352 G. F. Wright— Unity of the Glacial Epoch. 



glacier retreated, during the interglacial epoch, to such an 

 extent that the glaciated area was as free from ice as it is at 

 the present time ; and that subsequently the conditions were 

 repeated and there was a re-advance to nearly the farthest 

 limit of the previous movement. It is this view of the case 

 which is advocated so vigorously, in this country by Professor 

 Chamberlin and some of his associates on the United States 

 Geological Survey, and by Professor James' Geikie in Scotland, 

 Professor Wanschaffe in Germany, Baron De Geer in Sweden 

 and others. In discussing the problem it will be natural for 

 me to give special prominence to the facts of the American 

 field, and, with all respect to individuals mentioned, to the 

 discussions and reports of mj associates in the explorations of 

 this country. But I will not wholly neglect the facts of other 

 lands. 



In approaching the subject it is important to notice the fact 

 that Professor Chamberlin inaugurated his induction as di- 

 rector of the glacial division of the United States Survey by 

 publishing a monograph on " The Terminal Moraine of the 

 Second Glacial Epoch," thus assuming the truth of his theory 

 in the title. In the introduction to this paper, however, 

 nothing could be more indicative of the proper spirit with 

 which to enter upon the discussion, or nothing more cordially 

 welcoming discussion, than the following remarks : 



"Perhaps no department of geological investigation has 

 greater need of careful discrimination than that which deals 

 with the complex deposits of the Quaternary age. Most 

 formations betray their origin in their salient characteristics, 

 but those of the Quaternary age are apparently capable of 

 diverse interpretation if their general nature alone is con- 

 sidered. It is only by critical discrimination of their special 

 and often quite unobtrusive features that they can be deci- 

 sively referred to the several agencies that produced them. 

 Most formations owe their origin to the action of some one 

 dominant agency. The Quaternary deposits are, on the con- 

 trary, the product of a combination of agencies, the relative 

 work of which is often distinguishable only with difficulty. 

 In these discriminations the individual judgment of the inves- 

 tigator plays an important part. The influence of personal 

 predisposition, therefore, is here liable to be most gravely felt. 

 Probably no investigator is entirely free from the influence of 

 his own preconceptions and methods of interpretations. He, 

 perhaps, does best, who, while duly appreciating these influences 

 and assiduously applying checks for their correction, frankly 

 submits his methods of interpretation to the correction of 

 others." 



