TRANSACTIONS OF SECTION C. Gol 



The retreat of the last ice sheet was followed by the Iroquois episode, leaving a 

 well-marked elevated beach. 



The length of time required for the first interglacial period is probably to be 

 estimated at thousands of years ; and during this time, at the beginning of which 

 the climate was very warm, the ice sheet of the Laurentide glacier must have com- 

 pletely disappeared. 



The correlation of the series of events described with those of the drift of the 

 United States and of Europe is difficult, but probably the chief iuterglacial period 

 corresponds to Geikie's Neudeckian, or the interval between the lowan and 

 Wisconsin glacial advances. 



7. On the Continental Elevation of the Glacial Epochs 

 By J. W. Spencer, Ph.D., F.G.S. 



At the last meeting of the British Association, held in Liverpool, Professor 

 Edward Hull presented a paper upon ' Another Possible Cause of the Glacial 

 Epoch,' in which the phenomena of the drowned valleys described by the present 

 writer in the ' Reconstruction of the Antillean Continent ' * are also accepted by 

 Professor Hull as due to river erosion, thus furnishing yardsticks for measuring 

 the recent elevation of the region. 



In that paper the writer described a large number of drowned valleys, often 

 extending from the mouths of the great modern rivers across the submarine 

 plateaus at various depths, reaching to even 12,000 feet or more. The writer now 

 submits evidence showing that similar drowned valleys and amphitheatres are 

 recognisable as far northward as Labrador, beyond which latitude surveys have 

 not been made. 



The submarine valleys radiating from the American Continent are no greater 

 than many observable upon the surface of the land, and are particularly comparable 

 to the valleys and canons traversing the plateaus of Mexico and the Western States 

 both in magnitude and in the declivity of the various steps which indicate the 

 pauses in the elevation of the land. 



Upon tracing northward the deposits occupying the great valleys, the writer 

 has found that glacial accumulations occur in New Jersey between the Lafayette 

 formation, which is the latest horizon dissected by the great valleys, provisionally 

 regarded as of late Pliocene age, and the Columbia formation, which is mid-Pleis- 

 tocene. From all these considerations the writer concludes that the eastern 

 portion of North America stood more than two miles above the sea during the 

 earUer Pleistocene epoch. 



From the occui-rence of certain fossils, and of many canons of recent date incising 

 the borders of the tablelands, it appears that the Mexican plateau was, at least 

 in part, depressed to near sea level during the times of the high elevation of the 

 eastern portion of the continent ; and that, with the subsidence of the eastern 

 region, the western side of the continent was elevated from 6,000 to 10,000 feet 

 or more. The separation of the Atlantic and Pacific Oceans is only of recent 

 date. 



The soundings in the eastern Atlantic have not always been along the lines 

 which show the best development of the submerged valleys, but the amphitheatres 

 and other valley-features in the subcoastal margin of Europe show some of the 

 phenomena of elevation, after studying their characteristics off the American coast. 

 While a submarine bridge exists between Europe and Greenland, there appears 

 to be no similar connection between Greenland and America. Under these 

 circumstances, the epochs of elevation on the two sides of the ALtlantic cannot bo 

 shown as simultaneous. On the other hand, it is suggested that the elevation upon 

 the two sides alternated similarly to the terrestrial waves between the eastern 

 region of America and Mexico. 



The theory of the Antillean ridge is strongly supported by the distribution of 



' Genl. Mag., Dec. 4, v. p. 32. - B:dl. Geol. Soc. Amer., vr. 1894-95, 103-140. 



