force-pump.

_Blasting with High Explosives._--High explosives are fired either by
ordinary fuze and detonating cap or by electric fuze. Detonating caps
of ordinary strength contain 10 to 15 grains of fulminating mixture.
The cap is crimped tight on the end of the fuze, embedded in the
cartridge, and on being exploded by fire from the fuze detonates the
charge. The number of cartridges charged depends on the depth of hole,
the length of the line of least resistance, and the toughness and
other characteristics of the rock. Each cartridge should be solidly
tamped, and, to avoid waste spaces in the hole, which would reduce the
effect of the blast, it is customary to split the paper covering
lengthwise with a knife. This allows the dynamite to spread under the
pressure of the tamping bar. The cap is often placed in the cartridge
preceding the last one charged, but it is better to insert it last, in
a piece of cartridge called a "primer." Though the dynamites are not
exploded by sparks, they should nevertheless always be handled
carefully. It is not so essential to fill the hole completely and so
thoroughly to compact the tamping, as in charging black powder,
because of the greater rapidity and shattering force of the explosion
of dynamite; tamping, however, should never be omitted, as it
increases the efficiency of the blast. In exploding dynamite, strong
caps, containing say 15 grains of fulminating powder, produce the best
results. Weaker caps are not economical, as they do not produce
complete detonation of the dynamite. This is specially true if the
weather be cold. Dynamite then becomes less sensitive, and the
cartridges should be gently warmed before charging, to a temperature
of not more than 80 deg. F. Poisonous fumes are often produced by the
explosion of the nitroglycerin compounds. These are probably largely
due to incomplete detonation, by which part of the nitroglycerin is
vaporized or merely burned. This is most likely to occur when the
dynamite is chilled, or of poor quality, or when the cap is too weak.
There is generally but little inconvenience from the fumes, except in
confined underground workings, where ventilation is imperfect.

Like nitroglycerin, the common dynamites freeze at a temperature of
from 42 deg. to 46 deg. F. They are then comparatively safe, and so
far as possible should be transported in the frozen state. At very low