Geology and Mineralogy 633 



The dynamics of river action, also, we understand better than 

 forty years ago. Few, if any, geologists to-day would at- 

 tribute the formation of valleys to the ocean ; and most 

 geologists doubtless would approve Gilbert's elegant trans- 

 formation * of Hitchcock's diagram exhibiting the structure 

 of terraces. But the paper is an interesting monument of the 

 early stages of the history of glacial geology, and much more 

 of the same sort of conscientious study of the facts in detail 

 will be requisite before all the problems of the Drift are 

 satisfactorily solved. 



The paper " On the Fresh- water Glacial Drift of the 

 Northwestern States," by Charles Whittlesey (1866), maps 

 approximately the southern boundary of the Drift from New 

 Jersey to Iowa (locating the boundary most of the way some- 

 what further north than more recent authorities). Attention 

 is called to the moraines far to the north of the boundary of 

 the Drift, and their characteristic surface pitted with kettle- 

 holes. Numerous small lakes and bays are attributed to gla- 

 cial erosion, and the basins of the great lakes are believed to 

 have been somewhat modified by the same agency. The un- 

 stratified Drift is referred to the action of glaciers, and the 

 stratified deposits to fresh waters. 



Colonel Whittlesey contributes also one paper in the depart- 

 ment of physiography, "On Fluctuations of Level in the North 

 American Lakes" (1860). This paper gives a large amount 

 of information bearing upon secular, annual, and transient 

 variations. Very curious are those transient oscillations, 

 which have been studied and described by a number of ob- 

 servers in the Swiss Lakes, under the name of "seiches," and 

 of which Colonel Whittlesey's paper is probably the first no- 

 tice in this country. They are doubtless connected with vari- 

 ations of atmospheric pressure. Although, in some cases 



1 " Report on Geology of the Henry Mountains," Washington, 1877, Figures 64, 65. 

 41 



