STEVENSON— INTERRELATIONS OF FOSSIL FUELS. 31 



shale associated with the coal ; but scales along with teeth and plant 

 impressions were seen at times in the upper part of the coal itself. 

 Rogers saw nothing answering to the Stigmaria-c[a.y of the Car- 

 boniferous. These descriptions by Rogers make clear that a faux- 

 toit is the ordinary feature ; while the presence of animal remains in 

 the coal indicates existence of pools on the swamp surface. Under- 

 clays are in this field, but they do not hold Stigmaria, for Lepido- 

 dendron and Sigillaria had become extinct. 



Lyell visited this field in 1845. He was much impressed by the 

 fact, already noted by Rogers, that stems are found so often erect 

 and compressed vertically ; he could think of no reason to doubt that 

 the greater number of such plants, in beds above and between coal 

 seams, and which he saw at localities miles apart, had grown where 

 they are now enclosed in sand or mud. The great coal seam rests at 

 times directly on the granite, but at others is separated from it by 

 an inch or two of shale. He was inclined to think that the absence 

 of deposits between the coal and the granite may be due to disturb- 

 ances, which were considerable, as shown by the extensive faults. 



Mining operations ceased at nearly all localities about 50 years 

 ago and the old mines, abandoned, soon became inaccessible. A 

 long interval passed before new studies were made and few" of 

 these dealt with details respecting the coals. Fontaine's detailed 

 stratigraphical work was done near Clover Hill in the southeastern 

 part of the field, where some work was going on at the time of his 

 examination. There he found thick deposits between the coal and 

 granite and assigned to them a thickness of 100 to 600 feet. Clif- 

 ford stated that in outlying districts of the Richmond basin there 

 is only one coal seam, usually of great thickness and separated from 

 the granite by a thin bed of shale, often not more than a few inches. 

 This refers to the northern part of the field. It should be noted 

 here that the earlier observers regarded the benches of coal as 

 separate seams. 



**W. M. Fontaine, "The Older Mesozoic Flora of Virginia," U. S. Geol. 

 Survey, Mon. VI., 1883; W. Clifford, "Richmond Coal Field, Virginia," 

 Trans. Manch. Geol. Soc, Vol. XIX., 1888, p. 320; I. C. Russell, "The Newark 

 System," U. S. G. S. Bull. 85, 1892, pp. 38-40, 63; N. S. Shaler and J. B. 

 Woodworth, " Geology of the Richmond Basin, Virginia," 19th Ann. Rep. 

 U. S. G. S., Part II., 1899, pp. 423-426, 429, 483. 



