244 



mm corrcftion for 

 different tem- 

 peratures* 



Syftem of Lam- 

 bert refpecting 

 the quantities o 

 vapour in air of 

 different den- 

 sities. 



STATU OF VAPOUR SUBSISTING IN THE ATMOSPHERE. 



Thus Sauffure found, barometer 28,77 and thermometer 82° 

 of Fahr. a cubic foot of air contained about 10 grains of moi- 

 fture at Geneva. Now the complement of 82° is nearly 15 

 grains, and the ratio of 10 to 15 is-}. Then at Mount Blanc, 

 on the fame hour, the barometer flood at 16° and the thermo- 

 meter at26°,8 ; the complement of a cubic foot of air at this 

 temperature is 5,3 grains, which diminifhed in the ratio of 2 

 to 3 becomes 3,5, and this, farther diminifhed by the ratio 

 which the barometrical height of 16 inches demands, namely 

 ,78 = 3,5 x ,78 = 2,7 grains, by obfervation it was found to 

 be 1,7 ; the difference is only one grain. Voy. aux Alpes, § 

 2007. How the temperature which prevails at thofe great 

 heights may be found, will be (hewn in the fequel. 



The celebrated Lambert, of Berlin, Mem. Berlin. 1772, 

 has alfo given an eltimate of the proportion of vapour which 

 prevails in the atmofphere at different barometrical heights, 

 deduced from calculations founded on many fictions, fuch as 

 that of an homogeneous atmofphere, of pure air difiinct from 

 common air, and an erroneous fyftem of the afcent of heat ; 

 yet as it is much eafier in its application and in the inftance 

 juft quoted, approaches very near the truth, I have calculated 

 the refults of his fyftem, which is nothing more than that the 

 quantity of vapour at different barometrical heights above the 

 earth is in the ratios of the fquares of thofe heights. By an 

 homogeneous atmofphere it is probable he meant fuch a ftate of 

 the atmofphere as prevails in ferene unclouded weather, and it 

 is certainly only in fuch an atmofphere that any calculation can 

 be inftkuted. 



Table of the Ratios of the Quantities of Vapour at different barome+- 

 trical Heights, theQuantity of the Surface of the Earth being given. 



Tims 



