Tests are in progress of insulating materials for use in mines, and of
electric fuses, lights, etc., in Gallery No. 2 (Fig. 3, Plate X), and in
the lamp-testing box (Fig. 2, Plate XI). It is proposed, at the earliest
possible date, to make comparative tests of the safety of various mine
locomotives and mine-hoisting equipment through the medium of this
laboratory, and it is believed that the results will furnish valuable
information as a guide to the safety, reliability, and durability of
these appliances when electrically operated.

_Electric Lamp and Fuse Testing Box._--An apparatus for testing safety
lamps and electric lights and fuses, consists of ¼-in. iron plates,
bolted together with 1½ in. angle-irons to form a box with inside
dimensions of 18 by 18 by 24 in. The box is placed on a stand at such a
height that the observation windows are on a level with the observer’s
eye (Fig. 2, Plate XI), and it is connected, by a gas-pipe, with a
supply of natural gas which can be measured by a gas-holder or meter
alongside the box.

By the use of this apparatus the effect of explosive gas on flames, of
electric sparks on explosive mixtures of gas and air, and of breaking
electric lamps in an explosive mixture of gas and air, may be studied.
The safety lamps are introduced into the box from beneath, through a
hole 6 in. square, covered with a hinged iron lid, admission to which is
had through a flexible rubber sleeve, 20 in. long.

The behavior of the standard safety lamp and of the safety lamps
undergoing test may be compared in this box as to height of flame for
different percentages of methane in the air, the effect of such flames
in igniting gas, etc.