172 EFFECTS of HEAT 



and I flill believe, that vaft torrents, of depth fufficient to over- 

 top our mountains, have fwept along the furface of the earth, 

 excavating vallies, undermining mountains, and carrying away 

 whatever was unable to refill fuch powerful corrofion. If fuch 

 agents have been at work in the Alps, it is difficult to conceive 

 that our countries mould have been fpared. I made it therefore 

 my bufinefs to fearch for traces of fimilar operations here. I was 

 not long in difcovering fuch in great abundance ; and, with the 

 help of feveral of my friends, I have traced the indications of 

 vaft torrents in this neighbourhood, as obvious as thofe I 

 formerly faw on Saleve and Jura. Since I announced my opi- 

 nion on this fubject, in a note fubjoined to my paper on Whin- 

 flone and Lava, publifhed in the fifth volume of the Tranf- 

 adions of this Society, I have met with many confirmations 

 of thefe views. The mofl important of thefe are derived from 

 the teftimony of my friend Lord Selkirk, who has lately 

 met with a feries of fimilar fads in North America. 



It would be difficult to compute the effects of fuch an agent ; 

 but if, by means of it, or of any other caufe, the whole mafs, 

 of fecondary flrata, in great tracts of country, has been remo- 

 ved from above the primary, the weight of that mafs alone mufl 

 have been fufficient to fulfil all the conditions of the Huttonian 

 Theory, without having recourfe to the preffure of the fea. But 

 when the two prefTures were combined, how great mufl have 

 been their united ftrength ! 



We are authorifed to fuppofe, that the materials of our flrata, 

 in this fituation, underwent the action of fire. For volcanoes 

 have burnt long before the earlieft times recorded in hiflory, as 

 appears by the magnitude of fome volcanic mountains ; and it 

 can fcarceiy be doubted, that their fire has a&ed without any 

 material cefTation ever fine© the furface of our globe acquired its 



prefent 



