464 CHREOTECHNICS. 



partly by experiments ; which are of course the decisive test of their 

 relative value. The soil, is the uppermost stratum of the earth's 

 surface ; and consists chiefly of pulverulent earthy matter, resulting 

 from the decomposition of ancient rocks ; mingled with vegetable 

 matter, by which it is distinguished from the subsoil beneath it. The 

 chief earthy constituents of soils, are gravel, and sand, of variable 

 fineness ; clay, consisting of alumina and silex ; chalk, or carbonate 

 of lime ; and the oxide of iron, usually communicating a red color. 

 Clay absorbs moisture, and thereby becomes soft ; but when dry, it 

 is too hard and stiff for the fibrous roots of plants to penetrate. Sand, 

 gives looseness and lightness to soil ; but, not retaining moisture, it 

 speedily becomes too dry for vegetation. Hence the best soil is 

 chiefly a mixture of clay and sand, with a due proportion of the 

 other earths, and a large supply of vegetable and animal matter. 

 Such a mixture is properly called loam. 



Soils have been classified, according to their chief ingredients, as 

 loamy, clayey, sandy, gravelly, chalky, and peaty, or mossy ; the 

 latter consisting chiefly of vegetable matter, or mould, which is 

 very retentive of moisture. Of these varieties, loamy soil, is, as we 

 have already explained, the best ; but the others may be ameliorated, 

 by adding the ingredients in which they are deficient ; as adding 

 sand and lime to a clayey soil, or clay to a gravelly one. Clayey 

 soils, when well prepared and manured, are suitable for wheat, oats, 

 beans, and clover : but they require breaking up, or fallowing, more 

 frequently than most other kinds. Sandy, or light and dry soils, are 

 suitable chiefly for barley, turnips, and the drier grasses ; and wet 

 soils are best appropriated for raising succulent grasses, and oats. 



Most soils are improved by the application of suitable manure: 

 but the kind required, varies with the nature of the soil. Lime is a 

 good manure for clayey soils; and gypsum, for sandy ones ; perhaps 

 because it attracts moisture. Marl, on account of its containing 

 potassa, mixed with clay, is an excellent manure, especially for sandy 

 soils ; and wood ashes, which also contain carbonate of potassa, are 

 of similar use. But vegetable and animal manures, especially with 

 proper mixtures of the preceding, are chiefly to be depended upon, 

 in rendering soils more fertile. The composts, thus formed with 

 refuse organic matter, should not be exposed to heavy rain, while 

 heating and fermenting ; as it would wash away their soluble salts, 

 and greatly diminish their value. Certain plants are found to require 

 a peculiar nourishment ; wheat, for example ; which will not grow 

 to a full kernel, in a soil wholly destitute of lime. Next to the 

 application of manure, and equally important, for some crops, is the 

 thorough breaking up of the soil, by ploughing or otherwise ; by 

 which it is loosened, exposed to the air, and its nutritious ingredients 

 brought into action. All plants exhaust the soil ; but in different 

 degrees, and of different ingredients ; and hence the importance of 

 due rotation of crops, to keep the land in good heart. 



4. The Cultivation of Vegetables, consists in sowing or plant- 

 ing the seed, in ground properly prepared ; in fostering its growth, 

 by stirring the soil and eradicating noxious plants, or weeds ; and 

 finally, in gathering and preserving the products of this labor. The 



