264 Review of (he Gtacial Theory. 



the valleys, so that a transverse section will be represented by the 

 lower part of the letter U. The valley of the Ohio, and each of its 

 tributaries, bear the unmistakable evidences of having been worn out 

 by the action of water alone, and not a single valley or hill bears any 

 evidence of having been hollowed out or polished oif by the action of 

 the ice. The valleys on the north side of the Ohio River, and some 

 of those on the south side, were filled up in part by sand and gravel 

 during the period of the drift, but the winding course of the streams 

 and the V-shaped valleys, where they wex'e unaffected by the drift, 

 and the cross sections of the valleys affected, where they have been 

 noticed, and the rough outliers on the hills, all alike testify to the ac- 

 tion of water and the absence of ice. I think this is the position 

 taken by Professor Andrews in his survey of Eastern Ohio, and I 

 think the reader will not discover that Professor Newberry has under- 

 taken very seriously to controvert it, but rather tried to obviate 

 bringing his glacial sheet in conflict with the hills and valleys, by 

 moving it over westerly, beyond Prof. Andrews district, where it might 

 have easier sading. 



It is sometimes said that the climate of the world has so materially 

 changed during different geological periods, that there is nothing to 

 excite our astonishment, in the assertion, that the warm climate of the 

 Southern States, during the tertiary period, extended over the United 

 States and Canada and as far north as Greenland, and that at the 

 close of that period, the climate changed from the all-pervading warmth 

 of sunny climes to an all-pervading Arctic cold ; that the Arctic cli- 

 mate of Greenland extended south over Canada and the United States 

 to the Gulf of Mexico, and that nearly the whole country was covered 

 with a sheet of ice thousands of feet in thickness. But geology does 

 not teach us, that any such material changes of climate have ever 

 taken place, nor that any other changes have taken place, the cause 

 of which we may not readily account for. Let us look at some of the 

 effects of ocean currents now in operation. 



Captain Mack named an island " Mimosa, " in latitude 77° north, 

 longitude 66° east, because he there picked up chestnut or mimosa 

 beans — tropical growths carried by ocean circulation to foreign lands. 



Professor Campbell, speaking of this subject, says : "To that point 

 the equatorial current now reaches ; and there the warm water must 

 plunge under water, which, after a certain temperature, gets lighter 

 as it gets colder, till it floats ready to freeze. Solid ice was lighter 

 than sea water off Labrador as 9 is to 10 by bulk. Li Spitzbergen 

 the chestnuts get to 20° east, 77° north ; and the warm water of the 

 equatorial current then goes under the ice to warm the sea creatures 



