116 EXPERIMENTS WITH THE LANGLEY AERODROME. 



obvious that this phin could not l)e folloAved 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-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 paj-t at the point midway between 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, which it had been found protected the glued joints from 

 softening, even Avhen they Avere 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, 

 Avhich is probably one of the greatest wonders that nature has pro- 

 duced in the way of strength for weight. These measurements 

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

 faces of the large machine were equally as strong, weight for weight, 

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

 structions 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 b}^ 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 construe-' 

 tion of such an engine as was required. This search, howeA^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 necessar}' power 

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

 Avithout fuel or Avater). 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 Avings Avere already constructed. This work 

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



