fuse, but there is no danger that they will ignite the gas, and the
difference in cost is, in some measure, offset by the greater certainty
of action and the fact that they produce a much more powerful explosion,
thus again permitting the use of still smaller quantities of the
explosive and, consequently, reducing the cost. These investigations are
still in progress.

Concerning the shattering of the coal: This is being remedied in some of
the permissible explosives by the introduction of dopes, moisture, or
other means of slowing down the disruptive effect, so as to produce the
heaving and breaking effect obtained with the slower-burning powders
instead of the shattering effect produced by dynamite. There is every
reason to believe that as the permissible explosives are perfected, and
as experience develops the proper methods of using them, this difficulty
will be overcome in large measure. This matter is also being
investigated by the Survey mining engineers and others, by the actual
use of such explosives in coal-mining operations.

Of the gases given off by explosives, those resulting from black powder
are accompanied by considerable odor and smoke, and, consequently, the
miners go back more slowly after the shots, allowing time for the gases
to be dissipated by the ventilation. With the permissible explosive, the
miner, seeing no smoke and observing little odor, is apt to be
incautious, and to think that he may run back immediately. As more is
learned of the use of these explosives, this source of danger, which is,
however, inconsiderable, will be diminished. Table 1 gives the
percentages of the gaseous products of combustions from equal weights of
black powder and two of the permissible explosives. Of the latter, one
represents the maximum amount of injurious gases, and the other the
minimum amount, between which limits the permissible explosives