3 

 0| 



!D 



HUTTONIAN THEORY. 



n 



eonfolidated ; the former in particular lofe the 



granulated texture, 



ed into perfe(5l jafp 

 was firft m 

 it has been 



and are fometimes converts 



;r. This interefling remark 

 ade by Dr Hutton, and the truth of 



verified by a great number of fub- 



fequent obfervations. 



68. To the fame excellent geologift we are 

 indebted for the knowledge of an analogous fad. 



attenda 



on the pafTag 



of 



hinft 



vems 



through coal ftrata. As the beds of ftone wher 

 they are in contad with veins of whin, feem t 



acq 



additional ind 



fo thofe of 



in like circumftances, are frequently found to 

 have loll their fufibility, and to be reduced near- 

 ly to the condition of coke, or of charcoal. 



The 



exiltence of coal of this kind has been already 

 mentioned, and confidered as a proof of the ope- 



of fubterraneous heat 



I 



the 



fiances 



here referred to. that 



here the charring of 



the coal is limited to thofe parts of the flrata 

 which are in contad with the whin, or in its im 



d 



ty, th 



pointed 



fiding in the vein ; and this is to be accounted 

 for only on the fuppofition of 



the 



vvh 



at a period fubfequent to the confohdation of 

 the coal, having flowed through the openings of 

 the ftrata. The heat has been powerful enough. 



many cafes, to drive off the bit 



of 



£ J 



■I 



nd to force it into colder and more 



diilant 



