C. F. WRIGHT — A MORAINE OF RETROCESSION. 545 



tario. Oak Knolls is the name of a part of the continuous ridge separating Lake 

 Ontario from Lake Huron. The height of this ridge above tide does not vary much 

 from one thousand feet, as shown by the railway elevations. At King station, on the 

 Northern railway, the elevation is 955 ; but this is not the highest point of the road, 

 and the glacial summits rise on either side considerably higher. At Goodwood, on 

 the Midland division of the Grand Trunk, it is 1,090 feet. At Pontypool, on the 

 Canadian Pacific railway, fifty-two miles northeast of Toronto, the elevation is 1,064 

 feet. At Summit station, fourteen miles north of Port Hope, the elevation is 910 

 feet. Whether this is the highest point or not I do not know, nor have I the facts 

 concerning the farther extension to the east. West of the meridian of Toronto this 

 dividing ridge is continuous and still higher to the vicinity of Lake Huron. Here 

 its height is doubtless occasioned by the general elevation of the older geological 

 strata. Extensive deposits of gravel, however, are described by the Canadian geolo- 

 gists as extending along its northern slope to Collingwood and Owen sound (see Geol- 

 ogy of Canada, 1863, pp. 908, 909). 



In the section which I specially studied in York county the features were in every 

 respect those characteristic of a terminal moraine, corresponding as closely as is pos- 

 sible to the features presented on Cape Cod and in the kettle moraine of Wisconsin 

 and the coteaus of Dakota. Through the south part of the township of Whitchurch 

 it consists of a line of massive knolls and ridges of unmodified drift enclosing numer- 

 ous kettle-holes and lakelets, forming the watershed between Lake Simcoe and Lake 

 Ontario. On the northern slope it is bordered at very near the summit level with ex- 

 tensive deposits of stratified sand and gravel. Still farther to the north the land de- 

 scends rather rapidly to the level of Lake Simcoe — that is, to about the 600-foot level. 

 Lake Simcoe would thus appear to occupy a vast space which was filled with ice dur- 

 ing the time that these Oak Knolls were accumulating as a terminal moraine. 



The explanation suggested to me while on the ground, and later when coming up 

 from Lake Simcoe past Holland Landing and Newmarket to King station on the 

 Northern railway, was as follows : In the recession of the ice-sheet, when it had 

 reached the line of the Oak Knolls extending east and west from the vicinity of 

 Kingston to Lake Huron, it remained stationary long enough for the accumulation 

 of a vast terminal moraine which was high enough and solid enough to serve as a 

 barrier to the outflowing waters which accumulated behind it in the further recession 

 of the ice. Thus these stratified sands and gravels upon the north side of the Oak 

 Knolls mark the margin of a glacial lake whose drainage worked off to the east 

 somewhere in the vicinity of Kingston, and I should expect that a minute examina- 

 tion of the country would show evidences of this. Probably, however, this ridge 

 existed as a long island, projecting above the surface of that great glacial lake which 

 Professor Claypole has denominated Lake Erie-Ontario, and whose outlet was through 

 the pass at Fort Wayne, Ind., into the Wabash river. But the melting of the ice in the 

 rear of the moraine would cause currents to pass around in front of the ice eastward 

 along the northern margin of the moraine, and thus account for the special deposits 

 of sand and gravel there to be observed. 



As obviating some objections to this theory, it should be borne in mind that in es- 

 timating the extent and continuity of the obstruction furnished by this moraine, we 

 are not limited to the deposits as they now exist. While a moraine is forming, vast 

 masses of ice arc covered up by the debris, and, thus protected, may remain for a 

 long while to add to the apparent height of the deposit and to serve as important ele- 

 ments in the obstructive barriers presented. 



