176 NEWTON S PRINCIPIA. 



ascents. The former will not furnish us with the re 

 quired law, because the presence of the mountain will 

 affect the temperature of the air by its radiation of the 

 solar rays. Gay Lussac, in his celebrated aerostatic ascent 

 of 3816*12 fathoms, found the temperature at the upper 

 station 14 9, giving a depression of 1 for every 95 14 

 fathoms. A great variety of observations have been 

 made, and many empirical laws invented to suit them. 

 To mention only one : Mr. Atkinson, in the second volume 

 of the Transactions of the Astronomical Society, asserts, 

 that at an altitude of h feet the depression in temperature 

 will be given by 



h 



nearly. We might make use of these results, and by 

 repeating our calculation in the manner indicated, obtain 

 various formulas to determine the density at any point. 

 But such results can never be very trustworthy. 

 II. 2. Note II. 



