QUATERNARY AGE. — GLACIAL PERIOD. 529 



3. Maten'ut, of the Drift. — The unstratified Drift consists of (1) un- 

 stratified clay-beds, often with intermingled stones ; (2) the bowlder- 

 clay, already mentioned ; (3) sand, or (4) gravel, in great deposits ; 

 (5) bowlders, small or large, distributed in or over the other deposits, 

 — these bowlders sometimes fifty feet across, and weighing over 1,000 

 tons. About 11 cubic feet of trap make a ton, and 12 to 13 of other 

 rocks. 



The material, though varying much in different regions, is in gen. 

 eral coarsest to the north, and becomes gravel and sand, without stones, 

 or only small ones, toward the southern limit of the Drift region. 

 Nearing this limit, it stretches farther south in the north-and-south 

 valleys than on the hills. 



The stones or bowlders sometimes lie in long trains, as in Richmond, 

 Berkshire County, Mass., and Huntington, Vt., crossing hills and val- 

 leys, without following the line of slope ; or going obliquely across a 

 valley ; or the stones of one ridge are found on another ridge sepa- 

 rated from it by a deep valley. 



One bowlder in Bradford, Mass., is 30 feet each way (Hitchcock), and weighs not less 

 than 1,250 tons. Another, in "Whitingham, Vt., in the Green Mountains, is 43 feet 

 long and 32 in average width, and full 40,000 cubic feet in bulk. It lies on the top of a 

 naked ledge. Many on Cape Cod are 20 feet in diameter, and one at Winchester, N. 

 H., is 29 feet across. 



4. Source of the Material and Course of Travel. — By comparing 

 the Drift with the rocks of the country, it has been found that the 

 course of travel was mostly from the north, — from the northeast, the 

 north, or the northwest. To the eastward it was mainly from the 

 northwest ; but in western New York and Canada, and north of Lake 

 Superior to and beyond Lake Winnipeg, generally from the northeast. 

 The distance transported varies from a mile or less to more than one 

 hundred. 



From southwestern Vermont, the granite of a high hill, between Stamford and Pow- 

 nal, which is almost as high as the Green and Hoosac Mountains lying to the east and 

 southeast, has been carried southeastwardly across the western sides of these moun- 

 tains, nearly across the State of Massachusetts. 



Large bowlders strew thickly the north shores of eastern Long Island, which are the 

 crystalline rocks, trap, and sandstone of New England; and others, on western Long 

 Island, are from the Palisades and heights along the Hudson River. South of Lake 

 Superior, there are bowlders which have come from the north shore of the lake. 



The iron-ore bed of Cumberland, Rhode Island, furnished bowlders for the country 

 south of Providence, thirty-five miles distant, while none are found to the northward. 



South of the Lake Superior region (where native copper occurs) masses of this metal 

 are found in the Drift, over Michigan, Ohio, Indiana, Illinois, Wisconsin, and Iowa: 

 and bowlders full of fossils, derived from various Paleozoic rocks of the upper Missis- 

 sippi, in the Drift of the States to the south, even down to Mississippi. The stones of 

 the Mississippi Drift have been traced in part to Tennessee. Masses of native copper 

 occur also in the Drift of Connecticut and New Jersey, that were taken from veins 

 nearly north of the places where they occur. Native gold, from the rocks north of 

 Lake Superior, occurs in the Drift of Ohio, Indiana, and the States west. 

 34 



