68 



ILLUSTRATIONS OF THE 



bears, in all its varieties, a mofl fkriking refem. 

 blance to the lavas which h^ve adlually flowed 

 from volcanoes on the fufface of the earth. 

 This refemblance is fo great, that the two fub- 

 fiances have been often miflaken for one ano« 

 ther ; and many rocks, which have been pro. 

 nounced to be the remains of extinguiflied vol. 

 canoes, by mineralogifls of no inconfiderable 

 name, have been found, on clofer examination, 

 to be nothing elfe than mafles or veins of whin- 

 ilone. This latter flone is indeed only to be 

 dillinguiflied from the former, by a careful ex- 

 amination of the internal characters of both; 

 and chiefly from this circumfl:ance, that whin- 

 Hone often contains calcareous fpar and zeolite, 

 •whereas neither of thefe fubflian^^es is found in 



■t 

 4 



fuch lavas, as are certainly known to have been 

 thrown out by volcanic explofions. 



Now, from thefe circumfliances of affinity be- 

 tween lava and whinfl:one, on the one hand, and 

 of diverfity on the other, as the formation of 

 the one is known, it fliould feem that fome pro- 

 bable conclufion may be drawn concerning the 

 formation of the other. The affinity in que- 

 ikion is confl:ant and eflTential ; the difference 

 variable and accidental ; and this naturally leads 

 to fufped:, that the two ftones have, the fame 

 origin ; and that, as lava is certainly a produc- 



tion of fire, fo probably is whinfl:one. 



. But 



