1847.] LYELL ON THE COAL-FIELD OF EASTERN VIRGINIA. 265 



Section at the Midlothian Fit, half a mile south of Blackheath, on 

 the eastern outcro'p of the Coal. 



Feet. Inches, 



Sandstone and shale 570 



Slate with Calamites 1 6 



Sandstone and shale 43 10 



Sandstone with Calamites 8 



Sandstone and slaty shale 48 



Slate and long vegetable stems 2 6 



Sandstone 6 6 



Slate with Calamites, numerous 5 6 



Sandstone 14 



Black rock (carbonaceous ?) 13 



Slate 5 



Main coal 36 



Sandstone, not laminated 5 



Slate 4 



Coal 1 



Slate 3 



Sandstone or grit 7 



773 10 

 Granite, depth unknown. 



It will be seen that here, within a quarter of a mile of the Black- 

 heath pit, there are two seams of coal — one, the uppermost, more than 

 30 feet thick, and the other separated from it by 9 feet of intervening 

 shale and sandstone about one foot thick ; this lowest seam being 

 within four feet of the fundamental granite, and parted from it by 

 beds of grit and shale. Some deduction must be made from all the 

 estimated thicknesses of the beds as above stated, the inclinations of 

 the beds cut through by the vertical shaft being at an angle of 20°. 

 After making this deduction, however, the magnitude and persistency 

 of this seam, from 30 to 40 feet in thickness, consisting of as pure a 

 mass of rich bituminous coal as can perhaps be found in the world, 

 even in the old carboniferous formations, are truly remarkable, espe- 

 cially when we take into account its geological age. I was indeed not 

 a little surprised when I first arrived at Blackheath and descended a 

 shaft 800 feet deep, to find myself in a chamber more than 40 feet 

 high, caused by the removal of the coal. Timber props of great 

 strength are required to support the roof, and although the use of 

 wood is lavish here as everywhere in the United States, the props are 

 seen to bend under the incumbent weight. The great seam in some 

 places at Blackheath is seen actually to touch the fundamental granite, 

 or is parted from it only by an inch or two of shale. The unevenness 

 of the granite floor is extremely great, as represented in the annexed 

 drawing. Fig. 2 * ; and the manner in which, in these troubles as they 

 are called, the coal is squeezed out at one point and made to swell and 

 thicken at another, B, must be referred to movements of the rocks 



* For this and several other documents relating to this coal-field, and for nume- 

 rous organic remains, I am indebted to the kindness and exertions of my friend 

 Mr. A. F. D. Gifford, under whose superintendence 1 found the Blackheath mines. 

 I have also to acknowledge the liberaUty of Dr. Samuel H. Royal of Blackheath, 

 who presented me with fossil fish, and plants of great rarity and beauty. 



