all built of Portland stone. As the Portland quarries were carried to
great depths the thickness of bed increased, as it usually does in
quarries. With beds from 10 to 20 ft. deep, all of solid and valuable
brownstone, it became a matter of importance that some device should
be applied which would shear the stone from its bed without loss of
stock and without the necessity of making artificial beds at short
distances. A system was adopted and used successfully for a number of
years which comprised the drilling of deep holes from 10 to 12 in. in
diameter, and charging them with explosives placed in a canister of
peculiar shape. The drilling of this hole is so interesting as to
warrant a passing notice. The system was similar to that followed with
the old fashioned drop drill. The weight of the bit was the force
which struck the blow, and this bit was simply raised or lowered by a
crank turned by two men at the wheel. The bit resembled a broad ax in
shape, in that it was extremely broad, tapering to a sharp point, and
convex along the edge.

[Illustration: Fig. 1]

Fig. 1 illustrates in section one of the Portland drills, and a drill
hole with the canister containing the explosive in place. The canister
was made of two curved pieces of sheet tin with soldered edges, cloth
or paper being used at the ends. It was surrounded with sand or earth,
so that the effect of the blast was practically the same as though the
hole were drilled in the shape of the canister. In other words, the
old Portland system was to drill a large, round hole, put in a
canister, and then fill up a good part of the hole. Were it possible
to drill the hole in the shape of the canister, it would obviously
save a good deal of work which had to be undone. The Portland system
was, therefore, an extravagant one, but the results accomplished were