W. M. Fontaine—-Mesozoie Strata of Virginia. 35 
The lower series, from three hundred to five hundred feet 
thick, rests immediately on the granitoid gneiss, which forms 
the floor of the basin. It contains all the coal found in the 
field. The number of coal beds is variable, but the most 
important are usually two or three in number, all contained 
within the space of about one hundred feet, and the lowest 
lying near the floor. In placing this coal-bearing portion next 
rock to resemble granite. Subordinate beds of shale exist, 
This series shows less disturbance than the lower. The dip is 
_ that it is difficult to determine its depth, and determinations 
_ from shafts and borings cannot be relied upon absolutely. To 
