ANNIVERSARY ADDRESS OF THE PRESIDENT. xli 



riation of direction above-mentioned may probably indicate a similar 

 law of divergency from the original sites of the blocks. In one instance 

 in particular Dr. Bigsby has shown this to be the case. He was able 

 to trace the well-marked angitic trap of Montreal up the St. Lawrence 

 to a point on the south shore of Lake Ontario, distant 2 70 miles from 

 Montreal to the south-west. At the same time this rock had been 

 carried southward to the tract about Lake Champlain, in much greater 

 quantity. The angle between the extreme lines of radiation from this 

 point must be at least 50°. 



The distant erratics are not uniformly spread over the area of the 

 Drift, there being in some places comparatively few. They are ge- 

 nerally abundant in the higher localities, such as the top of Cape 

 Tourment, Lower Canada, 2100 feet above the sea; on the summit 

 of Montreal Hill, and on the high mainland north of Lake Superior. 

 But they exist in the greatest number along the courses of most of the 

 Canadian rivers at all the points where the configuration of the land 

 is such as to oppose the greatest impediments to their transport along 

 the river-valleys. This clearly indicates the operation of strong cur- 

 rents and floating river-ice in again transporting such blocks from the 

 places in which they were first deposited by some more general 

 agency. 



The near or Lake erratics may be due in a considerable degree to 

 existing causes, and not unfrequently radiate from the parent rock in 

 diiferent directions. In other cases, however, their prevalent southerly 

 direction of transport and their numbers indicate the action of some more 

 general and energetic cause. In the Lake of the Woods, for instance, 

 the author remarks that, though the current is from south to north, 

 it brings none of the loose masses of limestone at the south end of the 

 lake to the shores of the northern end ; while innumerable blocks from 

 the latter end of the lake have been carried to its southern extremity. 

 The author also remarked several piles of angular blocks which he 

 conceives to be due to recent action, having been probably left there 

 on shallows on which floating ice had stranded during the spring- 

 freshets. 



The author describes the Canadas and the northern and western 

 parts of the United States as characterized by terraces and ridges 

 which form a prominent feature in the configuration of the surface. 

 They fringe the hills and define the hollow spaces, and in the more 

 open country stretch out into elevated plains or low and swampy 

 surfaces. They are generally formed of native gritty debris, but also 

 contain foreign materials. The deposition of this general detrital mass 

 is obviously referable to the period of submersion of this region, and 

 the formation of the terraces to the denudation which accompanied 

 the subsequent rise of the land. These effects of denudation natu- 

 rally lead to the idea that the osars of Sweden and the eskers of Ire- 

 land may probably be due to a similar cause. 



In connexion with these beds it is important to state that Dr. Bigsby 

 was unable to recognize any indication of two distinct erratic periods, 

 separated by a period of repose, which I have already spoken of as 

 the opinion of some American geologists. This appears to justify 



