Channcting is the process of cutting long narrow channels in rock to free the sides of large blocks of stone. Channeling machines, o• channelers, are made in a variety of forms, the most common of which is a vertical steam boiler mounted on wheels and provided with mechanism for self propulsion, having on the same carriage with the boiler a steam cylinder which operates, like a percussion drill, a flat bar with a cutting edge. In operation the machine is run forward and back so as to carry the cutter back and forth along the line on which the channel cut is to be made. If the rock is in layers the channel cut is often not made the full depth of the layer, but is sunk deep enough to permit the insertion of wedges by which the rock is split, the cut or groove guiding the fracture. When the rock is not in layers it is often necessary to undercut the block as well as to cut a channel around it. This is clone by drilling a series of holes along the bottom, the process being called gadding by quarrymen. Wedges inserted in the drill holes serve to separate or split the rock at the bot tom. A special form of machine called a gadder
is used for undercutting. It consists essentially of a rotary drill, generally a diamond drill, ar ranged to be operated horizontally and receiving motion from an engine taking steam from a vertical boiler, the whole being mounted on a carriage. The channeling and wedging process of quarrying is extensively used in quarrying marble, sandstone, limestone, and the other softer rocks, but is not a successful process for granite and other similarly hard stones. For a de•crip tion of the methods and tools used in cutting quarry stone into suitable shapes for structural purposes, see STONE CUTTING AND DRESSING. For full details of quarrying processes and machin ery, consult Merrill, Stones for Building and Decoration (New York, 1891), and Report on the Quarry Industry, vol. x., Tenth United States Census. See illustration with the article MAR L:LE; also the articles BUILDING STONE; DRILL; EXPLOSIVES.