82 



SCIENCE. 



[N. S. Vol. V. No. 107. 



Conte described his own visit to the lake in 

 earlier years with Capt. Dutton, and H. F. 

 Eeid inquired as to the amount of erosion 

 visible in the cliffs suri-ounding the water, 

 to which Mr. Diller replied that there were 

 no beaches to indicate it. On this line 

 Prof. Shaler remarked the great increase in 

 size that had been brought about in the 

 Italian lakes by wave action and the need 

 of caution in estimating the amount of rock 

 that had been engulfed. He also cited the 

 complex character of certain of the Italian 

 ones. Mr. Diller replied that Crater Lake 

 was a unit and gave reasons for thinking 

 that it had not been much enlarged. Mr. 

 Turner cited the vast tuff deposits of the 

 Sierras, which he attributed to mud-fiows 

 of tuffs on a grand scale and suggested the 

 applicability of the idea to some of the 

 earlier phenomena in the history of Crater 

 Lake. 



THie Leucite Hills, Wyoming. J. F. Kemp, 



New York, K. Y. 



After a brief review of the occurrence 

 of leucite the world over and especially 

 in North America, the lantern was used 

 to ghow the geographical situation and 

 distribution of the Leucite Hills. Three 

 of the outcrops, viz : the Leucite Hills 

 proper, Orenda Butte and Black Kock 

 Butte were described with photogi-aphs. 

 Photomicrographs were next used to illus- 

 trate the rocks. It was shown that while 

 leucite was as rich in some parts of the 

 southern mesa as described by Zirkel, yet 

 in other places and in the buttes to the 

 north it became more rare and sanidine 

 came in in much greater amount. Hauyne, 

 large augite phenocrj'sts with rims of bio- 

 tite and inclusions of limestone and sand- 

 stone, were also described. Zirkel's descrip- 

 tion was quoted in extenso and corroborated 

 for the portions of the flows visited by the 

 geologist of the Fortieth Parallel Survey, 

 but the fuller field work has indicated con- 



siderable variability. The cones which look 

 like craters were shown to be solid and were 

 explained as portions which were viscous 

 when intruded so that they remained over 

 the old vents. Pilot Butte, north of Rock 

 Springs, was also described, and the rock 

 was shown to consist of augites and biotite 

 in an isotropic base, regarded as glass. The 

 determination of it as trachyte in Volume II. 

 of the Fortieth Parallel Survey was there- 

 fore questioned. 



Mr. Cross in discussion spoke of his own 

 visit to the Hills twelve years before, and 

 of the general pai-allelism of his observations 

 with those of the speaker. Mr. Kemp ex- 

 pressed the hope that Mr. Cross would pub- 

 lish his observations and analyses at the 

 earliest convenient date. 



The Solution of Quartz under Atmospheric Con- 

 ditions. C. WiLLAED Hayes, Washing- 

 ton, D. C. 



The projecting portions of quartz pebbles 

 in conglomerates at a number of localities in 

 the South have been found deeply etched, 

 and chalcedonic quartz nodules partially 

 dissolved. The chemical conditions under 

 which the solution may have been effected 

 were considered, and the bearing of the facts 

 observed on the problems of erosion briefly 

 pointed out. The latter point was more 

 fully discussed in Mr. Campbell's paper on 

 ' Erosion at Baselevel,' which followed. Mr. 

 Hayes described the solution of the silica as 

 occurring in a region of heavy forest where 

 fires are frequent. In this way both or- 

 ganic acids and alkaline salts are afforded 

 which effect the solution. Specimens were 

 passed around in illustration which were 

 very significant. Mr. Kemp, in discussion, 

 called attention to the parallel conclusions 

 reached by Dr. A. A. Julien in his study of 

 the talus of the Palisades some years before. 

 Mr. Gilbert cited the recent cementation 

 of sands with silica in the arid regions of 

 the West, and remarked the varying be- 



