GEOLOGY OF THE ATLANTIC OCEAN. 189 



but with the plains out of water this would be impossible. "We see 

 evidence of this at the present day in the fact that in unusually 

 cold winters the great precipitation of snow takes place south of 

 Canada, leaving tbe north comparatively bare, while as the tempera- 

 ture becomes milder the area of snow deposit moves farther to the 

 north. Thus, a greater extension of the Atlantic, and especially of 

 its cold, ice-laden Arctic currents, becomes the most potent cause of a 

 glacial age. 



I have long maintained these conclusions on general geographical 

 grounds, as well as on the evidence afforded by the Pleistocene de- 

 posits of Canada ; and, in an address the theme of which is the ocean, 

 I may be excused for continuing to regard the supposed terminal mo- 

 raines of great continental glaciers as nothing but the southern limit 

 of the ice-drift of a period of submergence. In such a period the 

 southern margin of an ice-laden sea where its floe-ice and bergs 

 grounded, or where its ice was rapidly melted by warmer water, and 

 where, consequently, its burden of bowlders and other debris was de- 

 posited, would necessarily present the aspect of a moraine, which, by 

 the long continuance of such conditions, might assume gigantic dimen- 

 sions. Let it be observed, however, that I fully admit the evidence of 

 the great extension of local glaciers in the Pleistocene age, and espe- 

 cially in the times of partial submergence of the land. 



I am old enough to remember the sensation caused by the delight- 

 ful revelations of Edward Forbes respecting the zones of animal life 

 in the sea, and the vast insight which they gave into the significance 

 of the work on minute organisms previously done by Ehrenberg, 

 Lonsdale, and Williamson, and into the meaning of fossil remains. A 

 little later the soundings for the Atlantic cable revealed the chalky 

 foraminiferal ooze of the abyssal ocean ; still more recently the wealth 

 of facts disclosed by the Challenger voyage, which naturalists have 

 not yet had time to digest, have opened up for us new worlds of deep- 

 sea life. The bed of the deep Atlantic is covered for the most part 

 by a mud or ooze largely made up of the debris of foraminifera and 

 other minute organisms mixed with fine clay. In the North Atlantic 

 the Norwegian naturalists call this the Biloculina mud. 



Farther south the Challenger naturalists speak of it as Globige- 

 rina ooze. In point of fact it contains different species of forami- 

 niferal shells, Globigerina and Orbulina being in some localities domi- 

 nant, and in others other species, and these changes are more apparent 

 in the shallower portions of the ocean. It is also to be observed that 

 there are means for disseminating coarse material over the ocean-bed. 

 There are in the line of the Arctic current on the American coast 

 great sand-banks, and off the coast of Norway, and constitute a con- 

 siderable part of the bottom material. Soundings and dredgings off 

 Great Britain, and also off the American coast, have shown that frag- 

 ments of stone referable to Arctic lands are abundantly strewed over 



