During the summer, some experiments have been made with this explosive
agent. A quantity, costing $934.29, was brought to the works by Colonel
Schaffner, who exhibited the action of the material in various ways,
with a view of testing its power, and the comparative safety of
introducing it instead of powder. After repeated trials outside of the
works, during which about three-fifths of the material was consumed, it
was introduced into the tunnel at the West Shaft with the following
result: It was used for three days at the East heading of the West
Shaft; the advance made in the heading was for the time, 14-1/2
feet;--being an advance of 4.82 feet per day, and at the rate of 125.33
feet per month.
In these three days there were taken out of the enlargement
151.76 yards of stone. To remove this quantity
with powder would cost, on an average, per yard, $9 84
Actual cost with glycerine, 6 20
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Difference, $3 64
Multiplied by 151.76, gives. $552 40
In the same time there was removed of heading
60.15 yards.
To remove an equal amount by powder
costs, per yard, $16 25
Actual cost with glycerine, per yard, 6 05
------
Difference, $10 20
$10.20 multiplied by 60.15, gives 613 53
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$1,165 93
Cost of the glycerine used during the three days,
being 2/5 of $934.29, 350 36
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Saved, by using glycerine, in three days, $815 57
Which is a saving by the use of glycerine, per day,
of $276 85.4
and allowing three hundred successful working
days in the year, an annual saving of $81,557 40
The progress made at the West Shaft on the East heading the present
year, ending December 31, 1866, is 626 feet and 8 inches. This progress
was somewhat lessened by the influx of water in December. The monthly
advance has been 52 feet and 2 inches. The average of the eleven months
ending with November is 53 feet and 6 inches. Assuming the progress made
with glycerine during the three days of its use to be obtainable
throughout the year, the monthly progress, using that material, would be
120 feet and 10 inches, on a calculation of twenty-five days to a month,
which would give an annual advance of 1,450 feet.
Without vouching for results so favorable to the progress of the work,
it is impossible to overlook the importance of the experiment; and the
Committee are of opinion that this material, if it can be procured,
should be introduced into the tunnel and shafts, and a thorough
experiment made, in order to determine whether it can be used with an
advantage even approximating to that shown by the first trial.
Experience has proved that the rock at the Hoosac Mountain is of a
peculiar character: comparatively easy to drill, but extremely hard to
displace, and that its advantageous excavation requires a strong
explosive agent. The difference in the use of weak and strong powder is
at once observed, and the effect of simultaneous blasting, by the aid of
electricity, is proved by the increased progress of the work since it
has been used. It would seem evident, then, without the aid of
experiment, that an explosive agent, possessing eight times the power of
common powder, would be a valuable auxiliary to this undertaking; and
that if such an one could be obtained, and safely used, no time should
be lost in procuring a supply.
The use of nitro-glycerine in England is not uncommon; its components
are well known; and the Committee are informed that it might be
advantageously manufactured at any point where it is used.