ANNIVERSARY ADDRESS OF THE PRESIDENT. XXXIX 



later than the latest drift in which its remains are found ; nor do I 

 understand how the cause just assigned could eifect its final extinc- 

 tion. If, however, we admit the submergence of that continent to 

 the extent which many geologists are now disposed to admit, there 

 can be no difficulty in explaining the extinction of any of the great 

 pachyderms which might have previously inhabited that region. 



Without dwelling further on the characters of the Drift of this re- 

 gion, or on the minor details of the general phsenomena of accumula- 

 tions of drifted materials, I will proceed to give a short analysis of Dr. 

 Bigsby's paper, to which I have already alluded, '' On the Erratics 

 of Canada." It is composed from notes made by the author several 

 years ago, a circumstance to which the want of more frequent ob- 

 servations on polished and striated rocks must be attributed. The 

 importance of those phsenomena was not then recognized. The author, 

 however, has been enabled by his general knowledge of the physical 

 geography and geological structure of this region, and by a careful 

 observation of the erratic materials, to make valuable additions to 

 our previous knowledge of the Drift, derived from American geolo- 

 gists. His observations extend much farther to the north and west 

 than those of the latter observers, as is best seen by a glance at the 

 map which accompanies the memoir. 



The author commences his observations at the Lake of the Woods 

 lying to the north-west of Lake Superior. He then proceeds east- 

 ward successively to the lakes La Pluie, Superior, Huron, Erie, and 

 Ontario, describing the rock-formations and the blocks, and other 

 detritus which line their shores, and the banks of the streams con- 

 necting them. The water from Lake La Pluie runs westward and ul- 

 timately discharges itself into the Arctic Sea, while that from Lake 

 Superior runs eastward to the Atlantic. The watershed between 

 them rises to the height of about 1200 feet above the sea-level. In 

 this tract are numbers of large erratics, which Dr. Bigsby was gene- 

 rally able to identify with rocks existing in situ to the north, but never 

 on the south. 



Lake Superior is about 600 feet above the level of the sea. On its 

 northern shore are a considerable number of erratic blocks which have 

 come from north and north-east. Such is the case also with the nu- 

 merous large blocks on the banks of the St. Mary River which con- 

 nects Lake Superior and Lake Huron. On the banks of Lake Su- 

 perior are many terraces consisting of detrital matter derived for the 

 most part from neighbouring rocks. The most important of these 

 is that about the mouth of Black River, and rises to the height of 

 330 feet above the lake, extending far along the banks of the lake, 

 and intervening between the neighbouring hills for several miles to 

 the foot of an elevated range. Its mass consists of coarse unstratified 

 native detritus imbedded in sand. Assuming the sea to have risen 

 above this level during the glacial period, the masses now forming ter- 

 races of this kind must be considered as submarine deposits formed 

 under comparatively tranquil conditions, the present lake-basiils having 

 been scooped out of them by denuding agents during or after their 

 emergence from beneath the surface of the ocean. 



