174 T. C. Ghamberlin — Diversity of the Glacial Period. 



1. Doubtless nearly or quite all the older students of drift, 

 of the glacial school, once entertained views that should be 

 placed under the first class. Such views linger with some 

 whose later attention has been turned in other directions 

 chiefly, and with some whose studies have been confined to 

 areas presenting only one time-phase of the drift conspicu- 

 ously, and some hold these views for reasons less felicitously 

 explained. I should class Professor Wright's views in the 

 primitive group. He is doubtless in advance of many phases 

 of the older views and his papers show some progress, but he 

 has failed to definitely recognize and accept two stages of 

 depression separated by an important stage of elevation. This 

 is best illustrated by his position respecting the formations of 

 the Delaware region, which will be noted further on. His 

 impression of the extent and complexity of the ice age is of 

 the earlier rather than of the later order. He does indeed use 

 terms that by themselves would signify great extension and 

 complexity, but he employs arguments and interpretations 

 which show that they carry a significance very different from 

 that which is given them by those who take the newer and 

 enlarged views of unity. For instance, he objects to the 

 reference of the erosion of the lower gorge of the Allegheny 

 and Upper Ohio Rivers to an interglacial epoch on the ground 

 of the length of time required by the erosion, and speaks of 

 such views as " m eking unnecessary demands on the forces of 

 nature." (Man and the Glacial Epoch, p. 218.) His descrip- 

 tions of the Ice age in his two books and elsewhere seem to 

 me to convey an archaic and bedwarfed impression both of the 

 extent and complexity of the period. I cannot, therefore, 

 think that his views of the glacial period have any such exten- 

 sion as would entitle them to be classified under the newer 

 views of unity. The most serious phase of the matter is that 

 neither analytical methods nor their results seem to find even 

 an approximately accurate reading, much less exposition and 

 discussion, at his hands. 



2. The later views of unity seem to have few, if any, 

 declared advocates, due, doubtless, to the fact that as soon as a 

 glacialist comes to realize the nature of the phenomena invol- 

 ved to an extent sufficient to cause him to dismiss the primary 

 views, he quickly passes on into the third or fourth class, or 

 else takes an attitude of conservatism and reserve, and awaits 

 further evidence before engaging in a definite advocacy. 

 These views are, however, entitled to a distinct place and to 

 full recognition, because they not only represent the attitude, 

 whether transient or otherwise, of a considerable body of gla- 

 cial students, but they are still kept among the working hy- 

 potheses of many who employ the method of multiple working 



