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



calls a " Map of Laurentian land." It is, of course, again a map of 

 Laurentian rocks, and therefore not of land of Laurentian times. 

 But being evidently intended as a map of land of some time, and 

 being given in the chapter on Pre-Laurentian history, the inference 

 is unavoidable that it is intended to represent the land at the 

 beginning of the Laurentian (Archaean) time. It is hardly necessary 

 to say it is, again, approximately a map of earliest Palaeozoic 

 (Primordial) times. Thus it has come to pass that many, without 

 reflection, have held that the development of the American continent 

 may be traced from a nucleus existing in Archaean times. But of 

 this there is in fact not the slightest evidence. 



On the other hand, Prof. Hull has recently published a very 

 interesting and suggestive paper " On the Geological Age of the 

 North Atlantic Ocean," 1 in which he tries to show that the places 

 of the present continents were not declared until the Mesozoic. If 

 this be so, then indeed the doctrine of the permanence of continents 

 must be given up entirely ; for the Mesozoic and Cainozoic together 

 form but a small part of the entire history of the earth. 



I believe that the truth lies between these extreme views. 

 I believe that the place of the American continent was established 

 and its nucleus formed at the beginning of the Primordial time ; and 

 that thus, in regard to the development of earth features, no less 

 than of earth faunas, the name Primordial is peculiarly appropriate. 

 This, I think, is the real view of Dana. I wish now to give 

 as clearly and as briefly as possible what seem to me the main 

 steps in the history of the American continent from the earliest times. 



1. Of all rocks the Archaean are by far the most widely diffused 

 on the American continent, although of course largely covered by 

 later deposits. Not only do they form the surface rocks over large 

 areas, but they seem everywhere to underlie other rocks; for wher- 

 ever these latter have been pierced by wells or cut through by 

 canons, we find the Archaean beneath. It is hardly too much to say 

 that they form the foundation rocks of the whole continent. If so, 

 then, of course, in Archaean times the American Continent was all sea- 

 bottom. Where was the land at that time ? We know not for certain ; 

 but the subsequent development of the continent southward and 

 westward suggests that its place was to the north-eastward. This 

 view is farther strengthened by the fact that the development of the 

 European continent south-westward would point to the north-west- 

 ward as the place of the earliest land. Prof. Hull therefore, with 

 much show of reason, assigns the North Atlantic as the place of the 

 Archaean continent. The land from which such enormous masses of 

 sediments were derived must have been indeed of continental pro- 

 portions, and must have existed during immense periods of time, 

 perhaps equal to all subsequent times put together. Its debris 

 carried into south-eastward and south-westward seas formed the 

 Archaean rocks of Europe and America. 



2. At the end of the Archaean, America (and probably Europe 

 also) became largely land. This is a point of very great importance, 



1 Trans. Eoy. Dub. Soc, 1885, vol. iii. p. 305. 



