fig. 48), with the 
 bottom side dead level, it produces a 
 decided lifting effect no matter which 
 way it is being propelled through the 
 air. This is not because the bottom 
 side produces any lifting effect of itself, 
 but because the air running over the 
 top follows the surface. The aeroplane 
 encounters air which is not moving at 
 all. The air is first moved upwards 
 slightly, but it also has to run down 
 the incline to the rear edge of the 
 aeroplane, so that, when it is discharged, 
 it has a decided downward trend ; 
 therefore, the air passing over the top 
 side instead of under the bottom side, 
 produces the lifting effect, showing 
 that the top side of an aeroplane as 
 well as the lower side should be con- 
 sidered. The top side should, therefore, 
 be free from all obstructions.
 
 88 ARTIFICIAL AND NATURAL FLIGHT. 
 
 The top of the aeroplane as well as the bottom should be 
 covered with some light material, if the very best results 
 are to be obtained. In another chapter I have shown a 
 form of fabric-covered aeroplane, made by myself, that was 
 not distorted in the least by the air pressure, and produced 
 just as good effects as it would have done if it had been 
 carefully carved out of a piece of wood. On more than one 
 occasion Lord Kelvin came to my place ; he said that my 
 workshop was a perfect museum of invention. At the 
 Oxford Meeting of the British Association for the Advance- 
 ment of Science, Lord Salisbury in the chair, I was much 
 gratified when Lord Kelvin said that he had examined my 
 work, and found that it was beautifully designed and 
 splendidly executed. He complimented me very highly 
 indeed. While at my place, he said that the most ingeni- 
 ous thing that he had seen was the way I had prevented 
 my aeroplanes from being distorted by the air. He spoke 
 of this several times with great admiration, and, I think, if 
 the fabric-covered aeroplane is to be used at all, that my 
 particular system will be found altogether the best. 
 
 Fig. 48. The paradox aeroplane that lifts no matter in which 
 direction it is being driven. 
 
 Regarding the motors now being employed, I think 
 that there is still room for a great deal of improvement 
 in the direction of greater lightness, higher efficiency 
 and reliability. At the present time, flying machine 
 motors have such small cylinders, the rotation is so rapid, 
 and the cooling appliances so imperfect, that the engine 
 soon becomes intensely heated, and then its efficiency 
 is said to fall off about 40 or 50 per cent., some say even 
 60 per cent. This is probably on account of the high 
 temperature of the cylinder, piston, and air inlet. The 
 heat expands the air as it enters, so that the actual weight 
 of air in the cylinder is greatly reduced, and the engine 
 power reduced in a corresponding degree. There is no 
 trouble about cooling the motor, and a condenser of high 
 efficiency may be made that will cool the water perfectly, 
 and, at the same time, lift a good deal more than its 
 own weight. All the conditions are favourable for using
 
 HINTS AS TO THE BUILDING OF FLYING MACHINES. 89
 
 90 ARTIFICIAL AND NATURAL FLIGHT. 
 
 a very effective atmospheric condenser (see Figs. 30 
 
 may be considered as 2400 times as efficient as 
 air, volume for volume, in condensing steam. When a 
 condenser is made for the purpose of using water as a 
 cooling agent, a large number of small tubes may be closely 
 grouped together in a box, and the water pumped in at one 
 end of the box and discharged at the other end through 
 relatively small openings ; but when air is employed, the 
 tubes or condensing surfaces must be widely distributed, so 
 that a very large amount of air is encountered, and air 
 which has struck one tube and become heated must never 
 touch a second tube (see Figs. 30 and 31, also Appendix). 
 
 Fig. 60. Section showing the Antoinette motor, such as used in 
 the Farraan and De la Grange machines. 
 
 Fig. 51 shows a pneumatic buffer which I have designed, 
 in which a, a, is a steel tube highly polished on the inside ; 
 b, a nozzle for connecting the air-pump, which is of the 
 bicycle variety; c, a nipple to which is attached a strong 
 india-rubber bulb ; d, a piston which is made air-tight by 
 a leather cup ; and /, the connection to the lever carrying 
 the wheels on which the machine runs. While the machine 
 is at a state of rest on the ground, the piston-rod d, is run 
 out to its full extent, and supports the weight of the 
 machine the pressure being about 150 Ibs. to the square 
 inch. When, however, the machine comes violently down
 
 HINTS AS TO THE BUILDING OP FLYING MACHINES. 
 
 to the earth, the piston is pushed 
 inward, compressing the air, and by 
 the time it has travelled, say, one- 
 half the stroke, the air pressure will 
 have mounted to 300 Ibs. to the 
 square inch. At this point, the 
 rubber bulb c, ought to burst and 
 allow the compressed air to escape 
 under a high pressure. Air escaping 
 through a relatively small hole ab- 
 sorbs the momentum of the descent 
 and brings the machine to a state 
 of rest without a destructive shock. 
 It is, of course, necessary for the 
 navigator to select a broad and level 
 field for descent, and then to ap- 
 proach it from the leeward and slow 
 up his machine as near the ground 
 as possible, tilting the forward end 
 upwards in order to arrest its for- 
 ward motion, and touching the 
 ground while still moving against 
 the wind at a fairly high velocity. 
 If all these points are studied, and 
 well carried out, very little danger 
 will result; then, again, the aero- 
 planes b, b, and the forward rudder 
 d (Fig. 41), should be so arranged 
 that, in case of an accident, their 
 outward sides may be instantly 
 turned upwards, in such a manner 
 as to prevent the machine from 
 plunging, and keep it on an even 
 keel while the engines are not 
 running. 
 
 ct 
 
 Fig. 51. Pneumatic buffer 
 a, a, cylinder; b, at- 
 tachment for pumping 
 up ; c, air outlet, covered 
 with a rubber thimble 
 made to burst under about 
 300 Ibs. pressure ; d, the 
 piston.
 
 92 ARTIFICIAL AND NATURAL FLIGHT. 
 
 STEERING BY MEANS OF A GYROSCOPE. 
 
 A ship at sea has only to be steered in a horizontal 
 direction; the water in which it is floated assures its 
 stability in a vertical direction ; but when a flying machine 
 is once launched in the air, it has to be steered in two 
 directions that is, the vertical and the horizontal. More- 
 over, it is constantly encountering air currents that are 
 moving with a much higher velocity than any water 
 currents that have ever to be encountered. It is, therefore, 
 evident that, as far as vertical steering is concerned, it 
 should be automatic. Some have suggested shifting 
 weights, flowing mercury, and swinging pendulums; but 
 none of these is of the least value, on account of the 
 swaying action which always has to be encountered. A 
 pendulum could not be depended upon for working 
 machinery on board a ship, and the same laws apply to 
 an airship. We have but one means at our disposal, and 
 that is the gyroscope. When a gyroscope is spun at a very 
 high velocity on a vertical axis, with the point of support 
 very much above the center of gyration, it has a tendency 
 to maintain a vertical axis ; a horizontal or swinging motion 
 of its support will not cause it to swing like a pendulum. 
 It therefore becomes possible by its use to maintain an air- 
 ship on an even keel. In a steam steering apparatus, such 
 as is used on shipboard, it is not sufficient to apply steam- 
 power to move the rudders, unless some means are pro- 
 vided whereby the movement of the rudder closes off the 
 steam, otherwise the rudder might continue to travel after 
 the effect had been produced, and ultimately be broken ; 
 and so it is with steering a flying machine in a vertical 
 direction. Whenever the fore and aft rudders respond to 
 the action of the gyroscope and are set in motion, they 
 must at once commence to shut off the power that works 
 them, otherwise they would continue to travel. In the 
 photograph (Fig. 52) I have shown an apparatus which I 
 constructed at Baldwyn's Park. It will be seen that the 
 gyroscope is enclosed in a metal case ; a tangent screw, just 
 above the case, rotates a pointer around a small disc, which 
 admits of the speed of the gyroscope being observed. 
 Steam is admitted through a universal joint, descends 
 through the shaft and escapes through a series of small 
 openings placed at a tangent, so as to give rotation to the
 
 STEERING BY MEANS OF A GYROSCOPE. 93 
 
 wheel after the manner of a Barker's mill. The casing 
 about the rotating wheel is extremely light as relates to the 
 wheel, so that, when the gyroscope is once spun on a 
 vertical axis, the rest of the apparatus may be tilted in any 
 direction, while the gyroscope and its attachments maintain 
 a vertical axis. The gyroscope and its attachments are 
 suspended from a long steel tube, which in reality is a 
 steam cylinder. The sleeve which supports the gyroscope 
 moves freely in a longitudinal direction, and the whole is 
 held in position by a triple-threaded screw on the small 
 tube above the cylinder. The steam is admitted through 
 a piston value operated by a species of link motion, as 
 shown. The piston-rod extends to each end of the cylinder, 
 and regulates the rudders by pulling a small wire rope, the 
 travel of the piston being about 8 feet. At the end of the 
 cylinder (not shown) 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 that, as the piston 
 moves, the top tube is rotated, and thereby slides the 
 gyroscope's support, and changes its position as relates to 
 the piston valve. It will, therefore, be seen that the action 
 is the same as with the common steam steering gear used 
 on shipboard. A little adjusting screw at the right hand of 
 the print is shown. The upward projecting arm of the bell 
 crank lever is for the purpose of attaching the wooden 
 handle, making it possible to move the connecting-rod 
 instantly into a position where the steam piston will move 
 the rudders into the position shown (Fig. 56). 
 
 I copy the following from a description which I wrote 
 of this apparatus at the time : 
 
 " GYROSCOPE APPARATUS FOR AUTOMATICALLY STEERING 
 MACHINE IN A VERTICAL DIRECTION. 
 
 " This apparatus consists of a long steam cylinder which 
 is provided with a piston, the piston-rod extending beyond 
 the cylinder at each end ; the ropes working the fore and 
 aft rudders are attached to the ends of this piston-rod, and 
 steam is supplied through an equilibrium valve. The 
 gyroscope is contained in a gunmetal case, and is driven by 
 a jet of steam entering through the trunnions. When the 
 gyroscope is spinning at a high velocity, the casing holding 
 it becomes very rigid and is not easily moved from its
 
 94 
 
 ARTIFICIAL AND NATURAL FLIGHT. 
 
 vertical position. If the machine rears or pitches, the 
 cylinder and valve are moved with the machine while 
 the gyroscope remains in a vertical position. 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 position. 
 As the fore and aft rudders are moved, 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 steam. The apparatus may be 
 
 Fig. 52. Gyroscope, used for the control of the fore and aft horizontal 
 rudders, thus keeping the machine on an even keel while in the air. 
 
 made to regulate at any angle by adjusting the screw 
 which regulates the position of the tubular shaft. The link 
 that suspends the end of the steam valve connecting-rod is 
 supported by a bell crank lever, and while the machine is 
 moving ahead, the lever occupies the position shown in the 
 photograph (Fig. 52) ; but if the machinery and engine 
 stop, the bell crank lever may be moved so as to throw the 
 connecting-rod below the centre, when the steam will move 
 the piston in the proper direction to throw both the rudders 
 into the falling position, as shown in Fig. 56.
 
 STEERING BY MEANS OF A GYROSCOPE. 
 
 95
 
 ARTIFICIAL AND NATURAL FLIGHT.
 
 STEERING BY MEANS OF A GYROSCOPE. 97 
 
 
 I 
 
 / 3 
 
 II 
 
 If 
 rs 
 
 || 
 
 11
 
 98 
 
 ARTIFICIAL AND NATURAL FLIGHT.
 
 CHAPTER VII. 
 THE SHAPE AND EFFICIENCY OF AEROPLANES. 
 
 IN Prof. Langley's lifetime, we had many discussions 
 regarding the width and shape of aeroplanes. The Professor 
 had made many experiments with very small and narrow 
 planes, and was extremely anxious to obtain some data 
 regarding the effect that would be produced by making the 
 planes of greater width. He admitted that by putting 
 some two or three aeroplanes tandem, and all at the same 
 angle, the front aeroplane a (Fig. 57), would lift a great 
 deal more than b, and that c, would lift still less. He 
 suggested the arrangement shown at a', b', c', in which b' is 
 set at such an angle as to give as much additional accelera- 
 tion to the air as it had received in the first instance by 
 passing under a', and that c, should also increase the 
 acceleration to the same extent. With this arrangement, 
 the lifting effect of the three aeroplanes ought to be 
 the same, but I did not agree with this theory. It seemed 
 to me that it would only be true if it dealt with the 
 volume of air represented between j, and k, and that he did 
 not take into consideration the mass of air between k, and I, 
 that had to be dealt with, and which would certainly have 
 some effect in buoying up the stream of air, j, k. Prof. 
 Langley admitted the truth of this, and said that nothing 
 but experiment would demonstrate what the real facts 
 were. But it was a matter which I had to deal with. I 
 did not like the arrangement a', b', c, as the angle was so 
 sharp, especially at c', that a very large screw thrust would 
 be necessary. I therefore made a compromise on this 
 system which is shown at a", b", c". In this case a", has an 
 inclination of 1 in 10, b" an inclination of 1 in 6, and 
 c" an inclination of 1 in 5. It will be seen that this form, 
 which is shown as one aeroplane at a"', b"', c"', is a very 
 good shape. It is laid out by first drawing the line c, d, 
 dropping the perpendicular equal to one-tenth of the 
 distance between c and d, and then drawing a straight line 
 from c, through e, to /, where another perpendicular is
 
 100 ARTIFICIAL AND NATURAL PLIGHT. 
 
 dropped, and half the distance between d and e laid 
 off, and another straight line drawn from e, through g, to h, 
 and the perpendicular h, i, laid off the same as /, g. We 
 then have four points, and by drawing a curve through 
 these, we obtain the shape of the aeroplane shown above, 
 which is an exceedingly good one. This shape, however, 
 is only suitable for velocities, up to 40 miles per hour; 
 at higher velocities, the curvature would be correspondingly 
 reduced. 
 
 THE ACTION OF AEROPLANES AND THE POWER 
 REQUIRED EXPRESSED IN THE SIMPLEST 
 TERMS. 
 
