ON BITUMENS, &C. J93 



fome vegetable extract, which I could not difcover in the Bovey 

 coal. They agree however in every other refpect ; as they both 

 contift of woody fibre in a Hate of femicarbonization, impreg- 

 nated with bitumen, and a fmal! portion of refin, perfectly 

 limilar to that which is contained in many recent vegetable 

 bodies; and thus it Ceems, that as the woody fibre, in thefe 

 cafes, ftill retains fome part of its vegetable characters, and is 

 but partially and imperfectly converted into coal, fo, in like 

 manner, fome of the other vegetable principles have only 

 fuffered a partial change. Undoubtedly, there is every rea- which m'oft pro- 

 fon to believe that, next to the woody fibre, refin is the fub- ^hi'ch'lftbrds' 

 ftance which in vegetables palling to the foffil ftate, mo ft the bitumen, 

 powerfally refifts any alteration ; and that, when this is at 

 length effected, it is more immediately the fubftance from 

 which bitumen is produced. The inftances which have been 

 mentioned corroborate this opinion ; for the vegetable extract 

 in one of them, and more efpecially the refin which was 

 difcovered in both, muft be regarded as part of thofe prin- 

 ciples of the original vegetables which have remained, after 

 fome other portions of the fame have been modified into 

 bitumen. 



The fmallnefs of the quantity of refin obtained in both the 

 preceding cafes, by no means invalidates the proof of the above? 

 opinion ; but, as an additional confirmation of it, I fhall now 

 give an account of a very lingular fubftance, which is found 

 with the Bovey coal. 



$v. 



Dr. Milles, in his remarks on the Bovey coal, (which I Singular fub- 



have feveral times had occafion to notice in the conrfe of this ftan L ce /° und 



- . . . ,. , with the Bovey 



Paper,) ftates, that " amongfr. the clay, but adhervng tothe CO al. 



coal, are found lumps of a bright yellow loam,' extremely 



light, and fo faturated with petroleum, that they burn like 



fealingwax, emitting a very agreeable and aromatic fcent*"* 



This fubftance, I alfo obferved, when I vifited the Bovey It is a peculiar 



coal-pits, in 1794- and 1798. At that time, however, it was bitumea - 



fcarce, and I could only procure one fmall fpecimen, which is 



now in the Britifh Mufeum; but, from a curfory examination of 



it, I was convinced that it was a peculiar bitaminous fubftance, 



* Phil. Tranf. Vol. LI. p. 536. 



Vol. X.~ March, 130*. O and 



