Abstract :
The classes of electrical equipment that have been approved by the Department of the Interior, through the Bureau of Mines, for use in mines, are steadily growing and the number of each type are as follows: Electric cap lamps, 5; electric hand lamp, 1; a-c. and d-c. shortwall coal-cutting machines, 20; portable electric drills, 4; single-shot firing devices, 2; storageb attery locomotives, 5. These are all described in Technical Paper 333.
