DESICCATION AS A PHASE OF THE GLACIAL EPOCH. 191 



leran Glacial epoch. At least, this is the inference which the writer has been 

 compelled to draw from his own observations, as well as from the study of 

 the published works of other geologists. Everything indicates a great slack- 

 ening of the erosive forces, and a gradual diminution in the quantity of water 

 flowing over the surface during the later geological times, and that the glacial 

 development through tliat whole region was neither the beginning nor the 

 ending of this diminution. And there is every reason to believe that the 

 melting of the Cordilleran glaciers did not cause floods which raised the riv- 

 ers to anything like the magnitude they had had in Tertiary times, while 

 there is no proof that this melting was attended with effects justifying, in 

 any degree, our considering it as constituting an event of any great geo- 

 logical importance in that region. 



But it may be said that what is true for the glacial period of the Cordil- 

 leras need not necessarily be so for the same epoch in other parts of the 

 world. This ma}* be admitted ; and it may be added, that the time of the 

 greatest extension of the ice over the Sierra Nevada may not have coin- 

 cided with that of the development of the great ice-sheet in Eastern North 

 America; or it may even be doubted whether the phenomena on the two 

 sides of this continent were at all of the same order of magnitude. This, 

 however, does not affect the question at issue. If the proved drying-up of 

 the vast region of the Cordilleras constitutes a geological and climatological 

 occurrence independent of the Glacial ejjoch, then, even granting all that 

 Professor Dana claims, in regard to the importance of the melting glacier on 

 the eastern side of the continent, this latter occurrence can only be consid- 

 ered as a local one, and evidently cannot be connected with a general desic- 

 cation going on over the whole earth, such as seems so plainly to be inferred 

 from the facts set forth in the preceding chapter. 



What has just been stated in reference to Western North America is still 

 more forcibly impressed upon us by the conditions existing in Asia. Here 

 phenomena similar to those occurring in our own country have been displa}'- 

 ino- themselves on a still a;rander scale than witli us. Desiccation is the most 

 marked climatological Hict which there presents itself to us. It was begun 

 at least as far back as early in the Tertiary epoch, and there seems to be 

 little if any doubt that it has been prolonged into the historical period and 

 is still going on. But Asia is a continent which has never had a '• Glacial 

 epoch," as will be set forth in a succeeding chapter. In no part of that vast 

 continental mass has there ever been any essentially greater development 



