22 SOILS AND MANURES. [CHAP. II. 



In fields and uncultivated places, the surface 

 soil is almost as hard and as coarse in its tex- 

 ture as the subsoil on which it rests ; but in 

 gardens which have been long in cultivation, 

 the surface soil becomes so thoroughly pul- 

 verised by frequent diggings, and so mixed 

 with the manure and decayed vegetables which 

 have been added to it from time to time, that 

 it is changed into the soft, light, fine, powdery 

 substance, called garden mould. If the subsoil 

 be naturally porous or well drained, this mould, 

 however rich it may be made by the addition 

 of decayed vegetable matter or animal manure, 

 will always continue friable ; and, as long as it 

 does so, it will be fit for the growth of plants : 

 but if no vent be allowed for the escape of the 

 water, and it be continually enriched with 

 manure, it will be changed in time into a black 

 slimy substance, and become what the gar- 

 deners technically term sour. 



Surface soil is called peat earth, when it is 

 composed principally of vegetable matter partly 

 decayed, but the decomposition of which has 

 been stopped by its immersion in water. As 

 this kind of earth cannot exist without abun- 

 dance of stagnant moisture, it is almost always 

 found on a clayey subsoil, which prevents the 

 water which falls upon it from escaping. Peat 

 earth has a spongy elastic feel when trodden 

 upon, arising from the quantity of water that 

 it holds, and it can only be rendered fit for cul- 

 tivation by draining, or by depriving it in some 

 other manner of its superabundant moisture. 

 In its elastic state it is what is called in Scot- 

 land a moss, and in England a peat bog. 



