V.] THE OKIGIN OF MOUNTAINS. 53 



and translation which have exposed the lower strata in the 

 anticlinal valleys, leaving the intermediate mountains capped 

 with lower strata. The effects of those great and mysterious 

 denuding forces which have so powerfully modified the surface 

 of the globe become less apparent as we approach the equatorial 

 regions, and accordingly we find that in the southern portions 

 of the Appalachian chain many of the anticlinal folds have 

 escaped erosion, and appear as hills of an anticlinal structure. 

 The same thing is occasionally met with farther north ; thus 

 Sutton Mountain in eastern Canada, lying between two anti- 

 clinal valleys, has an anticlinal centre, with two synclinals on 

 its opposite slopes. Its form appears to result from three 

 anticlinals, the middle one of which has to a great extent 

 escaped denudation. 



The error of the prevailing ideas upon the nature of mountain 

 chains may be traced to the notion that a disturbed condition 

 of the rocky strata is not only essential to the structure of a 

 mountain, but an evidence of its having been formed by local 

 upheaval ; and the great merit of De Montlosier and Lesley 

 (the latter altogether independently) is to have seen that the 

 upheaval has been in all cases not local but continental, and 

 that the disturbance so often seen in the strata is neither de- 

 pendent upon elevation nor essential to the formation of a 

 mountain. 



Such was the state of the question when Mr. Hall came for- 

 ward, bringing his great knowledge of the sedimentary forma- 

 tions of North America to bear upon the theory of continents 

 and mountains. These were first advanced in his address de- 

 livered before the American Association for the Advancement 

 of Science, as its president, at Montreal, in August, 1857. This 

 address was never published, but the author's views were 

 brought forward in the first volume of his Eeport on the 

 Geology of Iowa, p. 41, and with more detail in the Introduc- 

 tion to the third volume of his Paleontology of New York, from 

 which we have taken the abstract already given. He has 

 shown that the difference between the geographical features of 



