40 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 92 



" I am not prepared to say that the relations of power, area, weight, 

 and speed, here experimentally established for planes of small area, 

 will hold for indefinitely large ones ; but from all the circumstances of 

 experiment, I can entertain no doubt that they do so hold far enough 

 to afiford assurance that we can transport (with fuel for a considerable 

 journey and at speeds high enough to make us independent of ordinary 

 winds), weights many times greater than that of a man. 



" In this mode of supporting a body in the air, its specific 

 gravity, instead of being as heretofore a matter of primary impor- 

 tance, is a matter of indifference, the support being derived essen- 

 tially from the inertia and elasticity of the air on which the body is 

 made to rapidly run. The most important and it is believed novel 

 truth, already announced, immediately follows from what has been 

 shown, that whereas in land or marine transport increased speed is 

 maintained only by a disproportionate expenditure of power, within 

 the limits of experiment in such aerial horizontal transport, the higher 

 speeds are more economical of poiver than tJie lower ones. 



" While calling attention to these important and as yet little known 

 truths, I desire to add as a final caution, that I have not asserted 

 that planes such as are here employed in experiment, or even that 

 planes of any kind, are the best forms to use in mechanical flight, and 

 that I have also not asserted, without qualification, that mechanical 

 flight is practically possible, since this involves questions as to the 

 method of constructing the mechanism, of securing its safe ascent and 

 descent, and also of securing the indispensable condition for the eco- 

 nomic use of the power I have shown to be at our disposal — the con- 

 dition, I mean, of our ability to guide it in the desired horizontal 

 direction during transport — questions which, in my opinion, are only 

 to be answered by further experiment and which belong to the in- 

 choate art or science of aerodromics on which I do not enter. 



" I wish, however, to put on record my beHef that the time has 

 come for these questions to engage the serious attention, not only of 

 engineers, but of all interested in the possibly near practical solution 

 of a problem, one of the most important in its consequences, of any 

 which has ever presented itself in mechanics; for this solution, it is 

 here shown, cannot longer be considered beyond our cajmcity to reach." 



The data secured by these experiments have long since been super- 

 seded by more accurate observations in modern wind tunnels. Even 

 the conclusions would not now all be considered sound. For instance, 

 " Langley's law," that the more rapid the horizontal flight the less is 

 the power required for support and advance, does not hold for speeds 



