NO. 3 LANGLEY! MEMOIR OX MECHANICAL FLIGHT 257 



large aerodrome would certainly he concluded within four weeks, the expen e 

 of the work, which had been met from the Bodgkins Fund of the Smithsonian 

 Institution since the original allotment from the Board of Ordnance and Forti- 

 fication was exhausted more than a year previously, had already made such 

 heavy drafts on this fund that Mr. Langley was most reluctant to draw further 

 on it, even to the extent which seemed necessary to meet the expenses of a 

 month of " field-work." 



Before making the tests of the large aerodrome, it was intended to give 

 the quarter-size model a preliminary trial to test the balancing which it was 

 proposed to use on the large machine. For this test it was planned to employ 

 the small launching apparatus mounted on top of the small house-boat, which 

 had been used in the experiments with the steam-driven models Nos. 5 and 6 

 in 1899, and later with the quarter-size model in 1901. However, after arriv- 

 ing down the river, it was found that the small house-boat which had been 

 anchored at Chopawamsic Island since the experiments in 1901 had deteriorated 

 to such an extent that it was unsafe to take it out into the river. The launching 

 apparatus for the model was, therefore, removed from it and placed on the turn- 

 table of the large house-boat, alongside the launching track for the large ma- 

 chine. After completing this transfer of the model-launching apparatus every- 

 thing was thought to be in readiness for a test of the quarter-size model, but 

 upon making a shop test of the model to make sure that its engine was work- 

 ing properly, it was found impossible to get it to work at all. A few explosions 

 eould be obtained once in a while, but very irregularly. After spending consid- 

 erable time in trying to locate the difficulty, it w r as found that the commutator 

 which distributes the high-tension sparking current to the proper cylinder at 

 the proper time was short-circuited. This commutator had been made of " in- 

 sulating fibre " and had never caused any previous trouble. It was now found, 

 however, that the very damp atmosphere which had been experienced during 

 the preceding two weeks, when the fog for a large portion of the time was so 

 heavy that objects at a short distance across the water could not be seen, had 

 caused the moisture to penetrate the fibre and thus destroy its insulating qual- 

 ities. After much trouble some vulcanite and mica were secured and a new com- 

 mutator made to replace the fibre one, and, then, after some minor difficulties 

 had been remedied, the engine for the model was got into good condition again. 

 After getting satisfactory shop tests on the model aerodrome, and having every- 

 thing in readiness for a flight, it was necessary to wait many days before the 

 weather was calm enough for a test. However, on August 8 the weather quieted 

 down and the model was launched at 9.30 a. m. into a wind blowing about 12 

 miles per hour from E. SE. 



Referring to Plate 86, which shows the quarter-size model mounted on its 

 launching car on top of the large house-boat, and which was taken only a few 



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