 IN designing aeroplanes for flying machines, we should not 
 lose sight of the fact that area alone is not sufficient. Our 
 planes must have a certain length of entering edge that is, 
 the length of the front edge must bear a certain relation to 
 the load lifted. An aeroplane 10 feet square will not lift 
 half as much for the energy consumed as one 2 feet wide 
 and 50 feet long ; therefore, we must have our planes 
 as long as possible from port to starboard. At all speeds of 
 40 miles per hour or less, there should be at least 1 foot of 
 entering edge for every 4 Ibs. carried. However, at higher 
 speeds, the length may be reduced as the square of 
 the speed increases. An aeroplane 1 foot square will not 
 lift one-tenth as much as one that is 1 foot wide and 10 feet 
 long. This is because the air slips off at the ends, but this 
 can be prevented by a thin flange, or & la Hargrave's kites. 
 An aeroplane 2 feet wide and 100 feet long placed at 
 an angle of 1 in 10, and driven edgewise through the air at a 
 velocity of 40 miles per hour, will lift 2'5 Ibs. per square 
 foot. But as we find a plane 100 feet in length too long to 
 deal with, we may cut it into two or more pieces and place 
 them one above the other superposed. This enables us to 
 reduce the width of our machine without reducing its 
 lifting effect ; we still have 100 feet of entering edge, we 
 still have 200 feet of lifting surface, and we know that each 
 foot will lift 2-5 Ibs. at the speed we propose to travel. 
 200 x 2-5 = 500 ; therefore our total lifting effect is 500 
 Ibs., and the screw thrust required to push our aeroplane 
 through the air is one-tenth of this, because the angle above 
 the horizontal is ] in 10. We, therefore, divide what Prof.
 
 THE ACTION OP AEROPLANES. 101 
 
 Langley has so aptly called the "lift" by 10 ; = 50. 
 
 It will be understood that the vertical component is the 
 lift, and the horizontal component the drift, the expression 
 " drift " also being a term first applied by Prof. Langley. 
 Our proposed speed is 40 miles per hour, or 3,520 feet in a 
 minute of time. If we multiply the drift in pounds by the 
 number of feet travelled in a minute of time, and divide the 
 product thus obtained by 33,000, we ascertain the H.P. 
 required 
 
 50 x 3,520 
 33,000 
 
 It therefore takes 5 '33 H.P. to carry a load of 500 Ibs. at a 
 rate of 40 miles per hour, allowing nothing for screw slip or 
 atmospheric resistance due to framework and wires. But 
 we find we must lift more than 500 Ibs., and as we do not 
 wish to make our aeroplanes any longer, we add to their 
 width in a fore and aft direction that is, we place another 
 similar aeroplane, also 2 feet wide, just aft of our first 
 aeroplane. This will, of course, have to engage the air 
 discharged from the first, and which is already moving 
 downwards. It is, therefore, only too evident that if we 
 place it at the same angle as our first one viz., 1 in 10 it 
 will not lift as much as the first aeroplane, and we find that 
 if we wish to obtain a fairly good lifting effect, it must be 
 placed at an angle of 1 in 6. Under these conditions, the 
 screw thrust for this plane will be th part of the lift, or 
 8-88 H.P. against 5'33 H.P. with our first aeroplane. In 
 order to avoid confusion, we will call our first plane a", our 
 second plane b", and the third c", the same as in Fig. 57. 
 Still we are not satisfied, we want more lift, we therefore 
 add still another aeroplane as shown (c", Fig. 57). This 
 one has to take the air which has already been set in 
 motion by the two preceding planes a" and b", so in order 
 to get a fair lifting effect, we have to place our third plane 
 at the high angle of 1 in 5. At this angle, our thrust has 
 to be ith of the lifting effect, and the H.P. required is twice 
 as much per pound carried as with the plane a", where the 
 angle was 1 in 10; therefore, it will take 10*66 H.P. to 
 carry 500 Ibs. As there is no reason why we should have 
 three aeroplanes placed tandem where one would answer 
 the purpose much better, we convert the whole of them 
 into one, as shown (a", b'", c'", Fig. 57), and by making
 
 102 
 
 ARTIFICIAL AND NATURAL FLIGHT. 
 
 the top side smooth and uniform, we get the advantage of 
 the lifting effect due to the air above the aeroplane as well 
 as below it. The average H.P. is therefore 5'33 + 8'SS + 
 
 
 Fig. 57. Diagram showing the evolution of a wide aeroplane. 
 
 10-66 - 3 = 8-29 H.P. for each plane, or 25 H.P. for the 
 whole, which is at the rate of 60 Ibs. to the H.P., all of 
 which is used to overcome the resistance due to the weight
 
 THE ACTION OP AEROPLANES. 103 
 
 and the inclination of the aeroplanes, and which is about 
 half the total power required. We should allow as much 
 more for loss in screw slip and atmospheric resistance due 
 to the motor, the framework, and the wires of the machine. 
 If, however, the screw is placed in the path of the greatest 
 resistance, it will recover a portion of the energy imparted 
 to the air. We shall, however, require a 50 H.P. motor, 
 and thus have 30 Ibs. to the H.P. 
 
 From the foregoing it will be seen that at a speed of 
 40 miles an hour, the weight per H.P. is not very great. If we 
 wish to make a machine more efficient, we must resort to a 
 multitude of very narrow superposed planes, or sustainers, as 
 Mr. Philipps calls them, or we must increase the speed. If an 
 aeroplane will lift 2*5 Ibs. per square foot placed at an angle 
 of 1 in 10, and driven at a velocity of 40 miles an hour, the 
 same aeroplane will lift 1*25 Ibs. if placed at an angle of 
 1 in 20, and as the lifting effect varies as the square of the 
 velocity, the same plane will lift as much more at 60 miles 
 per hour, as 60 2 is greater than 40 2 that is, 2 '81 Ibs. per 
 square foot instead of T25 Ibs. At this high speed, pro- 
 viding that the width of the plane is not more than 3 feet, 
 it need be only slightly curved and have a mean angle of 
 1 in 20. 
 
 An aeroplane 100 feet long and 3 feet wide would have 
 300 square feet of lifting surface, each of which would lift 
 2-81 Ibs., making the total lifting effect 843 Ibs. 843 -T- 20 = 
 42'15, which is the screw thrust that would be necessary to 
 propel such a plane through the air at a velocity of 60 miles 
 per hour. 60 miles per hour is 5,280 feet in a minute, 
 therefore the H.P. required is 42 15 X 5,280 -=- 33,000 = 67 
 H.P. Dividing the total lifting effect 843 by 67, we 
 have 843 -r- 67 = 125'8, the lift per H.P. If we allow one- 
 half for loss in friction, screw slip, etc., we shall be carrying 
 a load of 843 Ibs. with I3'4 H.P. It will, therefore, be seen 
 that a velocity of 60 miles an hour is much more economical 
 in power than the comparatively low velocity of 40 miles 
 an hour; moreover, it permits of a considerable reduction in 
 the size and weight of the machine, and this diminishes the 
 atmospheric resistance.
 
 104 
 
 ARTIFICIAL AND NATURAL FLIGHT. 
 
 HORIZONTAL LIHE 
 
 Fig. 58. In a recently published mathematical treatise on Aerodynamics, 
 an illustration is shown, representing the path that the air takes on en- 
 countering a rapidly moving curved aeroplane. It will be observed that 
 the air appears to be attracted upwards before the aeroplane reaches 
 it, exactly as iron filings would be attracted by a magnet, and that 
 the air over the top of the aeroplane is thrown off at a tangent, pro- 
 ducing a strong eddying effect at the top and rear. Just why the air 
 rises up before the aeroplane reaches it is not plain, and as nothing 
 could be further from the facts, mathematical formulae founded on 
 such a mistaken hypothesis can be of but little value to the serious 
 experimenter on flying machines. 
 
 Fig. 59. An illustration from another scientific publication also on the 
 Dynamics of Flight. It will be observed that the air in striking the 
 underneath side of the aeroplane is divided into two streams, a 
 portion of it flowing backwards and over the top of the edge of the 
 aeroplane where it becomes compressed. An eddy is formed on the 
 back and top of the aeroplane, and the air immediately aft the aero- 
 plane is neither rising nor falling. 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 clear.
 
 THE ACTION OF AEROPLANES. 
 
 105 
 
 Fig. 60. This shows another illustration from the same mathematical 
 work, and represents the direction which the air is supposed to take 
 on striking a flat aeroplane. With this, the air is also divided, a 
 portion moving forward and over the top of the aeroplane where it is 
 compressed, leaving a large eddy in the rear, and, as the dotted lines 
 at the back of the aeroplane are horizontal, it appears that the air is 
 not forced downwards by its passage. Here, again, fornmla founded 
 on such hypothesis is misleading in the extreme. 
 
 Fig. 61. This shows the shape and the practical angle of an aeroplane. 
 This angle is 1 in 10, and it will be observed that the air follows both 
 the upper and the lower surface, and that it leaves the plane in a 
 direction which is the resultant of the top and bottom angle.
 
 106 
 
 ARTIFICIAL AND NATURAL PLIGHT. 
 
 #O*,ZONTAI. LINK 
 
 Fig. 62. This shows an aeroplane of great thickness, placed at the 
 highest angle that will ever be used 1 in 4 and even with this the 
 air follows the upper and lower surfaces. No eddies are formed, and 
 the direction that the air takes after leaving the aeroplane is the 
 resultant of the top and bottom angles. 
 
 Fig. 68. Section of a screw blade having a rib on the back. The resist- 
 ance caused by this rib is erroneously supposed to be skin friction.
 
 THE ACTION OF AEROPLANES. 
 
 Fig. 64. Shows a flat aeroplane placed at an angle of 45, an angle which 
 will never be used in practical flight, but at this angle the momentum 
 of the approaching air and the energy necessary to give it an acceler- 
 ation sufficiently great to make it follow the back of the aeroplane 
 are equal, and at this point, the wind may either follow the surface or 
 not. Sometimes it does and sometimes it does not. See experiments 
 with screws. 
 
 Fig. 65. The aeroplane here shown is a mathematical paradox. This 
 aeroplane lifts, no matter in which direction it is driven. It 
 encounters air which is stationary and leaves it with a downward 
 trend; therefore it must lift. However, if we remove the section b, 
 and only subject a to the blast, as shown at Fig. 66, no lifting effect 
 is produced. On the contrary, the air has a tendency to press a, 
 downwards. The path which the air takes is clearly shown ; this is 
 most important, as it shows that the shape of the top side is a factor 
 which has to be considered. All the lifting effect in this case is pro- 
 duced by the top side.
 
 108 
 
 ARTIFICIAL AND NATURAL FLIGHT. 
 
 Fig. 67. In this drawing a represents an aeroplane, or a bird's wing. 
 Suppose that the wind is blowing in the direction of the arrows ; the 
 real path of the bird as relates to the air is from i to j, that is, the 
 bird is falling as relates to the air although moving on the line c, d, 
 against the wind. In some cases, a bird is able to travel along the line 
 g, h, instead of in a horizontal direction, thus rising and apparently 
 flying into the teeth of the wind at the same time.
 
 SOME RECENT MACHINES. 109 
 
 SOME RECENT MACHINES. 
 
 Professor S. P. Langley, .of the Smithsonian Institute, 
 Washington, D.C., made a small flying model in 1896. 
 This, however, only weighed a few pounds ; but as it did 
 actually fly and balance itself in the air, the experiment 
 was of great importance, as it demonstrated that it was 
 possible to make a machine with aeroplanes so adjusted 
 as to steer itself automatically in a horizontal direction. In 
 order to arrive at this result, an innumerable number of 
 trials were made, 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 front, and then pitching backwards, 
 or plunging while moving forward. 
 
 The Wright Brothers of Dayton, Ohio, U.S.A., often 
 referred to as " the mysterious Wrights," commenced 
 experimental work many years ago. The first few years 
 were devoted to making gliding machines, 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 time ; but they were not satisfied with mere gliding 
 machines, and so turned their attention in the direction of 
 motors. After some years of experimental work, they 
 applied their motor to one of their large gliding machines, 
 and it is said that with this first machine they actually 
 succeeded in flying short distances. Later on, however, 
 with a more perfect machine, they claim to have made 
 many flights, amongst which I will mention three : 12 miles 
 in 20 minutes, on September 29th, 1905 ; 2075 miles in 33 
 minutes, on October 4th ; and 24r2 miles in 38 minutes, on 
 October 5th of the same year. As there seems to be much 
 doubt regarding these alleged flights, we cannot refer to 
 them as facts until the Wright Brothers condescend to show 
 their machine and make a flight in the presence of others ; 
 nevertheless, 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 achievments of Messrs Farman and 
 De la Grange. It is interesting to note in this connection 
 that all flying machines that have met with any success 
 have been made on the same lines ; all have superposed 
 aeroplanes, all have fore and aft horizontal rudders, and all 
 are propelled with screws ; and in this respect they do not
 
 HO ARTIFICIAL AND NATURAL FLIGHT. 
 
 differ from the large machine that I made at Baldwyn's 
 Park many years ago. I have seen both the Farman and 
 the De la Grange machines; they seem to be about the same 
 in size and design, and what is true of one is equally true 
 of the other ; I will, therefore, only describe the one that 
 seems to have done the best the De la Grange. The general 
 design of this machine is clearly shown in the illustrations 
 (Figs. 68 and 69). The dimensions are as follows : The two 
 main aeroplanes are 32'8 feet long and 4'9 feet wide ; the 
 tail or after rudder is made in the form of a Hargraves' box 
 kite, the top and bottom sides of the box being curved and 
 covered with balloon fabric, thus forming aeroplanes. This 
 box is 9'84 feet long from port to starboard, and 6'56 feet 
 wide in a fore and aft direction. The diameter of the screw 
 is 7'2 feet and it has a mean pitch of 57 feet. The screw 
 blades are two in number and are extremely small, being 
 only 6'3 inches wide at the outer end and 3'15 inches at 
 the inner end, their length being 21 feet. The space 
 between the fore and aft aeroplanes is 4'9 feet. The total 
 weight is about 1,000 Ibs. with one man on board. The 
 speed of this machine through the air is not known with 
 any degree of certainty ; it is, however, estimated to be 
 32 to 40 miles per hour. When the screw is making 
 1,100 revolutions per minute, the motor is said to 
 develop 50 H.P. 
 
 In the following calculations, I have assumed that the 
 machine has the higher speed 40 miles per hour. I have 
 been quite unable to obtain any reliable data regarding the 
 angle at which the aeroplanes are set, but it would appear 
 that the angle is about 1 in 10. The total area of the two 
 main aeroplanes is 321'4 square feet. A certain portion of 
 the lower main aeroplane is cut away, but this is com- 
 pensated for by the forward horizontal rudder placed in the 
 gap thus formed. The two rear aeroplanes forming the tail 
 of the machine have an area of 128-57 square feet. The 
 area of all the areoplanes is, therefore, 450 square feet. As 
 the weight of the machine is 1,000 Ibs., the lift per square 
 foot is 2'2 Ibs. Assuming that the angle of the aeroplanes 
 is 1 in 10, the screw thrust would be 100 Ibs., providing, 
 however, that the aeroplanes were perfect and no friction 
 of any kind was encountered. Forty miles per hour is 
 at the rate of 3,520 feet in a minute of time, therefore, 
 
 = 10 ' 66 KR K We all W another 10 H ' R for
 
 SOME RECENT MACHINES. 
 
