44 THE CANADIAN NATURALIST. [Feb. 



dental geographical conditions ; more especially to the distribution 

 of the waters of the Gulf stream, which might be changed by a 

 comparatively small subsidence in Central America. To assume 

 the former existence of glaciers in a country in north latitude 56°, 

 and with its highest hills, under the present exceptionally favour- 

 able conditions, snow-capped during most of the year, is a very 

 different thing from assuming a covering of continental ice over 

 wide plains more than ten degrees farther south, and in which, 

 even under very unfavourable geographical accidents, no snow can 

 endure the summer sun, even in mountains several thousand feet 

 high. Were the plains of North America submerged and invaded 

 by the cold Arctic currents, the Gulf stream being at the same 

 time turned into the Pacific, the temperature of the remaining 

 North American land would be greatly diminished ; but under 

 these circumstances the climate of Scotland would necessarily be 

 reduced to the same condition with that of South Greenland or 

 Northern Labrador. As we know such a submergence of America 

 to have occurred in the Post-pliocene period, it does not seem 

 necessary to have recourse to any other cause for either side of 

 the Atlantic. It would, however, be a very interesting point to. 

 determine, whether in the Post-pliocene period the greatest sub- 

 mergence of America coincided with the greatest submergence of 

 Europe, or otherwise. It is quite possible that more accurate 

 information on this point might remove some present difficulties. 

 I think it much to be desired that the many able observers now 

 engaged on the Post-pliocene of Europe, would at least keep before 

 their minds the probable effects of the geographical conditions 

 above referred to, and enquire whether a due consideration of 

 these would not allow them to dispense altogher with the somewhat 

 extravagant theories of glaciation now agitated.* 



* While these sheets were in the press, I have seen with much gratification, 

 that Jamieson has recognized in Caithness a truly marine boulder-clay, holding 

 those elongated and striated stones heretofore regarded as characteristic of 

 glacier action ; but which are frequent in the marine boulder-clays of Canada, 

 and in the bed of the present Arctic current. 



