NO. 3 LANGLEY MEMOIR ON MECHANICAL FLIGHT (ii 



drome was subjected while preparations for the launch were being made. More 

 over the flame was so nearly invisible in the sunlight that it was uncertain 

 whether it was burning in the critical instants just before the launch, when doubt 

 might be fatal. These conditions resulted in a final decision in favor of gaso 

 line, on account of its greater inflammability, and in the provision of such hull 

 covering that the fires could be lighted and maintained in a breeze. 



In June, I tried a modification of the burner, in which the gasoline was de- 

 livered under the pressure of air to the evaporating coil. In the first trial steam 

 was raised to a final pressure of about 70 pounds, and a run of 45 seconds was 

 secured under a pressure of 40 pounds in the gasoline tank, which was thought 

 to be altogether too high ; for, at the end of the run, the whole apparatus was 

 enveloped in flames, because of the gasoline that was projected through the 

 burner-tips. 



Continual experiments with different forms of burner, illustrated in Plate 

 12, occupied the time, with delays and imperfect results, which were trying to the 

 investigator, but are omitted as of little interest to the reader. They had, how- 

 ever, the incidental result of proving the practical superiority of gasoline over 

 alcohol, and culminated in the evolution of the burner that was finally used 

 successfully. It consisted of a tank for the gasolme, from which compressed 

 air delivered the liquid to a small coil surrounded by asbestos, in which it was 

 vaporized. At the rear end of this coil three pipes were led off, one of which 

 was a small " bleeder," which fed the burner for heating the gasoline, the other 

 two leading to the main burners. After the generation of gas in the small coil 

 bad been started, the heat from the small burner was expected to continue the 

 vaporization, so that nothing but gas would be able to reach the main burners. 

 A device was also introduced, which had greatly increased the amount and uni- 

 formity of the draft and consequently made the burners and boilers more effi- 

 cient than before. Tins consisted simply in passing the exhaust steam from the 

 engines into the smoke-stack, and it is remarkable that it was not thought of 

 earlier. 



By the middle of September, 1894, both aerodromes were completed and 

 ready for another test. On September 27 the condition of Aerodrome No. 4 

 was as follows: The general type of construction, namely, that of a single 

 midrod, to which all the steam generating apparatus was attached, and which 

 supported also the cross-frame and the wings, was the same as in the construc- 

 tion of 1893. On account of the increased weight of the model, and the substi- 

 tution of an inferior piece of tubing in place of the former midrod, it was found 

 necessary to stiffen it by the use of temporary trusses. Permanent bearing 

 points for holding the aerodrome securely to the newly devised launching appa- 

 ratus were also attached to this midrod. 



