302 THE POPULAR SCIENCE MONTHLY. 



of Xature, we will not say ; certain it is, however, that the former 

 work suggested the latter, though the prior claim does not seem to 

 have been considered by the American Commissioner of Patents. 



"On the 18th of October, 1870," we read, "letters-patent of the 

 United States were granted to General B. C. Tilghman, of Philadel- 

 phia, for the cutting, grinding, etching, engraving, and drilling stone, 

 metal, wood, or any hard substance, by means of a jet or blast of 

 sand." We are also informed, from the same official source, that the 

 inventor of the sand-blast process obtained his first hints from Na- 

 ture, and, by means of a mechanism which is a marvel of simplicity, 

 has been able to utilize this same force so as to make it render most 

 efficient service in several departments of the applied arts. 



It is the object of the present paper to describe and illustrate the 

 invention known as the Tilghman Sand-Blast, an invention which, in 

 simplicity of construction, and yet extent of application, has hardly 

 an equal in the annals of the American Patent-Office. We are aware 

 that this is a broad claim, when it is remembered that under the pro- 

 tection of the same authority the sewing-machine, reaper, and mower, 

 positive-action loom, and a score or more of great mechanical devices, 

 first saw the light. It is possible that there is that in the idea of the 

 sand-blast which adds to its charm, and secured for it the admiring 

 indorsement of Torrey, Tyndall, and other men of science ; and yet a 

 careful study of ils principle, and an observance of its practical op- 

 eration, seem to justify all and more than is claimed for it by the 

 inventor or his distinguished indorsers. 



If the reader will refer to the simple " claim " as given above, he 

 will notice that it is proposed to accomplish the several results there 

 named " by means of Q.jet or blast of sand." The italics are our own, 

 and are now introduced since it is in this idea of njet of sand that the 

 first principle of the device rests; and, moreover, it was an attempt 

 made by others to adopt this falling jet of sand that compelled the 

 inventor to institute his first proceeding against infringement. With 

 the legal history of the sand-blast, however, we have nothing to do, 

 save as it concerns the general history of the invention and its prog- 

 ress. In order that the methods by which a simple falling column or 

 stream of sand is made to do service as an engraver of glass and 

 metal plates may be understood, attention is directed to Fig. 2, which 

 may be described as follows : 



J. is a box, elevated as high above the engraver's table as the height 

 of the ceiling will permit. When designed for several workmen, this 

 box may be divided into com})artments, as indicated, each compart- 

 ment being filled with common quartz or sea-sand, of varying degrees 

 of fineness. From the'bottom of each division a metal tube, c, depends, 

 reaching to within a few inches of the table below. A slide, B, serves 

 to regulate or check the flow of the sand. Thus much for the simplest 

 form of sand-blast. A word as to the manner of its operation ; and 



