SOIL. 



common clay, or clay mixed wilh car- 

 bonate of lime, a sandy substance is 

 produced rescnihling l)urncd brick, 

 wbicli tends greatly to improve the 

 texture oC those chiys whicli contain 

 little or no sand in tlieir composilioti. 

 It must be remembered that tlie siiH- 

 est clays contain a large portion of 

 Bilica in an imjjalpable state ; but 

 this, instead of correcting their im- 

 permca!)le and |)lastic nature, rather 

 adds to it. It is only palpalile sand 

 which, with clay, forms what is C(jm- 

 inonly called loam, and whicii, when 

 the sand is in due proportion with a 

 mixture of organic matter, forms the 

 richest and most easily cultivated 

 Boils. Some of the rocks of second- 

 ary formation contain a considerable 

 portion of alumina and lime ; and 

 when these earths meet with crys- 

 tallized saud, a compound, or, rather, 

 a mixture is formed, which has all the 

 requisite qualities, as to texture, to 

 produce the most fertile loams. The 

 only deficiency is that of organic mat- 

 ter ; but this is so readily accumula- 

 ted wherever vegetation is establish- 

 ed, or can be so easily added artifi- 

 cially, that these loams may always 

 be looked upon as the most favoura- 

 ble soils for the usual agricultural op- 

 erations : and if a considerable depth 

 of loam is found which neither re- 

 tains water too long nor allows it to 

 percolate too rapidly, it may be look- 

 ed upon as a soil eminently capable 

 of the highest degree of cultivation, 

 and on which no judicious outlay of 

 labour will ever cause loss or disap- 

 pointment to the farmer. 



" The alluvial soils formed by the 

 deposite of a variety of earths in a 

 state of great division, and mixed 

 with a considerable portion of organ- 

 ic matter, form by far the most pro- 

 ductive lands. They will bear crop 

 after crop with little or no additional 

 manure, and with a very slight culti- 

 vation. These soils are found along 

 the course of rivers which traverse 

 extensive plains, and which have 

 such a current as to keep very fine 

 earth suspended by a gentle but con- 

 stant agitation, but not sufficiently 

 rapid to carry along with it coarse 

 730 



gravel or sand. Wherever there is 

 an obstruction to the current and an 

 eddy is formed, there tlie soil is de- 

 posited in th(> form of mud, and grad- 

 ually accumulating, forms those allu- 

 vial soils whicli are so remarkable for 

 their fertility when carefully protect- 

 ed from the inroads of the water.- 

 In these soils the impalpable matte 

 greatly predominates; but the inti- 

 mate mixture of the earths with or- 

 ganic matter, in that state in which 

 it has been called hiunus, prevents 

 their consolidating into a stiff clay ; 

 and the gases which are continually 

 evolved from the organic matter keep 

 the pores open, and give scope to the 

 growth as well as the nourishment of 

 the roots. It is in the alluvial sods 

 principally that an accurate analysis 

 is useful ; because the proportion of 

 their constituent parts varies in in- 

 numerable degrees. It may be laid 

 down as a general rule, that the mos"; 

 fertile of these soils are those in 

 which the primitive earths are nearly 

 in equal proportions, silica being the 

 most abundant, with about ten per 

 cent, of organic matter; a greater 

 proportion of this last would form too 

 loose and spongy a soil to bear good 

 crops of corn, especially of wheat. 

 But four per cent, of hunms, with a 

 good mixture of earths, and some 

 phosphate of lime from the decompo- 

 sition of bones and marine shells, 

 produces a very good wheat soil. 

 The rich warp-lands along the Hum- 

 ber are artificial alluvial soils, and 

 although they contain but a small 

 proportion of humus, are highly fer- 

 tile after their first deposition, but it 

 is observed that they gradually be- 

 come more tenacious and difficult of 

 cultivation as this humus is carried 

 off by the crops, and that it is soon 

 necessary to add animal and vegeta- 

 ble manures to supply its deficiency. 

 " Organic matter is no doubt essen- 

 tial to great fertility in a soil, but 

 some soils require more of it than 

 others. Humus, which is the form 

 which organic matter naturally comes 

 to by slow decomposition in the 

 earth, gives out certain elements 

 which tl)e roots can take up in their 



