GEOLOGY OF THE MESOZOIC AEEAS. 9 



main bed. The section of the coal beds at Clover Hill is as follows, begin- 

 ning 1 with the highest coal seam: 



° Thickness. 



15. Coal seam, local (?), 18 inches to . 4 feet. 



14. Interval, sandstone and shale 14 feet. 



13. Coal seam, local 12 inches. 



12. Interval, sandstone and shale 12 feet. 



11. Coal seam, local 14 inches. 



10. Interval, sandstone and shale 25 feet. 



9. Coal seam, local 18 inches. 



8. Interval, sandstone and shale 40 feet. 



7. Upper bench of main coal 5 feet. 



6. Interval, shale, varying in thickness 5 feet +. 



5. Main coal, lower bench 15 to 26 feet. 



4. Interval, sandstone and shale 40 feet. 



3. Lower persistent coal bed 4 feet 9 inches. 



2. Interval, sandstones and shales, about 250 feet. 



1. Gneissic floor. 



The coal seam No. 15 may be a persistent bed. In that part of the 

 field that lies north of James River there is a coal seam at nearly the same 

 height above the main or big bed, and it is the bed that at Carbon Hill is 

 partially coked by an overlying sheet of trap. This bed may exist at other 

 localities and be overlooked, owing to its insignificance as a source of fuel. 

 Its great variation in thickness at Clover Hill is due to the large amount of 

 crushing that it has been subjected to. The thicker portions are caused by 

 the concentration of the coal in them, it having been squeezed out of the 

 thinner parts. This same action has, no doubt, caused the variation in the 

 thickness of the lower bench in the main seam, viz., 15 to 26 feet. This coal 

 bed No. 15 has a shale roof that is rich in plants,, some of which are not 

 found at any other horizon. 



With the possible exception of this bed, the small seams occurring above 

 the main seam at Clover Hill appear to be local. 



Above No. 15 of this section there is at Clover Hill a considerable 

 thickness of barren strata; perhaps 500 feet in all. Among these we find 

 sandstones composed of granitic matter only partly sorted. 



This brief account of the several Mesozoic areas may perhaps suffice to 

 render intelligible the occurrence of the different species of plants. 



