150 TRANSACTIONS OF THE CANADIAN INSTITUTE. [VoL. 1. 



varying in extent and thickness, we have limestones, slates and sand- 

 stones, and limestones again succeeding each other until the Detroit 

 River is reached. These have a general westerly dip or incline, varied, 

 however by escarpments, anticlinals and synclinals, probably to a much 

 greater extent than at present we have any idea of. Thus the Guelph 

 limestone is about 900 feet above the sea, the Niagara escarpment reach- 

 ing in some places nearly lOOO feet, while along the Detroit River and 

 Lake Erie the rock level does not exceed, if it reaches, 600 feet, descend- 

 ing again from this at the level of Lake Ontario to but little more than 

 200 feet above the sea level. Overlying these rock surfaces of varying 

 elevation, we have deposited in widely extended areas along the lower 

 Lake Huron and Detroit River district, the whole of the Lake Erie 

 shore, and a large portion of the Lake Ontario shore far east beyond 

 Toronto, the boulder or Erie blue clay, overlaid in differing degrees of 

 regularity and thickness by Saugeen clays, everywhere interspersed with 

 layers of sands and gravels. On the higher levels, as of the Guelph 

 plateau and the Oak Ridges, we have deposits of varying consistency from 

 the tenacious argillaceous gravels of the central plateau, as at Guelph, to 

 the arenaceous gravels of portions of the Oak Ridges and the stony and 

 sandy soils of the lands dipping towards Georgian bay. 



In addition, however, to these broad divergencies in the post-glacial 

 deposits overlying the rock strata, we have the innumerable local differ- 

 ences, nowhere better marked than about Toronto, depending upon the 

 denuding agencies which have hollowed out the whole Lake Ontario 

 basin and produced the valleys of denudation such as the Humber and 

 Don valleys, and the many smaller ravines distinctive in the sharp-cut 

 outlines which deep erosion of these blue clays everywhere presents. 



From this tesimie it will at once appear that an endless variation in 

 the conditions regulating the direction, depth and amount of the flow of 

 ground-waters must exist, and we have two problems everywhere present- 

 ing themselves for investigation : the geological and the topographical. 

 Let me give one or two illustrations. 



The little river Avon, beginning on the high ground eastward from 

 Stratford at a probable height of 900 feet or more, takes a general south- 

 westerly course, flowing into the east branch of the Thames, which 

 receives a similar stream at London, and passing westward through 

 Chatham empties into Lake St. Clair some 575 feet above the sea. 

 There are abundant outcrops of rocks along the Thames at St. Mary's 

 and elsewhere in the vicinity, while at Chatham it is reached by borings 

 at from 40 to 80 feet below the surface alluvium. Apart from the syn- 

 clinal or depressed area, which practically forms the oil-boring region of 



