528 



SCIENCE. 



[N. S. Vol. XIX. No. 483. 



A Prc-glacial reneplain in the Driftless 

 Area: U. S. Grant and H. F. Bain. 

 In southwestern Wisconsin and adjacent 

 portions of Illinois and Iowa is a well-de- 

 veloped peneplain cutting across part of 

 the Maquoketa shales, the whole of the 

 Galena, Trenton, St. Peter and Lower 

 Magnesian, and terminating to the north in 

 a sharp scarp developed in the soft Pots- 

 dam sandstone. It rises gradually to the 

 north. Above it are the so-called 'mounds' 

 capped with Niagai-a limestone and form- 

 ing monadnocks left in the dissection of an 

 older peneplain. Below it the streams 

 have cut valleys with sides of simple con- 

 tinuous slope. The valleys are arranged in 

 normal dendritic fashion. Streams head- 

 ing outside the area show terraces of gla- 

 cial-derived material and their tributaries 

 show commonly a low terrace developed by 

 silting up of slack water. The peneplain 

 represents the last great period of base- 

 leveling before the oncoming of the gla- 

 ciers. It was followed by one of sharp 

 downward stream-cutting which continued 

 apparently with but slight interruption 

 through the Pleistocene to the present. 

 Possible correlation of the peneplain with 

 a similar one of Tertiary age in southern 

 Illinois is discussed. 



The New Cone of Mont PeU and Other 

 New Features of the Mountain: E. 0. 



HOVEY. 



Some Striking Erosion Phenomena Ob- 

 served on the Islands of St. Vincent and 

 Martinique in 1903: E. 0. Hovey. 

 The two papers announced in the above 

 titles are essentially an exhibition of lan- 

 tern slides illustrating facts brought out in 

 recent publications. 



The Grand Soufriere of Guadaloupe: E. 0. 



Hovey. 



This paper emphasizes by means of lan- 

 tern views the idea that this cone has been 



formed in the same way as that of Mont 

 Pele. 



Domes and Dome Structure in the High 

 Sierra: G. K. Gilbert. (Illustrated with 

 lantern views.) 



In many dome-like granite hills the rock 

 is divided into plates by curved joints ap- 

 proximately parallel to the surface. Some 

 observers call the structure exfoliation, 

 others regard it as an original structure of 

 the granite. Under one view the surface 

 forms determine the structure; under the 

 other the structure determines the surface 

 forms. A study of the High Sierra of 

 California in the summer of 1903 has led 

 the author to accept the former view, and 

 to believe that the forms of the parting 

 planes are conditioned by the forms of the 

 •topography. As to the cause of the phe- 

 nomenon, the following hypothesis is ad- 

 vanced: Formed deep within crust, the 

 granite was initially subject to compressive 

 stress, which was balanced by internal ex- 

 pansive stress. As the unloading involved 

 in subsequent denudation reduced the com- 

 pressive stress, the unbalanced expansive 

 stress caused strains which eventually re- 

 sulted in exfoliation. 



The Trent Biver System and the St. Law- 

 rence Outlet: Alfred W. G. Wilson. 

 (Read by title.) 



The St. Lawrence River in the vicinity 

 of the Thousand Islands crosses the Fron- 

 tenac axis, a narrow neck of Archean rocks 

 which connects the Adirondack region with 

 the greater Archean areas of Canada. 

 West of this axis, the country which lies 

 to the north and east of Lake Ontario is 

 underlain by flat-lying, Ordovician rocks, 

 chiefly Trenton limestones. The drift cover 

 of the area is very thin, averaging perhaps 

 two feet in depth, while the relief has an 

 average measure of at least one hundred 

 and fifty feet. There are numerous areas 

 where the bed-rock exposures are very ex- 



