SOIL. 



by far the most important circum- 

 stance. To improve this texture 

 permanently is the great object of 

 all the labours of the husbandman. 

 For this purpose, he carries various 

 earths from one spot to another ; 

 clays one field, and limes or chalks 

 another ,• brings peat upon sands and 

 clays, and carries gravel and lime on 

 his peat bogs. Without an adequate 

 knowledge of the composition and 

 te.xture of a soil, it is impossible to 

 make permanent improvements with 

 any certainty, or without incurring 

 the risk of failure or of useless outlay. 



" The soils which have been form- 

 ed from the disintegration and de- 

 composition of the primitive rocks, 

 such as granite, basalt, schist, or 

 limestone, and especially those which 

 contain all these minerals, minutely 

 divided and intimately mixed, are al- 

 ways naturally fertile, and soon en- 

 riched by cultivation. The hard par- 

 ticles of quartz maintain a certain 

 porosity in the soil, which allows air 

 and moisture to circulate, while the 

 alumina prevents its too rapid evap- 

 oration or filtration. The silicate of 

 potash also seems highly favourable 

 to the vegetation and growth of those 

 plants which contain silica in their 

 stems, such as the graminea?, espe- 

 cially wheat, of all plants the most 

 important to the husbandman in our 

 northern climates. If organic mat- 

 ter be an essential ingredient in a 

 fertile soil, it is soon produced by 

 cultivation, or added by judicious 

 manuring. 



"Where there is a deficiency of 

 impalpable matter, and the fragments 

 of the rocks of which the soil is com- 

 posed are large, and lie loosely, it is 

 in vain to expect vegetation, except 

 along gently flowing streams, which 

 supply the roots with moisture, and 

 thus form a bed of vegetable matter ; 

 but in a climate suited to the vine, 

 and in a good exposure, these loose 

 soils often produce excellent wine, 

 as may be seen along the steep banks | 

 of the Rhine and other rivers. The 

 roots of the vine run deep into the fis- ', 

 sures of the rocks below, and there find 

 nourishment suited to their nature [ 



"The primitive limestone, which 

 is very hard, is yet gradually decom- 

 posed by the action of air and water, 

 being, in a very small degree, soluble 

 in the latter. The water which flows 

 through these rocks is soon satura- 

 ted ; but when it springs out and 

 comes to the light, the carbonate of 

 lime is deposited by the evaporation 

 of the w^ater ; and if this meets with 

 the clay which results from the de- 

 composition of the slate, it forms a 

 marl, which, naturally or artificially 

 added to silieious sand, forms the ba- 

 sis of a very good soil, particularly 

 well adapted to pasture. 



" The soils which have been evi- 

 dently formed from the rocks which 

 are supposed to be of secondary for- 

 mation are fertile according to the 

 proportion of the earths of these rocks 

 which they contain. It is of these 

 chiefly that those loose, sandy soils 

 are formed of which the particles ap- 

 pear as distinct crystals, easily dis- 

 tinguishable with the aid of a lens, or 

 even by the naked eye. Air and wa- 

 ter have been the chief agents in the 

 decomposition of those secondary 

 rocks called sandstones, and agita- 

 tion in water has washed from them 

 the finer portions, which have remain- 

 ed suspended. The immense sandy 

 plains which are either barren, or 

 have been fertilized with great trou- 

 ble and expense, have probably once 

 been the shores of the sea, from which 

 the waves have washed all that por- 

 tion which was impalpable and easily 

 suspended in water, depositing this 

 in the depths, which, by some con- 

 vulsion of nature, may some time or 

 other be raised above the level of the 

 waters, and form hills or plains of 

 clay, such as are often found in ex- 

 tensive basins of great depth. 



" Argillaceous earth exists in some 

 proportion in almost every rock. 

 Some of the hardest gems are chief- 

 ly composed of alumina. It has the 

 property, when mixed with other sub- 

 stances, as silica or lime, of fusing 

 into a stone of great hardness and 

 insolubility. In this state its effect 

 on the soil is not to be distinguished 

 from that of silica ; and by burning 



729 



