342 CLIMATIC CONDITIONS OF THE GLACIAL ErOCH. 



since the time of the Glacial epoch — that is, of their greatest extension. 

 He also believes that, although the present period of recession may be fol- 

 lowed by one of advance, yet, on the whole, ground will be lost, and tliat in 

 accordance with what we see to be going on all over the world lessened pre- 

 cipitation will continue to manifest itself in glacier regions by a diminution 

 of the ice masses as elsewhere by a decrease of the lakes and rivers, until 

 an equilibrium shall have been reached between the various natural forces 

 which promote and retard precipitation and evaporation. How much ice 

 and snow will remain upon the earth's surface at that time, and how it will 

 be distributed, it is no easy matter to indicate. 



Section IV. — The Former Exienmn of Snoio and Ice over Regions not so covered 

 at the Present Time. The so-called " Glacial Epoch!'' 



In continuing the investigation upon which we have entered, we have 

 next to examine the question whether ice and snow have, at any previous 

 time, occupied a considerably larger area on any part of the earth's surface 

 than they do at present. If this he the case, as may without hesitation be 

 admitted, we wish to state, as concisely as is consistent with a satisfactory 

 development of the discussion here entered upon, where and how extensive 

 the regions are which have in foi'mer times been thus differently circum- 

 stanced from what they now are : it will then be in order to inquire into the 

 nature and extent of the topographical and climatic changes which appear to 

 have been the efficient agents in bringing about the indicated results. 



The phrase " considerably larger area " has been used in the preceding 

 paragraph, as limiting and explaining the kind of change in the amount of 

 glaciation intended to be sought for and explained in the present section. 

 It will be evident from what has already been stated in this chapter that a 

 small amount of change in the size of the area covered by ice or snow in any 

 region could not be considered as of any importance as indicative of a cli- 

 matic change, much less as characterizing an epoch. The shortening of all 

 the glaciers of Europe within the past half-century, in some cases to the 

 amount of nearly a mile, does not by any means justify us in assuming that 

 we have, in the course of that time, entered upon a new epoch in geology. 

 Any such change, although it be but a small one, is, no doubt, of importance 

 in the immediate vicinity of its occurrence; l)ut it would surely be absurd 

 for the Swiss mountaineer to maintain that a new cycle of geological events 



