some of the Principtes of Vegetables into Bitumen, 31 



fey alcohol^ was but small, as it did not exceed 3 grains. 

 Bat this small quantity was sufficient to prove, that alUiouoU 

 the Bovey coal does not contain any vegetable extract, like 

 the schistus formerly mentioned, yet the whole ot" the 

 proximate principles of the original vegetable have not been 

 entirely changed j as a small portion of true resin, not con- 

 verted into bitumen, still remains inherent in the coal, al- 

 though the bituminous part is by much the most prevalent, 

 and causes the fetid odour which attends the combustion of 

 this substance. 



Upon a comparison of the general external characters of 

 the Bovey coal with those of the substance which forms 

 the leaves contained in the Iceland schistus, a very e;reat 

 resemblance will be observed ; and this is further confirmed 

 by the similarity of the products obtained from each of them 

 in the preceding experiments, with the single exception that 

 the leaves contain some vegetable extract, which I could 

 not discover in the Bovey coal. They aaree however iu 

 every other respect ; as they both consist of woody fibre in 

 a state of semicarbonization, impregnated with bitumen, 

 and a small portion of resin, perfectly similar to that whicli 

 is contained in many recent vegetable bodies; and thus it 

 seems, that as the woody fibre, in these cases, still retains 

 some part of its vegetable characters, and is but partially and 

 imperfectly converted into coal, so, in like manner, some 

 of the other vegetable principles have only suffered a partial 

 change. Undoubtedly there is every reason to believe that, 

 next to the woody fibre, resin is the substance which, iu 

 vegetables passin<i to the fossil stale, most powerfully resists 

 anv alteration ; and that, when this is at length effected, it 

 is more immediaiely the substance from which bitumen is 

 produced. The instances which have been mentioned cor- 

 roborate this opinion ; for the vegetable extract in ojie of 

 them, and more especially the resin which was discovered 

 in both, must be regarded as part of those principles of the 

 original vegetables which have remained, after some other 

 portions of the same have been modified into bitumen. 



The smallness of the quantity of resin obtained in both 

 the preeeJiug eases by no means invalidates the proof of 

 the above opinion ; but, as an additional confirmation of it, 

 I shall now give an account of a very singular substance, 

 w))ich is found with the Bovey coal. 

 [To be toiitinuid ] 



D 2 VHJ. On 



