Mr. F. Fobster's Observations on the South Welsh Coal Basin. 91 



are not materially altered in texture, shape, or bulk, and siill preserve 

 all tlie external characters of Coal. Stone Coal is hard and brittle, 

 breaking into sharp-edged fragments ; colour, greyish black ; lustre, 

 splendent and semi-metaUic ; fracture, imperfectly conchoidal ; cleav- 

 age, presenting large and highly-polished surfaces, generally perpen- 

 dicular to the strata ; gives, when struck, a ringing sound, so that a 

 number of small pieces when thrown from the shovel sound like broken 

 china. The specific gravity of this Coal is about 1*380. The consti- 

 tuent parts of an average specimen were 



Carbon, ,., 89 



Volatile Matter, 8 



Earthy Residuum, affording in combustion, whitish light Ashes, 3 



100 



There is a variety which I have not had an opportunity of examining, 

 that contains a much greater proportion of earthy matter. It is 

 not, I believe, of frequent occurrence. 



Although Iron Pyrites is seldom found in the Stone Coal 

 seams, yet many of them appear to contain Sulphur disseminated in 

 some form or other through the mass, which, though invisible to the 

 eye, affords abundant evidence of its existence in combustion, by its 

 suffocating smell, and the rapid decay of the fire-irons and other 

 utensils with which it comes in contact. Many seams of Stone Coal 

 are, however, free from any mixture of this pernicious ingredient. The 

 practical uses of Stone Coal, from the peculiar proportion of its com- 

 ponent parts, are very limited. It is difficult to ignite and slow in 

 combustion, but affords a strong and steady heat, emitting neither smoke 

 nor flame, except, indeed, a thin yellowish-blue or green flame, similar 

 to that given out by Coke in combustion. Considerable quantities are, 

 however, exported for drying Malt ; and, from its important property 

 of burning without smoke, it has been partially adopted in London by 

 brewers and distillers, and for the use of steam-engines, being first 

 mixed with different proportions of Newcastle Coal. 



Owing to the extensive range of the Stone Coal seams through this 

 Mineral Basin, in close connection with its rich and abundant beds of 