 Ill 
 
 atmospheric resistance due to the motor, the man, and the 
 framework of the machine, it would require 20'66 H.P. to 
 
 Fig. 68. The De la Grange machine on the ground and about to make 
 a flight. 
 
 Fig. 69. The De la Grange machine in full flight and very near the 
 ground. 
 
 propel the machine through the air at the rate of 40 miles 
 per hour. If the motor actually develops 50 H.P., 29 H.P. 
 will be consumed in screw slip and overcoming the re-
 
 112 
 
 ARTIFICIAL AND NATURAL FLIGHT. 
 
 sistance due to the imperfect shape of the screw. The 
 blades of the De la Grange screw propeller are extremely 
 small, and the waste of energy is, therefore, correspondingly 
 great their projected area being only 1*6 square feet for 
 both blades. Allowing 200 Ibs. for screw thrust, we have 
 
 200 
 the following: - = 125 Ibs. pressure per square foot on 
 
 1'bO 
 
 the blades. If we multiply the pitch of the screw in feet 
 by the number of revolutions per minute, we find that if it 
 were travelling in a solid nut it would advance over 70 
 miles an hour. By the Eiffel tower formula P = O'OOS V 2 , 
 a wind blowing at a velocity of 70 miles per hour produces 
 a pressure of 14'7 Ibs. per square foot on a normal plane ; 
 therefore, assuming that the projected area of the screw 
 
 Fig. 70. Farman's machine in flight. 
 
 blades is 1*6, we have 1/6 x 147 = 23'52 Ibs., which is only 
 one-fifth part of what the pressure really is when the 
 screws are making 1,100 turns a minute. It is interesting 
 to note that the ends of the screw blades travel at a velocity 
 of 414 feet per second, which is about one-half the velocity 
 of a cannon ball fired from an old-fashioned smooth bore. 
 
 A flying machine has, of course, to be steered in two 
 directions at the same time the vertical and the horizontal. 
 In the Farman and De la Grange machines, the horizontal 
 steering is effected by a small windlass provided with a 
 hand wheel, the same as on a steam launch, and the vertical 
 steering is effected by a longitudinal motion of the shaft of 
 the same windlass. As the length of the machine is not 
 very great, it requires very close attention on the part of 
 the man at the helm to keep it on an even keel; if one is
 
 SOME RECENT MACHINES. 
 
 113 
 
 not able to think and act quickly, disaster is certain. On 
 one occasion, the man at the wheel pushed the shaft of the 
 
 Fig. 71. Bleriot's machine. This machine raised itself from the ground, 
 but as the centre of gravity was very little, if any, above the centre 
 of lifting effect, it turned completely over in the air. 
 
 Fig. 72. Santos Dumont's flying machine. 
 
 windlass forward when he should have pulled it back, and 
 the result was a plunge and serious damage to the machine : 
 
 8
 
 114 
 
 ARTIFICIAL AND NATURAL FLIGHT. 
 
 happily no one was injured, though some of the bystanders 
 were said to have had very narrow escapes. The remedy 
 for this is to make all hand-steered machines of great 
 length, which gives more time to think and act ; or, still 
 better, to make them automatic by the use of a gyroscope. 
 
 VELOCITY AND PRESSURE OF THE WIND. 
 
 THE pressure varies as the square of the velocity or P <x V 2 . The old 
 formula for wind blowing against a normal plane was P = 0'005 x V 2 . 
 The latest or Eiffel Tower formula gives a much smaller value, being 
 P = 0'003 V-, where V represents the velocity in miles per hour, and P 
 the pressure in pounds per square foot. 
 
 VELOCITY. 
 
 Pressure 
 on a 
 Sq. Foot. 
 
 Character of the Wind. 
 
 Per Hour. 
 
 Per Minute. 
 
 Per Second. 
 
 Miles. 
 
 Feet. 
 
 Feet. 
 
 Lbs. 
 
 
 1 
 2 
 3 
 
 88 
 176 
 264 
 
 1-5 
 2-9 
 4-4 
 
 003 
 012 
 027 
 
 Barely observable. 
 j- Just perceptible. 
 
 4 
 
 352 
 
 5-9 
 
 048 
 
 Light breeze. 
 
 5 
 
 440 
 
 7'3 
 
 075 
 
 \ 
 
 6 
 
 528 
 
 8-8 
 
 108 
 
 > Gentle, pleasant wind. 
 
 8 
 
 704 
 
 11-7 
 
 192 
 
 \ 
 
 10 
 
 880 
 
 14-7 
 
 3 
 
 Fresh breeze. 
 
 15 
 
 1,320 
 
 22 
 
 675 
 
 Brisk breeze. 
 
 20 
 
 1,760 
 
 29-4 
 
 12 
 
 Stiff breeze. 
 
 25 
 
 2,200 
 
 36-7 
 
 1-875 
 
 Very brisk breeze. 
 
 30 
 35 
 
 2,640 
 3,080 
 
 44 
 51-3 
 
 2-7 
 3-675 
 
 | High wind. 
 
 40 
 45 
 
 3,520 
 3,960 
 
 58-7 
 66 
 
 .4-8 
 6075 
 
 Very high wind. 
 Gale. 
 
 50 
 
 4,400 
 
 73-4 
 
 7-5 
 
 Storm. 
 
 60 
 70 
 
 5,280 
 6,160 
 
 88 
 102-7 
 
 10-8 
 14-7 
 
 j- Great storm. 
 
 80 
 
 7,040 
 
 117-2 
 
 19-2 
 
 Hurricane. 
 
 90 
 100 
 
 7,920 
 8,800 
 
 132 
 146-7 
 
 24-3 
 30 
 
 i Tornado. 
 
 110 
 
 9,680 
 
 161-2 
 
 36-3 
 
 
 120 
 
 10,560 
 
 176 
 
 43-2 
 
 
 130 
 140 
 
 11,440 
 12,320 
 
 191 
 205-3 
 
 50-7 
 58-8 
 
 " Washoe zephyrs." * 
 
 150 
 
 13,200 
 
 220 
 
 67-5 
 
 
 * With apologies to Mark Twain.
 
 SOME RECENT MACHINES. 
 A 
 
 115 
 
 Fig. 72a. Angles and degrees compared. It will be observed that 
 an angle of 1 in 4 is practically 14. 
 
 TABLE OF EQUIVALENT INCLINATIONS. 
 
 Rise. 
 
 Sine of Angle. 
 
 Angle in Degrees. 
 
 1 in 30, 
 
 0333 
 
 1-91 
 
 1 25, ... 
 
 04 
 
 2-29 
 
 1 20, ... 
 
 05 
 
 2-87 
 
 1 18, ... 
 
 0555 
 
 3-18 
 
 1 16, ... 
 
 0625 
 
 3-58 
 
 1 14, ... 
 
 0714 
 
 4-09 
 
 1 12, ... 
 
 0333 
 
 4-78 
 
 1 10, ... 
 
 1 
 
 573 
 
 1 9, ... 
 
 1111 
 
 6-38 
 
 1 8, ... 
 
 125 
 
 7-18 
 
 1 7, ... 
 
 143 
 
 8-22 
 
 1 6, ... 
 
 1667 
 
 9-6 
 
 1 5, ... 
 
 2 
 
 11-53 
 
 1 4, ... 
 
 25 
 
 14-48 
 
 1,3, 
 
 3333 
 
 19-45
 
 116 
 
 ARTIFICIAL AND NATURAL FLIGHT. 
 
 TABLE OF EQUIVALENT VELOCITIES. 
 
 Miles 
 per Hour. 
 
 Feet 
 per Second. 
 
 Feet 
 per Minute. 
 
 Metres 
 per Minute. 
 
 Metres 
 per Second. 
 
 1, 
 
 1-5 
 
 88 
 
 26-8 
 
 447 
 
 2, 
 
 2-9 
 
 176 
 
 53-6 
 
 894 
 
 3, 
 
 4-4 
 
 264 
 
 80-5 
 
 1-341 
 
 4, 
 
 5-9 
 
 352 
 
 107-3 
 
 1-788 
 
 5, 
 
 7-3 
 
 440 
 
 134-1 
 
 2-235 
 
 6, 
 
 8-8 
 
 528 
 
 160-9 
 
 2-682 
 
 8, 
 
 11-7 704 
 
 214-6 
 
 3-576 
 
 10, . . 
 
 14-7 
 
 880 
 
 268-2 
 
 4-470 
 
 15, 
 
 22 
 
 1,320 
 
 402-3 
 
 6-705 
 
 20, 
 
 29-4 
 
 1,760 
 
 536-4 
 
 8-940 
 
 25, . . 
 
 36-7 
 
 2,200 
 
 670-5 
 
 11-176 
 
 30, 
 
 44 
 
 2,640 
 
 804-6 
 
 13-411 
 
 35, 
 
 51-3 
 
 3,080 
 
 938-8 
 
 15-646 
 
 40, 
 
 58-7 
 
 3,520 
 
 1,072-9 
 
 17-881 
 
 45, 
 
 66 
 
 3,960 
 
 1,207 
 
 20-116 
 
 50, 
 
 73-4 
 
 4,400 
 
 1,341-1 
 
 22-352 
 
 60, 
 
 88 
 
 5,280 
 
 1,609-2 
 
 26-822 
 
 70, 
 
 102-7 
 
 6,160 
 
 1,877-5 
 
 31-292 
 
 80, 
 
 117-2 
 
 7,040 
 
 2,145-8 
 
 35-763 
 
 90, 
 
 132 
 
 7,920 
 
 2,414 
 
 40233 
 
 100, 
 
 146-7 
 
 8,800 
 
 2,682-2 
 
 44-704 
 
 110, 
 
 161-2 
 
 9,680 
 
 2,950-2 
 
 49-174 
 
 120, 
 
 176 
 
 10,560 
 
 3,218-4 
 
 53-644 
 
 130, . . 
 
 191 
 
 11,440 
 
 3,486-6 
 
 58-115 
 
 140, . . 
 
 205-3 
 
 12,320 
 
 3,755-1 
 
 62 '585 
 
 150, 
 
 220 
 
 13,200 
 
 4,023-3 
 
 67-056 
 
 To convert feet per minute into metres per second, multiply by -03508.
 
 SOME RECENT MACHINES. 
 
 117 
 
 eo <N i -* T < 
 
 so" <o" eo" of -H" " -T 
 
 | * 
 
 t- O CO O Q OO Q 
 
 a o co o 5 <M t^ 
 oo t>. co co MS -* eo 
 
 op ip 
 
 CN Ol 
 
 T** W 
 
 ii 
 
 QO eo 
 
 cp ep 
 
 >o sc i -< 
 
 p ao 
 
 - rf 2" 2 8" 8 g 8 S" !8 8" 8" 8" 8" S
 
 118 
 
 ARTIFICIAL AND NATURAL FLIGHT. 
 
 Fig. 726. When an aeroplane is driven through the air, it encounters 
 stationary air and leaves it with a downward trend. With a thick 
 curved aeroplane, as shown, the air follows both the top and the 
 bottom surfaces, and the direction that the air takes is the resultant 
 of these two streams of air. It will be seen that the air takes the 
 same direction that it would take if the plane were flat, and raised 
 from a to c, which would be substantially the same as shown at /, h, g. 
 It has, however, been found by actual experiment that the curved 
 plane is preferable, because the lifting effect is more evenly distri- 
 buted, and the drift is less in proportion to the lift. 
 
 O 
 
 Fig. 72c. Aeroplanes experimented with by Mr. Horatio Philipps. In 
 the published account which is before me, the angles at which these 
 planes were placed are not given, but, by comparing the lift with the 
 drift, we may assume that it was about 1 in 10. | 
 
 Fig. 5 seems to have been the best shape, and I find that this plane 
 would have given a lifting effect of 2 -2 Ibs. per square foot at a velocity 
 of 40 miles per hour.
 
 SOME RECENT MACHINES. 
 
 119 
 
 1 
 
 s 
 
 IQ co co co co eo 
 
 3 
 
 M 
 
 q 
 
 ^bbbbb"* 00 
 
 c 
 
 
 
 E 
 
 S^ 
 
 obbbobbo 
 
 i 
 
 III 
 
 & q? c5 
 
 
 h 
 
 co oo oo co eo co 
 ppSSpppp 
 
 | 
 
 _ 
 
 
 
 in 
 
 ....*..-.. 
 
 1 
 
 1 
 
 5 
 
 l . " 
 
 
 
 
 w 
 
 PH 
 
 X X X X X X XojO 
 
 g 
 
 i 
 
 olso^tooasj 
 
 
 
 
 
 
 !L 
 
 05 ^ CO 05 -H 05 
 
 Sg 
 
 
 <N T*( CO <N -H (M 
 
 * 
 
 * 
 
 
 I 4 
 
 }^ 
 
 .<*;.' 
 
 
 
 
 
 o 
 
 
 
 L 
 
 I 
 
 1 . . . | 
 
 1 
 
 
 | -T of co" TiT 10" o" 
 
 
 
 th g 
 
 
 
 g g PS
 
 120 
 
 CHAPTER VIII. 
 BALLOONS. 
 
 As far as the actual navigation of the air is concerned, 
 balloonists have had everything to themselves until quite 
 recently, but we find that at the present moment, experi- 
 menters are dividing their attention about equally between 
 balloons or machines lighter than the air, and true flying 
 machines or machines heavier than the air. In all Nature. 
 we do not find any bird or insect that does not fly by 
 dynamic energy alone, and I do not believe that the time 
 is far distant when those now advocating machines lighter 
 than the air, will join the party advocating machines heavier 
 than the air, and, eventually, balloons will be abandoned 
 altogether. No matter from what standpoint we examine 
 the subject, the balloon is unsuitable for the service, and it is 
 not susceptible of much improvement. On the other hand, 
 the flying machine is susceptible of a good deal of improve- 
 ment ; there is plenty of scope for the employment of a 
 great deal of skill, both mechanical and scientific, for a good 
 many years to come. 
 
 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 Times, from which I quote the 
 following ; 
 
 " The result of recent experiments must have convinced 
 every thinking man that the day of the balloon is past. A 
 balloon, from the very nature of things, must be extremely 
 bulky and fragile. 
 
