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its degree of purity and the nature of the earths which enter into 
its composition. It has obtained various names, derived from cer- 
tain varieties of its appearance, nature, &c. Thus, from its pitch- 
like colour and fracture, it has been sometimes called coal; 
from the great degree of hardness which it sometimes possesses, 
stone coal ; from its being obtained from a mine or pit, coal ; 
and in London, for no better reason than its having been brought 
hither by sea, sea coal. 
There are certain varieties of pit coal, which obtain their par- 
ticular denominations from their mode of burning, or from their 
most obvious and predominant combinations. Hence we have 
blind or deaf coal ; such is the Welsh and Kilkenny coal, kindling 
slowly, and burning without flame or smoke to a stony flag. Open- 
burning coal, which does not cake, but burns with much flame and 
smoke, and is soon reduced to ashes. Close-burning coal, which 
kindles quickly, and melts and runs together like bitumen. Some 
coal is termed slaty coal, from its texture ; and when it also contains 
a larger proportion of bitumen, it is called slaty Cannel coal. Culm 
is a coal in small rough fragments, which does not melt or cake, but 
leaves behind it a slag of the same bulk with the coal employed, 
which yields a large portion of ashes, formed by argillaceous earth 
impregnated with iron. 
If the translation of Sir John Hill* be admitted, and his argu- 
ments in support of it undoubtedly appear to be forcible, fossil 
coal was known in the time of Theophrastus. The passage is, 
“Those fossil substances that are called coals (av6?«jifl!c), and are 
broken for use, are earthy; they kindle, however, and burn like 
wood coals (av0§«K£s). These are found in Liguria, where there is 
also amber, and in Elis, in the way to Olympias over the mountains. 
These are used by the smiths.” 
* Theophrastus’s History of Stones, translated by Sir John Hill, p. 63. 
Y 
VOL, I. 
