216 DECOMPOSITION OF SOIL. 



consider that the potash washed out of the wall has 

 done this, and the mystery disappears. The agents 

 to hasten this natural production of alkali, are salts 

 and geine. The abundance of these has already been 

 pointed out in peat manure. Next to this, dry crops 

 ploughed in ; no matter how scanty, their volume 

 constantly will increase, and can supply the place of 

 that swamp muck. Of all soils to be cultivated, or 

 to be restored, none are preferable to the sandy, light 

 soils. By their porousness, free access is given to 

 the powerful effects of air. They are naturally in 

 that state, to which trenching, draining, and subsoil 

 ploughing are reducing the stifFer lands of England, 

 Manure may as well be thrown into water, as on land 

 underlaid by water. Drain this, and no matter if 

 the upper soil be almost quicksand, manure will con- 

 vert it into fertile arable land. The thin covering of 

 mould, scarcely an inch in thickness, the product of 

 a century may be imitated by studying the laws of 

 its formation. This is the work of " Nature's 'pren- 

 tice hand ;" man has long been her journeyman, and 

 now guided by science, the farmer becomes the mas- 

 ter workman, and may produce in one year, quite as 

 much as the apprentice made in seven. 



