My own observations have been chiefly in the eastern part of North America. My son, Dr. G. M. Dawson, has much more ably and thoroughly explored those of the west; and after describing the immense Cordilleran ice mass which extended for a length of 1,200 miles along the mountains of British Columbia and discharged large glaciers to the north, as well as to the west and south, and stating his reasons for believing in that differential elevation and depression which caused the greatest height of the mountains to coincide with the greatest depression of the plains, and _vice versâ_, and showing the Cordilleran glacier must have been separated by a water area from that of the Laurentide hills on the east, thus concludes:-- "It is now distinctly known, as the result of work done under the auspices of the Geological Survey of Canada, and more particularly of observations by the writer and his colleagues, Messrs. McConnell and Tyrrell, that the extreme margins of the western and eastern glaciated areas of the continent barely overlap, and then only to a very limited extent, while the two great centres of dispersion were entirely distinct. For numerous reasons which cannot be here entered into, the writer does not consider it probable, or even possible, that the great confluent glacier of the north-eastern part of the continent extended at any time far into the area of the great plains; but erratics and drift derived from this ice mass did so extend, and are found between the 49th and 50th parallels, stranded on the surface of moraines produced by the large local glaciers of the Rocky Mountains. Recognising, however, the essential separateness of the western and eastern confluent ice masses, and the fact that it is no longer appropriate to designate one of these the "continental glacier," the writer ventures to propose that the eastern _mer de glace_ may appropriately be named the great _Laurentide glacier_, while its western fellow is known as the "_Cordilleran glacier_." It may be added that there is good evidence to show that both the Laurentide and Cordilleran glaciers discharged into open water to the north." These conclusions, based on a large induction of facts applying to a very large area of the North American Continent, coincide with my own observations in the east, and with the inferences deducible from the present condition of Greenland and Arctic America.