688 LAWS OF MARYLAND. [CH. 307

If the first results are confirmed, the mine shall be rated as
gaseous.

Whenever the operator of a mine previously rated as gas-
eous shall improve the ventilation thereof until the percentage
of methane in the main return falls below one-half of one per
cent, and in each individual split falls below three-tenths of
one per cent, as shown by samples taken and duly analyzed,
and such condition has been maintained continuously for a
period of not less than thirty days, the district mine inspector
may by written certificate authorize the rating of such mine,
during maintenance of such condition, as a non-gaseous mine.

Grounding means the establishment of an effective elec-
tric connection between the object grounded and the earth,
whether the object grounded be a machine frame, a cable
armor or an electric system.

Live or Alive applies to any part of an electric system,
circuit, or apparatus or object in contact with or adjacent
thereto, charged with electricity or generating voltage to an
extent that the difference of potential between such system,
circuit, apparatus or object and the earth is measurable by
a voltmeter; or in ease of a static charge, by an electrostatic
voltmeter.

Methane is a hydrocarbon gas (CH₄) frequently encoun-
tered in coal mines; when it is diffused through air in certain
proportions of the mixture, 5 1/2 to 14 1/2 per cent., the mixture
will explode in the presence of a flame or hot spark.

Mine includes the shafts, slopes, drifts or inclined planes
connected with the excavations penetrating coal stratum or
strata, which excavations are ventilated by one general air
current, and all appliances and equipment 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 sys-
tem 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 when the sense so requires.

The provisions of this Act shall not apply to any mine
employing less than ten persons excepting that the provisions
of Section 54, Chapter 7, Title V, Mine Management and
Operation, requiring an annual report in such form as the
Bureau may prescribe, shall apply to all mines without regard
to the number of their employees.