staken one. There are, of course, some quarries which
formerly used channeling machines without this system, but which now
do a large part of the work by blasting. Instances, however, are rare
where the system has replaced the channeler. The two go side by side,
and an intelligent use of the new system in most quarries requires a
channeling machine. There are those who may tell of stone that has
been destroyed by a blast on the new system, but investigation usually
shows that either the work was done by an inexperienced operator, or
an effort was made to do too much.

A most interesting illustration of the value of this system, side by
side with the channeler, is shown in the northern Ohio sandstone
quarries. A great many channeling machines are in use there, working
around the new form of holes, and when used together in an intelligent
and careful manner, the stone is quarried more cheaply than by any
other process that has yet been devised.

To a limited extent the system has been used in slate. The difficulty
is that most of the slate quarries are in solid ledges, where no free
faces or beds exist; but it has been used with success in a slate
quarry at Cherryville, Pa., since 1888. Among notable blasts made by
this system are the following: At the mica schist quarries, at
Conshohocken, Pa., a hole 11/2 in. in diameter was drilled in a block
which was 27 ft. long, 15 ft. wide and 6 ft. thick. The blast broke
the stone across the "rift," only 8 oz. of black powder being used. At
the Portland, Conn., quarries a single blast was fired by electricity,
15 holes being drilled with 2 lb. of coarse No. C powder in each hole,
and a rock was removed 110 ft. long, 20 ft. wide and 11 ft. thick,
containing 24,200 cu. ft., or about 2,400 tons, the fracture being
perfectly straight. This large mass of stone was moved out about 2 in.
without injury to itself or the adjoining rock.

Another blast at Portland removed 3,300 tons a distance of 4 in.
Seventeen holes were drilled, using 2 lb. of powder in each hole, the
size of the block being 150 x 20 x 11 ft. In a Lisbon, O., quarry a
block of sandstone 200 ft. long, 28 ft. wide and 15 ft. thick was
moved about 1/2 in. by a blast. This block was also afterward cut up by
this system in blocks 6 ft. square. A sandstone bowlder 70 ft. long,
average width 50 ft., average thickness 13 ft., was embedded in the
ground to a depth of about 7 ft. A single hole 8 ft. deep was charged
with 20 oz.