7(J SMITHSONIAN CONTRIBUTIONS TO KNOWLEDGE VOL. -7 



In view of the disasters from trials in the field, due to inability to obtain 

 automatic equilibrium in flight and to the flexure of the large wings rather than 

 to defects of the engines, the conditions at this time, after three years of failure, 

 seemed so nearly hopeless, that without abandoning the work on these steam 

 aerodromes, I again had recourse to the early plan of constructing smaller mod- 

 els driven by India rubber, in which the small wings employed could be made of 

 the requisite stiffness. Instead of employing twisted rubber, however, the de- 

 fects of which had been amply proved in previous trials, these new construc- 

 tions were meant to employ rubber directly stretched and pulling. In this con- 

 dition the rubber exercises nearly six times the power in proportion to weight 

 that it does when twisted, but on the other hand it requires a very strong frame 

 and subordinate parts. 



I spent an inordinate amount of time and labor during this year in attempt- 

 ing to employ this latter form of construction and finally got a few useful re- 

 sults from it, but none in proportion to the labor expended. 



During March, Aerodrome No. 5, the frame of which had proved on test to 

 be radically weak, was completely refinished except for the wings. The propel- 

 lers had hitherto been made of wood, but in May, I commenced a new construc- 

 tion of steel, wood and cloth, on a plan giving a figure which, though not rigor- 

 ously helicoidal, was practically near enough to the theoretical form and was 

 also both lighter and more elastic than the wooden construction. 



On May 8 and June 7 Aerodrome No. 5 was again tried at Quantico, 

 and although the tests were unsuccessful, in that the aerodrome failed to fly, 

 partly because of the fact that so much time was spent in raising steam that prac- 

 tically the entire supply of fuel and water was exhausted before the aerodrome 

 was actually launched, yet it had come so much nearer flying than any machine 

 had previously done, that it was felt that if either the power could be increased 

 or the weight decreased even a slight amount, the aerodrome would probably 

 fly. In view of the great care that had been exercised in keeping down the weight, 

 it seemed almost hopeless to attempt to reduce it, and it also seemed equally 

 hopeless to attempt to get more power without increasing the weight. How- 

 ever, something had to be done to increase the ratio of power to weight, and as 

 it was seen that this would involve extensive changes in No. 5, it was decided to 

 entirely rebuild No. 4 with this idea in view, though it was evident that it in- 

 volved a plan of construction even lighter than the dangerously light plan on 

 which No. 4 had already been constructed. 



During Mr. Langley's absence in Europe in the summer, Aerodrome No. 4 

 was entirely reconstructed and made to embody many new characteristics, the 

 changes introduced being SO radical that this model was henceforth designated 

 as" New No. 4." The new characteristics of this model were its unprecedent- 



