i6o 



C. W. TOMLINSON 



composition is brought out strikingly by the following analyses, 

 which are at least sufficient to show that the differences in color in 

 the Red Beds are caused by the same differences in chemical compo- 

 sition as those which cause corresponding differences in color in 

 slates. The analyses are plotted graphically in the diagram 

 (Fig. 2). 



The following analyses are taken from Dale: 1 



* K* is same slate as K, but finer grained. M =red slate near green spot. 

 R = green part of spot. 



Q = purple rim of spot. 



X T. N. Dale, "The Slate Belt of Eastern New York and Western Vermont," 

 Ann. Rept. U.S. Geol. Survey No. ig, 1899, Part 3, pp. 232, 246-53, 257, 264; and 

 "The Roofing Slates of the United States," U.S. Geol. Survey Bull. No. 275, 1905, 

 pp. 34-36. 



