6o Transactions of the Canadian Institute. [vol. x 



this part of Ontario. Then the Erie and Huron ice lobes became separated 

 in the region northeast of London, though still united toward the south- 

 west. Soon the two lobes parted and were sharply defined, until the ice 

 had melted far back in each of the basins. Up to this time the ice in 

 the basin of Lake Ontario had not become differentiated into a separate 

 lobe, but was simply the basal part of the Erie lobe, and the same was 

 true of the Georgian Bay-Lake Simcoe ice mass. But when it had re- 

 treated nearly to Buffalo the ice in the basin of Lake Ontario began to 

 take shape as a sharply defined lobe. It not only ceased to occupy any 

 part of the basin of Lake Erie, but it became sharply separated from 

 the ice to the north of it in the basins of Lake Simcoe and the Trent 

 valley, the line of division being along the high ridge of land — the Oak 

 Ridges — north of Lake Ontario. By the shrinking of the Lake Huron 

 lobe and its separation from the Lake Ontario lobe, the ice mass in the 

 basins of Georgian Bay and Lake Simcoe and the Trent valley became 

 a separate lobate mass. It was blunt in shape and less pronounced in 

 its lobate form, but it took on a system of movements of its own which 

 clearly make it a separate lobe in this stage of the retreat. 



Map showing Distribution of Moraines. 



The accompanying map, in colours, shows the present state of 

 knowledge concerning the terminal moraines of this part of Ontario. All 

 the moraines represented, excepting the two small fragments shown 

 northeast of Lake Simcoe, were studied and mapped by the writer. 

 Parts of these beyond the border of the map were studied by the 

 writer in 1907. The parts shown were mapped by W. A. Johnston of 

 the Canadian Geological Survey and his assistants. Some of the moraines 

 are shown extending across the border into Michigan and New York. 

 These were also mapped by the writer, excepting parts of some of those 

 east and south of Buffalo. Those in Michigan and New York are put 

 upon the map in order to show the continuity of the individual moraines 

 beyond the boundary, and especially in order to make more clear the 

 symmetrical relations of the moraines to the lake basins. The area in 

 Ontario is a large one, covering approximately 30,000 square miles, and 

 the moraines shown are a part of the results of numerous field excursions 

 beginning in the summer of 1893. The mapping is still far from complete; 

 some of the moraines are known as yet only in fragments and the rela- 

 tions of some are not yet worked out. But enough has been done to 

 show the system of the moraines and their relations to the several ice 

 lobes. Some parts of the region have not yet been studied and the com- 

 pletion of the mapping awaits the exploration of those parts. The map- 



