MARL, is compact limestone and argillaceous matter, and essentially com posed of carbonate of lime and clay, in various proportions. Marl frequently contains sand and other foreign ingredi ents. It occurs in masses, either com pact, or possessing a slaty structure. All solid marl crumbles by exposure to the atmosphere, and it crumbles more easily, or forms a more tenacious paste, in pro portion as it is more argillaceous. All marls effervesce with acids, sometimes very briskly and sometimes feebly, accor ding to their solidity and the proportion of carbonate of lime, which may vary from 25 to 8.0 per cent. Earthy marl, like the indurated, may be either calca reous or argillaceous. It sometimes greatly resembles clay, but may be dis tinguished by its effervescence in acids. Marl is found associated with compact limestone, chalk, gypsum, or with sand or clay, and contains various organic re mains, as shells, fish, bones of birds of quadrupeds, and sometimes vegeta bles. Its most general use is as a ma
nure, and whether a calcareous or an ar gillaceous marl will be more suitable to a given soil, may be determined by its tenacity or looseness, moisture or dry ness.
Loam is sand and clay, marl is lime stone and clay ; and the more lime tho better as manure, and the less the better for brick-making.
The composition of marl varies in proportion to its origin. Some of the marls in western New York are gypsum containing 20 per cent. of plaster. Al most all marls contain phosphate of lime, sometimes as much as 2 per cent. It is a valuable dressing for land, but it should be dug out and frosted previously to laying on.