104 B. K. EMERSON — TETRAHEDRAL EARTH : INTERCONTINENTAL SEAS 



In North America the opposite ideas have developed. Dana, Leconte, 

 Dutton, and other important students have espoused different modifica- 

 tions of the theory that mountain chains are formed by the sinking of 



the oceans — that is, that they have, as if by a force from without, been 

 joined to or thrust against the old preexistent nucleus of stable land (in 

 this case the Laurentian mass). The theory of isostacy has developed 

 itself from this position, namely, the view that the heavier loading of 

 the surface by sediments produces sinking and a complementary eleva- 

 tion in some other place. 



In these contrasts of the general conceptions of the nature of the con- 

 tinents and their relation to the seas which have arisen from the obser- 

 vation of nature, on the one hand in Asia and on the other in America, 

 is reflected a complete contrast of structure; and since the American 

 views are based on the particular build of the North American continent 

 they have not received the same degree of recognition in Europe. 



But this is not the only contrast which can be gathered from former 

 writings. As early as 1887, also, Marcel Bertrand drew a line of junc- 

 tion from the Armoricanfolds right across the ocean to Newfoundland.* 

 This means, in other words, that these chains which were folded up be- 

 fore the close of the Carboniferous are continued westerly, either directly 

 or by the junction of independent ranges now sunk beneath the Atlantic ; 

 appear again with similar structure on the northeast coast of America, 

 then make a concave bend and end at last in the Ouachita mountains. 

 It follows further from this that the north Atlantic is younger than this 

 range. This agrees with other observations. It is more difficult to under- 

 stand the role of the much older Pacific ocean. One sees in Asia chain 

 behind chain. Often two or more chains joining at acute angles are 

 spanned b}^ a single larger curve, as in Asia Minor and in Iran. The 

 Burman curve becomes very large. 



One can imagine that the great curves, finally meeting a. hindrance, 

 transformed themselves into long lines that at last became concave like 

 Mie Appalachians and the Sierra Madre. Such an idea assumes that the 

 original outlining of the west American Cordillera is older than the 

 Pacific; that the northern coast ranges with their long granite chains, 

 which do not reach back before the Mesozoic time, and with their very 

 late movements, are a later interposition, and that the Cretaceous over- 

 thrusts of the northeast Cordillera are caused by later (" posthumous ") 

 movements. 



* Bull. Soc. Geol., 2d ser., vol. xv, p. 442. 

 M Marcel Bertrand goes still further and unites the Green mountains with the Caledonian 

 zone, They represent, in fact, folds that are older than the Armoriean discordance. 



