Revicio of (he Glacial Theory. 263 



are not found in the Ohio Valley, and that there is not a vestige of 

 evidence, in this part of the country, indicating in the slightest degree 

 any su bsidence of the continent, we may well pause at this step, in the 

 progress of this theory, until the Professor is able to ascertain whether 

 that nodule, figured on page 39, was held in the glacier or in the shale 

 while part of it was rubbed off It seems to me that an author able 

 to see with such certainty such vast changes and startling phenomena, 

 so directly adverse to every known geological fact, and so contrary to 

 that uniformity in the laws of nature, which every department of 

 natural history teaches, ought not to hesitate, on finding a scratched 

 bowlder, in uncertainty as to whether the bowlder was held in the 

 ice while it was ground off on another rock, or held in a matrix while 

 the ice rubbed the other rock over it. Such minor points as deter- 

 mining which stone was on the upper side, when the scratching was 

 done, ought to be definitely settled before we pin our faith too strongly 

 to the larger obstacles in this theory. Professor Newberry says, 

 however, that there can be no doubt that it was ground off by glacial 

 action. There is some consolation in this, for we may now know as a 

 scientific fact that he can tell by looking at a scratched bowlder, 

 whether it was scratched by an iceberg, a glacier, or a land-slide. 

 Indeed, he says, " The track of a glacier is as unmistakable as that of 

 a man or a bear, and is as significant and trustworthy as any other 

 legible inscription." It has never been my fortune to see the track of 

 a glacier, but if it is so distinct, one so conversant as he, might readily 

 tell us whether the track on this bowlder is right side or wrong side up. 

 It is not necessary, to pursue the glacial theory step by step through 

 all its continental oscillations and changes of climate, to become con- 

 vinced of its inadequacy to account for the phenomena witnessed, nor 

 is the time ordinarily occupied in an evening essay sufficient to follow 

 it through its elaborate details and criticise it. Without, therefore, 

 following it farther, though meaning no disrepect to the continent by 

 leaving it in baptism, I will call your attention to some of the laws 

 governing denudation by water and ice, to some of the evidences of 

 the wide distribution of plants and animals, by forces now in opera- 

 tion, and to some of the facts tending to account for what we very 

 correctly call the drift. 



Water courses of all sorts and sizes are alike, and record the same 

 kind of aqueous denudation everywhere. Water invariably cuts out 

 a winding course having a transverse section like the letter V. Ice 

 marks, of all kinds, differ from water marks. A glacier passing over 

 a hill country will round off the hills, so that a transverse section will 

 be represented by the arc of a circle, and hollow out and straighten 



