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winds through the ricli, but alluvial plain below. In this 

 sort of subsoil, the excess of the water collected from the 

 sky, and the heights above, passes through the fissures, and 

 is received and retained in its subterraneous cavities ; by 

 which means the rock, being always damp, and never exsic- 

 cated, can communicate its moisture to the soil above, in 

 seasons of drought. It is true, this rock sends out frequent 

 springs, from its internal reservoirs, to the surface : but they 

 are often useful, instead of being pernicious ; and they may 

 generally be carried olT, by drains of inconsiderable depth, if 

 cut across the outcropping extremity of the rock. 



The subsoils of an unfavourable quality are, First, such as 

 are composed of dense and argillaceous substances, through 

 which no water can pass, it being retained stagnant at the 

 bottom of the soil. In this situation, it has the most inju- 

 rious effects, not only by chilling the roots that reach it, but 

 by disabling the soil from exerting that sort of repulsive 

 force, which, as has been seen, is necessary to fertility. Se- 

 condly, those open beds of loose stones and sand, froiii the 

 bottom of which water is readily drawn off, by subterraneous 

 outlets. These strata are sometimes continuous, but they 

 oftener occur in narrow lines or strips ; they are named 

 " scalds" by the Norfolk farmers, and are as injurious to crops 

 in a wet, as in a dry season. Thirdly, there may be added 

 those extensive ranges, or strata of dry rocks, of a hard 

 texture, composed of slate, sometimes granite, but most com- 

 monly of gneiss, accompanied in some districts with a con- 

 siderable proportion of iron, proljably in the state of orange 

 oxide. These rocks run in long ridges through the districts 

 where they lie, sometimes narrow, and sometimes of a con- 

 siderable breadth. They are dry to a great breadth, and 

 full of fissures, through which the Avater quickly passes. The 

 orange oxide always appears in thin lamina among the 

 fissures. As thcv are, like the sandy bottoms, not retentive 



