INTRODUCTION AND GEOLOGICAL SUMMARY. 



Toronto began about ioo years ago as a village at the 

 mouth of the small river Don, where a sand bar, now called 

 Toronto island, enclosed an excellent harbor. It has since 

 expanded six miles west to the Humber river, four or five 

 miles to the east and as much to the north. Its geographical 

 centre is not far from the Meteorological Observatory, on 

 Bloor street West, which is in lat. 43 40' o" .8 and long. 

 79° 2 3' 54-"- Toronto is situated on the north shore of lake 

 Ontario about forty miles from its western end. 



In discussing the geology of the region it will be advis- 

 able to include the suburbs of the city as far east as High- 

 land creek, 13 miles from the Don, and as far north as 

 York Mills, 6 miles from Toronto bay. 



Physiographically the region may be divided into two 

 parts, a terrace formed by ancient lake Iroquois, sloping 

 gently upwards from lake Ontario to a height of 176 to 200 

 feet, and a somewhat higher upland formed of rolling hills 

 of glacial origin, reaching at its highest points 380 feet 

 above the lake, which is 246 feet above the sea. 



The comparatively level surfaces of the terrace and the 

 morainic region beyond are broken by the deep valleys of 

 the Don and Humber rivers and their tributaries, which 

 have been cut almost to base level for a mile or two from 

 the shore and ramify as steep walled ravines for several 

 miles inland. 



The lake shore is greatly varied, including the flat sand 

 and gravel spit which projects westwards from the Don 

 and then bends northward to enclose Toronto bay, as well 

 as the cliffs of Scarboro heights to the east, which rise 

 355 feet above the water and form the highest point on the 

 whole shore of lake Ontario. This line of cliffs, extending 

 for nine and a half miles, has been carved by wave action 

 from an ancient promontory and has provided the materials 

 which have been transported ten miles west by the easterly 

 storms to build up Toronto island. 



The vicinity of Toronto includes only small outcrops 

 of solid rock, Lorraine shale of Ordovician age; but has 

 a varied and interesting series of Pleistocene deposits un- 

 equalled in complexity and importance by any other North 

 American locality. Its ■ thick series of interglacial beds, 



