584 
propelling slot. The latter may be 
placed with a greater or less slope, 
so as to actuate either one, two, 
three, or four teeth in the ratchet- 
wheel, and thus to move the screw 
more or less quickly. 
Figure 4 represents a machine 
intended for quarries of every de- 
scription, and Figure 6 is for sinking 
perpendicular shafts. 
With regard to the whole ma- 
chine, I may add that the carriage 
frame is provided with a propelling 
gear, to draw it to or from the face 
of the rock to be acted on at inter- 
vals required for blasting. The 
various moving gears are so ar- 
ranged that one man can draw and 
adjust the borers to work in the 
necessary direction in a few mo- 
ments ; and the machine may be 
worked either by compressed air, 
steam, or water, the first-named 
Notes and Correspondence. 
[July, 
being preferable in tunnels, as the 
escape air provides ventilation. In 
case steam is used for quarries and 
perpendicular shafts, it is provided 
with a condensing apparatus, and 
the condensed water is injected into 
the holes at every stroke, whereby 
these are kept clean. The machines 
are constructed with carriage frames 
of different forms, so as to adapt 
them for driving incline levels, 
adits, tunnels, perpendicular, slope- 
face, and flat surface of quarries, 
open cuttings, &c. ; and, according 
to recent trials, we have been en- 
abled to bore holes with them in 
hard rocks at the rate of two to four 
inches per minute. 
I trust this brief account may be 
deemed interesting to your readers. 
GEORGE Low. 
Newark-on-Trent, 
June, 1864. 
