from the introduction of drill-holes
for blasting by Caspar Weindel in Hungary, to the invention of
the first practicable steam percussion drill by J. J. Crouch of
Philadelphia, in 1849, all drilling was done by hand. Since Crouch's
time a host of mechanical drills to be actuated by all sorts of
power have come forward, and even yet the machine-drill has not
reached a stage of development where it can displace hand-work
under all conditions. Steam-power was never adapted to underground
work, and a serviceable drill for this purpose was not found until
compressed air for transmission was demonstrated by Dommeiller
on the Mt. Cenis tunnel in 1861.

The ideal requirements for a drill combine:--

a. Power transmission adapted to underground conditions.
b. Lightness.
c. Simplicity of construction.
d. Strength.
e. Rapidity and strength of blow.
f. Ease of erection.
g. Reliability.
h. Mechanical efficiency.
i. Low capital cost.

No drill invented yet fills all these requirements, and all are
a compromise on some point.

POWER TRANSMISSION; COMPRESSED AIR _vs_. ELECTRICITY.--The only
transmissions adapted to underground drill-work are compressed
air and electricity, and as yet an electric-driven drill has not
been produced which meets as many of the requirements of the metal
miner as do compressed-air drills. The latter, up to date, have
superiority in simplicity, lightness, ease of erection, reliability,
and strength over electric machines. Air has another advantage in
that it affords some assistance to ventilation, but it has the
disadvantage of remarkably low mechanical efficiency. The actual
work performed by the standard 3-3/4-inch air-drill probably does
not amount to over two or three horse-power against from fifteen to
eighteen horse-power delivered into the compressor, or mechanical
efficiency of less than 25%. As electrical power can be delivered to
the drill with much less loss than compressed air, the field for a
more economical drill on this line is wide enough to create eventually
the proper tool to apply it. The most satisfactory electric drill
produced has been the Temple drill, which is really an air-drill
driven by a small electrically-driven compressor placed near the
drill itself. But even this has considerable deficiencies in mining
work; the difficulties of setting up, especially for stoping work,
and the more cumbersome apparatus to remove before blasting are
serious drawbacks