536 PROCEEDINGS OF THE ROCHESTER MEETING 



Remarks were made on Dr Clarke's paper by I. C. White, A. P. Brig- 

 ham, and A. W. Grabau. 



In the absence of the authors, the following ten papers were read by 

 title, having been carried to the end of the program under the rule : 



NOTES ON MOUNTS HOOD AND ADAMS AND THEIR GLACIERS 

 BY HARRY FIELDING REID 



[Abstract \ 



These two mountains belong to the group of volcanic cones which were built up 

 in Tertiary times along the line of the Cascade range. Though probably extinct, 

 steam and gases still issue in small quantities from cracks at high altitudes. The 

 mountains consist of both lava and lapilli, the latter being more abundant on 

 mount Hood and the former on mount Adams. Some lava flows exist on the 

 slopes of the mountains, whose age is probably not more than a few hundred 

 years. A number of parasitic cones are found on the flanks of mount Adams, two 

 at least with well-marked craters. 



Mount Hood has no parasitic cones. About one-half of the original crater wall 

 of Hood still remains, the southern half having disappeared. A rock, known as 

 Crater rock, stands up through the snow in about the center of the original crater. 

 The summit of Adams is long and broad and does not outline a crater. The 

 stratification seen in the cliffs on the sides of the mountain suggests that there 

 were several craters, which may have been active at the same time or successively. 



Many interesting glaciers cover the slopes of both mountains, but they are not 

 sunk in valleys. In several cases the depressions outside the lateral moraines 

 are apparently quite as deep as the bed of the glacier, and the canyons formed 

 below the ends of the ice are deeply eroded, in strong contrast to the ice-covered 

 parts of the mountains. It is evident that the main erosion on these mountains 

 has been done by water, and that the ice and snow, by preventing the concentra- 

 tion of the water, have acted rather to prevent erosion. 



There is little indication of a much greater extension of the glaciers of Hood in 

 former times, but on Adams glacial scratches abound in positions which could not 

 be reached by the present glaciers except by a very great increase in size. 



K RE W A TIN AND LAURENTIDE ICE-SHEETS IN MINNESOTA 

 BY A. II. ELFTMAN 



[Abstract'] 



Evidence was presented to show that the glacial drift of the upper Mississippi 

 River valley was deposited by independent lobes of the Keewatin and Laurentide 

 ice-sheets, alternating in their advance and retreat. Minnesota was first invaded 

 by a lobe of the Keewatin ice-sheet. This extended from the northwest to the 

 southeast into Iowa and eastward to Wisconsin, deposited the Kansan and earlier 

 drift-sheets, and formed a glacial lake in the Saint Croix valley north of Taylors 

 falls. The retreat of this ice was followed by a marked interglacial period. 



The second great ice invasion, the Iowan, came from the northeast. The Rainy 



