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PROCEEDINGS OF THE AMERICAN ACADEMY 



0.00076 gram or 0.76 m.g. No exact observation of the temperature 

 of the balloon was necessary ; for a difference of 4° C. would not alter 

 the above value more than j^-q m.g., aud we may therefore assume that 

 the temperature of the balloon was the same as that of the laboratory, 



Fig. 2. 



which at the time was 21° C. The correction for lessened buoyancy 

 (increased weight) on account of the contraction of the balloon by 

 atmospheric pressure amounts, as has been shown, to 1.98 m.g.,* and 

 this added to 0.76 makes the total correction 2.74 m.g. When the 

 balloon was hung on the balance, the weight required to complete the 

 tare was 2.5600 grams. Hence we have, — 



Weight of balloon exhausted 2.5600 grams. 



Correction for residual gas . . . 0.7 G m.g. 



» « lessened buoyancy . 1.98 " 27 " 



Tare of empty balloon 2.5573 " 



Two other determinations were made in the same way, and the 

 three results are united in the following table. 



* These Proceedings, vol. x.xiii. p. 184. 



