Sct. IV. Agriculture and Vegetation. 17 



refifts, in fbme meafure, the entrance of 

 more water into its pores, is very flowly pe- 

 netrated by that fluid, and therefore is not 

 in any great degree foftened, loofened, or 

 otherwife affected by it. Clay, when preff- 

 ed by external force, or firmly compacted 

 by its natural fubfidence, as we find it at 

 the bottom of many of our foils, and of 

 moft of our moiTes, will even fuftain water, 

 and become impenetrable to it. Hence 

 foils, in proportion to the quantity of clay 

 they contain, will hinder the water from 

 paffing through them j will keep the vege- 

 tables continually fbaked in moifture ; will 

 not be fb much heated by the rays of the 

 fun as if they were dry; and, therefore, are 

 juftly deemed of a cold nature. 



WHEN expofed to the degree of heat of 

 a fummer fun, clay dries, and turns very 

 hard, fo that it requires a confiderable force 

 to feparate its parts. This quality of clay 

 is the more obfervable, if it has been full 

 of moifWe, and dried fuddenly. Hence 

 C clay 



