ON BITUMENS, &C. Jg3 



perties in proof of their vegetable origin. Fortunately, how- buttheprogref- 

 ever, they have been more frequently found under circum- jn^ucliveln"' 

 fiances which have ftrongly indicated the fource from whence thefe refpe£te. 

 they have been derived ; and much information has been ac- 

 quired from obfervations made on the varieties of turf, bitu- 

 minous wood, and pit coal, on the nature of their furrounding 

 ftrata, on the veftiges of animal and vegetable bodies which 

 accompany them, and on various other local facts; all- of 

 which tend considerably to elucidate the hiftory of their 

 formation, and to throw light upon this interefting part of 

 geology. 



Some inftances have already been mentioned, which fhow 

 that foffil animal fubftances form a feries, commencing with 

 fuch as are fcarcely different from thofe which are recent, and 

 terminating in productions which have totally loft all traces of 

 organization. » 



Similar inftances are afforded by the vegetable kingdom; but 

 without entering into a minute detail of every gradation, I (hall 

 only cite three examples in this ifland, namely, 



1. The fubmarine foreft at Sutton, on the coaft of Lincoln- Series of change. 

 fliire, the iimber of which has not fuffered any very apparent ^ d ubmarine 

 change in its vegetable characters *. 



2. The ftrata of bituminous wood (called Bovey Coal) found 2 - . Bove y co . al In 

 at Bovey, in Devon; which exhibits a leries of gradations, 



from the moft perfecl ligenious texture, to a fubftance nearly 

 approaching the characters of pit coal, and, on that account, 

 diftinguitlied by the name of Stone Coal. 



3. And laftly, the varieties of pit coal, fo abundant in many 3- Perfect pit- 

 parts of this country, in which almoft every appearance of 

 vegetable origin has been deftroyed. 



The three examples above-mentioned, appear to form the 



extremities and centre of the feries ; but as, from Come local 



circumftanees, the procefs of carbonization, and formation o f Thefec0nd flatc 



• /t j LT ofrers the moft 



bitumen, has not taken place in the nrft initance, and as tnele ; n ft ru aive fub- 



effetls have proceeded to the ultimate degree in the laft, it je&for refearch. 



feems moft proper that we fliould feek for information, and 



for pofitive evidence, in the fecond example, which appears 



to be the mean point, exhibiting effects of natural operations, 



by which bitumen and coal have been imperfectly and partially 



* Account of a fubmarine Foreft on the Eaft Coaft of England, 

 by Dr. Correa de Semi. Phil. Tranf. for 1799, p. 115. 



formed 



