186 



SCIENCE 



[X. S. Vol.. XXXII. No. 8U 



the Valdez and Shoup glaciers are slowly receding. 

 The Columbia Glacier has advanced rapidly since 

 1908 and is building moraines and destroying the 

 forest, as was observed by Professor U. S. Grant 

 early in 1909 and by the National Geographic 

 Society expedition later in the season. The events 

 in the glaciation of Prince William Sound differ 

 decidedly from those in the Yakutat Bay region. 



Discussed by Francois E. ^latthes. 

 Some Effects of Glacier Action in Iceland: Fbed 



E. Weight, Washington, D. C. 



For the study of both glacial and volcanic phe- 

 nomena Iceland is unique. Extensive remnants of 

 its former ice cap still exist, while its land areas 

 now free of ice are large and without forest cover 

 and are admirably adapted for the physiographic 

 study of the effects of glacier action, both of the 

 continental ice sheet and also the valley glacier 

 types. In a country covered by an ice cap, the 

 surface of the ice sheet is an important plane of 

 reference, which in its physiographic effect is 

 often similar to that of a water surface, as sea 

 level, toward which all exposed land surface tends 

 to be reduced. Mountains and rock cliffs above 

 the ice sheet undergo rapid changes in tempera- 

 ture, with accompanying shattering due to expan- 

 sion of included moisture on freezing and tend to 

 break down rapidly and to be reduced to the level 

 of the ice surface. Beneath the ice cap, on the 

 other hand, ice erosion tends to accentuate the 

 differences in elevation by cutting deeper into the 

 existing valleys, especially if these lie in the 

 direction of the main ice flow, while the mountain 

 tops, nearer the surface of the ice sheet and con- 

 sequently under less pressure and of gentler 

 gradient, are eroded less than other areas. The 

 net result of such action, if continued long enough, 

 would be to reduce the mountain peaks to about 

 the same general elevation, so that taken together 

 they would eventually resemble an old uplifted 

 and dissected base level of erosion. 



Discussed by W. M. Davis. 

 The Cliff Sculpture of the Yosemite Valley: F. E. 



JNlATTHES, Washington, D. C. (Introduced by 



M. R. Campbell.) 



The Yosemite Valley may be epitomized as a 

 glacial canyon laid in structurally aberrant ma- 

 terials. It is to the latter circumstance chiefly 

 that the valley owes its remarkable wealth of 

 sculptured forms. These are not inherently a 

 product of either stream or ice erosion — they are 

 a function of the structure of the country rock. 

 The granites of the Yosemite region may be pic- 

 tured as consisting of many huge monolithic 



masses imbedded in a matrix of more or less 

 strongly fissured rock. This unusual structural 

 habit naturally carries with it extreme inequality 

 of resistance to disintegration. As a consequence, 

 rock structure has played a prominent role in the 

 evolution of the topography of the region. The 

 Yosemite landscape indeed reflects in its features 

 the structural character of the materials from 

 which it has been carved: its dominating heights 

 consist invariably of intractable monoliths, its 

 canyons and gulches are due to zones of easily 

 eroded fissile rock. The glacial cross cliffs and 

 lake basins in the valley floors, the headlands and 

 embayments of the rock walls, have in each case 

 evolved in obedience to local structural controls. 

 The very trend and profile of each cliff has been 

 determined by structural planes. Indeed, every 

 rock form and monument of the valley is to be 

 interpreted as an expression of its associated 

 structures. This applies also to those notches and 

 niches about the waterfalls which have heretofore 

 been explained as the result of the shifting of the 

 falls in glacial times. 

 Further Light on the Gorge of the Hudson: 



James F. Kemp, New Y'ork, N. Y''. 



The paper gave the latest evidence furnished 

 by the deep borings in the Hudson Valley at the 

 Storm King crossing of the New Y'ork City aque- 

 duct, and cited the results of the Pennsylvania 

 Railroad tunnels opposite Thirty-third Street, 

 New Y'ork, made public through Dr. E. 0. Hovey. 

 The facts were interpreted and involved the gen- 

 eral problem of glacial over-deepening. The paper 

 practically continues one by the writer in the 

 American Journal of Science for October, 1908, 

 p. 301. 



Discussed by J. W. Spencer with reply by the 

 author. 

 The Richmond Bowlder Trains: F. B. Tatloe, 



Fort Wayne, Ind. 



The paper described the well-known trains of 

 bowlders of amphibolite schist which extend 

 southeastward into southwestern Massachusetts 

 from " The Knob," formerly called Frye's Hill, 

 which is on the line between the towns of New 

 Lebanon and Canaan in the northeastern part of 

 Columbia County, N. Y. The hill is about nine 

 miles west of Pittsfield, Mass. The train which 

 has been described heretofore and which was 

 visited by Sir Charles Lyell many years ago is 

 composed of large angular blocks strewn along a 

 line running southeast from Frye's Hill. It takes 

 a nearly straight course over mountain and valley 

 with but little curvature or interruption for about 



