BOILS. 



65 



org^inic 

 matter. 



tention of water. Hence too the importance of frequently stir- 

 ring and disturbing the dry surface of the soil, in time of 

 drought, by hoeing, plowing, &c., in order to present a moist 

 surface to the atmosphere ; without which, nutritious gases 

 cannot be absorbed. 



Carbonate of lime, sulphate of lime, and all the soluble salts, "^f 



nures and 



as well as putrifying vegetables and animals, should be con- 

 sidered as manures. They all act, either as absorbents, like 

 charcoal ; stimulants, like gypsum, muriate of lime, &c.j or as 

 furnishing nutritious matter by their decomposition, like fish, 

 rotted straw, &c. Therefore the geological agriculturist stu- 

 dies chiefly the proportions of stones, pebbles, clay and sa7id. 

 The study of that part of geology which relates to detritus^ tee^hes^a^ 

 is the true study of the first principles of elementary agricul- riculture. 

 ture. 



By a reference to the system of classification, in the pre- 

 ceding part of this text-book, it will be seen, that all detritus 

 is distributed into eight deposites. 1. Plastic clay. 2. Mar- Eight ele- 

 ly clay. 3. Marine sand. 4. Shell marl. 5. Diluvion. 6. kiadi^of soil. 

 Ultimate diluvion. 7. Post diluvion. 8. Analluvion. Af- 

 ter studying the characters of these deposites, nothing more is 

 required than a mere application of common sense to each par- 

 ticular case. 



CHARACTERS OF THE EIGHT KINDS OF 

 EARTHY SOILS, AND THEIR COMPOUNDS. 



1. Plastic clay. This stratum is rarely found at the sur- B^dsoil 

 face of the earth, excepting at its out-croppings in banks. It 



is destitute of any material portion of carbonate of lime . 



being the clay used by potter-bakers. Without any intermix- 

 tures, it would bake in the dry season, and be loose mortar in 

 rainy weather. Intermixed with marine sand, it would be tol- 

 erably productive. Wheat winter-kills in it more than in any 

 other soil. 



