54 SMITHSONIAN CONTRIBUTIONS TO KNOWLEDGE VOL. 27 



atmospheres. If the weigh! of the cylinder, with its contents and adjuncts, be 

 taken as 800 grammes (1.76 lbs.), the total weighl of the aerodrome was 2698 

 grammes (5.95 lbs.). The wings were plane surfaces of silk, stretched over a 

 very lighi frame, with no intermediate ribs to prevent the wing from being com- 

 pletely distorted by the upward pressure of the air. Even if they had been suffi- 

 ciently strong and stiff, the total surface of both wings and tail was but 2601 sq. 

 cm. (2.8 sq. ft.) Or approximately 0.5 sq. ft. of supporting surface to the pound, 

 much less than was found adequate, even under the most favorable circum- 

 stances. The weigh! was much more than had been contemplated when the 

 wings wciv designed, yet, if all the other features of the aerodrome had been 

 satisfactory, and sufficient power had been secured, the work of providing suit- 

 able supporting surfaces would have been attempted. But as it was found that 

 the engines when supplied with carbonic-acid gas were unable to develop any- 

 thing like the power necessary to propel the aerodrome, and that the construc- 

 tion could be greatly improved in many other ways, this aerodrome was entirely 

 rebuilt. The work of the engines with carbonic acid had been so completely un- 

 satisfactory thai the idea was entirely abandoned, and no further attempts to 

 develop an efficient motor other than steam were made. 



It now became realized more completely than ever before that the primary 

 requisite was to secure sufficient power, and that this could be obtained only by 

 the use of steam. This involved a number of problems, all of which would have 

 to he solved before any hope of a successful machine could be entertained. In 

 the first place, engines of sufficient power and strength, but of the lightest pos- 

 sible construction, must be built. Second, a boiler must be constructed of the 

 leas! possible weight, which would develop quickly and maintain steadily steam 

 at a high enough pressure to drive the engines. This demanded some form of 

 heating apparatus, which could work under tl*e adverse condition of enclosure 

 in a narrow hull, and steadily supply enough heat to develop the relatively large 

 quantity of steam required by the engines. 



The firs! of these problems, that of procuring suitable engines, was at least 

 temporarily solved by the construction of two engines witli brass cylinders, 

 which had a diameter of l!.4 cm. (0.9.1 in.), and a piston stroke of 5 cm. (1.97 in.). 

 The valve was a simple slide valve of the piston type, arranged to cut off steam 

 at niie half stroke. Xo packing was used for the piston or the valve, which were 

 turned to an accurate fit to the cylinder and the steam chest respectively. In 

 the engines buill up to this time, the parts had frequently been soldered together, 



and a ureal deal of trouble and delay had arisen from this cause. In these new 

 engines, however, as strong and careful a construction was made as was possi- 

 ble within the very narrow limits of weight, with the result that the engines, 

 though by no means as efficient as those constructed later, were used in all Hie 

 experiments of IS!).", ami also during the first part of 1894. 





