Sand Blast
one of the most wonderful uses of sand, by means of which glass, stone, metals, or any other hard substance may be cut or engraved. If a stream of sharp sand be let fall from a high box (as high as the ceiling of a room) through a tube on to a plate of glass held under it, the sand will cut away little grains of the glass till at length the whole surface will be cut or scratched and it will look like ground glass. If, instead of cutting the glass all over, it is wanted to engrave a pattern or figure on it, the workman has only to cover the parts of the glass which he does not want cut with a stencil plate made of leather, rubber, paper, wax, etc., for the sand will not cut any soft substance. By this means only the uncovered parts are cut, and when the stencil is taken off the pattern will be seen. General Tilghman of Philadelphia, who first found out how to do this, made a machine in which the sand is blown on to the things to be cut by a blast of air or steam. Glass signs, glass globes for lamps and gas burners, tumblers, goblets, and other glassware may be engraved in this way very fast, and with the most beautiful designs.
Metals and stones also may be cut by means of the sand blast, which will not only scratch the surface, but will cut it away to any depth. The marble tombstones put up in the National cemeteries to the memory of soldiers killed in the war were made in this way. an