100 Prof. J. Le Conte — Permanence of Continents, etc. 



border. 1 This, the Primordial continent, was the nucleus, from which, 

 by gradual growth, as so well shown by Dana, the American con- 

 tinent was formed. This growth was somewhat regular during the 

 Palaeozoic, but with another large oscillation at its end. The 

 American continent existed, indeed, before, not however during the 

 Archaean, as many seem to think, but during the " lost interval " ; 

 but it was almost destroyed at the beginning of the Palaeozoic, to 

 recommence its development with the nucleus already described. 

 Thenceforward the plan thus outlined was apparently never lost. 



4. During the Palaeozoic the growth of the continent was com- 

 paratively regular, but at its end coincidently and correlatively 

 with the formation of the Appalachian Eange, the eastern land-mass 

 was greatly diminished by submergence, and the eastern coast-line 

 advanced westward far beyond its present position, especially in the 

 southern part, probably as far as the well-known position of the 

 Tertiary coast-line. After this oscillation, the development was again 

 more regular, and in its broader outlines is well known. The great 

 interior Palaeozoic sea was diminished and became the interior Cre- 

 taceous sea, and this later retreated southward, to become finally the 

 present Gulf of Mexico. There were probably many other times of 

 lesser oscillation. The last of these was in later Tertiary and early 

 Quaternary, during which the continent in its northern part again 

 extended to the submerged continental border, with probable con- 

 nection with Europe in the North Atlantic region. 



Prof. Hull, in his paper already referred to, makes the changes in the 

 latter part of the Palaeozoic and at its end much greater than I have 

 supposed, in fact equivalent to another almost complete exchange of 

 sea and land. According to him (see his map, fig. 3), during the 

 Carboniferous the whole of the North Atlantic and the northern 

 parts of North America and of Europe formed together an enormous 

 continental mass, the oceanic part of which was again submei-ged at 

 the end of this period, to nearly the present limits of the two con-- 

 tinents. It is not impossible nor even improbable that during the 

 later Palaeozoic the American continent may have grown on its 

 eastern margin ; or even that at some time during the long Palaeozoic 

 era there may have been a connection far to the north between the 

 two continents ; but of the complete abolition of the Atlantic Ocean, 

 as shown on his map, I confess I see no sufficient evidence. The 

 great thickness of the Carboniferous strata would, it is true, require 

 a large land-mass to the east; but there is no reason why the eastern 

 land-mass, which sufficed to contribute the 30,000 feet of Silurian 

 and Devonian sediments, should not have been sufficient to con- 

 tribute the much smaller amount of sediments of the Carboniferous 

 period. 



To re-capitulate briefly : 1. During the Archaean the American 

 continent probably did not exist at all. 2. The first evidence we find 



1 The Silurian continent has been thus extended by Prof. Hull in his map, fig. 2 ; 

 but why he has carried the northern part of the continental border westward so as to 

 cut through Labrador, I cannot imagine. The whole of Labrador was surely land in 

 Primordial times. 



