152 REPORT OF THE COMMISSIONER OF AGRICULTURE. 



underlying rocks. But in proportion to the slope of the ground and 

 the activity of the agents above mentioned the soil is transported from 

 higher to lower levels, and in many cases a good soil maybe found cov- 

 ering rocks which of themselves would only yield a poor soil. 



COMPOSITION OF THE SOIL. 



Soil is a mixture of sand, either quartzose or feldspathic, clay, carbon- 

 ate of lime, and humus or organic matter, and on the preponderance of 

 one or more of these constituents the usual classification of soils are 

 based. 



GENERAL CLASSIFICATION OF SOILS. 



Soils are usually classified as sandy, sandy or light loams, loams, 

 clayey loams, heavy or retentive clays, marls, calcareous loams, andpeaty 

 soils. This classification has reference chiefly to composition and text- 

 ure, a special chemical composition, silicious, calcareous, &c., being 

 necessary for the profitable growth of particular crops, and a certain 

 mechanical texture, friable, porous, &c., suiting best for the permeation 

 of rain and air, and the spreading of the roots of the plants. 



Loams, which may be considered as typical soils, are a mixture of 

 sand, clay, and humus, which are spoken of as light \yhei\ the sand pre- 

 dominates and as heavy when the clay is in excess. These terms, light 

 and heavy, do not refer to the actual weight of the soil, but to its tenac- 

 ity and degree of resistance it offers to the implements used in cultiva- 

 tion. Sandy soils are, in the farmer's sense of the word, the lightest of 

 all soils, because tbey are the easiest to work, whilst in actual weight 

 they are the heaviest soils known. Clay, though hard to work on ac- 

 count of its tenacity, is comparatively a light soil in weight. Peaty 

 soils are light in bot!i sensesof the word, being loose or porous and hav- 

 ing little actual weight. (See Table III.) 



GEOLOGICAL, CLASSIFICATION OF SOILS. 



Whatever their composition and texture, soils are, from a geological 

 standpoint, mainly of two sorts, soils of disintegration and soils of 

 transport. Under the former are comprehended such as arise from the 

 waste and decay of the immediately underlying rocks, the limestones, 

 traps, granites, and the like, together with a certain admixture of vege- 

 table and animal debris; and which are directly influenced in their 

 composition, texture, and drainage by the nature of the subjacent rocks 

 from which they are derived. Under the latter are embraced all drift 

 and alluvial materials, such as sand, shingly debris, miscellaneous silt 

 and clay, which have been worn from other rocks by atmosplieric agen- 

 cies and transported to their existing positions by winds, waters, or an- 

 cieat glacier actions. 



DIFFERENCE BETWEEN THE SOIL AND THE SUUSOIL. 



Besides the soils proper, which come immediately under cultivation, 

 there are in most places a set of siihsoils, difiering from the true soils, 

 and which cannot be ignored. The true soils are usually of a darker 

 color, from the large admixture of humus, whilst the subsoils are liglitcr 

 in hue, yellow, red, or bluish, from the great preponderance of tlie iron 

 oxides. The soils are more or less friable in their textiiie, whilst the 

 subsoils are tougher, more compact, and more largely commingled with 

 rubbly and stony debris. The soils are usually a little more than mere 

 surface covering, whilst the subsoils may be many feet in thickness. 



