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