3o8 



THE POPULAR SCIENCE MONTHLY. 



ately above the orifice through Avhich 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 descrip- 

 tion, 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, suffi- 

 ciently tough to resist the action of the blast. Then, again, it may 

 be seen how designs, direct from Nature, may be transfen-ed 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 



Ftg. 7. 



readily cut. The zinc plates which are now being svibstituted 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, regai'ding 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 hav- 

 ing 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 



