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THE PLANTEE's GUIDE. 



snbterraueous cavities ; by which means the rock, being 

 always damp, and never exsiccated, 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 off 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 stag- 

 nant at the bottom of the soil. In this situation it has 

 the most injurious 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. Secondly, those open beds of loose stones and 

 sand, from the bottom of which water is readily drawn off 

 by subterraneous outlets. These strata are sometimes 

 continuous, but they offcener 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 commonly of gneiss, accompanied in 

 some districts with a considerable proportion of iron, pro- 

 bably in the state of orange oxide. These rocks run in 

 long ridges through the districts where they lie, sometimes 

 narrow, and sometimes of a considerable breadth. They 

 are dry to a great breadth, and full of fissures, through 

 which the water quickly passes. The orange oxide always 

 appears in thin lamina among the fissures. As they are 

 like the sandy bottoms, not retentive of water, all vegeta- 

 tion is destroyed in dry seasons on the soils which cover 

 them, and woods, were they planted there, would share 



