The Centre reporter. [volume] (Centre Hall, Pa.) 1871-1940, 1871-11-03

A process Of grinding aud cutting
glass, aud Of piercing glass and other
hard substances, has been brought into
use. II consists in driving a jct of sand
with great velocity. by air or steam.
against the plate which Is to bc ground
or figured. Dwellers by the seashorc
know that the glass Of their windows, in
some places, loses It's polish through the
tie consant action OF drifting sands on
the pane and this same action, in n
concentrated form is now 10 serve the
arts, and put money into inventors pock-
cts. The mode Of operation. briefly
described. appears 10 be as follows " A
stream Of sand is driven hy fan into
large tabe ; 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. and in frem ten 20 fif-
teen seconds completely grinds as much
Of the sufface as corresponds with the
dimensions of the mouth Of the tube.
The plates of glass are moved by ma
chinerv. until the whole surface is dead
cned or ground and 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 pCrts of the surface Will
be dead Sometimes white glass, coat
ed on one side with thin film of rel
glass. is manufactured for ornamental
purposes any pattern can in like man
ner be cut through the red glass by the
sand-jet If plate of glass is covered
with lace, and then exposed 30 the jet,
the pattern of the lace viii appear. and
by properly regulating the blast delicate
fern leaves may be used as the covering,
aud the plate viii 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 ornamonted
by Jet 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, il driven by high
pressure steam. II is found in practice
that the rate of cutting is, in granite, L
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 artificer. II seems hard
iy credible, but JET of quartz sand,
impelled by steam-iet of 800 pounds
pressure. pierced an inch-and-a- half hole
through a slab Of corundum II inches
thick in % minutes. Between the hard
ness of corundum aud of diamond there
is but little difference. After this there
seems nothing remarkable in the fact
that plate Of glass covered with wire
gauze was pierced and converted into
glass-gau by the action of the Jet
Moreover, tits found that the jet can be
used for the dressing OF the surface of
stone. Some kinds OF granite cannot be
dressed by the chisel without present
ing what masons call stunned appear
ance. This in entirely avoided by using
the Jet. The inside Of cast.iron hollow
ware can be better cleaned and prepared
for timing by the sand-iet than by any
other way and the suggestion has been
made that the Egyptians smoothed and
carved their blocks OF porphyry and
sunk their hieroglyphics by means of
the sand which lay around them in such