﻿234 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Apr. 9, 



Boulders are distributed somewhat partially ; certain areas have 

 few or none ; and this over the whole country generally, without 

 reference to the present rivers and lakes. But they seldom fail on 

 high grounds, such as the top of Cap Tourment, Lower Canada, 2 1 00 

 feet above the sea, — on the high north mainland of Lake Superior, — 

 and on the summit of Montreal Hill. Still they are in the greatest 

 numbers — in quantities quite astonishing — at points of obstruction 

 on all the Canadian rivers, whether caused by narrows, islands, rapids, 

 or falls. They often overflow the vicinity of such spots, in like num- 

 bers, and without exhibiting much attrition. The smaller detritus 

 has been driven by winds and rains into hollows, leaving the larger — 

 the blocks — exposed and alone. 



These distant erratics have, therefore, been in motion since the 

 formation of the existing water-courses. 



The second class, the ho?ne or lake erratics, are, perhaps, the 

 products of causes now in operation, —frosts and thaws, freshets, 

 storms. In all these Canadian lakes, at least along-shore, large fields 

 of ice are formed, which entangle earthy matters of all sizes, and 

 transport them here and there. 



The cliffs and deep waters of the north side of Lake Superior are 

 well-fitted for the lodgement of considerable masses of mixed ice and 

 snow, which the warmth of summer would cause to drop into the 

 lake, there to be for a time the sport of the winds. I saw snow on 

 the heights of this lake in June, a month, indeed, in which it has 

 been known to snow all day. 



This class of erratics may radiate from a common centre, irrespect- 

 ive of present currents, as we see in the case of the jasper-pudding- 

 stone, which we find forty or fifty miles on the east, west, and south 

 of its parent-bed. It is possible that its boulders may also be found 

 on the north, but I doubt it. 



Fragments of the rocks of Lake Huron travel into Lake Superior, 

 from the east ; — strengthening the belief that these two lakes were 

 once united ; — a union, which, if Lake Huron were raised only ten 

 yards, would be effected. At the Falls of the River St. Mary, con- 

 necting these two lakes, boulders from both meet in great numbers 

 and size ; these were left, perhaps, by opposing currents, independent 

 of the watercourses we now have. 



It was curious to trace the well-marked augitic trap of Montreal, 

 stretching up the St. Lawrence, and occurring at successive distances 

 until the last bit I observed was on the Genesee River, on the south 

 shore of Lake Ontario, 270 miles to the S.W. The boulders of this 

 rock are, however, in far greater quantity on the southern levels, 

 between Montreal and Lake Champlain. 



Canadian rivers annually bring down a certain quantity of detritus; 

 and winds disperse fragments of ice-borne rocks over lake-shores ; 

 but in Lake Huron, at least, this latter operation goes on but slowly. 

 The opposing beaches of two very narrow straits in Lake Huron 

 (those of Pelletau, near St. Joseph Isle, and Lamorandiere, Collin's 

 Sound) are lined with totally distinct detritus. In like manner, 

 among the incredible quantities of debris on the north shore of the 



