THE LANGLEY AERODROME 465 



obvious that this plan could not be followed in the large surfaces on 

 account of the necessity, already alluded to, of making them relatively 

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

 most painstaking construction, and tests of various sizes and thick- 

 nesses of hollow square, hollow round, I-beam, channel, and many 

 other types of ribs. I finally devised a type which consisted of a hollow 

 box form, having its sides of tapering thickness, with the thickest part 

 at the point midway between contiguous sides and with small parti- 

 tions 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, which 

 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 probably one of the greatest wonders that nature has produced 

 in the way of strength for weight. These measurements showed that 

 the large, 11-foot ribs ("quills") for the sustaining surfaces of the 

 large machine were equally as strong, weight for weight, as the quill 

 of the eagle; but much time was consumed in various constructions 

 and tests before such a result was finally obtained. 



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

 linear dimensions, was constructed, and a second contract was made 

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

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

 contract engines were failures for the purpose for which they were 

 intended, as neither one developed half of the power required for the 

 allotted weight. 



I accordingly again searched all over this country, and, finally, ac- 

 companied by an engineer (Mr. Manly), whose 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 was required. This search, however, was 

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

 believed it impossible to construct an engine of the necessary power 

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

 without fuel or water). I was, 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 work 



VOL. lxxiii.— 30. 