 " It has always appeared to the writer that it would be 
 absolutely impossible to make a dirigible balloon that would 
 be of any use, even in a comparatively light wind. Experi- 
 ments have shown that only a few hundred feet above the 
 surface of the earth, the air is nearly always moving at a 
 velocity of at least 15 miles an hour, and more than two- 
 thirds of the time at a velocity considerably greater than 
 this. In order to give a balloon sufficient lifting power to 
 carry two men and a powerful engine, it is necessary that
 
 BALLOONS. 
 
 it should be of enormous bulk. Considered as a whole, 
 including men and engine, it must have a mean density 
 less than the surrounding air, otherwise it will not rise. 
 Therefore, not only is a very large surface exposed to the 
 wind, but the whole thing is so extremely light and fragile 
 as to be completely at the mercy of wind and weather. 
 Take that triumph of engineering skill, the ' Nulli Secundus,' 
 for example. The gas-bag, which was sausage-shaped and 
 30 feet in diameter, was a beautiful piece of workmanship, 
 the whole thing being built up of goldbeater's skin. The 
 cost of this wonderful gas-bag must have been enormous. 
 The whole construction, including the car, the system of 
 suspension, the engine and propellers, had been well thought 
 out and the work beautifully executed ; still, under these 
 most favourable conditions, only a slight shower of rain was 
 sufficient to neutralise its lifting effect completely that is, 
 the gas-bag and the cordage about this so-called airship 
 absorbed about 400 Ibs. of water, and this was found to be 
 more than sufficient to neutralise completely the lifting 
 effect. A slight squall which followed entirely wrecked the 
 whole thing, and it was ignominiously carted back to the 
 point of departure. 
 
 " We now learn that the War Office is soon to produce 
 another airship similar to the ' Nulli Secundus,' but with a 
 much greater capacity and a stronger engine. In the news- 
 paper accounts it is said that the gas-bag of this new balloon 
 would be sausage-shaped and 42 feet in diameter, that it is 
 to be provided with an engine of 100 horse-power, which it 
 is claimed will give to this new production a speed of 
 40 miles an hour through the air, so that, with a wind of 
 20 miles an hour, it will still be able to travel by land 
 20 miles an hour against the wind. Probably the writer of 
 the article did not consider the subject from a mathematical 
 point of view. As the mathematical equation is an extremely 
 simple one, it is easily presented so as to be understood by 
 any one having the least smattering of mathematical or 
 engineering knowledge. The cylindrical portion of the gas- 
 bag is to be 42 feet in diameter ; the area of the cross-section 
 would therefore be 1,385 feet. If we take a disc 42 feet in 
 diameter and erect it high in the air above a level plain, 
 and allow a wind of 40 miles an hour, which is the proposed 
 speed of the balloon, to blow against it, we should find that 
 the air pressure would be 11,083 Ibs. that is, a wind blowing 
 at a velocity of 40 miles an hour would produce a pressure
 
 122 ARTIFICIAL AND NATURAL FLIGHT. 
 
 of 8 Ibs. to every square foot of the disc.* Conversely, if the 
 air were stationary, it would require a push of 11,083 Ibs. to 
 drive this disc through the air at the rate of 40 miles an 
 hour. 
 
 " A speed of 40 miles an hour is at the rate of 3,520 feet 
 in a minute of time. We therefore have two factors the 
 pounds of resistance encountered, and the distance through 
 which the disc travels in one minute of time. By multi- 
 plying the total pounds of pressure on the complete disc by 
 the number of feet it has to travel in one minute of time, we 
 have the total number of foot-pounds required in a minute 
 of time to drive a disc 42 feet in diameter through the air 
 at a speed of 40 miles an hour. Dividing the product by 
 the conventional horse-power 33,000, we shall have 1,181 
 horse-power as the energy required to propel the disc through 
 the air. However, the end of the gas-bag is not a flat disc, 
 but a hemisphere, and the resistance to drive a hemisphere 
 through the air is much less than it would be with a normal 
 plane or flat disc. In the ' Nulli Secundus' we may take 
 the coefficient of resistance of the machine, considered as a 
 whole, as 0'20 that is, that the resistance will be one-fifth 
 as much as that of a flat disc. This, of course, includes not 
 only the resistance of the balloon itself, but also that of the 
 cordage, the car, the engine, and the men. 
 
 "Multiplying 1,181 by the coefficient '20, we shall have 
 236 ; therefore, if the new balloon were attached to a long 
 steel wire and drawn by a locomotive through the air, the 
 amount of work or energy required would be 236 horse- 
 power that is, if the gas-bag would stand being driven 
 through the air at the rate of 40 miles an hour, which is 
 extremely doubtful. Under these conditions, the driving 
 wheels of the locomotive would not slip, and therefore no 
 waste of power would result, but in the dirigible balloon 
 we have a totally different state of affairs. The propelling 
 screws are very small in proportion to the airship, and their 
 slip is fully 50 per cent that is, in order to drive the ship 
 at the rate of 40 miles an hour, the screws would have to 
 
 * Haswell gives the pressure of the wind at 40 miles an hour as 8 Ibs. 
 per square foot, and this is said to have been verified by the United 
 btates Coast Survey. Molesworth makes it slightly less; but the new 
 formula, according to most recent experiments (Dr. Stanton's experiments 
 at the National Physical Laboratory and M. Eiffel's at Eiffel Tower), 
 is P = 0-003 V 2 , which would make the pressure only 4 '8 Ibs. per square 
 foot, and which would reduce the total H.P. required from 472 to 283, 
 where P represents pounds per square foot and V miles per hour.
 
 BALLOONS. 123 
 
 travel at least 80 miles an hour. Therefore, while 236 horse- 
 power was imparted to the ship in driving it forward, an 
 equal amount would have to be lost in slip, or, in other 
 words, in driving the air rearwards. It would, therefore, 
 require 472 horse-power instead of 100 to drive the proposed 
 new balloon through the air at the rate of 40 miles an hour. 
 " It will be seen from this calculation that the new 
 airship will still be at the mercy of the wind and 
 weather. Those who pin their faith on the balloon as 
 the only means of navigating the air may dispute my 
 figures. However, all the factors in the equation are 
 extremely simple and well known, and no one can 
 dispute any of them except the assumed coefficient of 
 resistance, which is given here as '20. The writer feels 
 
 Fig. 73. The enormous balloon, "Ville de Paris," of the French Govern- 
 ment. This balloon is a beautiful piece of workmanship, and is said to 
 be the most practical balloon ever invented, not excepting the balloon 
 of Count Zeppelin. Some idea of its size may be obtained by 
 comparing it with the size of the men who are standing immediately 
 underneath. 
 
 quite sure that, after careful experiments are made, it 
 will be found that this coefficient is nearer '40 than "20, 
 especially so at high speeds when the air pressure 
 deforms the gas-bag. Only a slight bagging in the front 
 end of the balloon would run the coefficient up to fully '50, 
 and perhaps even more." Times, Feb. 26, 1908. 
 
 Since writing the Times article, a considerable degree of 
 success has been attained by Count Zeppelin. According
 
 124 ARTIFICIAL AND NATURAL FLIGHT. 
 
 to newspaper accounts, his machine has a diameter of 
 about 40 feet, and a length of no less than 400 feet. It 
 appears that this balloon consists of a very light aluminium 
 envelope, which is used in order to produce a smooth 
 and even surface, give rigidity, and take the place of 
 the network employed in ordinary balloons. It seems 
 that the gas is carried in a large number of bags fitted 
 in the interior of this aluminium envelope. However, 
 by getting a firm and smooth exterior and by making 
 his apparatus of very great length as relates to its 
 diameter, he has obtained a lower coefficient of resistance 
 than has ever been obtained before, arid as his balloon 
 is of great volume, he is able to carry powerful motors 
 and use screw propellers of large diameter. It appears 
 that he has made a circuit of considerable distance, 
 and returned to the point of departure without any 
 accident. A great deal of credit is, therefore, due to 
 him. His two first balloons came to grief very quickly; 
 he was not discouraged, but stuck to the job with true 
 Teutonic grit, and has perhaps attained a higher degree 
 of success than has ever been attained with a balloon. 
 However, some claim that the French Government balloon, 
 ' La Patrie " is superior to the Zeppelin balloon at all 
 points. When we take into consideration the fact that 
 the Zeppelin machine is 400 feet long and lighter than 
 the same volume of air, it becomes only too obvious 
 that such a bulky and extremely delicate and fragile 
 affair will easily be destroyed. Of course ascensions will 
 only be made in very favourable weather, but squalls 
 and sudden gusts of wind are liable to occur. It is 
 always possible to start out in fine weather if one waits 
 long enough, but if a flight of 24 hours or even 12 hours 
 is to be attempted, the wind may be blowing very briskly 
 when we return, and an ordinary wind will riot only 
 prevent the housing of Count Zeppelin's balloon, but will 
 be extremely liable to reduce it to a complete wreck in 
 a few minutes.* 
 
 I am still strongly of the opinion that the ultimate 
 mastery of the air must be accomplished by machines 
 heavier than the air. 
 
 * Shortly after this was written, the Zeppelin machine was completely 
 demolished by a gust of wind. y
 
 125 
 
 APPENDIX I. 
 
 MAJOR BADEN-POWELL'S DEMAND. 
 
 (From our oivn Correspondent.) 
 
 BERLIN, Friday. 
 
 Germany's fleet of " air cruisers," or dirigible airships, will, 
 it is proudly announced to-day, presently number six : 
 
 Count Zeppelin's III., rigid type. 
 
 Count Zeppelin's IV., rigid type, which has done a 
 
 twelve-hour flight and will be taken over by the 
 
 Government, with No. III., for 100,000, after a 
 
 twenty-four-hour test. 
 Major Gross's Army airship, half rigid. 
 Motor Airship Study Society's old airship, non-rigid. 
 Major von Parse val's non-rigid ship building for the 
 
 above society. 
 New airship, of which details are kept secret, nearly 
 
 ready at the works of the Siemens-Schuckert 
 
 Electric Company. 
 
 The first announcement of the last-named airship was 
 given in The Daily Mail several months ago. The company 
 has engaged a celebrated military aeronaut, Captain von 
 Krogh, as commander of the vessel. The Study Society's 
 new non-rigid ship will be sold to the War Office as soon 
 as she has completed her trial trips. 
 
 The Army will then possess three dirigibles, each re- 
 presenting one of the three opposed types of construction 
 rigid, half-rigid, and non-rigid with a view to arriving 
 at a conclusion on their merits. 
 
 " Only a year or so ago, our authorities were talking of 
 aerial navigation in its relation to war as 'an interesting
 
 126 ARTIFICIAL AND NATURAL FLIGHT. 
 
 and instructive study.' Now we must reckon it as the 
 gravest problem of the moment. The cleverest aeronauts 
 fn England should be called upon at once to design an 
 airship, not only as efficient as that of Count Zeppelin's, 
 but possessed of even greater speed. (His average was 
 said to be about 34 miles an hour.) In speed will lie the 
 supremacy of the air when it comes to actual warfare. Of 
 two opposing airships, the faster will be able to out- 
 manoeuvre its adversary and hold it at its mercy." Daily 
 Mail, July 11, 1908. 
 
 COMMAND OF THE AIR. 
 
 GERMANY AS THE AERIAL POWER. 
 TEUTONIC VISION. 
 
 A LANDING OF 350,000 MEN. 
 
 Herr Rudolph Martin, author of books on war in the air 
 and "Is a World-War Imminent ?" points out how England 
 is losing her insular character by the development of air- 
 ships and aeroplanes. 
 
 " In a world- war," he said to me, " Germany would have 
 to spend two hundred millions sterling in motor airships, 
 and a similar amount in aeroplanes, to transport 350,000 
 men in half an hour during the night from Calais to Dover. 
 Even to-day the landing of a large German army in England 
 is a mere matter of money. I am opposed to a war between 
 Germany and England, but should it break out to-day, it 
 would last at least two years, for we would conclude no 
 peace until a German army had occupied London. 
 
 " In my judgment it would take two years for us to build 
 motor airships enough simultaneously to throw 350,000 men 
 into Dover via Calais. During the same night, of course, a 
 second transport of 350,000 men could follow. The newest 
 Zeppelin airship can comfortably carry fifty persons from 
 Calais to Dover. The ships which the Zeppelin works in 
 Friedrichshafen will build during the next few months are 
 likely to be considerably larger than IV., and will carry one 
 hundred persons. There is no technical reason against the 
 construction of Zeppelin airships of 1,100,000 or even 
 1,700,000 cubic feet capacity, or twice or three times the 
 capacity of IV. (500,000 cubic feet).
 
 APPENDIX I. 
 
 " I am at present organising a German 'Air Navy League,' 
 to establish air-traffic routes in Germany. AluminiunTair- 
 ships could carry on regular traffic between Berlin and 
 London, Paris, Cologne, Munich, Vienna, Moscow, Copen- 
 hagen, and Stockholm. In war time these ships would be 
 at the disposal of the German Empire. 
 
 "The development of motor airship navigation will lead 
 to a perpetual alliance between England and Germany. 
 The British fleet will continue to rule the waves, while 
 Germany's airships and land armies will represent the 
 mightiest Power on the Continent of Europe." Daily Mail 
 July 11, 1908. 
 
 It is needless to say that the above was written before 
 the wreck of Zeppelin's machine. 
 
 For many years scientific mechanicians and mathema- 
 ticians have told us that the navigation of the air was quite 
 possible. They have said it is only a question of motive 
 power; " Give us a motor that is sufficiently light and strong, 
 and we will very soon give you a practical flying machine." 
 A domestic goose weighs about 12 Ibs., and it has been 
 estimated that it only exerts about one-twelfth part of a 
 horse-power in flying that is, it is able to exert one man- 
 power with a weight of only 12 lbs. ; which seems to be a 
 very good showing for the goose. However, at the present 
 moment, we are able to make motors which develop the 
 power of ten men that is, one horse-power with less than 
 the weight of a common barnyard fowl. Under these con- 
 ditions it is quite evident that if a machine can be so 
 designed that it will not be too wasteful in power, it must 
 be a success. It is admitted by scientific men that all 
 animals, such as horses, deer, dogs, and also birds, are able 
 to develop much more dynamic energy for the carbon con- 
 sumed than is possible with any thermodynamic machine 
 that we are able to make. It may be said that many 
 animals are able to develop the full dynamic energy of the 
 carbon they consume, whereas the best of our motors do not 
 develop more than 10 per cent, of the energy contained in 
 the combustibles that they consume ; but, as against this, 
 it must be remembered that birds feed on grass, fruit, fish, 
 etc., heavy and bulky materials containing only a small 
 percentage of carbon, 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
 
 128 ARTIFICIAL AND NATURAL PLIGHT. 
 
 ordinary food consumed by birds. I think, in fact I assert, 
 that the time has now arrived, having regard to the advanced 
 state of the art in building motors, when it will be quite 
 a simple and safe affair to erect works and turn out 
 successful flying machines at less cost than motor cars ; 
 in fact, there is nothing that stands in the way of success 
 to-day. The value of a successful flying machine, when 
 considered from a purely military standpoint, cannot be 
 over estimated. The flying machine has come, and come to 
 stay, and whether we like it or not, it is a problem that 
 must be taken into serious consideration. If we are laggards 
 we shall, unquestionably, be left behind, with a strong pro- 
 bability that before many years have passed over our heads, 
 we shall have to change the colouring of our school maps. 
 
