ectric power alternating current may be used to convert
alternating current to direct current, and to operate motors
permanently installed above ground and in underground substations,
or buildings especially prepared for them, in a manner subject to
the approval of the chief and district mine inspectors, but no wires
carrying alternating current shall be used underground except same
be carried in an entry or passageway where persons and animals are
not permitted to travel.

[=Relating to higher voltage mines hereafter equipped.=] At each
mine equipped with electric power after the passage and approval of
this act, when the current used to operate haulage locomotives,
pumps and other machinery not located in or about the working places
of the mine, is of a pressure or potential in excess of three
hundred and twenty-five volts, direct current, the entry or passage
way where such wires are carried shall not be designated or
permitted to be used as the principal traveling way, and when
designated or used as the escapement way, the wires shall be
protected so that persons required to travel near same in
emergencies will not inadvertently come in contact therewith. No
pressure in excess of six hundred and fifty volts at the switchboard
shall be used underground.

[=Relating to higher voltage, mines heretofore equipped.=] At each
mine equipped with electric power prior to the passage and approval
of this act, where the pressure or potential is in excess of three
hundred and twenty-five volts, direct current, or where alternating
current is used, and the conditions surrounding the use of same are
such, in the opinion of the chief inspector of mines, that the
provisions of the preceding section do not provide the required
protection from shock to persons employed therein, such additional
safeguards shall be employed as may be required by the chief
inspector of mines, and the district inspector of mines, jointly.
(See. 911, 947; Penalty, Sec. 976.)

Sec. 949. [=Relating to construction of new mines.=] Any person,
firm or corporation beginning the opening of a mine, whether such
person, firm or corporation be the owner, lessee or agent of the
property upon which such mine is located, or not, shall observe the
following in the construction of such mine: If the opening be a
slope or vertical shaft, no explosive used therein shall be fired by
means of a squib or fuse after the same is extended more than
twenty-five feet fr