Transactions of the American Society of Civil Engineers, vol. LXX, Dec. 1910 | Page 9

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 approximately vary.
Such noxious gases as may be produced by the discharge of the
explosive are diluted by a much larger volume of air, and are
practically harmless, as proven by actual analysis of samples taken at
the face immediately after a discharge.
TABLE 1.
--------+---------+-------------------------- | | Permissible Explosives. |
Black |-------------+------------ | powder. | Maximum. | Minimum.
--------+---------+-------------+------------ CO{2} | 22.8 | 14.50 | 21.4 CO
| 10.3 | 27.74 | 1.3 N | 10.3 | 45.09 | 74.4
--------+---------+-------------+------------
In addition to investigations as to explosives for use in coal mining, the
Explosives Section of the Geological Survey analyzes and tests all such
materials, fuses, caps, etc., purchased by the Isthmian Canal
Commission, as well as many other kinds used by the Government. It is
thus acquiring a large fund of useful information, which will be
published from time to time, relative to the kinds of explosives and the
manner of using them best suited to any blasting operations, either
above or under water, in hard rock, earth, or coal. There has been
issued from the press, recently, a primer of explosives,[7] by Mr.
Clarence Hall, the engineer in charge of these tests, and Professor C. E.
Munroe, Consulting Explosives Chemist, which contains a large
amount of valuable fundamental information, so simply expressed as to
be easily understandable by coal miners, and yet sufficiently detailed to
be a valuable guide to all persons who have to handle or use
explosives.

In the first chapters are described the various combustible substances,
and the chemical reactions leading to their explosibility. The low and
high explosives are differentiated, and the sensitiveness of fulminate of
mercury and other detonators is clearly pointed out. The various
explosives, such as gunpowder, black blasting powder, potassium
chlorate powders, nitro-glycerine powders, etc., are described, and
their peculiarities and suitability for different purposes are set forth.
The character and method of using the different explosives, both in
opening up work and in enclosed work in coal mines, follow, with
information as to the proper method of handling, transporting, storing,
and thawing the same. Then follow chapters on squibs, fuses, and
detonators; on methods of shooting coal off the solid; location of
bore-holes; undercutting; and the relative advantages of small and
large charges, with descriptions of proper methods of loading and
firing the same. The subjects of explosives for blasting in rock, firing
machines, blasting machines, and tests thereof, conclude the report.
The work of the chemical laboratory in which explosives are analyzed,
and in which mine gases and the gases produced by combustion of
explosives and explosions of coal-gas or coal dust are studied, has
been of the most fundamental and important character. The
Government is procuring a confidential record of the chemical
composition and mode of manufacture of all explosives, fuses, etc.,
which are on the market. This information cannot but add greatly to the
knowledge as to the chemistry of explosives for use in mines, and will
furnish the basis on which remedial measures may be devised.
A bulletin (shortly to go to press) which gives the details of the physical
tests of the permissible explosives thus far tested, will set forth
elaborately the character of the testing apparatus, and the method of
use and of computing results.[8]
This bulletin contains a chapter, by Mr. Rutledge, setting forth in detail
the results of his observations as to the best methods of using
permissible explosives in getting coal from various mines in which they
are used. This information will be most valuable in guiding mining
engineers who desire to adopt the use of permissible explosives, as to

the best methods of handling them.
Electricity in Mines.--In connection with the use of electricity in mines,
an informal series of tests has been made on all enclosed electric fuses,
as to whether or not they will ignite an explosive mixture of air and gas
when blown out. The results of this work, which is under the direction
of Mr. H. H. Clark, Electrical Engineer for Mines, have been furnished
the manufacturers for