92 TANNING MATTER, &C. 



Experiments, *^^^*^ °^ these circumstances must have taken place, in 

 &c. on an arti. order that the Tcgctable substances, such as ligneous mat- 



ficial substance ter, resin, oil, &c. should become coal and bitumen. 



having the cha- ^ > t^ 



racteis of tan- ^^ ^ lormer Paper I have endeavoured to shew, that 



jiing matter, these changes arc progressive, and having noticed the 

 perfect state of the submerged wood at Sutton and other 

 places, I next described the qualities of the different kinds 

 of Bovey coal, which exhibit a series of gradual changes 

 from bodies which retain the vegetable structure and tex- 

 ture, although imperfectly carbonized, to others in which 

 almost the complete characters of the common mineral or 

 pit-coal are absolutely established. 



From the alder leaves in the schistus from Iceland, I 

 obtained extractive vegetable matter, and although this 

 was not afforded by the varieties of Bovey coal, yet these, 

 as well as the alder leaves, and also a coal like that of 

 Bovey, found in Sussex, at Newick Park, (an estate be- 

 longing to Sir Elijah Impey,) and also the surturbrand 

 of Iceland, yielded some resin, which at Bovey is like- 

 wise found in distinct masses, intermixed with the strata 

 of coal, and combined with asphaltum, in the proportion 

 of about 41 parts of the latter with 55 of resin*. 



Now, exclusive of the other vegetable characters which 

 are so evident in many of the varieties of Bovey coal, of 

 the Sussex coal, of surturbrand, &c. &c. the presence of 

 resin must be regarded as a strong fact : for this sub- 

 stance has always been attributed to the organized bo- 

 dies, particularly to those of the vegetable kingdom, and 

 I do not know of any instance, previous to my own ex- 

 periments, in which, resin had been discovered as consti- 

 tuting part of any of the different species ^ind varieties of 

 coal. 



From the external vegetable characters possessed by 



Dr. CoRREA says, " In general the trunks, branches, and roots of 

 " the decayed trees, were considerably fattened ; which is a pheno- 

 - " menon observed in the surturbrand or fossil wood of Iceland, 

 *.* and which Scheuchzer remarked also in the fossil wood found 

 " in the neighbourhood of the lake of Thun, in Switzerland." 

 Phil. Trans. 1799, P* ^47« 



* Observations on the Change of some of the proximate Princi* 

 pies of Vegetables into Bituaicn, Phil, Trans. 1804, p. 405. 



the 



