COMPOSITION OF SIMPLE MINERALS. 41 



HvPERSTHENE. 



Silica, 51.35 



Lime, 1.84 



Magnesia 11.09 



Protoxide of iron, 33.92 



Water, 0.50 



98.70 



At ihe north, however, tliis substance existing in but a small proportion in the hyper- 

 sthene rock, has but little influence upon the qualitj' of llie soil ; besides, being mixed 

 largely with labradorite, which contains both lime and aliunina, the soil formed therefrom 

 may be considered as good for grains and grass. Quartz or silex, too, is extremely scarce 

 in this rock ; and hence there is no excess of sand in it, as there is usually in a pure 

 granitic soil. Hypersthene, upon the wliole, may be considered as rather a rare mineral 

 in New-York. It is found in gneiss in Johnsburgh, but in such small quantities that it 

 has no influence upon the soil. 



Serpentine is another primary rock, disposed to crumble into soil. It is one in which 

 magnesia is the characteristic element. It consists of 



Sehpentine. 



Silica, 40.08 42.69 



Magnesia, 41.40 40.00 



Water, 15.67 lfi.45 



Protoxide of iron, 2.70 1.00 



99.85 Shepard. 100.14 Vancxem. 



Serpentine may be known by its softness and yellowish green color. It is easily cut by 

 a knife, or easily impressed, and it is always found softer upon the outside than upon a 

 fresh fracture ; the color, too, is much paler on the weathered surface. 



In foreign treatises on agricultural geology, serpentine is set down with those rocks 

 which make a poor soil. Thus, Johnson speaks of the soil at the Lizard in Cornwall, as 

 being far from fertile, and so retentive of water as to form swamps and marshes ; and 

 even when drained, it rarely produces good grass, or average crops of corn. It is the 

 opinion of the same distinguished writer that the barrenness is due to the small quantity 

 of lime contained in the soil ; serpentine, as will be seen from the above anal3'sis, being 

 destitute of this clement. In New-York, and part of New-England, it would appear that 

 the serpentine exists under different conditions. Thus, in St. Lawrence, Jeflferson, Essex 

 and Warren counties, it is intermixed with lime, and the lime disintegrates more rapidly 

 than the serpentine; the soil, therefore, must contain a sufficient quantity of lime. How- 

 ever this may be, there is always a luxiuiant growth of vegetables about these beds. The 

 serpentine hills of New-England are not so productive as those of New- York. I allude 

 more particularly to the hills of Chester and Middlefield, along which the great Western 

 [Agricultural Report.] 6 



