IS47.] 



LYELL ON THE COAL-FIELD OF EASTERN VIRGINIA. 



269 



" In this (Fig. 3.) the fibres (A) are larger in diameter, covered with 

 prominent dots or glands, each often having a dark spot in the centre. 

 The perforations in the tubes (B) are often filled up with circular 

 discs (as at C), which have a central dark spot (D), or are transparent 

 throughout (E) . The perforations of some of the tubes are so closely 

 placed and so much elongated transversely (F), that the tube resem- 

 bles the scalariform ducts of a fern. 



Blackheath Specimen {Creek Mines). 

 Fig. 4. 



" The fibres of this specimen, fig. 4. (A), are smaller and moreclosely 

 packed, covered with more numerous prominent dots or glands ; the 

 latter have almost uniformly a central spot (A'), are extremely minute, 

 very caducous, and are often star-shaped (A"), or of various outline. 

 The tubes are very rarely seen, and have many series of generally 

 transversely elongated perforations (B)." 



Next to the ferns, the most abundant vegetable remains in the coal- 

 measures under consideration are two species of Calamites and the 

 Eqiiisetum columnare, especially the former, and the bark of the 

 Calamites is usually converted into coal. It is therefore natural to 

 conjecture, that the thin layers resembling charcoal may have been 

 derived from Calamites, a plant of which the botanical structure is 

 still unknown. Dr. Hooker, in reply to this suggestion, tells me that 

 some fossil charcoal in the Museum of the Geological Society, from 

 the English coal formation, supposed to be derived from Calamites, 

 is very like that of the Virginia coal above described. 



The cities of New York and Philadelphia have for many years 

 supplied themselves with coal from the Blackheath mines, for the 

 manufacture of gas for lighting their streets and houses. The annual 

 quantity taken by Philadelphia alone has of late years amounted to 

 10,000 tons. It will appear from the annexed table of analyses of 

 specimens of coal, which Mr. P. H. Henry has had the kindness to 

 make for me, that the proportion of volatile ingredients — hydrogen, 

 nitrogen and oxygen — in this newer coal of the James River comes 

 exceedingly close to that found in the older coal of America, which it so 

 much resembles in aspect and structure. The specimen from Tuscaloosa 

 in Alabama was from the old coal formation described by me in the 

 Journal of this Society for 1846, vol. ii. page 2/8, in which are found 

 precisely the same plants as in the coal of the Appalachians, of Nova 

 Scotia, and of the north of England. The other three specimens, from 



VOL. III. PART I. U 



