CHAP. 1. 10. OF CLOUDS. 29 



a considerable evaporation from the earth and 

 waters in the evening, which is condensed 

 again in the cold air. I readily allow that this 

 may take place; but it does not appear to me 

 to militate against what has been advanced in 

 the preceding Section. Evaporation may still 

 be going on from below, while there is a 

 precipitation from above; and thus we may 

 account for the stratus not always resting on 

 the ground, but frequently beginning at a 

 small distance from it, or increasing in density 

 for some feet upwards, there being a sort of 

 shallow vapour plane preserved so long as the 

 heat continued to be slowly transmitted from 

 the earth. 



M. De Luc asserts that clouds are not the 

 constant result of evaporation from the earth. 

 He accounts for them by supposing that the 

 air is decomposed by the sun's rays, so as to 

 deposit aqueous particles, which become clouds. 

 If this be admitted to take place, it does not 

 argue against the ascent of vapour: and whether 

 the watery particles arise immediately from the 

 ground, or are deposited by the air, they may 

 equally be supposed capable of becoming cloud 

 when operated upon by the nubific principle, 

 which is believed to be electrical: indeed, these 



