The general experience is that shot firers are necessary to a successful use of permissible explosives, whether the shots are fired while the men are in the mine or after they have left it. DELAY IN RETURNING AFTER FIRING. The same precautions should be exercised when blasting with permissible explosives as with black blasting powder, especially if fuse is employed. One should not be in a hurry to return to the working face when there has been a misfire or a delayed shot. At least onehalf hour should be allowed to elapse before returning to the face after a misfire when fuse or squibs have been used and 5 minutes when electric firing has been used. PRECAUTIONS TO BE TAKEN WITH PERMISSIBLE EXPLOSIVES. Never take more than one day's supply of permissible explosives into the mine at one time. Never leave permissible explosives in the mine over night. Never use weak detonators. Never fire a charge until it has been completely and carefully tamped. Never put black blasting powder and permissible explosives together in the same drill hole. Never break the covering of a cartridge of a permissible explosive until ready to charge. Never expect permissible explosives to yield entirely satisfactory results when coal is blasted off the solid. Never expect the first blast with permissible explosives in a newly opened coal bed to be satisfactory. Several trials are often required before satisfactory results are obtained. Never forget that permissible explosives are different from dynamite and entirely unlike black blasting powder. Never use fuse to fire permissible explosives when it is possible to use electric firing. PUBLICATIONS ON MINE ACCIDENTS AND METHODS OF MINING. The following Bureau of Mines publications may be obtained free by applying to the Director, Bureau of Mines, Washington, D. C.: BULLETIN 10. The use of permissible explosives, by J. J. Rutledge and Clarence Hall. 1912. 34 pp., 5 pls., 4 figs. BULLETIN 17. A primer on explosives for coal miners, by C. E. Munroe and Clarence Hall. 61 pp., 10 pls., 12 figs. Reprint of United States Geological Survey Bulletin 423. BULLETIN 20. The explosibility of coal dust, by G. S. Rice, with chapters by J. C. W. Frazer, Axel Larsen, Frank Haas, and Carl Scholz. 204 pp., 14 pls., 28 figs. Reprint of United States Geological Survey Bulletin 425, |