310 R. A. DALY OSCILLATIONS OF LEVEL 



Jersey and Newfoundland. It was then found that Barrell had adopted 

 the same hypothesis as a result of his deep study of the strength of the 

 earth's crusty founding his case on general principles of geology and on 

 the field-work of Fernald and Woodworth.^° Where so many lines of 

 evidence converge, initial speculation should rise to the status of a work- 

 ing hypothesis. If it be true, the extraglacial belt west of Massachusetts 

 might be expected also to have undergone recent oscillations of level. 

 Among the consequences of peripheral upwarping might be : special 

 trenching by rivers in the marginal bulge ; special alluviation in the strip 

 of relatively low land adjacent to the zero isobase; diversion of rivers 

 from valleys which had been too heavily alluviated because of the upwarp- 

 ing; and temporary reversal of some streams. Among the consequences 

 of subsidence following the peripheral upwarping might be : new local 

 reversal of drainage, and appropriate tilting of lake strands which were 

 established before the subsidence was completed. 



Evidence from the marginal Belt v^est of New England 

 scope of the discussion 



The application of these criteria is not a simple matter. According to 

 the hypothesis, each glacial stage — Kansan, Illinoisan, and Wisconsin — 

 was accompanied by a double oscillation of levels. The effects must be 

 associated in the field more or less complexly. One of the first steps 

 toward understanding the hypsometric changes involved is the mapping 

 of the zero isobases for each glacial stage. Practically nothing has been 

 done in locating the 23re-Wisconsin isobases. Existing maps of the Wis- 

 consin isobase for zero do not agree. Taylor suggests that in the Great 

 Lakes region this line may coincide with the Whittlesey hinge-line, while 

 De Geer and others have located it considerably farther south. 



Obviously the further testing of Jamieson's hypothesis, as applied to 

 the long stretch from New England to Montana, must await the deliberate 

 conclusions of many specialists who in the future make observations with 

 his idea in mind. Perhaps some geologists working in this part of the 

 marginal belt have considered it, but there seems to be no published 

 record of their findings. Eather to illustrate the kind of questions in- 

 volved than to appear to answer them, the writer offers the following 

 notes, which refer to : the testimony of lake strands ; the submarine chan- 

 nel of the Hudson Eiver; the ^'deeps" of the Susquehanna Eiver; the 

 abandoned channels of Ohio Valley and farther west; the testimony of 

 Europe (see plate 14). 



" M. L. Fernald : Rhodora, vol. 13, 1911, p. 109, and Am. Jour. Sci„ vol. 40, 1915, 

 p. 17. 



J. Barrell : Am. Jour. Sci., vol. 40, 1915, p. 13. 



