June, 1841.] 41 



by external characters. These in the Welsh coal are, 1st. A struc- 

 ture often lamellated, and tending to separate on the surfaces of 

 deposition, owing to the quantity of carbonaceous clod which occu- 

 pies the dull seams between the bright plies of coal. 



2d. The abundance and width of the reeds constituting the char- 

 coal deposits. 



3d. The shining and polished surfaces occasionally presenting 

 themselves to view at some of the natural partings. 



4th. The purplish tints of metallic oxide often observable on the 

 surfaces of fracture. 



5th. The general colour is deep black, and either dull or shining 

 according as the ply which is examined belongs to the coal proper, 

 or to the carbonaceous clod partings of the seams. 



The next circumstance worthy of attention in tracing the relation 

 of coals, is their specific gravity; and this in the Welsh anthracite 

 is from 1.336 to 1.372, not greater than that of many bituminous 

 coals. 



The next circumstance worthy of attention is the quantity of 

 volatile matter, and this by the mean of two trials is 9.18 per cent.; 

 that on the anthracite containing most clod is 10.7, and that of the 

 more compact variety is 7.66 per cent. 



Mr. Mushet makes it from 6.66 to 7.80 in the coals of the same 

 locality. Mr. Frazer analyzed a sample of the same coal, and 

 found 7.60 of volatile matter, 86.6 of carbon, and 5.08 of ashes. 



The quantity of earthy matter in the Iniscedwyn anthracite, 

 according to the mean of 3 analyses of Mr. Mushet, is 3.578 per 

 cent. Adopting this for the proportion in the sample which yielded 

 10.7 per cent, of volatile matter, we have the solid carbon = 85.722 

 per cent, and in the other 88.762. 



Among the Pennsylvania anthracite, that which according to the 

 observations of Prof. Johnson approximates most nearly to the 

 Inyscedwyn coal, is the coal of Lyken's valley, situated in the 

 northwestern fork of the southern coal field. This coal has all the 

 exterior characters of the Welsh anthracite ; containing in many 

 samples a large portion of carbonaceous clod, with well marked 



7 



