102 B. K. EMERSON TETRAHEDRAL EARTH: INTERCONTINENTAL SEAS 



appear to be the eastern ends or borders of regions which are covered by 

 the ocean. 



This series of surmises leads to the conclusion that under the north 

 Atlantic there is on the north a broad Archean region and south of the 

 same a curved chain folded toward the north, in which the Upper Car- 

 boniferous rests in discordance on older eroded folds. 



4. It is a very remarkable fact that the east coast of North America 

 actually corresponds to these surmises. There appear here, in fact, with 

 the exception of some possible Caledonian tracts, only two tectonic ele- 

 ments which show the essential characteristics of d and /. They are 

 separated by Belle Isle straits and the lower course of the Saint Lawrence 

 river. To the north lies the broad Laurentian Archean mass — the Cana- 

 dian shield — and probably extends broadly toward the pole beneath the 

 horizontal Paleozoic sediments of the Arctic American archipelago; also 

 extending across to Greenland. South of the same, in the rias coasts of 

 Newfoundland, Nova Scotia, and New Brunswick, appears a region of 

 folded rocks with discordant transgressing Upper Carboniferous, which 

 is as plainly the western continuation of a great folded chain as in 

 Europe the Armorican ridges are the east end of such a chain. The 

 Appalachians extend southwest as the continuation of this chain. New 

 observations teach us, however, that this chain, which is folded toward 

 the northwest, does not end where it was supposed to, but makes a con- 

 cave bend in the strike from southwest to west, and at the same time 

 shows strong overthrusts. These overthrusts are directed toward the 

 concavity of the curve, an occurrence which is nowhere known in Europe 

 or Asia, at least in anj'thing like so large a scale. The occurrences on the 

 concave section of the curve extending from the Alps to the Carpathians 

 near Vienna are too small for comparison. 



The western-striking continuation of the Appalachians reaches the 

 flat land of the Mississippi and disappears, but the new investigations 

 in Arkansas, in Texas, and the bordering Indian Territory show that 

 the continuation of the Appalachian folds appears again on the west side 

 of the depression of the Mississippi in the Ouachita mountains, which 

 extend nearly to the one hundredth meridian as a long tongue broken 

 into many separate folds. 



The contrast to the recognized arrangement of the curves in Eurasia 

 appears still more clearly here, since the foreland is surrounded by the 

 folds in a concave line. Nothing similar to this is seen in Europe or Asia. 



The fact has been established in late years that the Sierra Mad re, which 

 consists of granite and Archean rocks, following the west coast of Mexico, 

 continues across the gulf of Tehuantepec, and by a bend to the east 



