January 19, 1900.] 



SCIENCE. 



103 



uel fillings in the Devonian beds near 

 Ithaca, which threw light on the cases in 

 point. 



•Glacial erosion in the Aar Valley. By Al- 

 bert Perby Brigham, Hamilton, N. Y. 

 Observations were made between Meir- 

 ingen and the Abschwung. The valley has 

 several relatively broad and open sections, 

 containing small rock basins. These basins 

 are filled with alluvial material. One 

 double basin, however, that of the Grim- 

 sel Lakes, being out of the track of the 

 stream, keeps its water-filling. Between 

 the basins, in some cases, are narrow V- 

 shaped gorges, bordered bj' heavily gla- 

 ciated spurs thi'own out from the valley 

 sides. The sides of the gorges are often 

 glaciated nearly to the bottom. la other 

 cases rock barriers have crossed the valley 

 and are now breached by very narrow post- 

 glacial gorges, as above the Grimsel Hospice 

 and above Meiringen. Supplementary il- 

 lustrations were given from the Rhone and 

 Visp Valleys. 



W. M. Davis in discussion illustrated 

 the discordance between side valleys and 

 the main valley — the former discharging at 

 au altitude of some hundreds of feet above 

 the floor of the latter. These discordant, 

 lateral valleys were called * hanging val- 

 leys. ' I. C Eussell remarked the same 

 phenomena in the Sierras and Cascades. 

 Bailey Willis emphasized the excess of lat- 

 eral erosion by glaciers over the vertical 

 and that thus the natural grade of the side 

 valleys had been truncated. W. H. Mies 

 laid stress on the importance of subglacial 

 streams, along the sides of a glacier. G. 

 K. Gilbert urged the efficiency of glacial 

 erosion and stated that the profiles of lateral 

 valleys did not coincide with the idea of 

 truncation. The discordance may be met 

 in rivers, as along the Rio Virgin, where 

 the main stream deepens faster than the 

 laterals. J. J. Stevenson corroborated the 



same views by the valley of the Twin 

 Lakes in Colorado. J. W. Spenser de- 

 scribed the hanging valleys of Norway, 

 which are step-shaped at the discordance. 

 I. C. White described discordance along 

 the Monongahela Valley, where no glacier 

 had ever existed. S. F. Emmons cited 

 hanging valleys along the Columbia River, 

 where it crosses the national boundary. H. 

 W. Turner mentioned cases in the Sierras 

 in the Bidwell Bar quadrangle. A. P. 

 Brigham confirmed the power of a glacier 

 to erode. W. M. Davis closed the discus- 

 sion. 



Movement of glaciers. By Harry Fielding 



Reid, Baltimore, Md. 



The paper gave the results of from one to 

 three years' observations on the movement 

 of the Forno glacier, with special reference 

 to the vertical component of the movement. 

 The existence of surfaces of finite shear in 

 glaciers was discussed. The author de- 

 scribed the set of stakes that he had set up 

 at several places across the glacier and had 

 watched for two or three years. They 

 showed a slow movement at the end and a 

 more rapid one up the ice-stream, and some 

 interesting relations at the n6v6. He pro- 

 ceeded at once to the reading of his second 

 paper. 



Stratification and banded structure of glaciers. 



By Harry Fielding Reid, Baltimore, 



Md. 



Careful work on a number of the Swiss 

 glaciers has enabled the author to follow 

 the outcrops of the strata from the n6v6-line 

 practically to the end of the glacier, and 

 has convinced him that the banded struc- 

 ture is the modified appearance of the out- 

 crops. A reason is suggested why glacial- 

 ists have held divergent views on this 

 subject. With a beautiful and complete se- 

 ries of lantern slides the author illustrated 

 the evidences of stratification and the phe- 

 nomena of movement. He distinguished 



