IQg ANNUAL IlEPORT SMITHSONIAN INSTITUTION, 1936 



across the Atlantic and placed in the position which, according to 

 Wegener, it would fit into in the European coast ! Can the Pilgrim 

 Fathers have ever dreamed of such a link between the Old England 

 and the New ? 



The hypothesis of continental drift gave rich promise of solving 

 so many difficult problems that it was hailed by many classes of 

 investigators almost as a panacea. Geographers have seen in it 

 an explanation of the forms of continents and the position of 

 peninsulas, islands, and mountains; meteorologists have found it 

 the solution of some of the problems of past climates and their 

 anomalies of distribution over the world; biologists hope to get 

 help with the intense complexities in the distribution of forms of 

 life and many strange facts in migration, and paleontologists with 

 similar difficulties among the ancient faunas and floras as revealed 

 by their fossil remains; geodesists have welcomed escape from the 

 rising and sinking of the crust, so difficult to reconcile with the 

 demands of isostatic equilibrium; and it has been already stated 

 that drift forms a vital factor in Joly's thermal cycles. 



But there has been no lack of criticism in all these directions. It 

 has been assailed on the one hand for the detail attempted in its geo- 

 graphical restorations, and on the other hand for its vagueness. 

 Professor Schuchert quotes Termier as saying that it is "a beautiful 

 dream, the dream of a great poet. One tries to embrace it, and finds 

 that he has in his arms but a little vapor or smoke ; it is at the same 

 time alluring and intangible." It has been objected that "no plausible 

 explanation of the mechanics involved has been offered"; that the 

 continental connections postulated present by no means so close a 

 match, when fitted together, as has been claimed, in the structure 

 or the nature of either igneous or sedimentary rocks; that there is 

 good evidence of extensive vertical movements in recent earthquakes, 

 in the accumulation of tremendous thicknesses of sediment indicative 

 of shallow water from base to summit, and in the growth of coral 

 reefs; that Central America and the Mediterranean are a difficult 

 obstacle; and that the known distribution of the Karroo fossil 

 reptiles is not by any means what the hypothesis demands. 



If the idea of drift be accepted it cannot be regarded as a royal 

 road out of all our difficulties, nor can it be the only form of 

 earth movement to be reckoned with. The late J. W. Gregory, whose 

 life was sacrificed to geological discovery, has studied exhaustively 

 the geological history of the Atlantic and Pacific Oceans, both as 

 revealed by the sedimentary rocks and fossils on their borders, and 

 by the distribution of life today. He finds that, according to our 

 present loiowledge, in the two oceans, facilities for migration have 

 fluctuated from time to time, periods of great community of 



