given time, the foot-pounds of work are readily calculated.

Electric Testing Apparatus.

On the ground floor of Building No. 10, two rooms are occupied as
laboratories for investigating the electrical equipment used in mining
operations. The purpose of these investigations is to ascertain the
conditions under which electricity of various voltages may be used with
safety--in mine haulage, hoisting, pumping, or lighting--in the presence
of dangerous mixtures of explosive gases or of dust. It is also proposed
to test various kinds of insulation and insulators in this laboratory,
and to determine the durability of such insulation in the presence of
such corrosive gases and water as are found in mines.

A water-proof wooden tank, measuring 15 by 5 by 5 ft., is installed, in
which insulation and insulating materials are tested under either pure
or polluted water. Various electric lighting devices and equipment can
be connected from a switch-board in Building No. 17 with Gas-and-Dust
Gallery No. 2, for testing the effect of such lighting apparatus in the
presence of explosive mixtures of gas and dust, as set forth on page
220.

In the electrical laboratory, Building No. 10, is a booster set
developing 60 kw., and an appropriate switch-board for taking direct
current at 220 volts from the turbo-generator and converting it into
current varying from 0 to 750 volts. There are also transformers for
developing 60-cycle, alternating current at voltages of from 110 to
2,200. The switch-board is designed to handle these various voltages and
to communicate them to the apparatus under test in Building No. 10,
Gallery No. 2, or elsewhere.