Reviews. — Jl Muck Jilanualfor Farmers. 183 



entitled "The Physical Properties of the Soil." It presents 

 Dr. Dana's views of the important agency which geine per- 

 forms in vegetation. 



In all attempts at improving soil by manure, two objects are in- 

 tended, which form the golden rule of applying 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 oftered and said, differences in soil? Have not, it may be 

 asked, ail the preceding pages been based on the fact, that there is 

 but one soil? True it has been so said; it is said so now. Chemi- 

 cally, 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, from 80 to 90 per cent., and 

 the salts of liine, sulphate, and phosphate, from 1-2 to 3-4 per cent., 

 the geine varies from 1 to 20 per cent. The silicates may be finer 

 or coarser, more sandy or more clayey. All these circumstances af- 

 fect, not the chemical, but the physical properties of soil. The 

 physical properties, then, are the foundation of the great diversity 

 which soil exhibits. The sul)ject of soil will be very imperfectly 

 treated, if a few pages are not devoted to this important subject. 

 The physical characters of soil are embraced under the terms, cold, 

 hot, wet, and dry land. These characters are dependent on four 

 circumstances. 



First. The absolute weight of a given bulk of soil. 

 Secondly. Its color. 

 Thirdly. Its consistency. 

 Fourthly. Its power of retaining water. 



In other words, the physical characters of soil may be considered 

 under 



First. Its relation to heat. 

 Secondly. Its relation to moisture and gas. 

 Thirdly. Its consistency. 

 Fourthly. Its electrical relation. 



The relation to consistency makes soil light or heavy; the relation 

 to heat and moisture makes soil hot or cold, wet or dry. The great 

 natural varieties of soil are sand, clay, and loam; first, the great dis- 

 tinction in the scale of soil, is sand and clay: all intermediate varie- 

 ties proceed from mixtures of these with each other. Now the sand 

 may be silicious, or calcareous — that is, silicates, the distinguishing 

 character of soil in this country, or mixed with a salt of lime, the 

 feature of much European soil. By clay is meant common blue 

 clay, or sub-silicate of alumina, consisting of alumina, 36; silica, 68; 

 oxide of iron, and salts of lime, and alkalies, 6. 

 Sandy clay is — clay and sand, equal parts. 

 Loamy clay is — 3-4 clay, and 1-4 sand. 

 Peaty earth is — geine. 

 Garden mould is — 8 per cent, geine. 

 Arable land is — 3 per cent, ceine. 



Taking these several varieties, it is found, that sand is always the 

 heaviest part of soil, whether dry or wet; clay is among the lightest 



