296 BOARD OF AGRICULTURE. [Jan. 



the foundation rocks of the country are taken to pieces and 

 subjected to oxidation. The expanding action of frost 

 and of roots which penetrate the bed rock may produce a 

 certain amount of fragmental matter, which is commingled 

 with the earthy material ; but in all cases the larger part of 

 the detritus which constitutes the soil owes its formation to 

 the action of dissolving agents, among which we reckon 

 ordinary carbonic acid and the various acids of the nitro- 

 humic group. As these soils are essentially the product of 

 plant action, the grains of Avhich they are composed are to 

 a very great extent commingled with decayed vegetable 

 matter. This vesretable matter is most abundant in the 

 upper soil ; but, in the usual condition of the country, the 

 roots commonly penetrate to the depth of some feet beneath 

 the surface, and in their successive decay convey the humus 

 into the deeper portions of the deposit. As the disruption 

 of the bed rocks is mainly accomplished by the action of 

 roots, it necessarily follows that the decayed plant materials 

 penetrate the whole section of the soil. Though the quan- 

 tity of such substances in the subsoil may not be great, it is 

 still sufficient to affect the fitness of that layer for the uses 

 of plant life. 



In the soils which owe their origin to glacial wearing, the 

 conditions are sharply contrasted with those which are 

 formed by the action of vegetation. The material moved 

 from the bed rocks l)y the ice is in most cases much more 

 largely composed of coarse fragmental matter than in the 

 case of the plant-made soils. In the former class of soils 

 the process of disruption, accomplished by the ordinary 

 agents of decay, divides the detritus into fine bits, and 

 generally brings it into a state in which each grain is a chem- 

 ical unit. In such soils, even if composed of the waste 

 derived from crystalline rocks, each bit is made up altogether 

 of one chemical substance. Thus, in such soils we find 

 grains of quartz generally little dissolved, flakes of mica in 

 an advanced state of decay, bits of hornblende or feldspar 

 more or less afiected by corrosion. Rarely indeed in soils 

 of this nature do we find pebbles composed of these several 

 minerals united in a solid mass. The result of corrosive 

 decay is to separate in the grains of the soil the mineral con- 



