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AGRICULTURAL GEOLOGY.

The Science of Geology embraces the facts ascers tained in regard to the Physical and Chemical struc— ture of the earth. Extending to the soil, it contri- butes aid to practical agriculture, and by explaining :the causes to which the covering of the earth owes its origin, it points to improvement in the production :of plants.

The chief parts cfall the stratified rocks, are sand stones, limestones and clays, under diflerent degrees of hardness. Ifthese rocks, and even those of vol- canic origin, are exposed to the operations of frost, rain and atmosphere, a soil results. The soils produced by the disintegration of the solid masses ofthe crust of the earth, brought forth the plants

found in a fossil state, and therefore partake of the .‘character oftho rocks from which they had been de-

rived. The surface of a bed of diluvial gravel soon forms a soil, after its covering is removed, and the plants that grow upon it, soon deposit a quantity of vegetable matter, which adds fertility. Very fre- quently rocks are covered with a soil that has result- ed frnm dilapidation, and it has been already shewn that diluvial matter had been transported from one place to another, over great distances, and being in- ermixed with the native covering of other districts, a diversity of soils has followed, recognised by ‘eology. The sotls of granitic and trappean moun- ains are peculiar in themselves. In gypseous dis- ricts the soil frequently contains so much sulphate of ime that it is sterile, and in tracts of limestone the and is sometimes barren from a superabundance ’of carbonate of lime. It is by the mixture of mineral ingredients ofthe earth that the surface is fruitful, to produce which many powerful natural agenciea are mployed by a ruling Providence. B32