366 A. P. COLEMAN IROQUOIS BEACH IN ONTARIO 



It is natural to suppose that the ice withdrew slowly from the Ontario 

 basin, at first holding back the water poured in from Niagara at different 

 levels above that of lake Iroquois, and producing the channels which 

 Professor Fairchild has mapped in New York state, until finally the Rome 

 outlet was reached, beyond which the foothills of the Adirondacks pre- 

 vented any lower point of drainage for a long distance. The time taken 

 to retreat from the Rome outlet to the next lower spillway between the 

 northern flank of the Adirondacks and the shrinking ice-sheet to the 

 north fixed the duration of lake Iroquois. I am not aware that the most 

 westerly point where the waters began to escape past the ice-front has 

 yet been observed, but to determine its position would be of great in- 

 terest as giving an idea of the rate at which the ice retreated across a 

 given distance. Whether the ice withdrew northward with a front ex- 

 tending approximately east and west or southeast and northwest is also 

 a matter of importance. If it did so, the lower Saint Lawrence valley 

 must have remained blocked after the Champlain valley afforded a 

 second outlet toward the Hudson. This assumption would require a re- 

 treat of somewhat more than 100 miles from the vicinity of Watertown 

 before a lower outlet would become available, and would imply a rate 

 of retreat of only one mile in from 35 to 175 years, according to the 

 usual time estimates. However, there may have been a long halt or 

 halts during the existence of the lake. If the retreat was somewhat 

 uniform from the Rome outlet, the highest beaches should begin to dis- 

 appear, say between Constantia and Richland, beach after beach being 

 lost, until finally the lowest of all should extend to the first spillway 

 past the Adirondacks. That this succession will ever be traced is, of 

 course, somewhat improbable. 



As to the climate on the shores of lake Iroquois and the temperature 

 of its waters, we have only meager information. The mammoth lived 

 at Hamilton and at York, near Toronto, and the caribou was very com- 

 mon at Toronto junction, both animals of a relatively cold climate ; and 

 Professor Penhallow has named specimens of wood from an old soil 30 

 feet below the Iroquois bar at Hamilton Larix americana and Picea (prob- 

 ably nigra), trees of a cool, but not necessarily very cold, climate. The 

 shells found in Iroquois beach gravels at Toronto are of species still living 

 in our waters. 



The shore of ice to the northeast must have kept the water cold, but 

 perhaps no colder than that of lake Superior at present, where the tem- 

 perature is stated to be about that of greatest density. Lake Superior 

 has a marked effect in chilling the summer heat on its immediate shores, 

 but the effect does not extend very far inland. 



On the whole, we may suppose a cold temperate if not a subarctic 



