CLAYS, SHALES, AND SLATES. 



359 



The limey shales are almost exclusively shales which occur inter- 

 bedded, in comparatively thin layers, with limestones. Occasionally 

 a limey shale will owe its content of lime almost entirely to the fossil 

 shells it contains, the remainder of the shale being practically free from 

 carbonates. For both of the above reasons limey shales are apt to 

 be a source of trouble in the practical working of a plant and require 

 considerable care in quarry management to insure that the raw mate- 

 rials are anywhere near uniform in composition from day to day. 



Fig. 70 shows a shale deposit which consists of three horizontal 



TABLE 163. 

 ANALYSES OF LIMEY SHALES USED IN AMERICAN CEMENT- PLA NTS. 



1 Chicago P. C. Co., Oglesby, 111. Manufacturer's circular. 



2 Marquette Cement Co., Oglesby, 111. 25th Ann. Rep. U. S. Geol. Survey, pt. 6, p. 544. 



3 German-American P. C. Works, La Salle, 111. W. E. Trussing, analyst. 



4. lola P. C. Co., lola, Kansas. 



5. " 



6. Kansas P. C. Co., lola, Kansas. 



7. Alpena P. C. Co., Alpena, Mich. 

 8. 



10-18. Cayuga P. C. Co., Portland Point, N. Y. J. H. McGuire, analyst. 



19-22. Bronson P. C. Co., Bronson, Mich. W. H. Simmons, analyst. Vol. 8, Mich. Geol. Survey, 



p. 239. 

 23. Virginia P. C. Co., Craigsville, Va. "Cement Industry", p. 235. 



