at the upper part from a telodynamic wire that passes through the channel
of the horizontal pulley, P. This latter is supported by a frame
consisting of three uprights, Q Q, strengthened by stays, R R, fixed to
the ground.

In order that the cylinder, A, may be given a vertical motion, cords, M
M, fixed to a piece, S, loose on the hub, D, wind round the drum of a
windlass, T, after passing over the pulleys, p p.

The rapid gyratory motion of the cylinder, along with the erosive action
of the metallic agglomerate, rapidly wears away the rock, and causes the
descent of the perforator. During this operation a core of marble forms
in the cylinder. This is detached by lateral pressure, and is capable of
being utilized. The tool descends at the rate of from 20 to 24 inches per
hour, or from 8 to 10 yards per day in ordinary lime rock.--_Le Genie
Civil_.

* * * * *




PORTABLE PROSPECTING DRILL.


[Illustration: PORTABLE PROSPECTING DRILL.]

The Aqueous Works and Diamond Rock-boring Company, Limited, of London,
show at the Inventions Exhibition, London, a light portable rock-boring
machine for prospecting for minerals, water, etc. It is capable of