[ 29.^ ] 



And thus we fee, that depth is a circumftance of no importance, 

 except as far as it is conneded with temperature. But if we fup- 

 pofe, during the progrefs of the evaporation, fuch a change in the 

 temperature of the air as reduces it to an equality with that attu- 

 ally exifting in the larger vcffel, and below that which already 

 took place in the fmaller, (which may happen by the intervention 

 of a cloud) in that cafe the evaporation of the larger will be 

 checked, while that in the fmaller goes on. And thus we may 

 explain fome feeming anomalies in the experiments of Wallerius. 



This celebrated naturalift expofed to the open air, in the month 

 of Auguft, two tin parallelopipeds filled with water, whofe furfaces 

 were nearly equal, biit the height of one of them was one inch, 

 and of the other two inches, and found that the fmaller in three 

 hours loft 87 grains, and the larger only 77 ; but in thre; hours- 

 more, the fmaller further loft 148,75 grains, and the larger 1 5 1. 

 The total lofs of the larger in fix hours was 228 grains, and of the 

 fmaller 235,75. ^^^ in the month of June he found the larger 

 to lofe in feven hours 199 grains, and the fmaller only 183. That 

 • the inequality of temperature in thcfe experiments was the true 

 'caufe of the inequality of evaporation, he rendered evident by 

 -another experinient, in which, having coated cylinders of unequal 

 i capacities with clay, to prsvtot the quick communication of heat, 

 filled them with water, and expofed them to the air, he found the 



evaporation 



