grams), properly tamped.

“The above partial list includes all the permissible explosives that
have passed these tests prior to October 1, 1909. The announcement of
the passing of like tests by other explosives will be made public
immediately after the completion of the tests.

“With a view to the wise use of these explosives it may be well in
this connection to point out again certain differences between the
permissible explosives as a class and the black powders now so
generally used in coal mining, as follows:

“(_a_) With equal quantities of each, the flame of the black powder is
more than three times as long and has a duration three thousand to
more than four thousand times that of one of the permissible
explosives; the rate of explosion also is slower.

“(_b_) The permissible explosives are one and one-fourth to one and
three-fourths times as strong and are said, if properly used, to do
twice the work of black powder in bringing down coal; hence only half
the quantity need be used.

“(_c_) With 1 pound of a permissible explosive or 2 pounds of black
powder, the quantity of noxious gases given off from a shot averages
approximately the same, the quantity from the black powder being less
than from some of the permissible explosives and slightly greater than
from others. The time elapsing after firing before the miner returns
to the working face or fires another shot should not be less for
permissible explosives than for black powder.