 As the newspaper accounts that we receive from the 
 Continent give all weights and measures in the metric 
 system, it is convenient to have some simple means at hand 
 to convert their values into English weights and measures. 
 I therefore give the following, which will greatly simplify 
 matters both for French and English measurements : 
 
 One metre = 39-37 inches. 
 
 ,, decimetre = ... . 3-937 
 
 ,, centimetre = . -3937 i ncn . 
 
 ,, millimetre = .... '03937 
 
 In order to convert 
 
 Metres into inches, multiply by . . . . 39-37. 
 
 feet, , 3-28 
 
 yards, ,, , j-Qg. 
 
 miles, ,,.... -00062138. 
 
 Cubic metres into cubic yards, multiply by . 1 '30802. 
 
 .. " feet ' .. 35-31658'. 
 
 Miles per hour into feet per minute, multiply by 88. 
 
 , , second, ,, 1-46663. 
 
 ,, ,, kilometres per hour, ,, ,, 1-6093. 
 
 ., metres per second, ,, -44702. 
 
 Miles per minute into feet per second, ,, 88. 
 
 Pounds into grammes, multiply by . " ". 453*5926 
 
 ,, kilogrammes, ,, . . -45359. 
 Pounds pressure per sq. inch into atmospheres, 
 
 multiply by -06804. 
 British thermal units into 
 
 Pounds of water, 1 C., multiply by . . -55556 
 
 Kilogramme-calories, ,, ,, . -252 
 
 Joules (mechanical equivalent), multiply bv 1047-96 
 
 Foot-pounds, multiply by . . 778.
 
 APPENDIX I. 
 
 129 
 
 In order to convert 
 
 Pounds of water into pints, multiply by 
 cubic feet, , , 
 litres, 
 
 8. 
 
 016046. 
 454587. 
 cubic centimetres, multiply by454 '656. 
 
 Gallons of water into pounds, multiply by . . 10. 
 
 cubic feet, ,, ,, . . '16057. 
 
 kilogrammes,,, ,, . . 4 '5359. 
 
 litres, ,, ,, . . 4-54586. 
 
 Litres of water into cubic inches, multiply by . 61 '0364. 
 
 pounds, ,, . 2-20226. 
 
 gallons, . -21998. 
 
 Air, 1 cubic foot, weighs at 62 .... 532-5 grains. 
 
 Air, cubic feet into pounds, 32 F. , multiply by . "08073. 
 
 Pounds of dry air into cubic feet, ,, ,, . 13-145. 
 Kilogramme-calories into British thermal units, 
 
 multiply by 3 '9683. 
 
 ,, ,, ,, gramme-calories, ,, ,, 1000. 
 ,, ,, ,, mechanic equivalent in 
 
 foot-lbs., multiply by . 3065-7.
 
 130 
 
 APPENDIX II. 
 
 RECAPITULATION OF EARLY EXPERIMENTS. 
 
 IN my early " whirling table "* experiments, the 
 aeroplanes used were from 6 inches to 4 feet in width. 
 They were for the most part made of thin pine, being 
 slightly concave on the underneath side and convex on 
 the top, both the fore and aft edges being very sharp. 
 I generally mounted them at an angle of 1 in 14f that 
 
 Fig. 74. Photograph of a model of my machine, showing the fore and 
 aft horizontal rudders and the superposed aeroplanes. 
 
 is, in such a position that in advancing 14 feet they 
 pressed the air down 1 foot. With this arrangement, 
 I found that with a screw thrust of 5 Ibs. the aeroplane 
 would lift 5 x 14, or 70 Ibs., while if the same plane 
 was mounted at an angle of 1 in 10, the lifting effect 
 was almost 50 Ibs. (5 X 10). This demonstrated that 
 the skin friction on these very sharp, smooth and well- 
 made aeroplanes was so small a factor as not to be 
 
 *A name given by Professor Langley to an apparatus consisting of 
 a long rotating arm to which objects to be tested are attached. 
 
 tl found it more convenient to express the angle in this manner 
 than in degrees.
 
 APPENDIX II. 
 
 131 
 
 considered. When, however, there was the least irregu- 
 larity in the shape of the aeroplane, the lifting effect, 
 when considered in terms of screw thrust, was greatly 
 
 Ct 
 
 Fig. 75. The fabric-covered aeroplane experimented with. The 
 efficiency of this aeroplane was only 40 per cent, of that of a well-made 
 wooden aeroplane. 
 
 diminished. With a well-made wooden plane placed at 
 an angle of 1 in 14, I was able to carry as much as 
 
 Fig. 76. The forward rudder of my large machine, showing the fabric 
 attached to the lower side. The top was also covered with fabric. 
 This rudder considered as an aeroplane had a very high efficiency 
 and worked very well indeed. 
 
 113 Ibs. to the H.P., whereas with an aeroplane consisting 
 of a wooden frame covered with a cotton fabric (Fig. 75), 
 I was only able to carry 40 Ibs. to theH.P.* 
 
 * The actual power consumed by the aeroplane itself was arrived 
 at as follows: The testing machine was run at the desired speed 
 without the aeroplane, and the screw thrust and the power consumed 
 carefully noted. The aeroplane was then attached and the machine 
 again run at the same speed. The difference between the two readings 
 gave the power consumed by the aeroplane.
 
 132 ARTIFICIAL AND NATURAL FLIGHT. 
 
 These facts taken into consideration with my other 
 experiments with large aeroplanes, demonstrated to my 
 mind that it would not be a very easy matter to make a 
 large and efficient aeroplane. If I obtained the necessary 
 rigidity by making it of boards, it would be vastly too 
 heavv for the purpose, 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 way, the 
 distortion would be so great that it would require 
 altogether too much power to propel it through the 
 air. I therefore decided on making a completely new 
 form of aeroplane. I constructed a large steel framework 
 arranged in such a manner that the fore and aft edges 
 consisted of tightly drawn steel wires. This framework 
 was provided with a number of light wooden longitudinal 
 trusses, similar to those shown in Fig. 76. The bottom 
 side was then covered with balloon fabric secured at the 
 edges, and also by two longitudinal lines of lacing- 
 through the centre. It was stretched very tightly and 
 slightly varnished, but not sufficiently to make it absolutely 
 air-tight. The top of this framework was covered with 
 the same kind of material, but varnished so as to make 
 it absolutely airtight. The top and bottom were then 
 laced together forming very sharp fore and aft edges, 
 and the top side was firmly secured to the light wooden 
 trusses before referred to. Upon running this aeroplane, 
 I found that a certain quantity of air passed through 
 the lower side and set up a pressure between the upper 
 and lower coverings. The imprisoned air pressed the 
 top covering upward, forming longitudinal corrugations 
 which did not offer any perceptible resistance to the air, 
 whereas the bottom fabric, having practically the same 
 pressure on both sides, was not distorted in the least. 
 This aeroplane was found to be nearly as efficient as it 
 would have been had it been carved out of a solid piece 
 of wood. It will be seen by the illustration that this 
 large or main aeroplane is practically octagonal in shape, 
 its greatest width being 50 feet, and the total area 
 1,500 square feet.
 
 APPENDIX II. 133 
 
 EXPERIMENTS WITH A LARGE MACHINE. 
 
 Upon running my large machine over the track (Fig. 77) 
 with only the main aeroplane in position, I founcT that 
 a lifting effect of 3,000 to 4,000 Ibs. could be obtained with 
 a speed of 37 to 42 miles an hour. 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 blowing. Early in my experiments, I found 
 if I ran my machine fast enough to produce a lifting effect 
 within 1,000 Ibs. of the total weight of the machine, that it 
 was almost sure to leave the rails if the least wind was 
 blowing. It was, therefore, necessary for me to devise some 
 means of keeping the machine on the track. The first plan 
 tried was to attach some very heavy cast-iron wheels 
 weighing with their axle-trees and connections about 
 1^ tons. These were constructed in such a manner that 
 the light flanged wheels supporting the machine on the 
 steel rails could be lifted 6 inches above the track, leaving 
 the heavy wheels still on the rails for guiding the machine. 
 This arrangement was tried on several occasions, the 
 machine being run fast enough to lift the forward end 
 off the track. However, I found considerable difficulty in 
 starting and stopping quickly on account of the great 
 weight, and the amount of energy necessary to set such 
 heavy wheels spinning at a high velocity. The last experi- 
 ment with these wheels was made when a head wind was 
 blowing at the rate of about 10 miles an hour. It was 
 rather unsteady, and when the machine was running at its 
 greatest velocity, a sudden gust lifted not only the front 
 end, but also the heavy front wheels completely off the 
 track, and the machine falling on soft ground was soon 
 blown over by the wind. 
 
 I then provided a safety track of 3 X 9 Georgia pine 
 placed about 2 feet above the steel rails, the wooden track 
 being 30 feet gauge and the steel rails 9 feet gauge (Fig. 77). 
 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 1 inch clear of the steel rails, 
 these extra wheels would engage the upper wooden track.* 
 
 * Springs were interposed between the machine and the axle-trees. 
 The travel of these springs was about 4 inches ; therefore, when the 
 machine was standing still, the wheels on the outriggers were about 
 5 inches below the upper track.
 
 134 
 
 ARTIFICIAL AND NATURAL FLIGHT. 
 
 When fully equipped, my large machine had five long 
 and narrow aeroplanes projecting from each side 
 that are attached to the sides of the mam aeroplanes are 
 27 feet long, thus bringing the total width of the machine 
 up to 104 feet. The machine is also provided with a lore 
 and an aft rudder made on the same general plan as 
 the main aeroplane. When all the aeroplanes are in 
 position, the total lifting surface is brought up to about 
 6 000 square feet. 1 have, however, never run the machine 
 
 Fig. 77. View of the track used in my experiments. The machine was 
 run along the steel railway which was 9 feet gauge, and was prevented 
 from rising by the wooden track which was 35 feet gauge. 
 
 with all the planes in position. My late experiments were 
 conducted with the main aeroplane, the fore and aft 
 rudders, and the top and bottom side planes in position, 
 the total area then being 4,000 square feet. With the 
 machine thus equipped, with 600 Ibs. of water in the tank 
 and boiler and with the naphtha and three men on board, 
 the total weight was a little less than 8,000 Ibs. The first 
 run under these conditions was made with a steam pressure 
 of 150 Ibs. to the square inch, in a dead calm, and all four
 
 APPENDIX II. 
 
 135 
 
 of the lower wheels remained constantly on the rails, none 
 of the wheels on the outriggers touching the upper track. 
 The second run was made with 240 Ibs. steam pressure 
 to the square inch. On this occasion, the machine seemed 
 to vibrate between the upper and lower tracks. About 
 
 to A* 
 
 three of the top wheels were engaged at the same time, the 
 weight on the lower steel rails being practically nil. Pre- 
 parations were then made for a third run with nearly the 
 full power of the engines. The machine was tied up to a 
 dynamometer (Fig. 78), and the engines were started with a
 
 136 ARTIFICIAL AND NATURAL FLIGHT. 
 
 pressure of about 200 Ibs. to the square inch. The gas 
 supply was then gradually turned on with the throttle 
 valves wide open ; the pressure soon increased, and when 
 310 Ibs. was reached, the dynamometer showed a screw 
 thrust of 2,100 Ibs.,* but to this must be added the incline 
 of the track which amounts to about 64 Ibs. The actual 
 
 Fig. 79. Two dynagraphs, one for making a diagram of the lifting effect 
 off the main axle-tree, and the other for making a diagram of the lift 
 off the front axle-tree. By this arrangement, I was able to ascertain 
 the exact lifting effect at all speeds, and to arrange my aeroplanes in 
 such a manner that the center of lifting effect was directly over the 
 center of gravity. The paper-covered cylinders made one rotation in 
 2,000 feet. 
 
 thrust was therefore 2.164 Ibs. In order to keep the thrust 
 of the screws as nearly constant as possible, I had placed a 
 small safety valve f-inch in the steam pipe leading to 
 one of the engines. This valve was adjusted in such a 
 manner that it gave a slight puff of steam at each stroke of 
 
 * The quantity of water entering the boiler at this time was so great as 
 to be beyond the range of the feed- water indicator.
 
 APPENDIX II. 137 
 
 the engine with a pressure of 310 Ibs. to the square inch, 
 and a steady blast at 320 Ibs. to the square inch. As the 
 valves and steam passages of these engines were made very 
 large, and as the piston speed was not excessive, I believed 
 if the steam pressure was kept constant that the screw 
 thrust would also remain nearly constant, because as the 
 machine advances and the screws commence to run slightly 
 faster, an additional quantity of steam will be called for and 
 this could be supplied by turning on more gas. When 
 
 Fig. 80. The outrigger wheel that gave out and caused an accident 
 with the machine. 
 
 everything was ready, with careful observers stationed on 
 each side of the track, the order was given to let go. The 
 enormous screw thrust started the machine so quickly that 
 it nearly threw the engineers off their feet, and the machine 
 bounded over the track at a great rate. Upon noticing 
 a slight diminution in the steam pressure, I turned on 
 more o- as , when almost instantly the steam commenced 
 to blow a steady blast from the small safety valve, showing 
 that the pressure was at least 320 Ibs. in the pipes supplying
 
 138 
 
 ARTIFICIAL AND NATURAL FLIGHT. 
 
 the engines with steam. Before starting on this run, the 
 wheels that were to engage the upper track were painted, 
 and it was the duty of one of my assistants to observe 
 these wheels during the run, while another assistant 
 watched the pressure gauges and dynagraphs (Fig. 79). 
 The first part of the track was up a slight incline, 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 600 feet had been covered. The speed rapidly 
 
 Fig. 81. Shows the broken planks and the wreck that they caused. It 
 will be observed that the wheels sank directly into the ground 
 without leaving any track. 
 
 increased, and when 900 feet had been covered, one of the 
 rear axle-trees, which were of 2-inch steel tubing, doubled 
 up (Fig. 80), and set the rear end of the machine completely 
 free. The pencils ran completely across the cylinders 
 of the dynagraphs and caught on the underneath end. 
 The rear end of the machine being set free, raised con- 
 siderably above the track and swayed. At about 1,000 
 feet, the left forward wheel also got clear of the upper track 
 and shortly afterwards, the right forward wheel tore up
 
 APPENDIX II. 
 
 139 
 
 about 100 feet of the upper track. Steam was at once 
 shut oft and the machine sank directly to the earth 
 imbedding the wheels in the soft turf (Figs. 81 and 82) 
 without leaving any other marks, showing most conclu- 
 sively that the machine was completely suspended in 
 the air before it settled to the earth. In this accident, 
 one of the pine timbers forming the upper track went 
 completely through the lower framework of the machine 
 and broke a number of the tubes, but no damage was done 
 to the machinery except a slight injury toone of the 
 screws (Fig. 83). 
 
