Effects of Heat modified hy Compression. lo? 



have resulted from various heats acting under pressure of 

 various force. The substance to which he has given the 

 name of relinasphaltum seems to agree very nearly with what 

 I have obtained from animal substance, when the barrel was 

 opened bv means of low heat. And the specimen of wood 

 entering into fusion, but still retaining the form of its fibres, 

 seems very similar to the intermediate substance of Bovey 

 coal and surtur brand, which Mr. Hatchett ha* 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 experiment seems to afford a plausi- 

 ble solution of this puzzling phenomenon. 



In all parts of the globe we find proofs of slips, and va- 

 rious relative motions, having taken place amongst great 

 masses of rock, whilst they were soft in a certain degree, and 

 which have left uneo,uivocal traces behind them, both in the 

 derangement of the beds of strata, and in a smooth and 

 shining surface, called slickenside, produced by the direct 

 friction of one mass on another. During the action of sub- 

 terranean heat, were a single stratum to occur, 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 experi- 

 ment, whilst the substance of the contiguous strata retained 

 a considerable degree of firmness. In this state of things, 

 'the stratum just mentioned would very naturally become the 

 scene of a slip, occasioned by the unequal pressure of the 

 surrounding masses. Bv such a sliding motion, accom- 

 panied 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. At the same time the shells along 

 with the trees would be flattened like those described bv 

 Bergman, while those of the same species in the neighbour- 

 ing limestone rock, being protected by its inferior fusibilitv. 

 would retain their natural shape. 



[To be continued.] 



XXIV. he- 



