I 31 ] 



a fallow to red ore the particles neceflTary to vege- 

 tation would be unncccflary; the bod might be 

 replenifhed as faft as the moll 'cxhauiting crops 

 could weaken it, and in this way the land, inftead 

 of being impoverished, would be improved, and 

 the longer it was kept in culture the richer and 

 better it would grow, as is evidently the cafe of 

 all land that is cropped and cultivated with dis- 

 cretion. 



This may be called the natural means of pro* 

 viding the pabulum or food of plants, as properly 

 as giving grafs to a cow, or hay to a horfe. I Jut 

 there are other means of improving of foils, which 

 communicate none~of thefe particles which are 

 neceflary to the fupport and growth of plants. 

 This is done by means purely mechanical, by- 

 rendering fome foils more fufceptible of thofe fer- 

 tilizing particles which float in the atmofphere; 

 and others more capable of retaining them during 

 the (rage of the growth of plants in them, than 

 they were in their natural (late. Thus a very 

 ftrong adhefivc foil, which in its natural ftate may 

 be too compact for mod forts of vegetables to 

 thrive in, by the proper admixture of gravel or 

 fand, its ftaple may be fo Shortened and opened 

 as to favour the admiffion of atmofpherical parti- 

 clcs, and to encourage the extenfion of the roots 



and 



