362 A New Mechanical <A gent. [July, 



the sand, and finally strikes on the stone, which is held 

 about an inch distant from the end of tube. 



At the spot struck a red light is visible, as if the stone 

 was red-hot, though really it is below 212° F. The light 

 is probably caused by the breaking up of the crystals 

 of the sand and stone. 



The cutting effect is greatest when free escape is allowed 

 for the spent sand and steam. In making a hole of a 

 diameter but slightly greater than that of the steam jet, 

 the rebounding steam and sand greatly interfere with and 

 lessen the efficiency of the jet. 



Under favourable conditions, using steam which was esti- 

 mated as equal to about ij horse-power, at a pressure 

 of about 125 pounds, the cutting effect per minute was 

 about ij cubic inches of granite, or 3 cubic inches of 

 marble, or 10 cubic inches of soft brown sandstone. 



By means of flexible or jointed connecting tubes, the 

 blast-pipe is made movable in any direction : grooves and 

 mouldings of almost any shape can thus be made; or 

 by means of stencil plates, letters or ornaments can be 

 cut either in relief or intaglio with great rapidity in the 

 hardest stone. 



At a high velocity, quartz sand will cut substances much 

 harder than itself, as before stated. With a steam jet 

 of 300 pounds pressure, a hole ij inches in diameter was 

 cut through a piece of corundum, ij inches thick, in 25 

 minutes. 



A hole 1 inch long and J inch wide was cut through a 

 hard steel file J inch thick, in 10 minutes, with a jet of 100 

 pounds steam. 



A stream of small lead shot, driven by 50 pounds steam, 

 wore a small hole in a piece of hard quartz ; the shot were 

 found to be only very slightly flattened by the blow, showing 

 their velocity to have been moderate. 



Among the curious examples of glass cut by this sand 

 blast was shown a piece of ordinary window-glass, which, 

 having been partially protected by a covering of wire gauze, 

 had been cut entirely through, thus producing a glass sieve, 

 with openings of about i-i2th of an inch, the intervening 

 glass meshes being only i-i6th of an inch wide. This seems 

 to have been produced more as a curiosity than for any 

 practical purpose. Should such a sheet of perforated 

 glass be required, it is questionable if it could be produced 

 from a solid sheet by any other method. 



A microscopic examination of the sheet glass depolished 

 by this process shows a succession of pits formed by the 



