kY C0MPIIE3SIO1T* 505 



tlie action of some very powerful agent of destruction. Ana- 

 logy too, leads us to believe, that all the primary rocks have 

 once been covered with secondary ; yet, in Vast districts, no 

 secondary rock appears. In short, geologists seem to agree in 

 admitting the general position, that very great changes of this 

 kind have taken place in the solid surface of the globe, however 

 much they may differ as to their amount, and as to their causes. 



Dr. Hutton ascribed these changes to the action, during very — which is 

 long time, of those agents, which at this day continue slowly to ^^^^^^^^^^'^^^^ 

 corrode the surface of the earth ; frosts, rains, the ordinary and washed 

 floods of rivers, &c. which he conceives to have acted always ^^^y* °^^' 

 with the same force, and no more. But to this opinion I could 

 never subscribe, having early adopted that of Saussure, in which 

 he is joined by many of the continental geologists. My con- 

 viction was founded upon the inspection of those facts in the 

 neighbourhood of Geneva, which he has adduced in support of 

 his opinion, I was then convinced, and I still believe, that — but there are 



vast torrents, of depth sufficient to overtop our mountains, have '"''"^''tions of 



' , '■ vast torrents 



swept along the surtace of the earth, excavating vallies, under- having- swept it 



mining mountains, and carrying away whatever was unable to ^^^^y- 



resist such powerful corrosion. If such agents have been at 



work in the Alps, it is difficult to conceive that our countries 



should have been s^jared. I made it therefore my business to 



search for traces of similar operations here. I was not long in 



discovering such in great abundance ; and, with the help of 



several of my friends, I have traced the indications of vast 



torrents in this neighbourhood, as obvious as those I formerly 



saw on Saleve and Jura. Since I announced my opinion on 



this subject, in a note subjoined" to my paper on Whinstone 



and Lava, pubhshed in the fifth volume of the Transactions of 



this Society, I have met with many confirmations of these views. 



The most important of these are derived from the testimony of 



my friend Lord Selkirk, who has lately met with a series of 



similar facts in North America. 



It would be difficult to compute the effects of such an agent ; xhis siiperlu- 



but if, by means of it, or of any other cause, the whole masscumbent 



r , , weight would 



ot secondary strata, m great tracts ot country, has been remo- pioduce a com- 



ved from above tlfa primary, the weight of that mass alone must P.''^**^""^"^" 



have been sufficient to fufil all the conditions of the Huttonian the Huttonian 



Vol. XIV.—AUGUST,- 1S05\ Rr Theory, T^^eory. 



