514 



CEMENTS, LIMES, AND PLASTERS. 



Smith, G. 0. The Pacific Coast coal-fields (Oregon, Washington, California). 



22d Ann. Rep. U. S. Geol. Survey, pt. 3, pp. 473-514. 1902. 

 Storrs, L. S. The Rocky Mountain coal-fields (Mont., Wyo., Colo., Utah, 



N. Mex.). 22d Ann. Rep. U. S. Geol. Survey, pt. 3, pp. 415-472. 1902. 

 Taff, J. A. The southwestern coal-field (Ind. Terr., Ark., Texas). 22d Ann. 



Rep. U. S. Geol. Survey, pt. 3, pp. 367-414. 1902. 

 White, D. The bituminous coal-field of Maryland. 22d Ann. Rep. U. S. 



Geol. Survey, pt. 3, pp. 201-214. 1902. 

 White, D., and Campbell, M. R. The bituminous coal-field of Pennsylvania. 



22d Ann. Rep. U. S. Geol. Survey, pt. 3, pp. 127-200. 1902. 

 White, J. C. Report on coal (of West Virginia). Vol. 2, Reports W. Va. 



Geol. Survey, pp. 81-725. 1903. 

 Woodworth, J. B. The Atlantic Coast Triassic coal-fields (Virginia, North 



Carolina). 22d Ann. Rep. U. S. Geol. Survey, pt. 3, pp. 25-54. 1902. 



Crushing. Coal may be bought in the shape of slack, lump or run- 

 of-mine. In the former case no preliminary crushing is required, for 

 the slack can be readily handled by ball mills, Griffin mills, or Williams 

 mills. When slack is bought, therefore, it is sent direct to the drier 

 and then to the fine-reducing mills. But when lump or run-of-mine 

 are purchased the coal can profitably be crushed before being sent 

 to the drier. 



FIG. 127. Coarse, toothed rolls for lump coal. (Allis-Chalmers Co.) 



In such cases the preliminary crushing; seems to be accomplished 

 most effectually by rolls. Figs. 127 and 128 show rolls adapted to this 

 kind of work, both being made by the Allis-Chalmers Co. The rolls 

 shown in Fig. 127 are very coarsely toothed, and are intended for use 

 on large lump or run-of-mine coal. They are 24"X30" in size, and 

 can conveniently reduce large lump to about 1- or 2-inch size. In Fig 



