34 



character on the lakeward slope, as well as silt and clay 

 within the Don and Humber bays. At one point near 

 Reservoir park shells have been found in the gravels, species 

 of Campeloma, Pleurocera and Sphccrium, all still living 

 in lake Ontario. The commonest fossils are horns of 

 caribou, which are often found in the west Toronto gravel 

 bar. Less frequently teeth of mammoth have been obtained. 

 The mammoth and the caribou suggest a cooler climate than 

 the present. The caribou is essentially a northern animal, 

 and has not been found within 150 miles north of Toronto 

 during historic times. It is natural to suppose that the 

 waters of lake Iroquois, which had a shore of ice toward 

 the northeast, were colder than those of Ontario, and that 

 the climate was cool, if not even subarctic. 



When lake Iroquois was drained through the melting 

 of the ice dam at the Thousand islands, the water sank to 

 sea level, but there is no evidence of marine deposits on its 

 shore. The marine episode was comparatively short and 

 the water was probably kept fresh by the Niagara river. 

 The outlet was still rising toward the northeast, so that the 

 water was backed up toward the southwest end of the lake. 

 On the lower reaches of both the Don and the Humber 

 there is dead water owing to this rise of the lake level, and 

 well borings near the mouth of the Don show 100 feet of 

 stratified sand built up in the old channel. The growth of 

 Toronto island is, however, the most evident work of lake 

 Ontario near Toronto in recent times. Its materials have 

 been transported westwards from Scarboro heights, and 

 have been built out into deep water enclosing Toronto bay, 

 The growth of the island has been shown by Sir Sandford 

 Fleming, from a comparison of maps more than 100 years 

 old, to have been extensive. 



