GLACIAL DRIFT. 323 



in the earlier formed basin, but did not fill it up. There was rather more 

 subsidence, showing that the tendency in modern times has been to 

 enlarge rather than restrict the size of the bay. 



(6) The coldest part of the continent lies to the west and north of 

 Hudson's bay. A comparison of meteorological tables given in various 

 arctic expeditions indicates a greater average degree of cold in the west — 

 say at Fort Reliance in Rupert's Land — than very far north. No greater 

 degree of cold has been observed, but a lower average is reported for 

 Greenland. For example: the lowest temperature indicated during the 

 whole of one winter on the Hansa, which drifted along the entire east 

 coast, was only — 11° F. On the contrary, the average temperature for 

 the four winter months, — December, January, February, and March, — 

 for 1833-34, at Fort Reliance, as reported by Capt. Back, was — 13°.9. 

 For the winter ensuing, the average temperature for the same months 

 was — 21°. 8. The Mackenzie valley, and the regions to the north-east, 

 are noticed in meteorological treatises as remarkable for their cold. Be- 

 ing so very cold, the continental parts west and south-west from Green- 

 land would be favorable for the preservation of ice in the summer, and 

 thus for its accumulation in enormous sheets as time progressed. 



]Map of North Aisierica. 



I have prepared a small map of the northern part of the continent to 

 illustrate the dispersal of the drift. Observations will be found recorded 

 there, indicating the directions of the movements in all the states and 

 provinces so far as known. Reference to it will save much time in 

 description. There is also represented the southern limit of the ice- 

 sheet, the driftless area of the north-west, and the boundaries of the 

 territory occupied by the Champlain deposits, termed the " Orange 

 sand," by Prof. Hilgard. All the geological reports of the several states, 

 provinces, and territories, besides other volumes too numerous to be 

 cited here, have been consulted for the preparation of this map, and it is 

 believed to represent accurately the existing information respecting the 

 dispersal of the drift. Where several courses have been described in a 

 limited territory, only the predominant one can be given because of the 

 smallness of the scale. Nor is the Rocky Mountain area delineated, 

 since that belongs to a different centre of dispersion. 



