no. 3 langley memoir on mechanical plight 225 



a portion of the exhaust gases was passed in order to compensate for the cool- 

 ing of the tank caused by the evaporation of the gasoline. As a result of these 

 tests it was found that a type consisting essentially of a tank filled with small 



lumps of a porous cellular w I (tupelo wood) which was initially saturated 



with gasoline, and into which the gasoline was (<-<\ through a distributing pipe 

 as rapidly as it was taken up by the air, which was sucked through it by the 

 engine, gave the best results. Instead of jacketing this tank, the cooling effect 

 due to evaporation was compensated by drawing the somewhat heated air from 

 around the engine cylinders up through the loosely packed lumps of wood. When 

 tested in the shop this type was found to give such a very uniform mixture 

 that the engine ran as smoothly and regularly as an electric motor, the vibra- 

 tion in no way interfering with it, and even when the sudden change from a 

 state of rest to one of rapid motion through the air was imitated by suddenly 

 turning on the carburetor the blast of several large electric fans from various 

 angles, it was found to have no appreciable effect on the running of the en 

 gine, thus indicating that the trouble which was experienced with the model 

 aerodrome in the trials of 1901 was not likely to be repeated with the large 

 aerodrome. Somewhat more than a dozen carburetors of various forms were 

 constructed before this last type was devised, but this proved so satisfactory 

 that there were never thereafter any carburetor troubles. In fact, as will later 

 appear, a carburetor of this type kept the engine on the large aerodrome run 

 ning at full power not only when the aerodrome was in a vertical position in 

 the air, but also after it had turned completely over on its back. 



