WESTERN DISTRICT. 289 



The Onondaga limestone forms another terrace above the preceding. The soil is porous, 

 and hears good corn and wheat, but does not differ essentially from that of the Pentamerus 

 limestone. It is composed of 



Water of absorption 0*50 



Organic matter 4*85 



Silicates 85-50 



Peroxide of iron 4-62 



Carbonate of lime 0-62 



Alumina 3 "30 



Magnesia trace. 



Loss 0-61 



100-00 



The composition of the Onondaga limestone has been given. It contains a trace of 

 phosphate of lime, and two per cent of magnesia ; but as it is a hard rock, one which 

 resists decomposition, it slowly furnishes food for vegetables. 



The shales of the Salt group frequently give more magnesia than lime. A specimen 

 taken from the farm of Mr. Geddes, of Fairmount, gave 



Water 4-75 



Organic matter 6*20 



Silicates 75*62 



Carbonate of lime 0-50 



Magnesia 2*15 



Alumina and iron 10 '34 



99-56 



This arises from the fact that magnesia exists in all the shales and thin-bedded limestones, 

 from the red marl up to the pentamerus limestone, varying from two to eighteen per cent ; 

 and as it is less solubbe than carbonate of lime, it is retained in the soil when the lime 

 would disappear. 



An uncultivated soil near Clyde, upon the Salt group, gave, on analysis, 



Water of absorption 4-00 



Veg. table matter 6-50 



Silicates 78-82 



Peroxide of iron and alumina 4-69 



Carbonate of lime 3-71 



Magnesia 1-75 



Phosphate of alumina 0-24 



99-71 



The two following specimens of soil were taken from the farm of Mr. Ira Hopkins, of 

 Mentz, Cayuga county. The Salt group lies below, but the surrounding region contains 

 [ Agricui.ttrm. Report. | 37 



