OF TWO PLACES BY MEANS OF THE BAROMETER. 



389 



Part I. gives j 



for H 30.046 inches 

 for h = 23.66 inches 



Difference 

 Part II. gives for T T' = 7.2, 



Approximate altitude a, 

 ^ (t + t' 64) = 6.918 x 83.8, 



Second approximate altitude A, 

 Part III. gives for A = 6806, and L = 21, 

 Part IV. gives for 6806, 



Height above the sea, 



27649.7 

 21406.9 



6242.8 

 16.9 



6225.9 

 +579.7 



6838.2 feet. 



Example 2. 



M. Gay Lussac in his celebrated balloon ascent in 1805, found his barometer to 

 indicate 12.945 English inches, the temperature being 14. 9 Fahrenheit. The ba- 

 rometer at Paris at the same time indicated 30.145 English inches with a tempera- 

 ture of 87.44 Fahrenheit. Required the elevation of the balloon above Paris. 



Part I. gives j 



for H = 30.145 inches, 

 for h' = 12.945 inches, 



Difference, 

 Part II. gives for T T' = 72.54, 



- 



Approximate altitude a, 



_ t i __ 64) = 24.35 x 38.34, 



Second approximate altitude A, 

 Part III. gives for A = 22848, and L = 48 50' 

 Part IV. gives for 22848, 



Height of balloon above Paris, 



27735.6 

 5650.4 



22085.2 

 169.9 



21915.3 

 +933.6 



22848.9 



8.2 

 +82.1 



22922.8 feet 



49 



