64 [Senate 



The mixture of these elements is usually purely mechanical, and 

 always so with the silex and the lime ; but in- the clays, the sand and 

 alumina is frequently chemically combined, or in such a state that 

 mere agitation in water will not separate them. The purer kinds of 

 pipe and plastic clay are of this nature ; indeed what is called pure 

 clay, although composed of perhaps 60 per cent of silex and 40 of 

 alumina, is of this character. Where sand and alumina is mechani- 

 cally mixed, it becomes loam, the name and character of which is de- 

 termined by the proportion of the several elements of sand, clay and 

 lime it contains. Professor Johnston has in part classified the soils 

 thus formed as follow^s : Pure^ or pipe day ; about 40 per cent of 

 alumina, and 60 of silica. No sand subsides when agitated in w^ater. 

 Strong^ or unctuous clay ; pure clay, with from 5 to 15 per cent of 

 sand, which can be separated by boiling and settling. Clay loam 

 contains from 15 to 30 percent of sand mechanically united, and which 

 may be separated by washing. Loamy soils deposit from 30 to 60 

 per cent of sand by mechanical washing. Sandy soils contain no 

 more than 10 per cent, of pure clay. Marly soils, are those in which 

 the lime is more than 5, but does not exceed 20 per cent. Marls are 

 sandy, loamy, or clay marls, as these several substances preponderate 

 in the mass. Calcareous soils, are those in which the lime exceeds 

 20 per cent, and thus becomes a prominent constituent. Vegetable 

 soils, are those in which the decomposed organic matter exists in pro- 

 portion of from 5 to 10 per cent, as in garden mold, or from 60 to 

 75 per cent,?as in peat. It is also clear that these soils will be clayey, 

 sandy, or loamy, as these several earths may predominate in the mix- 

 ture. 



It sometimes happens that the surface soil, or the part usually cul- 

 tivated, is unproductive, or perhaps entirely barren, from the too 

 great predominance of one of the principal earths, while the subsoil 

 may be of precisely the character wanted to give it the greatest ferti- 

 lity. This occurs oftener on a sandy soil than any other, as on such 

 soils there is a constant tendency to permit clay and vegetable matter 

 to sink through the porous surface, to a more dense subsoil. , Thus 

 there are many tracts of sandy soils so light as to be unfit for cultiva- 

 tion, resting on subsoils that require only to be combined with the 

 surface one, to give the proper combination for the highest degree of 

 fertility. Such instances may be found in this country, and they will 



