34 Subsoil. 



stitution of the soil, it has been justly observed, are amply 

 repaid, by the great and permanent advantages which they 

 produce. Less manure is afterwards required ; the crops 

 cultivated, are more independent of particular seasons ; 

 while the capital thus expended, secures the futures-fertility, 

 and consequently the permanent value of the land ( II6 ). 



SECT. III. Subsoil (" 7 ). 



THE value of a soil depends much upon the nature of the 

 subsoil, or under-stratum. On various accounts the proper- 

 ties of the latter merit particular attention. By examining 

 the subsoil, information may be obtained in regard to the soil 

 itself; for the materials of the latter, are often similar to 

 those which enter largely into the composition of the former. 

 The nature of the soil, however, is necessarily altered, by the 

 various substances mixed with it, in the course of its cultiva- 

 tion. The subsoil may be of use to the soil, by supplying its 

 deficiencies, and correcting its defects ( J l8 ). The hazard and 

 expense of cultivating the surface, are often considerably aug- 

 mented by defects in the under-stratum, which, however, may 

 in some cases, be remedied ( II9 ). Disorders in the roots of 

 plants, are generally owing to a wet or barren subsoil. 



Subsoils are, 1. Retentive; or, 2. Porous. 



1. Retentive subsoils consist of clay, or marl, or of stone 

 beds of various kinds. 



A retentive, clayey, or fa'%( IZ ) subsoil, is in general 

 found to be highly injurious. The surface soil is soaked 

 with water, is ploughed with difficulty, and is usually in a 

 condition unfit for the exertion of its vegetative powers, until 

 the superabundant moisture which has accumulated during 

 the winter be exhaled. By the water being retained in the 

 upper soil, the putrefactive process is interrupted, and ma- 

 nures are restrained from operating ; consequently the plants 

 make but little progress. Hence, the produce of such a soil 

 in grain, is of inferior quality, and when in grass, its herbage 

 is coarse ( l21 )- 



A clayey subsoil, however, may sometimes be of material 

 advantage to a sandy soil, by retaining moisture in such a 

 manner, as to supply what is lost by evaporation, and the 

 consumption of plants ( ia *). Alluvial subsoils are those 

 which can be raised and mixed with the soil, to the greatest 

 advantage. 



When soils lie immediately on rock, they become sooner 



