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 their guidance in
perfecting safer fuses, a series of tests of which has been announced. A
series of tests as to the ability of the insulation of electric wiring
to withstand the attacks of acid mine waters is in progress, which will
lead, it is hoped, to the development of more permanent and cheaper
insulation for use in mine wiring. A series of competitive tests of
enclosed motors for use in mines has been announced, and is in progress,
the object being to determine whether or not sparking from such motors
will cause an explosion in the presence of inflammable gas.

In the grounds outside of Building No. 10 is a large steel gallery, much
shorter than Gallery No. 1, in fact, but 30 ft. in length, and much