RI 3304 Permissible Electric Mine Lamps - Supplement To Bulletin 332

"The last previous Bureau of Mines publication relative to details of permissible electric mine lamps is Bulletin 332, which describes 16 lamps approved prior to May 1930. Some of the lamps have become obsolete through the development of improved models which, with several new types, make it desirable to supplement the Bureau's published data relative to permissible electric mine lamps.In the following descriptions, lamps approved since May 1930 and prior to July 1, 1935, are placed in the three following groups: (1) Electric cap lamps, (2) electric hand lamps, and (3) lamps for miscellaneous applications,ELECTRIC CAP LAMPS APPROVED UNDER SCHEDULE 6B1. Edison model J lamp, approval no. 24. - The features that distinguish this lamp from earlier models of Edison electric cap lamps are:(a) The battery consists of two F-2 cells of square cross section and about 1-1/4 inches higher than M-14 cells in the model H lamp, making the battery narrower and higher than any of the earlier models of Edison cap lamps.(b) The cells are insulated from each other and the Monel-metal casing by enclosure in vulcanized-rubber baglike enclosures. Both cell terminals are insulated from the cell jar.(c) The battery is equipped with rubber-tube Bunsen-valve-type gas vents.(d) The battery casing is secured by a new-type magnetic lock.(e.) The battery and cover terminal clips have been redesigned to give a wiping contact."