Year: 1871

A process of grinding and cutting glass, and fof piercing glass and other hard substances, has been. brought into use. 1tconsists in driving a jet of sand with great velocity, by air or steam, against the plate which is to be ground or figured. Dwellers by the seashore know that the glass of their windows, in some places, loses its polish through the the consant action of drifting sands on the paue and this same action. ln 8 concentrated form is now to serve the arts, and put money into inventors, pock- cts. The mode of operation, briefly described, appears to be as follows :" stream of sand is driven hy a fan into large tube 1; the mouth of this tube is one inch wide and two feet long, and through this the stream of sand rushed against plates of glass, aDd in from ten to fif- teen seconds completely grinds as much of the surface as corresponds with the dimensions of the mouth of the tube. The plates of glass are moved by ma- chinery, until the whole surface is dead- ened or ground and a pattern may by produced at pleasure by any device, or with coat of oil-paint. The covered portions will then remain transparent, while the other parts of the surface will be dead Sometimes white glass, coat ed on one side with a thin film of red glass, is manufactured for ornamental purposes any pattern can in like man. her be cut through the red glass by the sand-jet If plate of glass is covered with lace, and then exposed to the jet. the pattern of the lace will appear, and by properly regulating the blast delicate fern leaves may be used as the covering, and the plate will present the effect of an engraving of ferns. More examples might be enumerated but these will suffice to indicate that there are many ways in which, with tubes of different sizes, glass may be cut or ornamented by irt of sand. There are also other applications in which it has been ad- vantageously employed. The jet will cut granite or any other kind of stone with great facility, if driven by high pressure steam. It is found in practice that the rateof cutting is, in granite, 1s cubic inches minute, marble 3, and soft brown sandstone 10 cubic inches

 hence, grooves, morldings, and geomet- rical patterns may be cut in stone at the

 pleasure of the artifcer. It seems hard

 ly credible, but jet of quartz sand, impelled by steam-jet of 300 pounds pressure, pierced an inch-and-a- half hole

 through slab of corundum II inches

 thick in 25 minutes. Between the hard ness of coruntlum and of diamond there

 is but little difference. After this there seems nothing remarkable in the fact } that plate of glass covered with wire.

 gauge was pierced and converted into

 glass gauge by the action of the jet , Moreover, it found that the jet can be

 used for the dressing. of the surface o

 stone. Some kinds of granite cannot be s dressed by the chisel without present ing what masons call stunned appear

 ance. This is entirely avoided by using the jet. The inside of cast-iron hollow , ware can be better cleaned anu prepared for timing by the sand-jet than by any

 other way and the suggestion has beer made that the Egyptians smoothed ant carved their blocks of porphyry ani

 sunk their hieroglyphics by means O , the sand which lay around them in such

 abundance