SCIENCE OF AGRICULTURE. 133 



Hitchcock's Analysis of Marsh mud by Dana's 

 method, from 



Cambridge. Newburyport. Medford. 



•Soluble geine, 13.0 1.5 7.5 



Insoluble geine, 7.4 0.1 5.6 



Sulphate of lime, 2.3 3.0 2.6 



.Phosphate of lime, 0.4 0.5 0.3 



Granitic sand, 76.9 94.9 84.0 



100.0 100.0 100.0 



Besides the above named constituents, it contains 

 more or less salts of soda, common salt, &.c. From 

 this analysis we may say, that if a soil be quite poor 

 those varieties should be chosen that contain the 

 most geine, and this can be judged of by their com- 

 parative lightness when dry, the lightest abounding 

 most in organic matter. But if the soil already 

 contain a good deal of inactive vegetable matter, the 

 varieties that abound most in salts, will probably be 

 most efficacious. 



Cow Dung. 



The analysis of the excrement of black cattle fed 

 on hay and turnips, given in Thomson's Chemistry, 

 from Thaer and Einhoff, gives, when evaporated to 

 dryness and burnt to an ash, (not reckoning sand,) 

 the following salts and earths in the proportion stated. 

 Lime 12, phosphate of lime 12.5, magnesia 2, iron 

 5, alumina with some manganese 14, silica 52, 

 murate and sulphate of potash 1.2, — 98.7. 



These mineral constituents then, together with 

 the vegetable and animal matter, which undergoing 

 putrefaction, forms geine, and gives out carbonic 

 acid and ammonia, shew us in what consists the 

 value of cow dung as a manure. 



Road Dust. 



It has been suggested by Hitchcock and Dana that 

 felspathic and micaceous rocks, if ground in a plaster 



