Sect. V. Agriculture and Vegetation. 173 



producing good plants, becaufe their roots 

 are not able to penetrate it. 



Cor. 2. Sand appears, in oppofition to the 

 common opinion, to be the worft manure 

 of thofe ufed. It cannot indeed feparate 

 the minute particles of the clay, which is 

 the only ufeful feparation for the growth 

 of vegetables. A little fand rather feems 

 to increafe the union of the particles of 

 clay, as appears from the manufacture of 

 brick. 



Cor. 3 . Lime feems to be a good manure 

 for clay. What I ufed had been foured 

 for fome time. The effect which the air 

 has on it, in changing it from quick-lime 

 to effete lime, muft open the ground con- 

 fiderably. 



Cor. 4. Dung and marl appear to be the 

 beft manures for clay. The former has a 

 flrong fermentation ; the latter lofes all co- 

 hefipn when water is added. 



SECT. 



