100 GLACIAL AND SURFACE GEOLOGY OF THE PACIFIC COAST. 



under review the author will be contented with giving references to the 

 sources from which full information may be obtained. Not, however, that it 

 is intended here to convey the impression that all has been ascertained that 

 is desirable in regard to the phenomena of the Glacial epoch. On the con- 

 trary, there is much yet to be learned, and there are many gaps in our knowl- 

 edge Avhich can only be filled by detailed and careful observations. This can 

 be done better than is at present possible after some definitely established 

 theory of the whole series of geological fiicts, of which former glaciation is 

 one, has become generally accepted. At present, as is evident from an 

 examination of the great mass of published materials, observers see, in many 

 instances, more of what they are inclined, from previously conceived theo- 

 retical notions, to expect, and less of what really does exist. 



The facts which have come under the writer's own observation in North 

 America, and especially on the western side of the Continent, during many 

 3'ears of continued investigation, forming, as it were, the basis of the present 

 discussion, have properly been set forth with considerable detail. This has 

 been the more proper course, because it has not elsewhere been attempted 

 to be done ; nor could it have been, except by some one who had with his 

 own eyes seen a large portion of the whole region ; for the published state- 

 ments of some observers are so at variance with the truth, that only utter 

 confusion could result from an indiscriminate use of all that has found its 

 way into print on the subject of glaciers and ice-work as manifested in the 

 Far West. 



Leaving, then, the glaciated regions of Northeastern America and of Europe 

 to be touched upon with more or less detail in a future chapter of this work, 

 we may now proceed to the consideration of certain phenomena of the 

 greatest possible interest as indicative of recent climatic change, and which 

 are manifested not only fxr and wide over the whole earth, but on an espe- 

 cially large scale, and with the greatest distinctness, in the region to which 

 our attention has been particularly directed in the preceding pages. We 

 refer to the diminution in the quantity of water running and standing on the 

 surface of the country ; to the drying-up which has been going on over a 

 large part of the earth during the later geological times, a phenomenon so 

 wide-spread and important in its manifestations as to demand a much more 

 careful study than it has hitherto received. 



