Many terms, in general use among scientific men, and usually employed in agricultural works, are obscure to young readers. For their sakes we will explain some of them; and shall not be angry if old men profit by the explanation.
Soil.—The surface-earth, of whatever ingredients it may be composed. It may be a clay-soil, a sand-soil, a calcareous soil, as the surface is composed of clay, or sand, or clay strongly mixed with lime, etc.
Subsoil.—The earth lying below the ordinary depth to which the plow or spade penetrate. Sometimes it has hardened by the running of the plow over it for a series of years; then it is called pan, as hard-pan, clay-pan, etc. It is sometimes of the same nature as the top-soil, as in clay-lands; in others it is a different earth; as when a coarse gravel underlies vegetable mold, or when clay lies beneath sandy soil.
Subsoil Plowing.—In ordinary plowing, the share runs from five to seven inches deep. A plow has been constructed (called subsoil plow), to follow in the furrow, and break up from six to eight inches deeper—so that the whole plowing penetrates from ten to sixteen inches.
Subsoil Plow.—A plow having a narrow “double share, or a small share on each side of the coulter, and no mold-board.” It is designed to break up and soften the subsoil, but not to bring it up to the top.
Mold.—A soil in which decayed vegetable matter largely predominates over earths. Thus, leaf-mold is soil principally composed of rotten leaves; dung-mold, of dung reduced to a fine powdery matter; heath-mold, a black vegetable soil found in heath-lands; peat-mold, forest-mold, garden-mold, etc.
Loam.—Clay, or any of the primitive earths, reduced to a mellow, friable state by intermixture of sand, or vegetable
matter, is called loam. Clay lands well manured with sand, dung, or muck, are turned, gradually, to a loam.
Argillaceous.—From the Latin (argillaceus,) soil principally composed of clay.
Alumina or Alumine.—Generally employed to signify pure clay. It is, chemically speaking, a metallic oxide; aluminium is the metallic base, and is an elementary substance.