CHAPTER II. 



THE DESICCATION OF LATER GEOLOGICAL TIMES. 



Section I. — Introductory. 



Climatic changes manifest themselves upon the earth's surface in a 

 variety of ways. The one essential cause underlying all tliat complex of 

 conditions to which the all-emhracing term " climate " is applied is, of 

 course, the solar heat. But the manifestations of the effects of this funda- 

 mental agency are powerfully influenced by many different causes, some of 

 which are liable to be profoundly modified by variations of geological con- 

 ditions. This subject will come up for more careful consideration at a later 

 period in this volume ; at present all that it is necessary to do is, to call 

 attention to the fact that a diminution of the water flowing or resting 

 motionless upon the surface of the earth — of the volume of rivers and of 

 the area of lakes, in short — is a phenomenon which must be admitted by all 

 to be indicative of a climatic change, the importance of which corresponds in 

 a measure to the amount of such diminution. That such a change is now 

 going on, and that it has been for a very considerable length of time, we 

 shall now proceed to set forth, leaving the causes and consequences of this 

 desiccation to be discussed in another chapter. It will become evident, on 

 examination, that while the evidences of climatic change presented by the 

 phenomena of extinct glaciation are extremely interesting, those of the dry- 

 ing-up are even more important, at least from a climatological j^oint of view, 

 for they can be traced over a much larger area of the earth's surface, and 

 have been continued during a longer period, than the glacial phenomena in 

 question. This desiccation is, moreover, especially interesting in that it is 

 an occurrence which is not only taking place at the present da}', but one 

 which is making itself felt in many ways as affecting the movements, the 

 prosperity, and even the life itself, of large masses of mankind. 



It is indeed remarkable that so little attention has been paid to the facts 

 which will be brought forward in the following pages. Many of them have 

 been reported singly, but apparently without much weight being attached 



