HUTTONIAN THEORY. 



t| 



tit 



i6 



51 



ceive, that vapours from the mineral reg 



heat to refer 



of 



f the earth, and may in th 



boiling 



may convey thei 



near the furface ( 



manner produce hot fprings, and even 



fountains, like thofe of Rycum and Geyfer. 



91. When, inftead of a heated vapour, melt- 

 ed matter is thrown up through the Jb aft s or 

 tubes, which thus communicate with the mi- 

 neral regions, veins of whinftone and bafal- 

 tes are formed in the interior of the earth. 



it 

 4 



When the melted matter reaches to the fur- 

 face, it is thrown out in the form of lava, and 

 all the other phenomena of volcanoes are produ- 

 ced. 



Lallly, Where melted matter of this kind, or 

 vapours without being condenfed, have their 

 progrefs obftrudLed, thofe dreadful concuffions 

 are produced, which feem to threaten the exift- 

 ence even of the earth itfelf. Though terrible, 

 therefore, to the prefent inhabitants of the 

 globe, the earthquake has its place in the great 

 fyllem of geological operations, and is part of a 

 feries of events, effential, as will more clearly ap- 

 pear hereafter, to 

 prefervation of the whole. 



Such,, according to this theory, are the chan- 

 ges which have befallen mineral fubftances in 

 the bowels of the earth ; and though different 

 for the llratihed and unflratified parts of thofe 



fubftances. 



the general order, and to the 



