[ 349 3 



only one grain. Voy aux Alpes, § 2007. How the temperature 

 which prevails at thofe great heights may be found, will be fhewii 

 in the fequel. 



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

 alfo given an eftimate of the proportion of vapour which prevails 

 in the atmofphere at different barometrical heights, deduced from 

 calculations founded on many fidions, fuch as that of an homo- 

 geneous atmofphere, of pure air diftind from commcn 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 no- 

 thing 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 inftituted. 



Vol. VIII. Xx Table 



