Calcareous Matter, consists of various kinds, which have their respective uses and value in agriculture. Lime-stone and marble are both calcareous substances, but the latter is in a crystalized state.

It is clearly ascertained, says Dr. Darwin, that calcareous earth, either alone, or in some of the states of chemical combination, may contribute to the nourishment both of animals and vegetables: first, because it constitutes a considerable part of them, and must therefore either be received from without, or formed by them; and, secondly, because from the analogy of all organic life, whatever has composed a part of a vegetable, or animal, may again, after its che mical solution, become a part of another vegetable, or animal; such is the general transmigration of matter.

Unburnt calcareous earth is said to forward the putrefaction of animal and vegetable substances; while pure lime, though it apparently prevents putrefaction, destroys, or dissolves, the texture of the flesh. If lime be mixed with oak-bark, after the tanner has extracted its soluble parts in water, the bark will, in two or three months, be reduced to a fine black earth; but, if it were only laid in heaps, as many years would be required to effect its spontaneous fermentation, or putrefaction. See Lime.

Yon Crell, a celebrated German chemist, a short time since made experiments, in order to ascertain the comparative effects of alum, magnesia, and calcareous earth, in the dying of cloths with madder; by which it appeared that no advantage was derived from the two last mentioned sub-stances, as alum, and its solutions, produce finer colours, and may always be employed in preference to the others.