278 ANALYSES OF SOILS. 



detect mica in the rock. The condition <>i' the Hamilton group enables it to resisl the action 

 of the weather, and hence it is common for it to appear in mural precipices or in well 

 exposed outcrops. A more important change, however, remains to be noticed; ii is the 

 disappearance of lime and magnesia, or rather s very perceptible diminution of both. Ii 

 •i supposed that any rock is entirely destitute of either of these elements, yet ii is not 

 uncommon that it is diminished bo far as to influence the growth of the cereals, as well as 

 of maize. The consideration of the Hamilton group will be deferred for the present. 



The soil derived from the red shale may he distinguished from the succeeding green 

 shales by its red color. Where n is unmixed, and consists wholly of the matter of the 

 rock, it is frequently a heavy tenacious clay ; and usually it has more tenacity, and is 

 more compact than the soils from the rocks helow or above. Its composition indicates the 

 'elation it hears to the wheat culture, and the confidence which m;i\ be placed in it as to 

 returns for many years in succession. It furnishes the phosphates of alumina and iron, and 

 the carbonates of lime and magnesia. We have already hinted that it may he unproved 

 by employing the hroken down rock ; a plan, which, if systematically pursued, would 

 forever prevent its deterioration. This opinion is justified by experience in a few instances. 



Soil of the green shales. 



We notice this product of the rocks next succeeding in the ascending order, though its 

 characters, when its components are taken into consideration, are much the same as tin' 

 of the red shale. Its color, however, is quite different,' and it is less compact ; and 

 these shales, we believe, never produce a stiff clay, but the soil has a good body, and can 

 never he ranked among the light soils. The standard specimen of this soil yields, on 

 analysis, 



Water of absorption 5-16 



Silex 35 '54 



Carbonate of lime 2-50 



M:r_rnesia 1*50 



Sulphate of lime 0'50 



Peroxide of iron and alumina 4*87 



Phosphate of alumina 0-06 



50-13 



Two hundred grains, submitted to the action of cold water for a few days, gave, of 



Soluble matter 1*34 



Organic matter 1 *00 



Saline matter 0-34 



Another specimen, from the vicinity of the Green lakes near Manlius centre in Onondaga 

 county, gave 



