1 87 1.] A New Mechanical Agent. 363 



blows of the impinging grains of sand, and looks more 

 uniform than do surfaces ground by any rubbing process. 



This steam sand jet has already been introduced to clean 

 cast-iron hollow ware previous to tinning the interior. Here- 

 tofore the interior surface has been turned, it having been 

 found necessary to remove a thin shaving in a lathe to obtain 

 a clean surface. The surface is cleaned more rapidly by the 

 sand blast, and even more perfectly, because it penetrates 

 into any holes or depressions which the turning tool could 

 not reach. It is also probable that the sand striking the 

 particles of plumbago, which separate the particles of 

 metallic iron in ordinary grey cast-iron, will remove them, 

 and thus expose a continuous metallic surface to take the 

 tin. 



In this relation Mr. Sellers notes that about twenty-five 

 years ago, some experiments were made in Cincinnati, 

 at the establishment of Mr. Miles Greenwood, by his 

 brother, Mr. George Escol Sellers, with a view to making 

 tinned hollow ware of ordinary grey iron. He made a 

 machine for scouring the inside of the pots and kettles with 

 sand and water ; afterwards the still wet scoured surfaces 

 passed into the chloride of zinc solution, and thence into the 

 molten metal, and were uniformly tinned. For some 

 reason, the process was not continued, and now it is only 

 recorded as an abandoned invention, never before made 

 public. The wet sand grinding could not, in this case, 

 have been so efficient as Mr. Tilghman's sand blast. To 

 speculate on the various uses to which this process may be 

 applied, would not serve any good end, and would take up 

 too much space. With this discovery we can hardly help 

 recurring to the works of the ancients, and wondering if 

 some such process could have aided the workers in the 

 stone age, or could have been used in carving the Egyptian 

 hieroglyphics. It has been noted by those familiar with the 

 cutting or dressing of stone, that some materials, such as 

 granite, are very much injured, or "stunned," by the blows of 

 the cutting tool, and after being hand dressed a thickness 

 of perhaps from Jth inch to Jth inch has to be ground 

 away, to produce a solid uniform surface. By this sand 

 cutting process the surface is not injured, is not " stunned," 

 and is ready for polishing at once. 



One curious fact connected with its use is, that when 

 3, surface to be cut in intaglio or otherwise is partially 

 protected by templates of metal, these templates curl up 

 under the blows of the sand, so that paper patterns are 

 really more durable than patterns cut from brass. Sheet 



