Presidential Address. 273 



warmth. I have elsewhere referred to the boulder con- 

 glomerates of the Huron ian, of the Cambrian and Ordo- 

 vician, of the Millstone-grit period of the Carboniferous and 

 of the early Permian ; but would not venture to affirm that 

 either of these periods was comparable in its cold with the 

 later glacial age, still less with that imaginary age of con- 

 tinental glaciation assumed by certain of the more extreme 

 theorists. 1 . These ancient conglomerates 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 super- 

 ficial 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 submerged under 

 a sea laden with ice, there were interior tracts in somewhat 

 high latitudes of America in which hardy forest trees and 

 herbaceous plants flourished abundantly; and these were by 

 no means exceptional ' inter-glacial ' 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 connected with the early history of 

 man and the modern animals, it may be proper to make a 

 few general statements bearing on the relative importance 

 of sea-borne and land ice in producing those remarkable 



1 Notes on Post-Pliocene of Canada. Hicks, Pre-Cambrian Glaciers, 

 Geol. Mag., 1880. 



