184 DISCUSSION OF THE DESICCATION QUESTION. 



great continental mass of Eurasia, leaving the interior desiccating regions for 

 the shores blown upon by the return trade-winds, carrying with them the 

 moisture necessary to comfort and welfare. The proportion of the earth's 

 surface which, at any one epoch, presents exactly those conditions necessary 

 for the development of a dominating and progressive race, appears to be 

 quite limited. A temperate climate, sufficiently supplied with moisture, is 

 a sine qua nou of intellectual development ; but such is not to be created by 

 man himself, nor can the deterioration Avrought by nature be artificially 

 removed or postponed in any but the most limited degree. 



Leaving for the present the question of precipitation as connected with 

 the power of man to increase or regulate it, we pass to the consideration of 

 another topic, namely, the phenomena of desiccation as indicating an epoch 

 during which the earth is recovering — so to speak — from the effects of a 

 previous condition of glaciation. 



Section III. — Desiccation as a Phase of the Glacial Epoch. 



From what has been stated in the preceding section it will appear evident 

 that the popular view of the phenomena of desiccation is, that they are the 

 result of man's interference with the course of nature. This theory is not 

 only the favorite one with the people, but it has been extensively advocated 

 by physical geographers ; that is, by the class of investigators which limits 

 its studies of the earth's surface to the consideration of its present aspect, 

 without having any special idea of connecting that present with a series of 

 precedent conditions. In extending our scientific inquiries, and endeavoring 

 to trace back the phenomena of the present into a distant past, and to estab- 

 lish a relationship between what is now happening and what did happen 

 during preceding ages, we enter the domain of geology. 



Geologists, as might naturally be expected, have not generally adopted 

 the views set forth and controverted in the preceding pages in relation to 

 the diminution of the water over certain portions of the earth. While not 

 ignoring altogether the important facts which immediately present them- 

 selves when we come to study almost any part of the earth's surface with 

 reference to the question before us, they have — so far, at least, as American 

 geologists are concerned — almost without exception taken up a position 

 which is, as the writer considers, far from satisfactory, since it neither ena- 

 bles them to account for past nor present climatic changes proved to have 



