202 ACTION OF HEAT BIODIFIED 



pfcsumpfion^ that the changes which, with true scientific ft)o- 

 desty, he ascribes to an unknown cause, may have resulted 

 from variotis heats acting under pressure of various force. 

 The substance to which he has given the name of Retinasp/ial- 

 fvm, seems to agree very nearly with what I have obtained 

 from animal substance, when the barrel was opened by meatus 

 of low heat. And the specimen of wood entering into fusion, 

 b,uf still retaining the form of its fibres, seems very similar to 

 the intermediate substance of Bovey-coal and Siirturhrand, 

 which JNIr. Hatchett has assimilated to each other. It is well 

 known, that the surturbrand of Iceland, consists of the stems 

 of large trees, flattened to thin plates, by some operation of 

 nature hitherto unexplained. But the last-mentioned experi- 

 ment seems to afford a plausible solution of this puzzling phe- 

 nomenon. 

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

 experiments to rclative motions, having taken place amongst great masses of 



othernatural rock, whilst they were soft in a certain degree, and which 

 cvent=^ o ' 



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

 ments of the beds of strata, and in a smooth and shining sur- 

 face, called sUckensidt^ produced by the direct friction of one 

 mass on another. During the action of subterranean heat^i 

 v.ere a single stratum to 6ccur, containing trees intermixed 

 with animal substances, shell-fish, &c. these trees would be 

 reduced, to a soft and unctuous state, similar to that of the 

 piece of wood in the last-mentioned experiment, whilst the 

 substance of the contiguous strata retained a considerable 

 degree of firimiess. In this state of things, the stratum jiist 

 mentioned, would very naturally become the scene of a slip, 

 occasioned by the unequal pressure of the surrounding masses. 

 By such a sliding motion, accompanied by great compression, 

 a tree would be flattened, as any substance is ground in a 

 mortar, by the combination of a lateral and direct force. Ai 

 the same time, the shells along with the trees, would be flat- 

 tened, like those described by Bergman; while those of the 

 same species in the neighbouring limestone-rock, being pro-, 

 lected by its inferior fusibility, would .1 their natural 



shape. 



Sect. 



