538 



CENOZOIC TIME. 



was the chief region of departure for the distribution eastward, southward, and west- 

 ward, and to some extent northward, of the North-European drift. 



The lower limit of the glacier off New England, may have been 

 over the shallow border of the ocean, perhaps as far out as the fifty 

 fathom or one hundred fathom line of soundings, which on the east 

 passes outside of St. George's Shoal, and off Sable Shoal east of Nova 

 Scotia. Long Island and the other islands off New England have been 

 made by Clarence King and some other writers the course of a part 

 of the terminal moraine; and a range of bowlder hills covering New 

 Jersey, west of Perth Amboy, have been pointed out by Professor 

 Smock as another portion of it. In Wisconsin the Green Bay Valley 

 is bordered on the east, south, and west, by a range of stony hills, 

 called the Kettle Range, and this range is described as of moraine ori- 

 gin by Chamberlin and Irving, and as directly connected with the 

 Green Bay Valley ice during part of the era of ice. At the time of 

 its greatest extension, the glacier reached to Southern Iowa and the 

 border of Missouri, where occur bowlders and even native copper, 

 derived from the Lake Superior region, and even into Kansas. A 

 mass of copper found in Lucas Co., Iowa, travelled 460 miles, if it 

 came from Keweenaw Point, the probable source. 



The glacier produced part of its effects by becoming a dam in some 

 places along the sides of the greater valleys, which set back the waters 

 of the lateral channels, and made at times great lakes beneath the ice, 

 and lacustrine depositions of clay, sand, or pebbles, at great elevations. 

 (W. H. Niles.) As urged by Belt, the glacier may have formed along 

 the Northern Coast of Asia an almost unbroken dam, preventing the 

 outflow of the Great Siberian rivers ; and the dam of ice may have 

 continued, owing to the high latitude of the coast line, long after 

 the ice had melted away farther south, and so have caused (in the 

 Champlain Period) immense floods from the waters of the combined 

 rivers, and thence the universal deposit of alluvium that characterizes 

 the Siberian Steppes. (Milne.) 



It is not generally possible to decide positively what Drift deposi- 

 tions were made in the Glacial period. Cases like the following, in 

 which evidence exists of deposit during the moving of the glacier, prob- 

 ably belong to the period. West of New Haven, Conn., a rocky ridge, 

 300 to 400 feet high, has for several miles a rather bold front to the 

 eastward, and thus stood obliquely to the glacier, which here moved 

 S. 30°-40° W. Along it, near the top, there are multitudes of great 

 bowlders, — one of them a thousand tons in weight, and many be- 

 tween fifty and five hundred tons, — which were evidently combed out 

 of the- passing ice by the projecting ledges. 



4. Erosion ; gathering of material for Transportation. — The Ero- 

 sion of the glacier included (1) abrasion, performed through the stones 



