346 W. UPHAM — PREGLACIAL AND POSTGLACIAL VALLEYS. 



fauna and flora, I attribute that glacial re-advance to a time after the 

 glacial lake Iroquois in the lake Ontario basin began to outflow eastward 

 by Rome to the Mohawk and Hudson. After the deposition of the fos- 

 siliferous sand and clay beds of the Scarboro' section in the gradually 

 shallowing water of lake Warren or of the succeeding glacial lakes Lundy 

 or Newberry, this outflow east from the Ontario basin began. On account 

 of the depression of the land which brought on this final Champlain epoch 

 of the Ice age, the relative height of the land in the vicinity of Toronto, 

 as compared with the depressed region about lUO miles eastward at Rome, 

 then permitted a stream to erode its valley near Toronto to a depth below 

 the present level of lake Ontario. Later, and after a temporarv advance 

 and second retreat of the ice border at Scarboro' and Toronto, forming a 

 thick till deposit, the differential re-elevation of the land, probably 200 

 to 303 feet more at Rome than in the western part of the Ontario basin, 

 caused the water level of lake Iroquois to rise gradually on the land west- 

 ward until it stood at last permanently during many years at tlie con- 

 spicuously developed Iroquois beach. 



The uppermost till of the Scarboro' Heights — that is, the second till 

 deposit above the fossiliferous beds — seems to be a retreatal moraine, 

 belonging to the second glacial recession, or to a third retreat after a 

 second slight re-advance, all considerably antedating the Iroquois beach, 

 which lies above all these drift accumulations. 



Climatic Conditions of the Champlain Epoch. 



The glacial and interglacial deposits thus found on the shore of lake 

 Ontario seem to me wholly referable to a portion of the time of general 

 glacial retreat subsequent to the Rocky river and Cleveland drift sections- 

 In these sections no evidence was obtained concerning the plant and 

 animal life of the adjoining land or of the glacial lake, referable to so 

 early a date as the Newburg moraine and time of formation of the upper 

 till in the sections specially noted. What the climatic conditions were, 

 and the incoming fauna and flora, may, however, ])e partially suggested 

 by the Toronto and Scarboro' sections, where we see that the interval 

 between the formation of successive and superposed till deposits had a 

 temperate climate nearly like that of the same district to-day. 



The predominantly wasting ice border rose probably to an altitude of 

 5,000 feet within 100 miles from its edge while being dissolved by the 

 warm Champlain climate wath somewhat lower altitude of the land than 

 now. If the retreat of the ice-sheet from the northern United States and 

 Canada occupied, as I think, some three to five thousand years, disappear- 

 ing earliest from the upper Missouri and Mississippi basins, and latest 



