review of study methods 189 



Methods of Study 



The failure to determine the facts relating to Pleistocene submergence 

 and to reach agreement in opinion must be due either to inherent diffi- 

 culty of the study, or to defect in methods of study, or to lack of clear, 

 unbiased vision. Probably all of these factors contribute, but especially 

 the second. A discussion of study methods is in order. 



(1) Successful attack of the submergence (uplift) problem requires 

 correlation of data over the entire glaciated area, but the studies have 

 usually been local and detached. 



(2) Equality of uplift over considerable area has too often been as- 

 sumed; but this is impossible, except perhaps in the central area of the 

 upraised dome. 



(3) Systematic exploration must postulate an irregular doming up- 

 lift, with the horizontal lines of equal uplift (isobases) curving about the 

 convexity and with declining gradients in radial directions. The gra- 

 dients on the radii must diminish to zero both at the margin and near 

 the center of the domed area. 



(4) The critical element everywhere is the maximum uplift in each 

 location, the determination of the initial or summit shoreline. This is 

 the difficult and elusive element, and most recorded elevations give only 

 the conspicuous, inferior phenomena. 



(5) For any district a working theory is needed of the approximate 

 direction and spacing of the isobases or, in other words, the direction and 

 gradient of the steepest slope. Then the location of two positive stations 

 on the summit level affords a reference or base for further search, and 

 with accumulation of data the search becomes proportionately easier. 



For success in determining at least approximately the total uplift over 

 a large area the writer has relied chiefly on criteria not generally recog- 

 nized. Instead of depending on bars, cliffs, and features of wave work, 

 which are excellent when found, but which are capricious, commonly 

 wanting, and rarely produced as initial or summit inscriptions, he has 

 depended primarily on stream deltas. These are almost unfailing and 

 are positive indications, even if not very precise, of the initial water plane. 

 In a new or unknown district the primary determination of the approxi- 

 mate level is made on larger streams, preferably in south-leading valleys, 

 and the more precise determination of the summit water level is made by 

 examination of the smaller deltas of lateral streams and the shore features 

 in the vicinity. As the railroads, with their elevations giving datum for 

 altitudes, nearly always follow river valle3's, .it has been feasible to trn- 

 verse rapidly a large territory with positive results. A proof of tlic sound- 



