740 



SCIENCE. 



[N. S. Vol. XVII. No. 436. 



sure. A little consideration shows that the 

 water pressure against the vertical front of 

 the glacier has no sustaining power. The ice 

 can be hydrostatieally supported only through 

 pressure communicated to its imder surface. 

 If there is water contact throughout the base 

 of the glacier, then no share of the weight 

 of the ice is directly borne by the rock bed, 

 but the whole weight comes upon the water; 

 and since earth heat keeps the base of a gla- 

 cier at the temperature of melting, there must 

 always be a film of water beneath it. This 

 £lm is not expelled by the pressure to which 

 it is subjected, but is reduced to capillary 

 thinness. It does not obey the hydrostatic 

 law, but the laws of surface tension. The 

 molecular forces associated with its two con- 

 tact surfaces are dominant, and give it quasi- 

 solid properties. The film sustains the whole 

 weight of the superincumbent ice, and com- 

 municates its pressure to the rock bed, and 

 this without reference to the absence or pres- 

 ence of sea water. The pressure conditions 

 at the base of the tidal glacier are practically 

 the same in its tidal portion and its land por- 

 tion, and it has the same power to erode its 

 bed below sea level as above." 



It follows, as a corollary, that the existence 

 of a fiord is not prima facie evidence that the 

 land had a different relation to sea level at 

 the time of its excavation. 



Mr. Whitman Cross, ' Observations on 

 Hawaiian Geology.' 



Mr. Cross gave a brief sketch of the geology 

 of the Hawaiian Islands, and described the 

 small but interesting eruptions of Kilauea 

 which have occurred within the past year. 

 Special attention was called to the long series 

 of eruptions of basaltic lavas which has con- 

 tinued from some unknown date in the Ter- 

 tiary to the present time. That no other 

 lavas should have alternated with basalt and 

 that no apparent progressive change in the 

 characters of the lavas has taken place, con- 

 trasts markedly with the history of most vol- 

 canic centers. The discovery of traohytic 

 rocks at one point on the island of Hawaii, 

 announced by Mr. Cross, is but the exception 

 proving the rule. In all the older, much 



dissected islands, no such unusual lavas have 

 been found. 



Mr. Cross spoke of the exceptional oppor- 

 tunities for the study of physiographic proc- 

 esses, since the various islands exhibit all 

 stages in the sculpturing and degradation of 

 volcanic mountains from the unmodified dome 

 of Mauna Loa to the islet, hardly more than 

 a reef, the remnant of a former basaltic vol- 

 cano. 



The recent eruptive activity of Kilauea, 

 beginning in June, 1902, was confined to the 

 pit crater of Halemaumau. This pit is 1,200 

 to 1,500 feet in diameter, and was about 1,000 

 feet deep before the lava appeared in its bot- 

 tom, last June. The sum total of many small 

 gushes of lava up to the end of 1902 was 

 enough to fill up the pit to a distance between 

 YOO and 800 feet below the crater rim. 



Mr. Bailey Willis, ' Post-Tertiary Deforma- 

 tion of the Cascade Eange.' 



Mr. Willis discussed the form of the moun- 

 tain block which had been elevated (or left 

 in relief through general subsidence) in the 

 development of the Cascade Range. The con- 

 ception of form was arrived at through study 

 of a warped peneplain of post-Miocene age, 

 which over a wide area is now elevated to 

 altitudes of 3,000 to 8,500 feet. The criteria 

 applied to test the deductions as to form are 

 of a physiographic nature; streams are found 

 to be in part antecedent, in part consequent, 

 and in part adjusted through piracy. In 

 valley profiles there are recognized monad- 

 nocks, the peneplain, the post-peneplain ma- 

 ture topography, and the still later canyon 

 topography, the last antedating the latest gla- 

 cial epoch. Lake Chelan, the central feature 

 of the district discussed, is found to have a 

 complex history, having developed through 

 stream robbing as an extensive canyon, and 

 having been excavated to a depth of a thou- 

 sand feet below its rock rim by glacial erosion, 

 under peculiar coilditions of constriction and 

 pressure of the ice. 



The subject discussed will be illustrated in 

 a forthcoming professional paper of the Geo- 

 logical Survey. W. C. Mendenhall, 

 Secretary. 



