28 REPORT— 1886. 



and the Gulf of Mexico were deep inland lakes.' The eflfect of such 

 conditions on the climates of the northern hemisphere must have been 

 prodigious, and their investigation is rendered all the more interesting 

 because it would seem that this continental period of the post- Glacial age 

 was that in which man made his first acquaintance with the coasts of the 

 Atlantic, and possibly made his way across its waters. 



We have in America ancient periods of cold as well as of warmth. I 

 have elsewhere referred to the boulder conglomerates of the Huronian, 

 of the Cambrian and Ordovician, of the Millstone-grit period of the Car- 

 boniferous and of the early Permian ; but would not venture to aflBrm 

 that either of these periods was comparable in its cold with the later 

 glacial age, still less with that imaginary age of continental glaciation 

 assumed by certain of the more extreme theorists.^ These ancient con- 

 glomerates were probably produced by floating ice, and this at periods 

 when in areas not very remote temperate floras and faunas could flourish. 

 The glacial periods of our old continent occurred in times when the 

 surface of the submerged land was opened up to the northern currents, 

 drifting over it mud and sand and stones, and rendering nugatory, in 

 so far at least as the bottom of the sea was concerned, the effects of the 

 superficial warm streams. Some of these beds are also peculiar to the 

 eastern margin of the continent, and indicate ice-drift along the Atlantic 

 coast in the same manner as at present, while conditions of greater 

 warmth existed in the interior. Even in the more recent Glacial age, 

 while the mountains were covered with snow and the lowlands sub- 

 merged under a sea laden with ice, there were interior tracts in some- 

 what high latitudes of America in which hardy forest trees and her- 

 baceous plants flourished abundantly ; and these wei'e by no means 

 exceptional ' interglacial ' periods. Thus we can show that while from 

 the remote Huronian period to the Tertiary the American land occupied 

 the same position as at present, and while its changes were merely 

 changes of relative level as compared with the sea, these have so in- 

 fluenced the ocean currents as to cause great vicissitudes of climate. 



"Without entering on any detailed discussion of that last and greatest 

 Glacial period which is best known to us, and is more immediately con- 

 nected with the early history of man and the modern animals, it may be 

 proper to make a few general statements bearing on the relative import- 

 ance of sea-borne and land ice in producing those remarkable phenomena 

 attributable to ice action in this period. In considering this question it 

 must be borne in mind that the greater masses of floating ice are pro- 

 duced at the seaward extremities of land glaciers, and that the heavy 

 field-ice of the Arctic regions is not so much a result of the direct freez- 

 ing of the surface of the sea as of the accumulation of snow precipitated 



' Dawkins, Popular Science Monthly, 1873. 



2 Notes on Post-Pliocene of Canada. Hicks, ' Pre-Cambrian Glaciers,' Geol. Mag., 

 1880. 