 Fig. 82. The condition of the machine after the accident. One of the 
 broken planks that formed the upper track is shown. It will be 
 observed that the wheels have sunk directly into the ground without 
 leaving any tracks, showing that the machine did not run along the 
 ground, but came directly down when it stopped. 
 
 In my experiments with the small apparatus for ascer- 
 taining the power required to perform artificial flight, 
 I found that the most advantageous angle for my aeroplane 
 was 1 in 14, but when I came to make my large machine, 
 I placed my aeroplanes at an angle of 1 in 8 so as to 
 be able to get a great lifting effect at a moderate speed with 
 a short run. In the experiments which led to the accident 
 above referred to, the total lifting effect upon the machine 
 must have been at least 10,000 Ibs. All the wheels which
 
 140 
 
 ARTIFICIAL AND NATURAL FLIGHT. 
 
 had been previously painted and which engaged the upper 
 track were completely cleaned of their paint and had made 
 an impression on the wood, which clearly indicated that the 
 load which they had been lifting was considerable.* 
 Moreover, the strain necessary to double up the axle-trees 
 was fully 1,000 Ibs. each, without considering the lift on 
 the forward axle-trees which did not give way but broke 
 the upper track. 
 
 Fig. 83. This shows the screw damaged by the broken planks; also a 
 hole in the main aeroplane caused by the flying splinters. 
 
 The advantages arising from driving the aeroplanes on 
 to new air, the inertia of which has not been disturbed, are 
 clearly shown in these experiments. The lifting effect of 
 the planes was 2 '5 Ibs. per square foot. A plane loaded at 
 this rate will fall through the air with a velocity of 
 22-36 miles per hour, according to the formula */ 200 P = V. 
 But as the planes were set at an angle of 1 in 8, and as 
 the machine travelled at the rate of 40 miles an hour, the 
 
 * The latest form of outrigger wheels for engaging the upper track is 
 shown in Fig. 84.
 
 APPENDIX II. 
 
 141 
 
 planes only pressed the air downwards 5 miles an hour 
 (40 -r- 8 = 5). A fall of 5 miles an hour without advancing 
 would only exert. a pressure of -125 lb. per square foot, 
 according to the formula (V 2 x '005 = P).* 
 
 Engineers and mathematicians who have written to 
 prove that flying machines were impossible have generally 
 computed the efficiency of aeroplanes moving through the 
 
 Fig. 84. This shows a form of outrigger wheels which were 
 ultimately used. 
 
 air, 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 air. According to this system of reasoning, 
 my 4,000 square feet of aeroplanes would have lifted only 
 125 lb. per square foot, and in order to have lilted 
 
 * This is the old formula used by Haswell The account of Jjhis 
 experimental work was written in the autumn of 1894 and Haswell s 
 formula was used. I have thought best to make no changes.
 
 142 
 
 ARTIFICIAL AND NATURAL FLIGHT. 
 
 10,000 Ibs. they would have to have had an area twenty 
 times as great. This corresponds exactly with the dis- 
 crepancy which Professor Langley has found in the formula 
 of Newton. 
 
 With aeroplanes of one -half the width of those I 
 employed, and with a velocity twice as great, the angle 
 could be much less, and the advantages of continually 
 running on to fresh air would be still more manifest. With 
 a screw thrust of 2,000 Ibs., the air pressure on each square 
 foot of the projected area of the screw blades is 21'3 Ibs., 
 while the pressure on the entire discs of the screws is 4 Ibs. 
 per square foot, which would seem to show with screws of 
 this size, that four blades would be more efficient than two. 
 
 Fig. 85. One pair of my compound engines. This engine weighed 310 Ibs. 
 and developed 180 H.P., with 320 Ibs. of steam per square inch. 
 
 The engines, as before stated, are compound (Fig. 85). 
 The area of the high-pressure piston is 20 square inches, and 
 that of the low-pressure piston is 50 '26 square inches. Both 
 have a stroke of 12 inches. With a boiler pressure of 320 Ibs., 
 the pressure on the low-pressure piston is 125 Ibs. to the 
 square inch. 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 
 pitches ; moreover, the steam in the high-pressure cylinder 
 is cut off at three-quarters stroke, while the steam in the 
 low-pressure cylinder is cut off at five-eighths stroke. If
 
 APPENDIX II. 143 
 
 we should compute the power of these engines with the 
 steam entering at full stroke, without any friction, and with 
 no back pressure on the low-pressure cylinder, the total 
 horse-power would foot up to 461-36 horse-power at the 
 speed at which the engines were run namely, 375 turns 
 per minute. If we compute the actual power consumed by 
 the screws, by multiplying their thrust, which is probably 
 2,000 Ibs. while they are travelling, by their pitch, 16 feet, 
 and this by the number of turns which they make in a 
 minute, and then divide the product by 33,000, 
 
 2,000 x 16 x 375 
 
 33,000 68 ' 
 
 we find that we have 363'63 horse-power in actual effect 
 delivered on the screws of the machine, which shows that 
 there is rather less than 22 per cent, loss in the engines, due 
 to cutting off before the end of the stroke, to back pressure, 
 and to friction. The actual power applied to the machine 
 being 363'63 horse-power, it is interesting to know what 
 becomes of it. When the machine has advanced 40 miles 
 (which it would do in an hour), the screws have travelled 
 
 68-1 miles ( 37 gggQ* 6 ) = 68-1 ; therefore, 150 horse- 
 power is wasted in slip, and 213*63 horse-power consumed 
 in driving the machine through the air. Now, as the planes 
 are set at an angle of 1 in 8, the power actually used in 
 lifting the machine is 133'33, and the loss in driving the 
 body of the machine, its framework and wires through the 
 air is 90'30 horse-power. 
 
 Power lost in screw slip, 150 H.P. 
 
 ,, ,, driving machinery and framework, . 80 '30 
 
 ,, actually consumed in lifting the machine, . 133-33 
 
 Total power delivered by the engines, . 363 '63 
 
 THE ADVANTAGES AND DISADVANTAGES OP 
 VERY NARROW PLANES. 
 
 My experiments have demonstrated that relatively narrow 
 aeroplanes lift more per square foot than very wide ones ; 
 but as an aeroplane, no matter how narrow it may be, must 
 of necessity have some thickness, it is not advantageous to 
 place them too near together. Suppose that aeroplanes 
 should be made -inch thick, and be superposed 3 inches
 
 144 
 
 ARTIFICIAL AND NATURAL FLIGHT. 
 
 apart that is, at a pitch of 3 inches one-twelfth part of the 
 whole space through which these planes would have to be 
 driven would be occupied by the planes themselves, and 
 eleven-twelfths would be air space (Fig. 86). If a group 
 of planes thus mounted should be driven through the air 
 at the rate of 36 miles an hour,* the air would have to be 
 driven forward at the rate of 3 miles an hour, or else it 
 
 Fig. 86. The path that the air has to take in passing between superposed 
 aeroplanes in close proximity to each other. By this arrangement the 
 drift is considerably increased. 
 
 would have to be compressed, or spun out, and pass between 
 the spaces at a speed of 39 miles an hour. As a matter of 
 fact, however, the difference in pressure is so very small 
 that practically no atmospheric compression takes place. 
 The air, therefore, is driven forward at the rate of 3 miles 
 an hour, and this consumes a great deal of power ; in fact, 
 
 The arrows in the accompanying drawings show the direction of the 
 air currents, the experiments having been made with stationary planes in 
 a moving current of air.
 
 APPENDIX II. 
 
 145 
 
 so much that there is a decided disadvantage in usino- 
 narrow planes thus arranged. 
 
 In regard to the curvature of narrow aeroplanes, I have 
 found that if one only desires to lift a large load in pro- 
 portion to the area, the planes may be made very 'hollow 
 on the underneath side ; but when one considers the lift in 
 terms of the screw thrust, I find it advisable that the planes 
 should be as thin as possible, and the underneath side nearly 
 flat. I have also found that it is a great advantage to 
 arrange the planes after the manner shown in Fig. 87. In 
 this manner the sum of all the spaces between the planes 
 is equal to the whole area occupied by the planes con- 
 sequently, the air neither has to be compressed, spun out, 
 
 Fig. 87. The position of narrow aeroplanes arranged in such a manner 
 that the air has free passage between them, and this arrangement has 
 been found superior to arranging one above the other after the manner 
 of a Venetian blind. 
 
 nor driven forward. I am, therefore, able by this arrangement 
 to produce a large lifting effect per square foot, and, at the 
 same time, to keep the screw thrust within reasonable limits.' 
 A large number of experiments with very narrow aero- 
 planes have been conducted by Mr. Horatio Philipps at 
 Harrow, in England. Fig. 88 shows a cross-section of one 
 of Mr. Philipps' planes. Mr. Philipps is of the opinion that 
 the air, in striking the top side of the plane, is thrown 
 upwards in the manner shown, and a partial vacuum is 
 thereby formed over the central part of the plane, and that 
 the lifting effect of planes made in this form is therefore 
 very much greater than with ordinary narrow planes. I 
 have experimented with these "sustainers" (as Mr. Philipps 
 calls them) myself, and I find it is quite true that they lift
 
 146 ARTIFICIAL AND NATURAL FLIGHT. 
 
 in some cases as much as 8 Ibs. per square foot,* but the 
 lifting effect is not produced in the exact manner that Mr. 
 Philipps seems to suppose. The air does not glance off in 
 the manner shown. As the " sustainer " strikes the air two 
 currents are formed, one following the exact contour of the 
 top, and the other that of the bottom. These two currents 
 join and are thrown downwards, as relates to the "sustainer," 
 at an angle which is the resultant of the angles at which 
 the two currents meet. These " sustainers " may be made 
 to lift when the front edge is lower than the rear edge, 
 because they encounter still air, and leave it with a down- 
 ward motion. 
 
 Fig. 88. The very narrow aeroplanes, or sustainers, employed by Mr. 
 Philipps. It has been supposed that the air in striking at A was 
 deflected in the manner shown, but such is not the case. The air in 
 reality follows the surface, as shown in the dotted line in the second 
 illustration. 
 
 In my experiments with narrow superposed planes, I 
 have always found that with strips of thin metal made 
 sharp at both edges and only slightly curved, the lifting 
 effect, when considered in terms of screw thrust, was always 
 greater than with any arrangement of the wooden aero- 
 planes used in Philipps' experiments. It would, therefore, 
 appear that there is no advantage in the peculiar form of 
 " sustainer " employed by this inventor. 
 
 If an aeroplane be made perfectly flat on the bottom side 
 and convex on the top, and be mounted in the air so that 
 
 * In my early experiments I lifted as much as 8 Ibs. per square foot with 
 aeroplanes which were only slightly curved, but very thin and sharp.
 
 APPENDIX II. 147 
 
 the bottom side is exactly horizontal, it produces a lifting 
 effect no matter in which direction it is run, because, as it 
 advances, it encounters stationary air which is divided into 
 two streams. The top stream being unable to fly off at a 
 tangent when turning over the top curve, flows down the 
 incline and joins the current which is flowing over the lower 
 horizontal surface. The angle at which the combined 
 stream of air leaves the plane is the resultant of these two 
 angles ; consequently, as the plane finds the air in a 
 stationary condition, and leaves it with a downward 
 motion, the plane itself must be lifted. It is true that small 
 and narrow aeroplanes may be made to lift considerably 
 more per square foot of surface than very large ones, but 
 they do not offer the same safeguard against a rapid descent 
 to the earth in case of a stoppage or breakdown of the 
 machinery. With a large aeroplane properly adjusted, a 
 rapid and destructive fall to the earth is quite impossible. 
 
 THE EFFICIENCY OF SCREW PROPELLERS, 
 STEERING, STABILITY, &c. 
 
 Before I commenced my experiments at Baldwyn's Park, 
 I attempted to obtain some information in regard to the 
 action of screw propellers working in the air. I went to 
 Paris and saw the apparatus which the French Government 
 employed for testing the efficiency of screw propellers, but 
 the propellers were so very badly made that the experi- 
 ments were of no value. Upon consulting an English 
 experimenter, who had made a "life-long study" of the 
 question, he assured me that I should find the screw pro- 
 peller very inefficient and very wasteful of power, and 
 that all screw propellers had a powerful fan-blower action, 
 drawing in air at the centre and discharging it with great 
 force at the periphery. I found that no two men were 
 agreed as to the action of screw propellers. All the data or 
 formulae available were so confusing and contradictory as to 
 be of no value whatsoever. Some experimenters were of 
 the opinion that, in computing the thrust of a screw, we 
 should only consider the projected area of the blades, and 
 that the thrust would be equal to a wind blowing against a 
 normal plane of equal area at a velocity equal to the slip. 
 Others were of the opinion that the whole screw disc would 
 have to be considered; that is, that the thrust would be
 
 148 ARTIFICIAL AND NATURAL FLIGHT. 
 
 equal to a wind blowing against a normal plane having an 
 area equal to the whole disc, and at the velocity of the slip. 
 The projected area of the two screw blades of iny machine 
 is 94 square feet, and the area of the two screw discs is 500 
 square feet. According to the first system of reasoning, 
 therefore, the screw thrust of my large machine, when 
 running at 40 miles an hour with a slip of 18 miles per hour, 
 would have been, according to the well-known formula, 
 
 V 2 x -005 = P 
 18 2 x -005 x 94 = 152-28 Ibs. 
 
 If, however, we should have considered the whole screw 
 disc, it would have been 18 2 x -005 x 500 = 810 Ibs. 
 However, when the machine was run over the track at this 
 rate, the thrust was found to be rather more than 2,000 Ibs. 
 When the machine was secured to the track and the screws 
 revolved until the pitch in feet, multiplied by the turns per 
 minute, was equal to 68 miles an hour, it was found that 
 the screw thrust was 2,164 Ibs. In this case, it was of course, 
 all slip, and when the screws had been making a few 
 turns they had established a well-defined air-current, and 
 the power exerted by the engine was simply to maintain 
 this air current. It is interesting to note that, if we 
 compute the projected area of these blades by the foregoing 
 formula, the thrust would be 68 2 x -005 x 94 = 2,173'28 Ibs., 
 which is almost exactly the observed screw thrust. 
 
 When I first commenced my experiments with a large 
 machine, I did not know exactly what sort of boiler, gas 
 generator, or burner I should finally adopt ; I did not know 
 the exact size that it would be necessary to make my 
 engines ; I did not know the size, the pitch, or the diameter 
 of the screws which would be the most advantageous ; 
 neither did I know the form of aeroplane which I should 
 finally adopt. It was, therefore, 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 results. The platform of the 
 machine is, therefore, rather larger than is necessary, and I 
 find if I were to design a completely new machine, that it 
 would be possible to greatly reduce the weight of the frame- 
 work, and, what is still more, to greatly reduce the force 
 necessary to drive it through the air. 
 
