Se<5t. I. Agriculture and Vegetation. 43 



may be followed in all places. It would 

 be particularly good for clay ground, as the 

 viciffitudes of the air pulverife greatly. 



D E w is reckoned by farmers a great fer- 

 tilifer of the earth. It arifes from the per- 

 fpiration of the earth, of vegetables and 

 animals in a found ftate, and their exhala- 

 tions in a corrupted one. The earth re- 

 taining its heat, after the fun's influence is 

 weakened, elevates thefe attenuated par- 

 ticles : but the air cooling fooner than the 

 earth, from its rarity, condenfes them at a 

 little diftance from the furface ; and thofe 

 which become fpecifically heavier than the 

 air, fall on the earth again. Hence dew 

 muft differ according to the difference of 

 the bodies from which it proceeds. Its 

 contents are therefore various ; but experi- 

 ments have difcovered, that it is compofed 

 in general of oils, fairs, and a great pro- 

 portion of water. Of what ufe thefe prin- 

 ciples are to vegetation, we mail after- 

 wards fee. 



RAIN- 



