Notices of Memoirs — George Maw. 455 



while the 18-6 year tide in the body of the earth would keep the 

 earth fast from 1862 only to June 30, 1871, Professor Newcomb's 

 observations would show that the earth has been going fast, at least 

 down to the latter part of last year — 1877 ; and besides the changes 

 caused by the 18-6 year tide could not, I believe, be as large as those 

 deduced by Professor Newcomb from the apparent variations of the 

 moon's motion. 



I. — Geological History of thk North American Lake Eegion.^ 

 By George Maw, F.L.S., F.G.S. 



FROM Haysville I proceeded to Toronto, thence down Lake 

 Ontario, with flat shelving shores here and there, with a low 

 cliff of lake silt, in which, as far as I could observe from the steamer, 

 glacial boulders were absent, though inland from the lake glacial 

 drift was everywhere visible. The " Thousand Islands," at the 

 eastern end of the lake, seemed to consist in part of glacial drift ; 

 some of the smaller islands of granite or a hard metamorphic rock, 

 the whole densely covered with low deciduous woods and Hemlock 

 Spruce. The low rocks were thoroughly rounded by ice action, 

 possibly by post-glacial floating-ice passing over them, prodigious 

 quantities of which are annually carried down the river during the 

 spring thaw. The lake gradually narrows amidst an archipelago of 

 little islands, and tapers imperceptibly into the great river. One of 

 the most striking features throughout its length to Montreal is the 

 absence of that sloping conformation of the land towards the river 

 channel, the result of graduated subaerial drainage which is character- 

 istic of most large river valleys, and the St. Lawrence seems placed 

 inharmoniously in relation to the adjacent land contour. It has its 

 channel between low banks, and that is all, and the observer fails 

 to detect that graduated contour which the contributory ramifications 

 of all ancient rivers have sculptured from their watersheds to their 

 main channels of drainage ; moreover, the St. Lawrence has an 

 indecisive, course, hei-e splitting itself up against trifling obstacles 

 into numerous channels, again uniting and spreading itself out into 

 broad shallow lakes over the land, reminding one of the behaviour 

 of a sudden rush of storm-water over a course unprepared for it. 

 The St. Lawrence is obviously a new river and supplies a fresh 

 line of drainage compared with the ages of many other rivers, and 

 its history must be viewed in relation to the origin of the great 

 chain of lakes of which it is the outlet. 



The surface levels of the lakes step gradually upwards. Ontario 

 is 235 feet above the sea; Erie, 564 feet; Huron, 595 feet ; Superior, 

 627 feet above the sea. But their depths have no relation to the 

 order in which they occur from the watershed to the sea, for the 

 bottom of Ontario nearest the sea is 365 feet below the sea-level. 

 The bottom of Erie is 462 feet above the sea-level of Huron, 145 

 feet above the sea ; and of Superior, at the inland end of the chain 



^ Extracted from "American Notes," Gardeners' Chronicle, 1878, pp. 169, 170. 



