I9I3-] 



STEVENSON— FORMATION OF COAL BEDS. 



61 



Upper Freeport coal bed 



Interval 



Lower Freeport coal bed .... 



Interval 



Upper Kittanning coal bed. 



Interval 



Middle Kittanning coal bed 



Interval 



Lower Kittanning coal bed. 



Interval 



Vanport limestone 



the same in both, while the intervening intervals show notable varia- 

 tion. If one should group the sections given in Piatt's report he 

 would find that while the two coal beds preserve an approximate 

 parallelism, the relations of the intervening beds would be indicated 

 by lines describing very irregular waves. This portion of the Alle- 

 gheny formation shows the same approximate regularity and the 

 associated irregularity in other parts of the region. 



The instance recorded by Jukes^^ has always been regarded as 

 exceptionally perplexing. The "Roofs coal" of the Thick bed at 

 Dudley rests on the bench below or is separated from it by, at most. 

 2 or 3 feet of clay ; but in going toward Bilston, one finds the 

 interval increasing, o, 10, 37, 55, 128, 118 and at length, 204 feet 

 near Bilston — ^these changes taking place within a mile and a half. 

 Near Dudley one finds the Brooch coal at 95 feet above the " Roofs 

 coal," known there as the " Flying Reed," and 108 feet above the 

 Thick. But where the "Flying Reed" is 115 feet above the Thick 

 it is only 30 feet below the Brooch ; so that while the interval 

 between Thick and Brooch has increased from 108 to 147 feet, that 

 between Thick and Flying Reed intervening, has increased from o 

 to 115 feet. 



The condition is not confined to the Carboniferous. Lipoid^'' 

 found splitting of coal beds by no means unusual in the Triassic. 

 At one locality, four coal beds were seen. The first and third con- 

 verge in a westerly direction, the interval decreasing from y2 to 18 



^'J. B. Jukes, "South Staffordshire Coal Field," pp. 36-40. 

 ^ M. V. Lipoid, " Das Kohlengebiet in der nordostlichen Alpen," Jahrb. 

 d. k. k. Geol. Reichsanst., Band 15, 1865, pp. 85, 99-101, 109. 



