G. I-'. WRIGHT — POST-GLACIAL OUTLET l'Lo.M GREAT LAKES. 423 



On reassembling at "2 o'clock the following communication was read: 



COMPARISON OF PLEISTOCENE AND PRESENT [CE-SHEETS 

 BY WARREN ll'HAM 



The paper provoked a spirited hut pleasant discussion, the chief point 

 of division being the evidence as to the existence of man in America 

 during glacial time. Remarks were made )>y \V .1 McCee, A. R. ( '. 

 Selwyn, G. F. Wright, R. 1). Salisbury and the author. The paper is 

 printed as pages 191-204 of this volume. 



The next paper Avas as follows: 



Till': SUPPOSED POST-GLACIAL OUTLET OK THE GREAT LAKES THROUGH 

 LAKE NIPISSING AND THE MATTAWA KIVER 



I1Y (I. FREDERICK WRIGHT 



During the early part of last September, in company with Judge C. C. Baldwin, 

 of Cleveland, D. C. Baldwin, of Elyria, and Professor Albert A. Wright, of Oberlin, 

 and while engaged in the work of collecting fragments of the rock in place along 

 the line of the Canadian Pacific railroad from the Sault Ste Marie to Ottawa to 

 aid in identifying the glacial bowlders of Ohio, we turned aside for a few days to 

 study the evidence which attracted our attention in support of Mr Gilbert's hy- 

 pothesis that upon the first melting back of the ice of the glacial period the main 

 part of the water of the great lakes ran for a, while from Lake Xipissing by way of 

 the Mattawa river into the Ottawa. This theory was, 1 believe, first presented by 

 Mr Gilbert at the meeting of the American Association for the Advancement of 

 Science at Toronto in August, 1881). The substance of his address upon that occa- 

 sion was published in the Sixth Annual Report of the Commissioners of the State 

 Reservation at Niagara (pages 61-84) and reprinted in the Smithsonian Report for 

 is; io (pages 231-257 \ 



The general facts suggesting such an outlet are those connected with the northerly 

 depression of land known to exist at the close of the glacial period, and revealed 

 in the familiar phenomena of the so-called Champlain epoch. The subsidence at 

 Montreal, as shown by the marine shells resting upon glacial deposits, was a little 

 over 500 feet, while in the valley of Lake Champlain it was considerably less, and 

 in the latitude of New York city very much le^s still, if it had not wholly disap- 

 peared. It is difficult to determine from direct evidence at hand what was the 

 subsidence in the region of the great lakes, though it is evident from Air [Jpham's 

 report upon the shore-lines of Lake Agassiz, from the investigations of Mr Gilbert 

 and Mr Spencer upon the raised beaches about Lake < hitario, and from the various 

 reports upon the old shore-lines north of Lakes Huron and Superior, that this dif- 

 ferential northern subsidence characterized the whole interior basin east of the 

 Rocky mountains. These facts, coupled with the known relative depression of 

 the col between Lake Nipissing and the Mattawa river, naturally created confi- 

 dence in Mr Gilbert's theory that the outlet of the great lakes by way of this col 

 was once a reality, for the difference of level between Lake Erie and the col at 



