STATISTICS AND INFORMATION 3239

"Gas" is used in the sense ordinarily employed by miners, to mean
"fire damp," and inflammable gas, chiefly composed of methane, some-
times accompanied by ethane (C₂H₆) in case of leakage of natural gas,
and explosives when mixed with air in certain proportions.

"Gaseous Mine" is one in which methane occurs in the mine atmosphere
in such quantities as may become dangerous. If the percentage of methane
in the main return exceeds one half of one per cent., or in any split, or
single return exceeds three-tenths of one per cent., the mine shall be con-
sidered a gaseous mine. Samples of the mine air shall be taken in dupli-
cate for testing purposes when the ventilating current in such mine and
mine conditions has been normal for at least twelve hours; and when a
sample is found to exceed the limits, duplicate samples shall be taken and
tested. If the first results are confirmed the mine shall be rated as gaseous.

Whenever the operator of a mine previously rated as gaseous shall im-
prove 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 electric connec-
tion 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 measur-
able by a voltmeter; or in case of a static charge, by an electrostatic
voltmeter.

"Methane" is a hydrocarbon gas (CH₄) frequently encountered 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 and/or fire clay stratum or strata,
which excavations are ventilated by one general air current, and all appli-
ances and equipment for hoisting and extracting coal and/or fire clay;
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/or fire clay; and which is connected by
one general system of mine railroads, over which coal and/or fire clay
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 sub-title shall not apply to any mine where less than five persons
are employed or engaged in work inside the mine, in any one period of
twenty-four hours; but any mine inspector shall, nevertheless, have the
right to enter and inspect all mines where from two to five persons are
employed or engaged in work for the purpose of determining the condi-
tions of safety in any such mine. In case a mine inspector 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