THE SAND-BLAST. 



309 



cast-iron letters which act as stencils. Thus equipped, the contractor 

 is able to turn out three hundred head-stones a day, upon eacli of 

 which is a handsomely-cut inscription averaging eighteen raised let- 

 ters. It is estimated that, to accomplish a like result by tlie old pro- 

 cess, a force of three hundred men would be needed. Another instance 

 of the rapidity with which these little sand-engines do their work is 

 shown in the engraving of glass globes, tumblers, etc., which can be 

 done at the astounding rate of one a minute. 



Fig. 8. Tilghman's Sand-blast Stone-machine. 



Extended space might be devoted to a mere recital of the actual 

 present accomplishments of the sand-blast, and, were we to enter the 

 field of speculation as to its possibilities, the range of its adaptation 

 would tax the reader's credulity. We will therefore be content to 

 refer to the following extract from the report of the judges at the 

 fortieth exhibition of the American Institute, which, in awarding thfe 

 inventor the great medal of honor, describes and commends his inven- 

 tion as follows : 



"The process is designed to execute ornaments, inscriptions in intaglio^ or 

 relief, or complete perforations, in any kind of stone, glass, or otlier hard and 

 brittle substance ; or to cut deep grooves in natural rocks, in order to facilitate 

 the process of quarrying; or to make circular incisions around 4;lie central mass 

 of rock in the process of tunneling ; or to remove slag, scale, and sand, from the 

 surfaces of metal castings ; or to clear the interior surfaces of boilers or boiler tubes 

 of incrustations ; or to cut ornaments or types from wood as Avell as from stone ; 

 or to depolish the surface of glass, producing by the aid of stencils or other par- 

 tial protections, as the bichromatized gelatine of photographic negatives, every 

 variety of beautiful figures, including copies of the finest lines, and the most 

 delicate line engravings ; or to prepare copper-plates in relief for printing, by 

 making gelatine photographic i;)ictures upon smooth surfaces of resin and pitch, 

 cutting them out by the blast, and afterward moulding from them, and electro- 

 typing the moulds. 