 At the present time, the body of my machine is a large 
 platform, about 8 feet wide and 40 feet long. Each side is
 
 APPENDIX II. 
 
 149 
 
 formed of very long trusses of steel tubes, braced in every 
 direction by strong steel wires. The trusses which give 
 stiffness are all below the platform. In designing a new 
 machine, I should make the trusses much deeper and at the 
 same time very much lighter, and, instead of having them 
 below the platform on which the boiler is situated, I should 
 
 Fig. 89. One of the large screws being hoisted into position. Its size 
 may be judged by comparison with the man. 
 
 have them constructed in such a manner as to completely 
 enclose the boiler and the greater part of the machinery.* 
 I should make the cross-section of the framework rect- 
 angular and pointed at each end. I should cover the 
 
 * This arrangement of the framework is now common to all successful 
 machines.
 
 150 ARTIFICIAL AND NATURAL PLIGHT. 
 
 outside very carefully with balloon material, giving it a 
 perfectly smooth and even surface throughout, so that it 
 might be easily driven through the air. 
 
 In regard to the screws, I am at the present time able to 
 mount screws 17 feet 10 inches in diameter (Fig. 89). I 
 find, however, that my machine would be much more 
 efficient if the screws were 24 feet in diameter and I 
 believe with such very large screws, four blades would be 
 much more efficient than two. 
 
 My machine may be steered to the right or to the left by 
 running one of the propellers faster than the other. Very 
 convenient throttle valves have been provided to facilitate 
 this system of steering. An ordinary vertical rudder placed 
 just after the screws may, however, prove more convenient 
 if not more efficient. 
 
 The machine is provided with fore and aft horizontal 
 rudders, both of which are connected with the same 
 windlass. 
 
 In regard to the stability of the machine, the centre 
 of weight is much below the centre of lifting effect; 
 moreover, 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 side. This simple arrangement 
 makes it automatic as far as rolling is concerned. I am 
 of the opinion that whenever flying machines come into 
 use, it will be necessary to steer in a vertical direction 
 by means of an automatic steering gear controlled by 
 a gyroscope. It will certainly not be more difficult to 
 manoeuvre and steer such machines than it is to control 
 completely submerged torpedoes. 
 
 When the machine is once perfected, it will not require 
 a railway track to enable it to get the necessary velocity 
 to rise. A short run over a moderately level field will 
 suffice. As far as landing is concerned, the aerial 
 navigator will touch the ground when moving forward, 
 and the machine will be brought to a state of rest by 
 sliding on the ground for a short distance. In this 
 manner very little shock will result, whereas if the 
 machine is stopped in the air and allowed to fall directly 
 to the earth without advancing, the shock, although 
 not strong enough to be dangerous to life or limb, might 
 be sufficient to disarrange or injure the machinery.
 
 APPENDIX II. 151 
 
 THE COMPARATIVE VALUE OP 
 DIFFERENT MOTORS. 
 
 So far I have only discussed the navigation of the 
 air by the use of propellers driven by a steam engine. 
 The engines that I employ are what is known as compound 
 engines that is, they have a large and a small cylinder. 
 Steam at a very high pressure enters the high-pressure 
 cylinder, expands and escapes at a lower pressure into 
 a larger cylinder where it again expands and does more 
 work. A compound engine is more economical in steam 
 than a simple engine, and therefore requires a smaller 
 boiler to develop the same horse-power, so that when 
 we consider the weight of water and fuel for a given 
 time, together with the weight of the boiler and the 
 engine, the engine motor with a compound engine is 
 lighter than a simple engine. However, 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 engine. For instance, if, instead of allowing 
 the steam to enter the small cylinder, 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 steam, and allow both 
 to discharge their exhaust directly into the air, I should 
 then have a pair of simple engines, and instead of 
 developing 363 H.P. they would develop fully 500 H.P., 
 or nearly 1 H.P. for every pound of their weight. I 
 mention this fact to show that the engines are exceedingly 
 light, and that when compared with simple engines their 
 power should be computed on the same basis. It will, 
 therefore, be seen that if we do not take into consideration 
 the steam supply or the amount of fuel and water 
 necessary, the simple steam engine is an exceedingly 
 light motor. 
 
 But, as before stated, great improvements have recently 
 been made in oil engines. I have thought much on this 
 subject, and am of the opinion that if one had an unlimited 
 supply of money, a series of experiments could be very 
 profitably conducted with a view of adapting the oil 
 engine for use on flying machines. If we use a steam
 
 152 ARTIFICIAL AND NATURAL FLIGHT. 
 
 engine, it is necessary to have a boiler, and at best a boiler 
 is rather a large and heavy object to drive through the 
 air. If we use an oil engine, no boiler is necessary, 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 power. 
 Therefore, the condenser only need be one-seventh part 
 the size, and consequently should be made lighter with 
 the tubes placed at a greater distance apart, and thus 
 reduce the amount of power necessary to drive the machine 
 through the air. Moreover, the supply of water necessary 
 will be greatly reduced, and a cheaper and heavier oil 
 may be employed, which is not so liable to take fire in 
 case of an accident. 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 motor; that is, an 
 oil engine in order to be available for the purpose must 
 be as light, including its water supply, as a complete 
 steam motor, which includes not only the engine, but 
 also the boiler, the feed pumps, the water supply, the 
 burner, the gas generator, and six -sevenths of the 
 condenser. It requires a very perfect steam engine and 
 boiler, not using a vacuum, to develop a horse-power 
 with a consumption of 1^ Ibs. of petroleum per hour; but 
 there are many oil engines which develop a horse-power 
 with rather less than 1 Ib. of oil per hour. It will, 
 therefore, be seen that, as far as fuel is concerned, the 
 oil engine has a decided advantage over the more com- 
 plicated steam motor. Moreover, with an oil engine, the 
 cooling water is not under pressure, so that the waste of 
 water would be much less than with a steam engine, where 
 the pressure is so high as to cause a considerable amount 
 of waste through joints and numerous stuffing-boxes. 
 
 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 engineering, 
 and a great deal has been written and said in regard 
 to navigating the air by flying machines driven by 
 electric motors. 
 
 Before I commenced my experiments, I made enquiries 
 of all the prominent electrical engineering establishments 
 where there was any likelihood of obtaining light and 
 efficient electric motors, and found that it was impossible
 
 APPENDIX II. 153 
 
 to obtain one that would develop a horse-power for any 
 considerable time that would weigh less than 150 Ibs. 
 Since that time, notwithstanding that a great deal has 
 appeared in the public prints about the efficiency and 
 lightness of electric motors, I am unable to learn of any 
 concern that is ready to furnish a complete motor, including 
 a primary battery, which would supply the necessary current 
 for two hours at a time, at a weight of less than 150 Ibs. 
 per horse-power, and as far as I have been able to ascertain 
 from what I have myself seen, I cannot learn that there are 
 any motors in practical use which do not weigh, including 
 their storage batteries, at least 300 Ibs. per horse-power. 
 The last electric motor which I examined was in a boat ; it 
 was driven by a primary battery which weighed over 
 1,000 Ibs. to the horse-power. 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 navigation. 
 
 ENGINES. 
 
 There is no question but what birds, and for that matter 
 all animals, when considered as thermo-dynamic machines, 
 are very perfect motors ; they develop the full theoretical 
 amount of energy of the carbon consumed. This we are 
 quite unable to do with, any artificial machine, but birds, 
 for the most part, have to content themselves with food 
 which is not very rich in carbon. 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 engine, but, as an off-set against this, a steam engine 
 is able to consume petroleum, which has at least twenty 
 times as many thermal units per pound as the ordinary 
 food of birds. The movement of a bird's wings, from long 
 years of development, has without doubt attained a great 
 degree of perfection. Birds are able to scull themselves 
 through the air with very little loss of energy. To imitate 
 by mechanical means, the exact and delicate motion of their 
 wings would certainly be a very difficult task, and I do not 
 believe that we should attempt it in constructing an artifi- 
 cial flying machine. In Nature it is necessary that an 
 animal should be made all in one piece. It is, therefore, 
 quite out of the question that any part or parts should 
 revolve. For land animals there is no question but what
 
 154 ARTIFICIAL AND NATURAL PLIGHT. 
 
 legs are the most perfect system possible, but in terrestrial 
 locomotion by machinery, not necessarily in one piece, 
 wheels are found to be much more effective and efficient. 
 The swiftest animal can only travel for a minute of time at 
 half the speed of a locomotive, while the locomotive is able 
 to maintain its much greater speed for many hours at a 
 time. The largest land animals only weigh about 5 tons, 
 while the largest locomotives weigh from 60 to 80 tons. In 
 the sea, the largest animal weighs about 75 tons, while the 
 ordinary Atlantic liner weighs from 4,000 to 34,000 tons. 
 The whale, no doubt, is able to maintain a high speed for 
 several hours at a time, but the modern steamer is able 
 to maintain a still higher speed for many consecutive days. 
 As artificial machines for terrestrial and aquatic loco- 
 motion have been made immensely stronger and larger than 
 land or water animals, so with flying machines, it will be 
 necessary to construct them much heavier and stronger 
 than the largest bird. If one should attempt to propel such 
 a machine with wings, it would be quite as difficult a 
 problem to solve as it would be to make a locomotive 
 that would walk on legs. 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 joints, and this we find in the 
 screw propeller. 
 
 When the Brayton gas engine first made its appearance, 
 I commenced drawings of a flying machine, using a modi- 
 fication of the Brayton motor which I designed expressly 
 for the purpose ; but even this was found to be too heavy, 
 and it was not until after I had abandoned the vertical 
 screw system that it was possible for me to design a machine 
 which, in theory, ought to fly. The next machine which I 
 considered was on the kite or aeroplane system. This was 
 also to be driven by an oil engine. Oil engines at that time 
 were not so simple as now, and, moreover, the system of 
 ignition was very heavy, cumbersome, and uncertain. Since 
 that time, however, gas and oil engines have been very 
 much improved, and the ignition tube which is almost 
 universally used has greatly simplified the ignition, so 
 that at the present time, I am of the opinion that an oil 
 engine might be designed which would be suitable for the 
 purpose.
 
 APPENDIX II. 155 
 
 In 1889 I had my attention drawn to some very thin, 
 strong, and comparatively cheap tubes which were being 
 made in France, and it was only after I had seen these 
 tubes that I seriously considered the question of making a 
 flying machine. I obtained a large quantity of them and 
 found that they were very light, that they would stand 
 enormously high pressures, and generate a very large 
 quantity of steam. Upon going into a mathematical calcu- 
 lation of the whole subject, I found that it would be possible 
 to make a machine on the aeroplane system, driven by a 
 steam engine, which would be sufficiently strong to lift 
 itself into the air. I first made drawings of a steam engine, 
 and a pair of these engines was afterwards made. These 
 engines are constructed, for the most part, of a very high 
 grade of cast steel, the cylinders being only ^ of an inch 
 thick, the crank shafts hollow, and every part as strong and 
 light as possible. They are compound, each having a 
 high-pressure piston with an area of 20 square inches, 
 a low-pressure piston of 50*26 square inches, and a 
 common stroke of 1 foot. When first finished, they were 
 found to weigh 300 Ibs. each ; but after putting on the oil 
 cups, felting, painting, and making some slight alterations, 
 the weight was brought up to 320 Ibs. each, or a total of 
 640 Ibs. for the two engines, which have since developed 
 362 horse-power with a steam pressure of 320 Ibs. per square 
 inch. A photograph of one of these engines is shown 
 in Fig. 85. 
 
 When first designing this engine, I did not know how 
 much power I might require from it. I thought that in 
 some cases it might be necessary to allow the high-pressure 
 steam to enter the low-pressure cylinder direct, but as this 
 would involve a considerable loss, I constructed a species of 
 an injector. This injector may be so adjusted that when 
 the steam in the boiler rises above a certain predetermined 
 point, say 300 Ibs. to the square inch, it opens a valve and 
 escapes past the high-pressure cylinder instead of blowing 
 off at the safety valve. In escaping through this valve, a 
 fall of about 200 Ibs. pressure per square inch is made to do 
 work on the surrounding steam and to drive it forward in 
 the pipe, producing a pressure on the low-pressure piston 
 considerably higher than the back pressure on the high- 
 pressure piston. In this way a portion of the work which
 
 156 ARTIFICIAL AND NATURAL FLIGHT. 
 
 would otherwise be lost is utilised, and it is possible, with 
 an unlimited supply of steam, to cause the engines to 
 develop an enormous amount of power. 
 
 Boiler Experiments. The first boiler which I made was 
 constructed something on the Herreshoff principle, but 
 instead of having one simple pipe in one very long coil, I 
 used a series of very small and light pipes, 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 generated. I intended that there should be a 
 pressure of about 100 Ibs. more on the feed water end of the 
 series than on the steam end, and I believed that this 
 difference in pressure would be sufficient to ensure a direct 
 and positive circulation through every tube in the series. 
 This first boiler was exceedingly light, but the workman- 
 ship, as far as putting the tubes together was concerned, 
 was very bad, and it was found impossible to so adjust the 
 supply of water as to make dry steam without overheating 
 and destroying the tubes. 
 
 Before making another boiler I obtained a quantity of 
 copper tubes, about 8 feet long, f inch external diameter, 
 and T \5- of an inch thick. I subjected about 100 of thes$ 
 tubes to an internal pressure of 1 ton per square inch 
 of cold kerosine oil, and as none of them leaked I did 
 not test any more, but commenced my experiments by f 
 placing some of .them in a white-hot petroleum fire. I 
 found that I could evaporate as much as 26| Ibs. of water 
 per square foot of heating surface per hour, and that with a 
 forced circulation, although the quantity of water passing was 
 very small but positive, there was no danger of over-heating. 
 I conducted many experiments with a pressure of over 
 400 Ibs. per square inch, but none of the tubes failed. I 
 then mounted a single tube in a white-hot furnace, also 
 with a water circulation, and found that it only burst 
 under steam at a pressure of 1,650 Ibs. per square inch. 
 A large boiler, having about 800 square feet of heating 
 surface including the feed-water heater, was then con- 
 structed. It is shown in Fig. 90. This boiler is about 
 4| feet wide at the bottom, 8 feet long and 6 feet high. 
 It weighs with the casing, the dome, the smoke stack 
 and connections, a little less than 1,000 Ibs. The water 
 first passes through a system of small tubes \ inch in
 
 APPENDIX II. 157 
 
 diameter and ^ inch thick which were placed at the 
 top of the boiler and immediately over the larger tubes 
 
 Fig. 90. Steam boiler employed in my experiments. With this boiler, 
 I had no trouble in producing all the steam that I could possibly use, 
 and at any pressure up to 400 Ibs. to the square inch. 
 
 not shown in the cut. This feed-water heater is found to 
 be very effective. It utilises the heat of the products of 
 combustion after they have passed through the boiler 
 
 Fig. 91. The burner employed in my steam experiments. This produced 
 a dense and uniform blue purple flame 20 inch deep. 
 
 proper and greatly reduces their temperature, while the 
 feed-water enters the boiler at a temperature of 250 F.
 
