WESTERN DISTRICT. 289 



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

 and bears good corn and wlicat, but does not dilfer essentially from tliat of the Pcntamorus 

 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 



IVIagncsia trace. 



Loss _ U-Cil 



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 liard rock, one wliich 

 resists decomposition, it slowly furnisiies 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*(32 



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 soluble than carbonate of lime, it is retained in the soil when tlie lime 

 would disappear. 



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



Water of absorption 4-00 



Vegetable matter 6-50 



Silicates 7? -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 

 [Agricclttir.u. Report] 37 



