4 SMITHSONIAN CONTBIBUTIONS TO KNOWLEDGE VOL. 27 



In view of the greal importance of these experiments, as demonstrating 

 beyond question the practicability of the art of mechanical flight, and also in 

 view of the yel inchoate state of this art, 1 have thonghl it worth while to pub- 

 lish an account of them somewhat in detail, even though they involve an account 

 of failures; since it is from them, that those to whom it may fall to continue 

 such constructions, will learn what to avoid, as well as the raisou d'etre of the 

 construction of the machines which have actually flown. 



In an established art or science, this description of the essays and failures 

 which preceded full knowledge would have chiefly an historical interest. Here 

 almost nothing is yet established beyond the fact that mechanical flight has 

 actually been attained. The history of failure is hi this case, then, if I do not 

 mistake, most necessary to an understanding of the road to future success, to 

 which it led, and this has been my motive in presenting what I have next to say 

 so largely in narrative form. 



important to remark that the small dimensions of the machine did not allow it to include any 

 apparatus for condensing the steam, so that it could only carry water enough for a very brief 

 course — a drawback which would not be encountered in one of a larger construction. 



It is also to be noted that the speed estimated by Mr. Bell was that obtained in a continuous 

 ascending flight, and much less than would have been attained in a horizontal course. 

 On Mechanical Flight. Letter of Mr. Alexander Graham Bell to Mr. Langley. 



Washington, May 6, 1S96. 



I am quite aware that you are not desirous of publication until you have attained more complete 

 -s in obtaining horizontal flight under an automatic direction, but it seems that what I have 

 been privileged to see to-day marks such a great progress on everything ever before done in this way. 

 that the news of it should be made public, and I am happy to give my own testimony on the results 

 of two trials which I have witnessed to-day by your invitation, hoping that you will kindly consent 

 to making it known. 



For the first trial, the apparatus, chiefly constructed of steel and driven by a steam engine, 

 was launched from a boat at a height of about 20 feet from the water. Under the impulse of its 

 engines alone, it advanced against the wind and while drifting little, and slowly ascending with a 

 remarkably uniform motion, it described curves of about 100 metres in diameter; till at a height 

 in tin- air which I estimate at about 25 metres (82 feet), the revolutions of the screws ceased for 

 want of steam, as I understood, and the apparatus descended gently and sank into the water, which 

 it reached in a minute and a half from the start. It was not damaged, and was immediately ready 

 for another flight. 



In the second trial it repeated in nearly every respect the action of the first, and with an 



identical result. It rose smoothly in great curves until it approached a prominent wooded promon- 



tory, which it crossed at a height of S to 10 metres above the tops of the highest trees, upon the 



islion of the steam descending slowly into the bay. where it settled in a minute and thirty-one 



ils from the start. You have an instantaneous photograph of it, which 1 took just after the 

 launch. [See plates 20, 21, and 22 of present work.] 



From the extent of the curves which it described, which I estimated with other persons, from 

 measurements which I took, and from the number of revolutions of the propellers, as recorded by 

 the automatic counter which I consulted. I estimate the absolute length of each course to be over 

 ball' an English mile, or, more exactly a little over 900 metres (2953 feet). 



The duration of flight during the second trial was one minute and thirty-one seconds, and the 



average velocity between twenty and twenty-five miles an hour, or, let us say 10 metres a second, in a 



course which was constantly ascending. I was extremely impressed by the easy regular course of 



! trial, and by the fact that the apparatus descended each time with such smoothness and 



as to render any jar or danger out of the question. 



It seemed to me that no one could have witnessed these experiments without being convinced 

 that the possibility of mechanical flight had been demonstrated. 



