until the ventilation has been restored, and his permission to enter
is given; if at a mine which generates fire-damp, he shall not order
them to return until the mine has been thoroughly examined by him,
or his assistant, and reported to be safe. (Sec. 922, 923, 924.)


[=Dangerous places fenced.=] He shall see that all dangerous places
are properly fenced off, and proper danger signal boards are hung on
such fencing that they may be plainly seen; he shall also travel all
air-ways, and examine all the accessible openings to old workings as
often as is necessary to insure their safety. (Sec. 925.)


[=Examination of working places.=] He shall examine each working
place, or have it examined by his assistant, at least once each
alternate day that persons are or should be at work therein and
oftener, when, in his judgment, the circumstances require. He shall
instruct pick miners and machine runners regarding the width of
working places. (Sec. 956.)


Sec. 953. [=When working place is unsafe.=] When a working place
becomes unsafe from any cause, he shall order the person or persons
working therein, to cease mining or loading, and not to remain in
such working place, except as may be necessary to make it safe,
until it is made safe. (Sec. 956.)


[=Supplying of props and timber.=] He shall see that the working
place of each miner is kept supplied with props of approximate