SOILS. 15 



their great preponderance in vegetables and animals, of which 

 they constitute from about !)!), to over 99 per cent of their 

 entire 1 substance. 



CLAY SOILS TIIJMU ( n VRACTKUISTICS AND TREATMENT. 

 Clay soils are usually denominated cold and wet, from their 

 strong affinity to water, which they generally hold in too great 

 -s for rapid or luxuriant vegetation. The alumina which 

 exists in clay, not only combines with water forming a 

 chemical compound, but the minute division of its particles 

 and their consequent compactness, oppose serious obstacles 

 to the escape of such us rests in or upon it. Hence the 

 necessity of placing it in a condition to obviate these essen- 

 tial defects. 



The most effectual method of disposing of the surplus 

 water in clay soils, is by underdraining. This draws off 

 rapidly yet by imperceptible degrees, all the excess of water, 

 and opens it to the free admission of atmospheric air ; and 

 this, in its passage through the soil, imparts heat and such of 

 the gases it contains, as are useful in sustaining vegetation. 

 When these are not constructed, open drains should be formed 

 wherever water stands after rains. The slight elevation 

 and depression ot the surface made by careful plowing, will 

 probably be sufficient, if they terminate in some ravine or 

 artificial ditch, and have size and declivity enough to pass off 

 the water rapidly. 



Clay soils are greatly improved by coarse vegetable manures, 

 straw, corn-stalks, chips, &c., which tend to the separation 

 of its particles. The addition of sand is very beneficial, but 

 this is too expensive for large fields. Lime is also a valuable 

 material for a clay soil, as by the chemical combinations 

 which are thereby induced, the extreme tenacity of the soil is 

 broken up, while the lime adds an ingredient of fertility, not 

 before possessed by it perhaps, to an adequate extent. 

 Gypsum has the same effect in a more powerful degree. 

 Paring and burning (by which the surface containing vegeta- 

 ble matter is collected into heaps and fired, reducing the mass 

 to a charred heap, which is again spread over and mixed with 

 the soil,) produce the same result. This is a practice which 

 has been long in use in different parts of Europe, and 

 although attended with immediate and powerful results, it 

 is too expensive for general introduction into a country, 

 where labor is high, and land and its products comparatively 

 cheap. 



