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attached. Another sliding plate fits closely over the first and is arranged to close the open ends of the standards when the lamp is used as a working lamp.

The A.-H.-G. lamp is designed to burn ordinary sperm, cottonseed or lard oil. The conical glass chimney has the advantage of throwing the light upward on the roof. The illuminating power of the lamp is 0.79 cp. When tested, this lamp has withstood a current velocity of 6000 ft. per min., which is one of the features that strongly recommended its use in this country.

ALCOHOL
VESSEL

a

Stokes Alcohol Lamp.-This lamp is designed by an English mine inspector, whose purpose was to supply an alcohol flame in an oil burning lamp, the oil flame to be used when the miner was working at the face, and. the alcohol flame to be used for testing for gas. The lamp is an AshworthHepplewhite-Gray lamp having small vessel for holding the alcohol when the lamp is to be used for testing for gas. As shown in the illustration, Fig. 56, this alcohol vessel is screwed into the bottom of the regular oil vessel of the lamp, its long slim wick tube passing up through a hollow tube fixed in the oil vessel of the lamp. In no other respect does the lamp differ from an A.-H.-G. lamp. When the Stokes, lamp is to be used for testing for gas, the alcohol vessel is screwed in place beneath the oil vessel. The oil flame is drawn down and the lamp tilted slightly to ignite the wick of the alcohol lamp, after which the oil flame is extinguished. The lamp is then ready for testing for gas.

OIL VESSEL with ALCOHOL VESSEL inserted from below FIG. 56.

The Clowes Hydrogen Lamp.-This lamp is also a modified. Ashworth-Hepplewhite-Gray lamp. Like the Stokes lamp, it is provided with an oil vessel and burner and a second burner

to which hydrogen gas is supplied from the strong brass

cylinder shown in the illustration, Fig. 57, and which can be attached to or detached from the lamp, as desired. There are but few of this type of lamp in the country where it has seldom been used, as it is heavy and cumbersome. The hydrogen flame, though extremely sensitive to gas, is easily extinguished when testing and the use of the lamp for that purpose requires extreme care and caution. A small scale with crossbars is at

FIG. 58.

tached to the

[graphic]

oil ves- FIG. 57.-Oil Vessel and Hydrogen sel for Cylinder Removed from Lamp. the purpose of observing and estimating more accurately the height of the flame in testing.

Hydrogen gas is compressed to 120 atmospheres or a pressure of 1800 lb. per sq. in. at sea level. This furnishes an ample supply for making a large number of tests in the mine. The gas cylinder is attached to the side of the oil vessel by a screw joint or union. A valve controls the flow of gas into the lamp when it is desired to make a test in the mine. The oil flame is then drawn down and extinguished after the hydrogen has been turned on and ignited in the lamp.

The Wolf Lamp.-The original Wolf lamp shown in the illustration, Fig. 58, is a German product that was widely introduced into this country and

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became very popular as a working lamp. At the present time, there are a number of lamps of this type in use and manufactured in this country, among which may be mentioned the Koehler, the American deputy, the Hughes acetylene lamp, and many others. All of these, like the Wolf lamp, are designed to burn a volatile oil contained in a strong oil vessel of pressed steel, in which absorbent cotton is placed to retain the oil and minimize the danger of leaking should the lamp be overturned.

The volatile oil flame is particularly sensitive to gas, which enables this lamp to show gas when less than 1 per cent. is present in the mine air. A volatile oil, however, cannot be recommended for the purpose of testing for gas, owing to the fuel cap that is often mistaken for a gas cap when no gas is present. Owing to the ease with which a volatile oil flame is extinguished in the mine, all such lamps are provided with igniters. The original Wolf lamp is claimed to have an illuminating power of 1.45 cp., while the average of this type of lamp will but slightly exceed a single candlepower.

On the two pages preceding will be found most of the important types of mine safety lamps grouped in a historical setting that cannot fail to be of interest in connection with the subject. These appear as Figs. 59 and 60.

PERMISSIBLE MINE SAFETY LAMPS

In "Schedule 7, issued by the Federal Bureau of Mines, the engineers of the bureau have defined what is to be understood as a "permissible" miners' safety lamp in the following words:

Definition. The Bureau of Mines considers a miners' safety lamp to be permissible for use in gaseous mines if the details of the construction of the lamp are the same as those of the type of lamp that has passed the tests made by the bureau and hereinafter described.

Conditions of Testing.-The conditions under which the Bureau of Mines will examine, inspect, and conduct tests on miners' safety lamps are as follows:

1. The examination, inspection and tests will be made at the experiment station of the Bureau of Mines, at Pittsburgh, Pa.

2. Applications for inspection, examination and test shall be made to the Director, Bureau of Mines, Washington, D. C., and shall be accompanied by a complete description of the lamp and a set of drawings showing all the details of the lamp's construction.

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