176 Chalmers — Shore Lines of the St. Lawrence Yalley. 



apparently abnormal feature is more particularly noticeable in 

 that portion of the highest shore line which extends along the 

 south side of the valley referred to for a distance of 100 to 120 

 miles east of the international boundary, where it rests on the 

 northwest "flank of the Sutton or Green Mountain range in its 

 extension into Canada. Similar deformations were also observed 

 on the north side of the St. Lawrence and Ottawa valleys, more 

 especially of the latter. On both sides of the St. Lawrence 

 marine plain, however, the shore lines become considerably 

 broken up before approaching the Archean rocks to the west. 



In the region of the Great Lakes high-level shore lines were 

 observed and described many years ago by Logan, Chapman, 

 Fleming, R. Bell, Spencer and others, while more recently Law- 

 son and Bell have explored and traced them along the north and 

 northwest side of Lake Superior, where they bounded a great 

 body of water to which the name Lake Warren was given. On 

 the north side of Lakes Erie and Ontario four or more of the 

 strands referred to occur. The lowest, which has been named 

 the "Iroquois beach" by Spencer, and was first traced by him, 

 is not horizontal, but has an average descent southwestward of 

 about two feet to a mile. It extends from the Trent river, or 

 from a point north of Belleville, to the head of Lake Ontario. 

 Another lies above it having a similar slope, not however much 

 more than about a foot? to the mile, the altitude falling from 

 775 feet at Myrtle, Grand Trunk railway, to 705 feet in Lamb- 

 ton county. This is probably a part of the so-called Algonquin 

 shore line, which has been traced on the south side of Georgian 

 Bay with such care and described by Mr. A. F. Hunter of 

 Bame*. The third is a well-defined one which was followed 

 from Trent river to Hyde Park, Middlesex county, a distance 

 of about 200 miles, and is practically horizontal throughout. 

 The altitude is 890-892 feet. The fourth and highest is 

 terrace-like, and may be called a plateau, as it is 1100 feet high 

 in its eastern extension in Durham county, near Pontypool, and 

 1200 feet near Stratford, Perth county. A depression crosses 

 it east of the Credit river, f 



These four Ontario shore lines are of lacustrine origin ; but 

 how the waters of the Great Lakes were held up to their level 

 is the great problem. As stated in the opening sentences of this 

 paper, there seems no doubt that the whole of the region of the 

 Great Lakes stood at a lower level than at the present day 

 during the existence of the earliest and largest of these bodies 

 of water — Lake Warren, — that is, at the period when the 

 shore lines now found at an altitude of 1100-1200 feet were 



* Summary Report, Geol. Surv. Can. for 1902, pp. 279-302. 

 fThe altitudes were all measured from railway stations and referred to 

 mean sea level. See Summary Report, Geol. Surv. Can., 1902, pp. 272-274. 



