i; 



J 1 pariijj; 



'^tcli y 



-"Uii 



" wlijti 



li 



^ 



auit 





11,111 



i^ 





,'jii' 



jiaff^'' 



Ic 



i; 



50 



1^ 



HUTTONIAN THEORY. 



303 



mark, that it is common to find wood-coal under 

 bafaltes, it mufl be underflood to arife from this, 

 that the coal in contact with the bafaites is fre- 

 quently charred, and its fibrous flrudure, by 

 that means, rendered more'vifible. 



. It has been objeded to the fuppofition 



f coal having its b 

 the heat of the \\ 



r 



hinft 



part dri 

 that this 



not, on Dr H 

 the mineral r( 



off 



ght 



principles, to happen in 



g 



B 



as 



h 



been done ab 



It 

 th 



ay b 

 the 



plied 



local 



ap- 



phcation of heat might certainly produce th 



effecl: 



d 



d 



ff the volat 



• ' ^liss from a hotter to a cold 



parts 



ft 



The b 



h 



part of the fame 

 not been fo vola- 



tilized and expanded as entirely to efcap 

 from 



the mineral regions ; but it has been 



pelled frorn fome parts of 



condenfed and concentrate 



fuppofition coinc 

 ances. 



fs 



nly 



b 



d in others. 



Th 



des exadly with the 



app 



268. The riative or fofliil-coke which accom- 



.^1 



r 



panics whinitone, has b 



een 



diftinguillied 



in- 



to two varieties. The firft is the moft common 



m 



hich 



though the coal is perfectly charred, 

 it IS folid, and breaks with a fmooth and fliining 

 furface. The fecond is alfo perfed charcoal, but 

 is very porous and fpungy. Thisfubftanceis much 



rarer than the other : Dr Hutton mentions an 



t 



inftance 



