January 27, 1899.] 



SCIENCE. 



139 



gas rock has an elevation of 131 feet above 

 tide, rising at no point more than 45 feet 

 above this. At this summit the largest 

 well of the field is located. The relations 

 were sliowu by a geological cross-section. 

 The importance of the fuel to the local zinc 

 industry was described. 



There was no important discussion. 



Tlie ConsJwhochen Plastic Clays. T. C. Hop- 

 kins, State College, Pa. 

 The plastic clays near Conshohocken, Pa., 

 form an isolated deposit. The resemblances 

 to the ISTew Jersey and Gay Head clays in 

 colors, texture and structural features sug- 

 gest clays of the same age. The location 

 and character of the deposits were briefly 

 described. There was no discussion. 



A Bemarkable Landslip on the Riviere Blanche, 

 Portneuf County, Quebec. Geoege M. 

 Dawson, Ottawa, Out. 

 In this paper a brief account was given 

 of the landslip that occurred on May 7th, 

 last. It affected the thick deposit of Leda 

 clay that floors this part of the St. Law- 

 rence plain and serves to indicate that 

 a clay of this character may, under 

 certain circumstances, for a short time, be- 

 have almost as a liquid. The paper was 

 illustrated by the lantern and threw light 

 on disturbed glacial or post-glacial deposits 

 elsewhere. 



Bipple-Marks and Cross- Bedding. G. K.Gil- 

 beet, "Washington, D. C. 

 The general theory of ripple-marks, as 

 developed by Darwin and others, was out- 

 lined and the relation of ripple-mark dimen- 

 sions to dimensions of water oscillation was 

 set forth. In general the distance between 

 the crests of the ripple-marks is half the 

 height of the wave that causes them. At 

 the surface the particles sharing in the wave 

 describe circles. In depths the circles flat- 

 ten to ellipses and at last to forward and 

 backward oscillations, which develop the 

 ripple-marks. Giant ripple-marks of Me- 



dina sandstones were described, with crests 

 up to 30 feet apart. The physical condi- 

 tions in which they were developed were 

 inferred, and waves up to 60 feet high were 

 indicated. When ordinary wind waves are 

 complicated by currents, compound and 

 complex cross-bedding is caused by deposi- 

 tion on rippled surface. The tops of the rip- 

 ple-marks are cut off and deposited on the 

 flanks of the ridges and lead to cross-bed- 

 ding of variable dip and strike, which in 

 this way differs from the cross-bedding of 

 deltas and currents. The paper was illus- 

 trated by the lantern. 



Volcanoes of Southeastern Russia. Harry 

 Fielding Reid, Baltimore, Md. 

 During the Russian excursion of 1897 

 the author visited the three very high vol- 

 canic mountains, Elbruz and Kazbek, in 

 the Caucasus, and Ararat, farther south. 

 This paper gives a brief description of these 

 mountains and was illustrated by lantern 

 views. The physiography of the region 

 traversed, its lake basins and glaciers were 

 all described. Special attention was given 

 to Mt. Ararat. The supposed thawing of 

 its snow fields by the heat developed from 

 oxididizing pyrites was set before the So- 

 ciety and discussion asked, and the question 

 of the abundance of fulgurites on one peak 

 of Ararat and their scarcity elsewhere was 

 proposed to the Society for explanation. 



L. V. Pirsson and others dismissed the 

 pyrites as a source of heat on account of 

 its manifest and absurd inefficiency, despite 

 the fact that it had been seriously advanced 

 abroad. Experience in the Sierras led C. 

 D. Walcott to attribute the absence of snow 

 in certain spots to the action of wind. E. 

 0. Hovey spoke of the occurx-ence of the 

 fulgurites oh Little Arai-at, and A. Heilprin 

 remarked their independence of the kind of 

 rock and cited the unusually large ones he 

 had met in the desert of Sahara. He also 

 spoke of the similarity of the profile of 



