Marble-chips
The chips from a marble-yard are the very best material to use as a limestone-flux in cupolas, being comparatively free from the deleterious substances usually found in the commoner kinds of limestone. See FLUX; LIMESTONE-FLUX.
Marsh-gas, usually called fire-damp by miners, is often abundantly disengaged in coal-mines from apertures or "blowers," which emit for a length of time a copious stream or jet of gas, probably existing in a state of compression pent up in the coal. When the mud at the bottom of pools in which water-plants grow is stirred it suffers bubbles of gas to escape, which if collected are found to be a mixture of marsh-gas and carbonic anhydride; and it is thought by some that these two gases represent the principal forms in which the hydrogen and the oxygen respectively were separated from wood during the process of its conversion into coal. See AIR; VENTING.
Martin Steel is made in the reverberatory furnace by adding malleable iron to the molten pig iron after the latter has been melted. See STEEL.