DETERMINATION OF THE ALTITUDE OF AEROPLANES. 



Bt Robert W. Willson. 

 Presented February 8, 1911. Received December 31, 1910. 



The object of this paper is to add something to the discussion of a 

 somewhat novel problem which has arisen as a result of certain devel- 

 opments in the art of aviation during the past year. 



Up to the time of the aviation meet at Los Angeles in February, 

 1910, no greater height had been recorded in the flight of a "heavier 

 than air " machine than about fifteen hundred feet. At that meet 

 Faulhan, in a Bleriot machine, reached a height of 4165 feet, the 

 height being determined by triangulation. The reading of his aneroid 

 was 46U0 feet. 



At the Montreal meeting, in June, Walter E. Brookins attained an 

 altitude of 3523 feet, determined by triangulation, his baroscope read- 

 ing 200 or 300 feet higher ; and at Atlantic City, in July, the same 

 aviator raised the record to 6175 feet, as determined by a triangulation 

 similar to that of the first method described in the following pages. 

 The height by barograph was 6200 feet. 



When the project of an aviation meeting at Cambridge was being 

 discussed, the writer agreed to be responsible for the accurate meas- 

 ure of altitudes ; and the results obtained and the methods used form 

 the subject of this paper. At that time no official accounts of the 

 e.xperience at other places in making such measurements had been 

 published, but it was agreed that it would be acceptable to the aviators 

 that they should attempt to reach their greatest altitudes when in a 

 vertical plane passing through the starting line of the course, and as 

 nearly as possible at a point over the grandstand. It was also agreed 

 that only one machine should be under observation at any time. Under 

 these conditions the arrangements now to be described were planned. 

 The accompanying map (Plate 1) of the S([uantum peninsula and the 

 surrounding country will serve to make the situation clear. The map 

 shows the positions of the two base lines, and gives the ground plan 

 of the flight of Brookins on September 8. 



First Method, — The Field B.\se. 



A measured base of 5000 feet was established on the line NS reaching 

 from the extreme northern limit of the course, across the field, passing 



