A Study of the Ontario Basin. 359 



ice as^e still continues, for there are still small glaciers iu 

 Labrador, larger ones in the Rocky Mountains, still larger 

 sheets in Alaska and the Arctic islands, and an ice cap in 

 Greenland. 



Can the question be settled by a reference to climates, 

 the Glacial Period implying Arctic conditions and ending 

 when the climate became cold temperate ? If that is the case 

 the Glacial Period ended for the Ontario region at the begin- 

 ning of Lake Iroquois, for large spruce and tamarack trees 

 grew at Hamilton while the lake was still young, the beaver, 

 the bison and the wapiti, as well as extinct mammals, inhabited 

 its shores before the great gravel bar in front of Dundas 

 marsh had been built, and unios, campelomas, plueroceras and 

 sphseriums like those in the waters of Lake Ontario occur in 

 an Iroquois gravel bar at Toronto. 



The climate was not Arctic but cold temperate on the shores 

 of Lake Iroquois and the shells and other remains found in the 

 old beaches of Lake Agassiz and of Lake Algonquin in the 

 more northern parts of the province of Ontario point to similar 

 climatic conditions, since they are the same as live in the 

 present waters of those regions. 



In spite of the presence of a stagnant, slowly thawing mass 

 of ice, reaching from the Adirondacks northwards and block- 

 ing the waters of Lakes Iroquois and Algonquin, the climate 

 was not Arctic any ujore than that of southern Alaska, with 

 great ice sheets not far off, is Arctic at the present day. 



Probably the most satisfactory account of the close of the Gla- 

 cial Period is to make it a progressive event beginning in Iowa 

 and adjoining states thousands of years before it reached 

 Ontario and taking place on the shores of Lake Iroquois thou- 

 sands of years before it reached James Bay and Hudson's Bay 

 and the last remnant of the continental ice sheet finally disap- 

 peared. 



To the stratigrapher striving to establish sharp boundaries 

 between formations this account of the slow and progressive 

 ending of one geological period and beginning of the next may 

 appear unsatisfactory ; but in reality most physical changes on 

 the earth have been gradual, spreading from point to point, 

 from region to region, requiring many thousands of years for 

 completion. It is only when looking back upon them from far 

 off that these events appear sudden and instantaneous for the 

 whole world. A discussion therefore as to the precise year in 

 which the Ice Age ended is not of much value since it really 

 ended at different times in different places. 



University of Toronto, Toronto, Canada. 