 158 ARTIFICIAL AND NATURAL FLIGHT. 
 
 A forced circulation is maintained in the boiler, the 
 feed-water entering through a spring valve, the spring 
 valve being adjusted in such a manner that the pressure 
 on the water is always 30 Ibs. per square inch in excess 
 of the boiler pressure. This fall of 30 Ibs. in pressure 
 acts upon the surrounding hot water which has already 
 passed through the tubes, and drives it down through a 
 vertical outside tube, thus ensuring a positive and rapid 
 circulation through all the tubes. This apparatus is found 
 to work extremely well. A little glass tube at the top 
 provided with a moving button, indicates exactly how 
 many pounds of water per hour are passing into the boiler. 
 By this means, the engineer is not only enabled to ascertain 
 at a glance whether or not the pumps are working, 
 but also to what degree they are working. 
 
 Water may be considered as 2,400 times as efficient as 
 air, volume for volume, in condensing steam. When a 
 condenser is made for the purpose of using water as a 
 cooling agent, a large number of small tubes may be 
 grouped together in a box, and the water may be pumped 
 in at one end of the box and discharged at the other end 
 through relatively small openings ; but when air is 
 employed, the tubes or condensing surface must be widely 
 distributed, so that a very large amount of air is encoun- 
 tered, and the air which has struck one tube and become 
 heated must never strike a second tube. 
 
 In order to accomplish this, I make my condenser some^ 
 thing in the form of a Venetian blind, the tubes being 
 made of very thin copper and each tube in the form of 
 a small aeroplane. These were driven edgewise through 
 the air, so that the actual volume of air passing between 
 them is several thousand times greater than the volume of 
 water passing through a marine condenser. I find that 
 with such a condenser I can recover the full weight of the 
 copper tubes in water every five minutes, and if I use 
 aluminium, in half that time. Moreover, experiments have 
 shown that a condenser may be made to sustain consider- 
 ably more than its own weight and the weight of its 
 contents in the air, and that all the steam may be condensed 
 into water sufficiently cool to be pumped with certainty. 
 
 I find that the most advantageous position for the 
 condenser is immediately after the screw propellers. In 
 this case, if the machine is moving through the air at the 
 rate of 50 miles an hour, and the slip of the screws is
 
 APPENDIX II. 159 
 
 15 miles an hour, it follows that the air will be passing 
 through the condenser at the rate of 65 miles an hour. At 
 this velocity, the lifting effect on the narrow aeroplanes 
 forming the condenser is very great, and at the same time 
 the steam is very rapidly condensed. The tubes are 
 placed at such an angle as to keep them completely drained 
 and prevent the accumulation of oil, the steam entering 
 the higher end and the water being discharged at the 
 lower end. 
 
 EXPERIMENTS WITH SMALL MACHINES 
 ATTACHED TO A ROTATING ARM. 
 
 These experiments demonstrated most conclusively that 
 as much as 133 Ibs. could be sustained and carried by the 
 expenditure of one horse-power, and that a screw was a 
 fairly efficient air propeller. They also demonstrated that 
 a well made aeroplane, placed at an angle of 1 in 14, would 
 lift practically fourteen times the thrust required to drive 
 it through the air, and that the skin friction on a smooth 
 and well finished aeroplane or screw was so small as not 
 to be considered. A large number of aeroplanes were 
 experimented with, and it was found that those which 
 were slightly concave on the underneath side and convex 
 on the top, both edges being very sharp and the surface 
 very smooth and regular, were the most efficient ; also that 
 with small screw propellers, two blades having slightly 
 increasing pitch were the most efficient. 
 
 Since writing the foregoing, great progress has been 
 made with flying machines, and great disasters have 
 happened to airships or balloons. Count Zeppelin's 
 gigantic airship encountered a squall or thunder shower, 
 and the work of years, which had cost over 100,000, 
 was reduced to scrap metal in a few minutes. Similar 
 disasters have happened to other balloons. 
 
 The British Dirigible No. 2 has not attempted a long 
 flight, but the Wright Brothers, Farman, and De la Grange 
 have all met with a certain degree of success.
 
 160 ARTIFICIAL AND NATURAL PLIGHT. 
 
 A few months ago, the remarkable feats of the Wright 
 Brothers in the States were discredited in Europe. It was 
 claimed that " the accounts were not authentic," " too good 
 to be true," etc., but recent events have shown that the 
 Wright Brothers are able to outdo anything that was 
 reported in the American Press. On many occasions they 
 have remained in the air for more than an hour, and have 
 travelled at the rate of 30 to 40 miles an hour ; in fact, the 
 remarkable success of the Wright Brothers has placed the 
 true flying machine in a new category. 
 
 It can no longer be ranked with the philosopher's stone 
 or with perpetual motion. Success is assured, and great 
 and startling events may take place within the next few 
 years. 
 
 V
 
 APPENDIX II. 
 
 161 
 
 Fig. 92. Count Zeppelin's aluminium-covered airship coming out of its 
 shed on Lake Constance. 
 
 
 
 Fig. 93. Count Zeppelin's airship in full flight. 
 
 11
 
 162 ARTIFICIAL AND NATURAL FLIGHT. 
 
 Fig. 94 The new British war balloon "Dirigible" No 2. 
 
 Fig. 95. The Wright aeroplane in full flight.
 
 163 
 
 GENERAL INDEX. 
 
 ACCIDENT to my large machine, .... 
 
 Action of aeroplanes and power required, 
 
 Adjustment of birds' wings, ..... 
 
 Admiralty specification for a steamship, 
 Advantages of driving aeroplanes on to new air, 
 Advantages and disadvantages of very narrow planes, 
 Aeroplanes : 
 
 Action of, . ... . . .31 
 
 Advantageous angle of, . 
 
 Advantages and disadvantages of very narrow, 
 
 ,, arising from driving aeroplanes on to new air, 
 
 Curvature of, . 
 Evolution of a wide aeroplane, . 
 Experiments with, 
 Fabric covered, . 
 Lifting effect of , . 
 Lifting surface of, 
 Philipps' sustainers, 
 Reduction of projected horizontal area 
 Shape and efficiency of, . 
 Superposed, 
 Testing fabrics for, 
 The paradox aeroplane, . 
 Air currents and the flight of birds, 
 Conclusions regarding, 
 Alpes Maritimes, . 
 Mediterranean, . 
 Mid-Atlantic, 
 
 2,000 feet above the earth's surf ce, 
 witnessed at Cadiz, 
 Angles and degrees compared, 
 Antoinette motor, The, 
 
 BALLOONS, . ' . 
 
 ,, spiders, 
 
 Birds as thermo-dynamic machines, 
 
 ,, Two classes of, . 
 Bleriot's machine, 
 Boiler experiments, 
 Brayton's gas engine, . 
 British war balloon, 
 Building up of my large screws, 
 Burner employed in my experiments, 
 
 CHARACTER of text-books recently published, 
 Circulation of air produced by differences in temperature, 
 
 PAGE 
 
 138 
 100 
 19 
 48 
 140 
 143 
 
 , 32, 100 
 . 139 
 . 143 
 . 140 
 . 145 
 . 102 
 . 49-59 
 . 131 
 . 141 
 . 103 
 . 146 
 . 3,4 
 99 
 
 144, 146 
 50 
 88 
 11 
 21 
 17 
 18 
 16 
 22 
 20 
 115 
 
 . 120 
 27 
 
 . 153 
 23 
 
 . 113 
 
 . 156 
 
 . 154 
 
 159, 162 
 
 41 
 
 157
 
 164 INDEX. 
 
 PAGE 
 
 Cody's kite, 28,30 
 
 Comparative value of different motors, 
 
 Conclusions regarding air currents, . . .21 
 
 Condensers, Testing of, 52 
 
 Condenser tubes, . .60 
 
 Continental flying machines, . . . 9 
 
 Crystal Palace experiments, . . . 72-76 
 
 DARWIN on the flight of condors, ... .11 
 
 Deflection of air coming in contact with aeroplanes, . 
 
 De la Grange machine, The, . . . . . . 1 10 
 
 "Dirigible "No. 2, 159,162 
 
 Drift at various distances from center to center, Table of, . . 58 
 
 Dynagraphs, ...... .136 
 
 Dynamic energy of animals, . . . . 127 
 
 EAGLES, Flight of, 
 
 Efficiency of screw propellers, . 147 
 
 ,, screws in steamships, . . 47 
 
 Energy developed by a bird, . 
 
 Engines, ... . 153 
 
 Equivalent inclinations, . 115 
 
 velocities, . . .116 
 
 Experiments of Count Zeppelin, . . . . .124 
 
 Horatio Philipps, . . . 9,118,119,145 
 
 Lord Ray eigh in reference to Newton's Law, . 6 
 
 Professor Langley, ... 9, 62, 99, 109 
 
 Wright Bros., ' . . . . .109 
 
 Experiments to show efficiency of Screw propellers, . . 33 
 
 apparatus attached to rotating arm, . . 62 
 
 boiler 156 
 
 hard rolled brass aeroplane, ... 3 
 
 my large machine, ... 10, 133 
 
 rotating arm, ..... 64-72 
 small machines attached to rotating arm, . 159 
 
 FABRIC covered screw, . . . . .."'.'' 40 
 
 Farman's machine, . . . . . . ,110 
 
 Flyinc of kites, . . . . . . 25, 28, 29 
 
 Forced circulation used by me, ..... 158 
 
 Formulae unsupported by facts, ..... 3 
 
 French and English measurements, .... 128, 129 
 
 . . . . ,; .... 20, 21 
 
 tryroscope apparatus, . . . . . . .' .'. 93 
 
 ,, Steering by means of, . . . . . 92 
 
 HAWKS and Eagles, . . . . . . 13 
 
 He"licoptere machine, . . . , . . . . : . ] 32 
 
 Hints as to the building of flying machines, . . 77-91 
 
 Horizontal movement of the air, . . ... . 14 
 
 Hub for flying machine, New form of, '..""-' 45
 
 INDEX. 165 
 
 PAGE 
 
 INTERSTELLAR temperature, . . . ' . . j v L - . 15 
 
 Introductory, ... ...... . 1 
 
 KlTES > '.-..". ... 21,22,25,26,28,29 
 
 Behaviour of, ... .. . . m . . . 26 
 
 Flying of, . ... . . .- . ' - ; ' ,. . 25, 28, 29 
 
 LANGLEY, Experiments of, . . . . ' 9, 62, 99, 109 
 
 ,, on the flight of birds, . '..'*> . . 11,22 
 
 on the power exercised by birds, . . . . ' 12 
 
 "La Patrie," . . . . . '.-;''. 124 
 
 Lifting effect of aeroplanes, . . . . 5 
 
 , , surface of aeroplanes, . . . .... 103 
 
 Low temperature of space, . . . . '. . 15 
 
 MAJOR BADEN POWELL'S demand, ..... 125 
 
 Mistral, The, . . . . . . .21 
 
 Motors, Development of, . . .:-." '.'.'-. . 31 
 
 Motor, The Antoinette, . . . . ' . . . 89 
 
 My compound engines, . . . - . . . 142 
 
 ,, experiments with aeroplanes, . . 7 
 
 ,, ,, large machine, . ; ' . .<.'" 10, 133 
 
 ,, steam engines, . ' . . "'-.'' . . ' . 155 
 
 NEWTON'S Law, . . . . . 2, 6 
 
 " Nulli Secundus," . . . ... '. ." 28,121 
 
 OIL engines, . . . . .' v . . 154 
 
 PHILIPPS' experiments, . . 9, 118, 119, 145 
 ,, sustainers, ....... 145 
 
 Pneumatic buffer, . . ' . . .90 
 
 Position of screw, . . . . ... 49 
 
 Power exerted by a land animal, . . . .13 
 
 required, . . . , , : -. - . 100 
 
 Principally relating to screws, ..... 31 
 
 RAYLEIGH'S experiments in reference to Newton's law, . . 6 
 
 Recapitulation of early experiments, . . 
 
 Recent machines, .... . 109 
 
 Relative value of woods for flying machines, . 
 
 Reserve energy necessary in flying machines, 
 
 Resistance encountered by various shaped bodies, 
 
 Rotating arm experiments, ... . 64-72 
 
 SANTOS DUMONT'S flying machine, ... .113 
 
 Screw blade on Farman's machine, 
 
 ,, blades, Testing of, . 36 
 
 ,, ,, used by the French Government, ... .39
 
 106 
 
 INDEX. 
 
 Screw blades with radial edges, 
 Fabric-covered, . 
 ,, Position of, 
 
 ,, propeller made of sheet metal, 
 propellers, Efficiency of, 
 Screws, .... 
 Building up of my large, 
 ,, their efficiency in steamships, 
 
 Shape and efficiency of aeroplanes, 
 
 Skin friction, . 
 
 Spider's webbing down from the sky, 
 
 Spirit lamp and ice box, 
 
 Stability of flying machines, . 
 
 Steam engines used by me, 
 
 Steering, ..... 
 
 Superposed aeroplanes, 
 
 System of splicing and building up wooden members, 
 
 ''-; . 43 
 
 40 
 49 
 41 
 
 33, 147 
 
 8 31, 35, 36, 40, 41, 46, 47, 49 
 40 
 47 
 
 . 41,48 
 27 
 62 
 
 147, 150 
 
 . 155 
 
 147, 149 
 
 144 
 
 TABLES : 
 
 Equivalent inclinations, ..... 
 
 ,, velocities, ...... 
 
 French and English measurements, . . . 128, 
 
 Philipps' experiments, ..... 
 
 Relative value of different woods, .... 
 
 Showing the relative power exerted by different birds, 
 Velocity and pressure of the wind, .... 
 
 ,, ,, thrust corresponding with various horse-powers, 
 
 Testing aeroplanes, condensers, etc., . . . . . 
 
 Teutonic vision of aerial power, ..... 
 
 VELOCITY and pressure of wind, ..... 
 
 ,, thrust corresponding with various horse-powers, 
 "Villede Paris," . 
 
 115 
 116 
 129 
 119 
 85 
 24 
 114 
 117 
 52 
 126 
 
 114 
 117 
 123 
 
 WEIGHT BROS.' experiments, 
 ZEPPELIN'S experiments, 
 
 . 109, 159, 162 
 . 124, 159, 161 
 
 UKLL AND BAIN, LIMITED, PRINTERS, GLASGOW.

 
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