TANNING MATTERj <SrC. QJ 



the Bovey coal, the Sussex coal, the surtiirbranrl, and Expcrincnts 

 many others, together with the resin, (allowed to be ex- Sec on anartl- 



cliKsiyely a vegetable substance, or at least one which r"''.^ substance 

 J ^ 7 havingthccha- 



enly appertains to the organized natural bodies,) there meters of tan- 

 cannot be any doubt, that such coals have been formed ^""* n^atter. 

 from wood and other substances belongii\^ to the vege- 

 table kingdom. 



But some mineralogists attempt to draw a line of sepa- 

 ration between the coals above mentioned and the others, 

 which therefore they call the true mineral coals. 



This opinion may in some degree be refuted even fron^ 

 the specimens afforded by the Bovey coal-pits, where, as 

 1 have observed, a regrtlar gradation may be seen from 

 wood which is but very imperfectly carbonized, to the 

 substance called stone coal, which in every respect ap- 

 pears to be most nearly if not absolutely similar to the 

 common pit-coals*. 



It may however be objected, that such a transition i:i 

 peculiar to this and similar places, and that the pit-coal 

 found in other situations, where nothing resembling the 

 Bovey coal can be discovered, is in reality of a diflierent 

 nature. 



But this objection I think may be answered by the 

 results of those experiments on pit-coal, Ca:mel coal, and 

 asphaltum, which I have related in the third section of 

 this Paper; for when these were subjected to the action 

 of nithic acid not too long continued, it was found, that 

 the acid first dissolved the principal part of the carbona- 

 ceous matter, and if then the process was stopped, there 

 remained a substance in v, proportion corresponding to 

 that of the bitumen cither in the pit-coal, or principally 

 forming the Cannel coal and asphaltum, which although 

 not absolutely in the state of resin, was however in a 

 state intermediate between it and the vegetable extracti\ j 

 matter. 



Moreover I have stated, that under similar circum- 

 stances, a substance possessing in a great measure the 

 game properties, may be obtained from the known vege, 

 lable resins by the action of nitric acid. 



* Phil. Tfans. 1804, p. 398. 



When 



