CHAPTER VIII. 



PHYSICAL PROPERTIES OF SOIL. 



291. In all attempts at improving soil by manure, two 

 objects are intended, which form the golden rule of apply- 

 ing salts and geine ; to make " heavy land lighter, light land 

 heavier, hot land colder, and cold land hotter." Are there then, 

 notwithstanding all that has been offered and said, differences 

 in soil ? Have not, it may be asked, all the preceding pages 

 been based on the fact, that there is but one soil 1 True, it 

 has been so said, it is said so now. Chemically, the inorganic 

 elements of all soil are alike. The silicates and salts are 

 nearly the same in all ; the organic portion, the geine, varies, 

 and that to a greater degree than any other ingredient. 

 "While the silicates compose with great uniformity about 89 

 per cent., and the salts of lime, sulphate, and phosphate, &c., 

 2 per cent., the geine varies from 1 to 20 per cent. The 

 silicates may be finer or coarser, more sandy or more clayey. 

 These circumstances affect not the chemical, but the physical 

 properties of soil. The physical properties, then, are the 

 foundation of the great diversity which soil exhibits. The 

 subject of soil will have been very imperfectly treated, if a 

 few pages are not devoted to this important subject. 



Liebig has observed that, " it is the duty of the chemist 

 to explain the composition of a fertile soil, but the discovery 

 of its proper physical state or condition belongs to the agri- 



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