1042 LAWS OF MARYLAND. [CH. 437

in certain proportions of the mixture, 5y% to 14^ per
cent., the mixture will explode in the presence of a flame or
hot spark.

^(1) "Mine" includes the shafts, slopes, drifts or in-
clined planes connected with the excavations penetrating
coal stratum or strata, which excavations are ventilated
by one general air current, and all appliances and equip-
ment for hoisting and extracting coal; and shall embrace
any and all parts of the mining property and plant on the
surface or underground, which contributes directly or
indirectly to the mining or handling of coal; and which is
connected by one general system of mine railroads, over
which coal may be delivered to one or more points outside
such mine. The word also includes a portion of a mine or
opening whether or not such mine or opening employs a
system of railroads, when the sense so requires. Any Mine
Inspector or the Director of the Maryland Bureau of Mines
shall have the right to enter and inspect all mines for the
purpose of determining the conditions of safety in any
such mine. In case a mine inspector or the Director shall
find any such mine to be unsafe, or to be operated in any
unsafe manner, he shall order such unsafe conditions to
be forthwith corrected, and in default of the owner or
operator doing so, shall order such mine or mines closed
until the unsafe conditions are corrected.

(m) A non-gassy mine is one in which methane gas has
not been detected by an approved or permissible flame
safety lamp or detector or device or by air analysis in an
amount of 0. 25 percent or more.

(n) "Operator" means any firm, corporation, associa-
tion or individual operating any coal mine or part thereof,
whether as an owner, lessee or otherwise, and also includes
the representative of such operator.

(o) "Panel" means a unit area in a system of mining
by which the mine is divided into large rectangles or
panels isolated or surrounded by solid pillars of coal into
which pairs of entries are driven for the development of
rooms and the extraction of pillars.

(p) "Permissible, " Unless the context requires a differ-
ent sense, means the admission of a device, plan, formula,
method, machine or course of action by the United States
Bureau of Mines to a list, after actual test thereof.

(q) Potential and Voltage shall be taken as synony-
mous, to mean electric pressure as determined by the
voltmeter.