522 Trof. J. S. Neichemj — Evolution ofN. America. 



The author, through want of personal knowledge and sufScient in- 

 formation, had been obliged to exclude from the paper the Archtean 

 rocks of Ireland. In conclusion, he briefly described the resemblances 

 which he had noticed between the Archsean rocks of Canada and 

 those of Britain, viz. that the Lower Laurentian of the former 

 country closely resembled the Hebridean of N. W. Scotland, and the 

 older gneisses of the Central Highlands : the non-igneous members 

 of the Upper Laurentian. so far as he knew them, had not specially 

 recalled to him any British rocks. The Montalban series of Dr. 

 Sterrj' Hunt reminded him of some of the Eastern gneisses of Scot- 

 land. The typical Huronian of Canada much resembled the Pebidian 

 of Wales, and probably like it, was a series rather older than the 

 Cambrian. Dr. Hunt had even shown to him specimens of red 

 felsites from the ' petrosilex group ' of Canada, which very closely 

 resembled those from North Wales called Arvonian by Dr. Hicks, and 

 regarded by the author as belonging to the lower part of the Pebidian. 



23. — Phases in the Evolution of the North American Continent. 



By Prof. J. S. Newberry ; 



of Columbia College, New York. 



AS the day had been assigned to papers bearing on the Ice Period, 

 Dr. Newberry limited his remarks to the condition of North 

 America during the Tertiary and the Glacial age. He exhibited a 

 map of North America on which the areas where glacial debris or 

 inscriptions had been found were coloured white. This showed move 

 than half of the Continent in the Glacial epoch was covered with 

 perpetual snow or ice. The margin of the drift area passed from 

 Newfoundland by George's Bank to Cape Cod, thence traversed the 

 middle of Long Island, crossed Staten Island near its southern 

 extremity, and New Jersey near Trenton. Thence it was deflected 

 northward through Pennsylvania, forming an angle in the southern 

 part of Western New York, thence passing diagonally across Ohio 

 to Cincinnati, reaching (as recently shown by Prof. G. F. Wright) 

 into Kentucky, thence running north-westerly or westerly through 

 the States of Indiana and Illinois into Missouri, whence it followed 

 nearly the course of the Missouri river to the Canada line. 



All the country included in this semicircle has been glaciated, its 

 topography profoundly modified, and the surface of a belt surrounding 

 the Canadian Highlands 2000 miles in length by nearly 500 in 

 breadth, covered with a sheet of debris, which, after much erosion, 

 is still from 30 to 50 feet in thickness. On the mountain ranges of 

 the west conspicuous evidence of glacial action is visible as far south 

 as the north line of New Mexico. These phenomena afford con- 

 clusive proof of the reality of the Ice Period, and that the present 

 climate and physical conditions of Greenland reached in that age as 

 far south as New York and Cincinnati. The elevation of the 

 Continent was at that time less than at present, since the Champlain 

 clays — the fine material ground up by the glaciers and washed down 

 to the ocean — reached the sea-level about New York. At Croton 

 Point, on the Hudson, they rise to 100 feet; at Albany 200; in 



