116 expp:riments with the langley aerodrome. 



obvious that this phui coiihl jiot be followed in the large surfaces on 

 account of the necessity, already alluded to, of making them rela- 

 tively lighter than the small ones, which were already very light. 

 After the most painstaking construction, and tests of various sizes 

 and thicknesses of hollow square, hollow round, I-l)eam, channel, and 

 njany other types of ribs, I finally devised a tyi)e which consisted of 

 a hollow box form, having its sides of tapering thickness, with the 

 thickest part at the point midwaj' betAveen contiguous sides and with 

 small partitions placed inside every few inches in somewhat the same 

 way that nature places them in the bamboo. These various parts 

 of the rib (corresponding to the quill in a wing) were then glued and 

 clamped together, and after drying were reduced to the proper 

 dimensions and the ribs covered with several coats of a special marine 

 varnish, wdiich it had been found protected the glued joints from 

 softening, even when they were immersed in water for twenty-four 

 hours. 



Comparative measurements were made between these large cross 

 ribs, 11 feet long, and a large quill from the wing of a harpy eagle, 

 which is proljabl}" one of the greatest wonders that nature has pro- 

 duced in the way of strength for weight. These measurements 

 show^ed that the large, 11-foot ribs ('' quills ") for the sustaining sur- 

 faces of the large nuichine Avere equally as strong, Aveight for Aveight, 

 as the quill of the eagle; but much time Avas consumed in various con- 

 structions and tests before such a result was finally ol)tained. 



During this time a model of the large machine, one-fourth of its 

 linear dimensions, w-as constructed, and a second contract Avas made 

 for an engine for it. The delay with the large engine Avas repeated 

 with the small one, and in the spring of 1900 it Avas found that both 

 contract engines Avero failures for the purpose for which they Avere 

 intended, as neither one dcA^eloped half of the poAver required for the 

 allotted weight. 



I accordingly again searched all OA'er this country, and, finally, ac- 

 companied by an engineer (Mr. Manly), Avhose services I had engaged, 

 went to Europe, and there personally visited large builders of engines 

 for automobiles, and attempted to get them to undertake the construc- 

 tion of such an engine as Avas required. This search, hoAvcA^er, was 

 fruitless, as all of the foreign builders, as Avell as those of this country, 

 believed it impossible to construct an engine of the necessary poAver 

 and as light as I required (less than 10 pounds to the horsepoAver 

 Avithout fuel or water). I Avas therefore forced to return to this 

 country and to consent most reluctantly, even at this late date, to 

 have the work of constructing suitable engines undertaken in the 

 shops of the Smithsonian Institution, since, as I have explained, the 

 aerodrome frame and wings were already constructed. This Avork 

 upon the engines began here in August, 1900, in the immediate care 



