100' Mr. T. Sterry Hunt 



mountains capped with lower strata. The effects of those great 

 and mysterious denuding forces which have so powerfully modi- 

 fied the surface of the globe become less apparent as we approach 

 the equatorial regions, and accordingly we find that in the south- 

 ern 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 further north ; 

 thus Sutton mountain in Canada, lying between two anticlinal 

 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 conti- 

 nental, and that the disturbance so often seen in the strata is 

 neither dependent upon elevation nor essential to the forma- 

 tion of a mountain. The synclinal structure of portions of the 

 Alps, previously observed by Studer and others, has been beautifully 

 illustrated by Ruskin in the fourth volume of his Modern Painters, 

 and in a late review of Alpine geology we have endeavoured to 

 show that the Alps, as a whole^ have likewise a synclinal structure. 

 (Am. Jour. Science, xxix. 118.) 



Such was the state of the question when Mr. Hall came forward 

 bringing his great knowledge of the sedimentary formations of 

 North America to bear upon the theory of continents and moun- 

 tains. These were first advanced in his address delivered 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 Report on the Geology of Iowa, p. 41, and with 

 more detail in the introduction to the third volume of his Paleon- 

 tology of New York, from which we have taken the abstract 

 already given. He has shown that the difference between 

 the geographical features of the eastern and central parts of North 

 America is directly connected with the greater accumulation of 

 sediment along the Appalachians. He has further shewn that so 

 far from local elevation being concerned in the formation of these 



