SOi 



SOI 



401 



of long tap-rooted plants, trees, 

 Sic. 



But the most comnnon dis- 

 tinction of soils is into rich and 

 poor. This difference, which is 

 certainly verv great, is not perhaps 

 natural. Richness, 1 imagine, is 

 rather to be considered as superin- 

 duced. All soils have, since the 

 creation, received large quantities 

 of fertilizing substances which were 

 adapted to improve them ; and by 

 which, in most places, they have 

 been greatly mended. Not only 

 vegetable substances fallen upon 

 the suiface, and changed by putre- 

 faction, have blended their salts 

 and oils in the soil : But the soil 

 has beeti drinking in vegetable food 

 by the dews and rains, and from 

 the air itself, which is loaded with 

 fertilizing particles But some 

 spots have retained the added rich- 

 ness better than others. 



As to land which has been long 

 tilled, and often plentifully manur- 

 ed, it is not easy always to dis- 

 tinguish what was its original soil ; 

 nor how rich or poor it was in its 

 natural state. 



It docs not follow, that all un- 

 cultivated soils ought to be equal- 

 ly rich, by means of the general 

 advantages mentioned above ; he- 

 cause some soils are better calcu- 

 lated than others to retain the food 

 of vegetables. Some are destitute 

 of a compact under-stratum ; and 

 it is no matter of wonder that such 

 should appear hungry. and barren ; 

 for whatever richness they receive, 

 is either washed by rains into the 

 bowels of the earth or evaporat- 

 ed again. Some soils are too 

 coarse, or too porous, to be a pro- 

 .51 



per matrix for ferlilizing substances. 

 Some are too steep to retain them, 

 so that they are washed into the 

 hollows below. Some are so wet 

 as to sour and corrupt them ; and 

 in some, there are are either mine- 

 ral waters, or steams which are un- 

 favourable to vegetation. 



Jn tillage, the surface mould and 

 the soil beneath are mixed, and 

 the more so the better, as the sur- 

 face mould is made up as it were 

 of the essences of vegetables. 



Soils, by some writers are divid- 

 ed into Sand ; — Gravel ; — Clay ; — 



Chalk ; — Peat ; Alluvial ; and 



Loam. 



1 . Sand consists of small grains 

 of silex, which are not soluble in 

 acids. If it has no mixture it can 

 hardly be cultivated, but it is rarely 

 found without a mixture of other 

 substances. The best mode of 

 injproving its texture is by a mix- 

 ture of clay marl, sea ooze, sea 

 shells, peat, or vegetable earth. 

 See Sandif Soil. 



2. Gravel. Gravelly soils are 

 composed of small soft stones, 

 sometimes of flinty ones ; but they 

 often contain granite limestone and 

 other rocky substances. They are 

 improved by deep ploughing ; by 

 mixing them with coats of clay, 

 chalk, marl or peat, &Co See Gra- 

 vel. 



3. Clay. A clay soil is tenacious, 

 smooth and unctuous, and often 

 holds water like a dish. Its tex- 

 ture is improved by a suitable mix- 

 ture of common sand, sea sand and 

 above all, of limestone gravel, 

 where it can be obtained. Peat 

 moss also, that has for some time 

 been dug up. and exposed to the 



