34 Ujpham — Review of the Quaternary Era, 



logic time. LeConte and Prestwich, however, consider the 

 Quaternary division of time as completed at the dawn of civil- 

 ization, with traditional and written history ; and they assign 

 recent geologic changes to a new era, which is separated from 

 the preceding principally on account of the supremacy of man. 

 The former view seems preferable, because man is known to 

 have been contemporaneous with the Ice age, and it is there- 

 fore adopted in this article, the Quaternary history of our 

 rivers being understood to include their formation and erosion 

 of deposits through all their vicissitudes during and since the 

 Glacial period. 



By most writers the terms Pleistocene, Post-tertiary, and 

 Post-pliocene, though etymologically applicable to the whole 

 extent of time from the Pliocene till now, are used restric- 

 tively as synonymous with the Glacial period, embracing its 

 stages of beginning, of alternating glacial and interglacial 

 epochs, and of final recession of the later ice-sheets, to which 

 closing stage of Glacial or Pleistocene time the name Cham- 

 plain period has been given by Hitchcock and Dana, from the 

 marine beds then deposited in the basins of Lake Champlain 

 and of the Saint Lawrence and Ottawa rivers. Investigations 

 of the Quaternary geology of the United States by McGee, 

 Chamberlin, Gilbert, Russell, and others, have shown that the 

 Glacial period or Ice age was complex, comprising in this 

 latitude three principal epochs, namely, the first glacial epoch, 

 with minor oscillations of the boundary of the ice-sheet upon 

 the northern United States, culminating in its maximum south- 

 ward extension to Cincinnati, Saint Louis, and Topeka, but 

 leaving a large tract unglaciated in southwestern Wisconsin 

 and the edges of adjoining states ; then, a long interglacial 

 epoch, in which the ice-sheet was melted back far to the north, 

 or indeed quite probably may have wholly disappeared from 

 this continent, while many of our rivers eroded deep channels 

 through the bed-rocks, leaving here and there high terraces and 

 deserted portions of the courses which they had occupied dur- 

 ing the earlier glaciation ; and, lastly, the second glacial epoch, 

 when again ice was accumulated in great thickness upon the 

 country, reaching south to Nantucket, Martha's Vineyard, 

 Long Island and Staten Island, and into northern New Jersey 

 and northern Pennsylvania, throughout this distance attaining 

 at least as great extension as the earlier ice-sheet, but farther 

 westward across the Mississippi basin falling short of the early 

 glacial boundary by a width that varies from a few miles to 

 about 275 miles. Both the growth and departure of the later 

 ice-sheet, and also of the earlier, appear to have been marked 

 by irregular stages of advance, retreat, and re-advance, many 

 times repeated, as shown by vegetal deposits, as trunks and 



