MODIFIED by COMPkESSION. 155 



trace could be difcovered of the original organization. In 

 others, the vegetable fibres were ftill vifible, and are forced afun- 

 der by large and fhining air-bubbles. 



Since the publication of the fketch of my experiments, I 

 have had the pleafure to read Mr Hatchett's very interefting 

 account of various natural fubftances, nearly allied to coal > 

 and I could not help being ftruck with the refemblance which 

 my refults bear to them, through all their varieties, as brought 

 into view by that able chemifl ; that refemblance affording a 

 prefumption, that the changes which, with true fcientific mo- 

 deity, he afcribes to an unknown caufe, may have refulted from 

 various heats acting under preffure of various force. The 

 fubftance to which he has given the name of Retinafphaltum, 

 feems to agree very nearly with what I have obtained from 

 animal fubftance, when the barrel was opened by means of low 

 heat. And the fpecimen of wood entering into fufion, but ftili 

 retaining the form of its fibres, feems very fimilar to the in- 

 termediate fubftance of Bovey-coal and Surturbrand, which Mr 

 Hatchett has aflimilated to each other. It is well known, 

 that the furturbrand of Iceland, conlifts of the (terns of large 

 trees, flattened to thin plates, by fome operation of nature hi- 

 therto unexplained. But the laft-mentioned experiment feems 

 to afford a plaufible folution of this puzzling phenomenon. 



In all parts of the globe, we find proofs of flips, and various 

 relative motions, having taken place amongft great mafles 

 of rock, whilft they were foft in a certain degree, and which 

 have left unequivocal traces behind them, both in the derange- 

 ment of the beds of ft rata, and in a fmooth and fhining fur- 

 face, called Jlickenfide, produced by the direct friction of one 

 mafs on another. During the action of fubterranean heat, were 

 a fingle ftratum to occur, containing trees intermixed with 

 animal fubftances, fhell-fifh, &c. thefe trees would be reduced, 

 to a foft and unctuous ftate, fimilar to that of the piece of wood 



U 2 in 



