[Footnote 3: “The Explosibility of Coal Dust,” by George S. Rice and others. Bulletin No. * * *, U.S. Geological Survey.] [Footnote 4: “Notes on Explosives, Mine Gases and Dusts,” by Rollin Thomas Chamberlin. Bulletin No. 383, U.S. Geological Survey, 1909.] [Footnote 5: “Prevention of Mine Explosions,” by Victor Watteyne, Carl Meissner, and Arthur Desborough. Bulletin No. 369, U.S. Geological Survey.] [Footnote 6: With a view to obtaining a dust of uniform purity and inflammability.] [Footnote 7: “The Primer of Explosives,” by C. E. Munroe and Clarence Hall. Bulletin No. 423, U.S. Geological Survey, 1909.] [Footnote 8: “Tests of Permissible Explosives,” by Clarence Hall, W. O. Snelling, S. P. Howell, and J. J. Rutledge. Bulletin No. * * *, U.S. Geological Survey.] [Footnote 9: “Structural Materials Testing Laboratories,” by Richard L. Humphrey, Bulletin No. 329. U.S. Geological Survey, 1908; “Portland Cement Mortars and their Constituent Materials,” by Richard L. Humphrey and William Jordan, Jr., Bulletin No. 331, U.S. Geological Survey, 1908; “Strength of Concrete Beams,” by Richard L. Humphrey, Bulletin No. 344, U.S. Geological Survey, 1908.] [Footnote 10: “Fire Resistive Properties of Various Building Materials,” by Richard L. Humphrey, Bulletin No. 370, U.S. Geological Survey, 1909.] [Footnote 11: “Purchasing Coal Under Government Specifications,” by J. S. Burrows, Bulletin No. 378, U.S. Geological Survey, 1909.] [Footnote 12: “Experimental Work in the Chemical Laboratory,” by N. W. Lord, Bulletin No. 323, U.S. Geological Survey, 1907: “Operations of the Coal Testing Plant, St. Louis, Mo.” Professional Paper No. 48, U.S. Geological Survey, 1906.] [Footnote 13: Also Bulletins Nos. 290, 332, 334, 363, 366, 367, 373, 402, 403, and 412, U.S. Geological Survey.] [Footnote 14: “Tests of Coal for House Heating Boilers,” by D. T. Randall, Bulletin No. 336, U.S. Geological Survey, 1908.] [Footnote 15: “The Smokeless Combustion of Coal,” by D. T. Randall and H. W. Weeks, Bulletin No. 373, U.S. Geological Survey, 1909.] [Footnote 16: “The Flow of Heat through Furnace Walls,” by W. T. Ray and H. Kreisinger. Bulletin (in press), U.S. Geological Survey.] [Footnote 17: The assumption is made that a metal tube free from scale will remain almost as cool as the water; actual measurements with thermo-couples have indicated the correctness of this assumption in the majority of cases.] [Footnote 18: “Heat Transmission into Steam Boilers,” by W. T. Ray and H. Kreisinger, Bulletin (in press), U.S. Geological Survey.] [Footnote 19: “The Producer Gas Power Plant,” by R. H. Fernald, Bulletin No. 416, U.S. Geological Survey, 1909; also Professional Paper No. 48 and Bulletins Nos. 290, 316, 332, and 416.] [Footnote 20: A Taylor up-draft pressure producer, made by R. D. Wood and Company, Philadelphia, Pa.]