ately above the orifice through which the sand rises, the stencil-covered globes are caused to revolve on spindles, and, when finished, have the appearance indicated in Fig. 7.
If the reader has been able to follow this necessarily brief description, he will readily perceive how, by the use of duplicate stencils, constructed of .any tough substance, the work of engraving, once an art in itself, becomes merely a mechanical process. As the result of experiments, now nearly completed, a form of rubber ink has been devised which, when laid on paper, converts it into a stencil, sufficiently tough to resist the action of the blast. Then, again, it may be seen how designs, direct from Nature, may be transferred to glass or metal by merely attaching a leaf or, vine to the surface, and exposing it to the action of the blast. Nor is glass the only substance that can be ground and engraved. All metals, when hardened, are as
readily cut. The zinc plates which are now being substituted for lithographic stone have their surfaces depolished by the sand-blast. As illustrative of the remarkable rapidity with which the sand-blast accomplishes its work, the following facts, regarding the cutting of inscriptions on the head-stones designed to mark the graves of soldiers buried in the national cemeteries, may be cited. The contractor having this work in charge at Rutland, Vermont, has three sand-blast machines, of the form indicated in Fig. 8.
In addition to the one man employed to tend these machines, he has a small force of boys, whose duty it is to attach and remove the