1 68 Vie Principles of Part IV. 



though well enough underftood, perhaps, 

 for common practice, yet has it not been 

 reduced to that mathematical exaclnefs 

 which all mechanical agents are capable 

 of. I wifh that fome practical farmer, 

 fkilled in mechanics, would lay down the 

 principles on which ploughs ought to be 

 conftru&ed, and ploughing conducted. He 

 would merit much from the community. 



SECT. V. 



Of compofts. 



THERE is another method which art 

 ufes to keep the foil loofe ; and that 

 is, by the admixture of putrid and fer- 

 menting bodies. We have feen that thefe 

 bodies have a ftrong intefline motion before 

 they are laid on the ground : they continue 

 that afterwards, though in a fmaller degree. 

 The fat foil of church-yards fwells fo much 

 when expofed to the air, by its fermenta- 

 tive power, that it will not go altogether 



into 



