Document MG6gn20zbmKrEdRNpJ2Q7y0gj

E. I. 3465 6. The average cost of rock-dusting in 27 mines where the practice is considered good amounts to $0.0089 per ton of coal mined, or $0.0229 per linear foot of entry. 7. During the past 9 years rock dust is credited with having stopped or limited explosions in P.6 of 60 partly rock-dusted mines and thereby unquestionably saved the lives of several hundred persons. Although the Bureau of Mines has advocated the use of rock dust as a preventive of widespread explosions since its establishment in 1910, comparatively few mines in the United States today are adequately rockdusted. Of the country*s approximately 6,000 bituminous- and lignitic-coal mines, probably fewer than 100 are adequately rock-dusted. This situation exists because State laws requiring protection of lifo against explosions are inadequate and the coal operator is inclined to take chances in the hope that he will not have the misfortune to suffer an explosion in his mine. The cost of rock-dusting is by no means prohibitive when the value of the protection it affords is taken into consideration, and unquestionably rock-dusting of coal mines of the United States should be more universal than it is at present. A OKNOWLEDGMEKT The author expresses his appreciation to the various coal-mining companies for data furnished concerning cost of rode-dusting; also to engineers of the Bureau of Mines for data furnished, and especially to. W. J. Fene and C. W. Owings for assistance in the preparation of this paper. 7239 22 -