130 



SCIENCE OF AGRICULTURE. 



Soot. 



I have given above the constituents of ashes, but 

 in decomposing wood and other vegetables by fire, 

 other elements escape in the form of smoke, the 

 more ponderous parts of which, are condensed on 

 the sides of the flues that convey the smoke into the 

 open atmosphere. Soot is a valuable article for 

 compost manures. Dr. Dana gives the following 

 analysis of soot from Braconnot. 



Geine, . 30.70 Acetate of potash, 



Extractive matter } ^o 'Muriate of potash, 



: Acetate of ammonia 

 lArr Acetate of magnesia, 



and azote, 

 Carbonate of lime 



and magnesia, 

 Acetate of lime, 

 Sulphate of lime 

 Phosphate of lime 



and iron 



5.65 

 5. I 



1.50| 



Silica, 



Carbon, 



Water, 



4.16 



0.36 



, 0.20 



.53 



.95 



3.85 



12.50 



100. 



Clay. 



I shall on this subject abridge the remarks of Hitch- 

 cock and Dana. There is abundant evidence that 

 our common clays are of great value when spread on 

 land. When spread on dry sandy and gravelly land 

 they render it a better reservoir of salts, geine, and 

 water. But they exert other than a mechanical in- 

 fluence; in fact, their effect is similar to that of lime. 



An analysis of our common blue clay, gives 



Water and organic } 



matter, ^ 



Silica, 



Alumina, 



9 



48 

 29 



Protoxyde of iron. 

 Lime, magnesia, } 

 and sulphur, \ 



11. 

 3 



100 



It is, therefore, probable that most of the good 

 effects of clay, as a manure, are owing to the large 

 quantity of iron it contains. Iron in clay exists 

 either in combination with oxygen or sulphur. Iron 

 combines with two proportions of oxygen, and forms 

 two oxids, the protoxide and the peroxide. The 



