TJpham — Review of the Quaternary Era, etc. 33 



The temperature remaining constant, as it is bound to do under 

 a constant pressure, we shall have a mass of water at —2° C. 

 underlying a mass of ice of enormous weight. This water has 

 not the properties necessary to prevent its escaping from 

 beneath the ice, for if the pressure be relieved at a crack or 

 break, only fa of the mass will congeal, which will scarcely 

 be sufficient to seal the means of escape. In other words, as 

 fast as water formed beneath the glacier, it would be squeezed 

 out by the pressure of the ice. The results of these experi- 

 ments appear to render questionable any theory accounting for 

 peculiar motions of glacial ice by supposing the existence of a 

 layer of pressure- molten water beneath the mass. 



Art. VI. — A Review of the Quaternary Era, with special 

 reference to the Deposits of Flooded Rivers / by Warren 

 Upham. 



Two stages of great progress in knowledge of Quaternary 

 geology were marked by the publication of the glacial theory 

 by Louis Agassiz fifty years ago, and of " The Great Ice Age " 

 by James Geikie sixteen years ago. And the degree of atten- 

 tion which deposits of this age are now receiving is even 

 greater than ever before. Besides the vast mass of glacial 

 literature which has appeared in the form of scientific papers 

 in magazines and in reports of societies and of government 

 surveys, two popular treatises have been recently published, 

 summarizing what has been done in this field of geologic in- 

 vestigation in this country and in France and the western 

 Alps.* The purpose of the present paper, based on my own 

 observations and on study of the work of others, is to trace 

 concisely the sequence of events during the Ice age and the 

 post-glacial epoch, to discuss the probable causes of the great 

 climatic changes of this era, and to notice especially its remark- 

 able fluvial deposits. 



The Quaternary era, according to definitions of recent text- 

 books of geology by Dana, Archibald Geikie, and Etheridge, 

 began with the change from the mild Pliocene climate to that 

 of the Glacial period, with its accumulation of vast sheets of 

 land ice in high latitudes, and has continued to the present 

 time. We are living in the Quaternary era, as thus defined, 

 and it must extend far into the future to be at all proportion- 

 ate in length with the previous co-ordinate divisions of geo_ 



* G. F. Wright, The Ice Age in North America, 1889. (Appleton & Co.) A. 

 Falsan, La Periode Glaciaire, 1889. (Felix Alcan, 108 Boulevard Saint-Germain, 

 Paris.) 



Am. Jour. Sci. — Third Series, Yol. XLI, No. 241. — January, 1891. 

 3 



