C 170 ] 



peat forced on soils originally dry, is always salu- 

 brious. 



The earthy matter of peats is uniformly analo- 

 gous to that of the stratum on which they repose ; the 

 plants which have formed them must have derived 

 the earths that they contained from this stratum. 

 Thus in Wiltshire and Berkshire, where the stratum 

 below the peat is chalk, calcareous earth abounds in 

 the ashes, and very little alumina and silica. They 

 likewise contain much oxide of iron and gypsum, both 

 of which may be derived from the decomposition of 

 the pyrites, so abundant in chalk. 



Different specimens of peat that 1 have burnt, 

 from the granitic and schistose soils of different parts 

 of these islands have always given ashes principally 

 siliceous and aluminous and a specimen of peat from 

 the county of Antrim, gave ashes which afforded very 

 nearly the same constituents as the great basaltic stra- 

 tum of the county. 



Poor and hungry soils, such as are produced 

 from the decomposition of granitic and sandstone 

 rocks, remain very often for ages with only a thin co- 

 vering of vegetation. Soils from the decomposition 

 of limestone, chalks, and basalts are often clothed by 

 nature with the perennial grasses ; and afford, when, 

 ploughed up, a rich bed of vegetation for every species 

 of cultivated plant. 



Rocks and strata from which soils have been de- 

 rived, and those which compose the more interior 

 solid parts of the globe, are arranged in a certain or- 

 der ; and as it often happens that strata very different 



