[=Emergency appliances.=] When the only means of egress is by vertical shaft, in which cages or elevators are used as a means of hoisting persons therein employed, and the power for operating same is derived from but one source, the owner, lessee or agent shall provide and keep on hand for use in the event of an accident to the hoisting apparatus or the power by which same is operated, a suitable windlass, capable of hoisting the persons from the mine. [=Competent engineers.=] The owner, lessee or agent of a mine worked by a shaft or slope, shall put in charge of an engine used for lowering into or hoisting out of such mine persons employed therein, only experienced, competent and sober engineers. (Sec. 916, 928; Penalty, Sec. 976.) Sec. 928. [=Metal speaking tube and safety appliances.=] The owner, lessee or agent of a mine operated by shaft, shall provide and maintain a metal tube suitable for conversation between persons, connecting the engine room with the top and bottom of such shaft; an approved safety catch, a sufficient cover, and rings or other adequate handholds for ten persons, on all cages used for lowering and hoisting persons: Such cages to be protected on each side by a boiler plate not less than one-fourth inch in thickness, and not less than three feet high, and shall provide an approved safety gate at the top of each shaft, an adequate brake to control the drum used for lowering or hoisting persons in shafts or slopes, and an indicator on all machines used for such purpose, to show the location of cages in shaft or slope. No cage having an unstable or self-dumping platform shall be used for the carriage of persons unless such platform is securely locked. (Sec. 916, 927; Penalty, Sec. 976.)