56 SMITHSONIAN CONTBIBXJTIONS TO KNOWLEDGE VOL. 27 



onstratiou of a principle rather than for actual service, but the construction of 

 this small aeolipile was an epoch in the history of the aerodrome. It furnished 

 immenselj more heat than anything that had preceded it, and weighed so little 

 and worked so well that in May the aeolipile marked B was made. In this de- 

 sign two ] . i pes were led from the upper portion of the cylinder, one to a large 

 Bunsen burner which heated the boiler, the other to a small burner placed under 

 the tank to vaporize the alcohol. This was followed by the one shown at C, 

 wherein the heating burner was smaller and the gas pipe, leading to the main 

 burner, larger. 



Figures D, E, F, and G (Plate 12) were really continuations and improve- 

 ments of the same idea. In C there was simply a tube or flue through the tank; 

 in F, however, this tube discharged into a smoke-stack fastened to the end of the 

 cylinder, while in G the flue turned upward within the tank itself and discharged 

 into the short stack on top. The object of these changes was to increase the draft 

 and heating power of the small flame, so that the gas would be more rapidly 

 generated and a greater quantity be thus made available for use under the boiler 

 in a unit of time. They were, however, though improvements in a construction 

 which was itself a great advance, still inadequate to give out a sufficient amount 

 of heat to meet the excessive demands of the required quantity of steam. The boil- 

 ers in connection with which these aeolipiles were used must now be considered. 



The first boiler E (Plate 13) made during this year was a double-coil boiler 

 of the Serpollet type, formed of 19 feet of copper tubing having an internal di- 

 ameter of about ^ inch. Attached to the boiler was a small vertical drum, from 

 the top of which steam was led to the engine, a pipe from the bottom leading to 

 the pump. This boiler was tested in April with an alcohol heater, the pump in 

 this trial being worked by hand. This apparatus developed a steam pressure 

 varying from 25 to 75 pounds, which caused the engines to drive a 60 cm. pro- 

 peller of 1.25 pitch-ratio 565 revolutions per minute. The greatest difficulty was 

 experienced in securing a sufficient and uniform circulation in the boiler coils. 

 The action in the present case was extremely irregular, as the pressure some- 

 times rose to 150 pounds, driving the engines at a dangerous speed and bending 

 the eccentric rod, while at other times it would fall so low that the engines stop- 

 ped completely. 



As the pump used in this trial had proved so unsatisfactory and unreli- 

 able, it was replaced by a reservoir of water having an air-chamber charged to 

 10 atmospheres, the flow from which could apparently be regulated with the 

 greatest nicety by a needle valve at flic point of egress; but for some reason 

 its performance was unsatisfactory and remained so after weeks of experiment. 



There was used in connection with this device the double-coil boiler shown 

 at F (Plate in) which was made of tubes flattened so as to be nearly capillary. 

 The idea of this was to obtain a larger healing surface and a smaller volume of 



