1064 LAWS OF MARYLAND. [CH. 437

Trolley and direct current and alternating current feed-
er wires shall be installed as follows:

1. On the opposite side of the entry from shelter holes and
clearance space, except where 6!/2 feet or more above the
rail or adequately guarded at shelter holes.

2. The hangers on curves shall be spaced so that the
trolley wire may become detached at any one hanger with-
out exposing the locomotive operator to a shock hazard.

3. Trolley wires and trolley-feeder wires shall be alined
properly and installed at least 6 inches outside the track-
gage line.

4. Provided with cut-out switches at intervals of not
more than 2, 000 feet and near the beginning of all branch
lines.

5. Kept taut and not permitted to touch the roof, rib,
or cross bars; particular care shall be taken where they
pass through door openings to preclude the possibility of
bare wires coming in contact with combustible material.

6. Trolley wires and trolley feeder wires shall be guarded
adequately where it is necessary for men to pass or work
'under them regularly, unless the wires are more than 6!/2
feet above the top of the rail. They shall also be guarded
adequately on both sides of doors.

7. Shall not extend beyond the last open crosscut and
shall be kept at least 150 feet from pillar workings.

8. Anchored securely and insulated properly at the ends.

9. Not in air known to contain 1. 0 per cent or more
methane or in air returning from pillar recovery work or
old workings where dangerous amounts of methane may
be liberated suddenly.

117. Grounding. Metal conduit and metallic coverings
and armor of cables shall be grounded effectively, and
shall be electrically continuous to afford a conductor path
for the ground circuit.

Metallic frames, casings, and other electric equipment
that can become "alive" through failure of insulation or
by contact with energized parts shall be grounded effec-
tively.

Casings of transformers shall be grounded effectively
unless protected by isolation (freedom from contact hazard
by position). Mining equipment mounted on rubber tires
or caterpillar treads, receiving power through a trailing