298 Tl NNKLING 



man. Miners' safety lamps should be employed where there is 

 danger from gas. A great variety of lamps for mining and 

 tunneling purposes are on the market, for descriptions of 

 which the reader is referred to the catalogues of their manu- 

 facture rs. 



Lamps for general lighting are always of larger size than 

 lamps for individual use. A common form consists of a cyl- 

 inder ten or twelve inches in diameter, provided with a hook or 

 bail for suspension, and filled with benzine, gasolene, or other 

 similar oil. Connected with this cylinder is a pipe of con- 

 siderable length and small diameter through which the benzine 

 or gasolene vapor runs, and burns when lighted with a brilliant 

 flame. Lamps of this type burning gasolene were extensively 

 employed in building the Croton Aqueduct Tunnel. Various 

 patented forms of lamps for burning coal-oil products are on 

 the market, for descriptions of which the manufacturers' cata- 

 logues may be consulted. 



Coal-gas Lighting. A common method of lighting tunnel 

 workings is by piping coal-gas into the headings and drifts from 

 some nearby permanent gas plant, or from a special gas works 

 constructed especially for the work. Gas lighting has the great 

 advantage over lamps and lanterns of giving a light which is 

 more brilliant and steady. Its great objection is the danger of 

 explosion caused by leaks in the pipes, by breaks caused by 

 flying fragments of rock, and by the carelessness of workmen 

 who neglect to turn off completely the burners when they ex- 

 tinguish the lights. In nearly every tunnel where gas has been 

 used for lighting, the records of the work show the occurrence 

 of accidents which have sometimes been very serious, partic- 

 ularly when fire has been communicated to the tunnel tim- 

 bering. 



Acetylene Gas Lighting. The comparatively recent devel- 

 opment of acetylene gas manufactured from carbide of calcium 

 has given little opportunity for its use in tunnel lighting, and 

 the only instance of its use in the United States, so far as the 



