358 



SCIENCE. 



[N. S. Vol. VII. No. 167, 



results so far indicate that antitoxic serums, 

 whicli have been of such inestimable value to 

 the health of man in many diseases, may prove 

 very valuable to the farmers. 



Professor O. P. Hay spoke on ' The Proto- 

 spondyli and .iEtheospondyli of A. S. Wood- 

 ward,' stating that the suborders of Mr. Wood- 

 ward were not natural and that the families 

 Semionotidfe and Pycnodontidse should be re- 

 moved from the group typified by Amia and 

 placed among the families whose modern re- 

 presentative is Lepisosteus. 



Dr. Theo. Gill spoke on ' The Classification 

 of Astacoidean Crustaceans,' saying that the 

 crayiish are of more than ordinary interest be- 

 cause since the appearance of Huxley's ' Intro- 

 duction to the Study of Zoology ' they have 

 been largely used in laboratories for purposes 

 of instruction. In connection with a univer- 

 sity course, the speaker had occasion to investi- 

 gate the group, and found differences of opinion 

 among recent authors respecting various ques- 

 tions. Such are the limits of the superfamily, 

 the limits of the families, the gradation of the 

 families, or which is the most specialized, the 

 origin of the different types, the nomenclature 

 of the genera and of the families and superfam- 

 ily. He had been led by his studies to re- 

 sults somewhat different from others in the 

 aggregate, but agreed in almost all points with 

 some one of the previous investigators. In his 

 opinion the name Asiaeoidea of Dana may be 

 retained as the name of a superfamily contain- 

 ing four families, which may be called Eryon- 

 idse, Somaridse, Parastacidse and Astacidas. 

 Reasons for the adoption of the families^ as well 

 as for their sequence and nomenclature, were 

 given. Special emphasis was placed on the de- 

 velopment and degrees of approximation of the 

 generative organs as indications of divergence 

 and specialization. 



F. A. Lucas, 



Secretary. 



GEOLOGICAL SOCIETY OF WASHINGTON, FEBRU- 

 ARY 23, 1898. 



One of the communications was by Mr. H. 

 W. Turner, U. S. Geological Survey, and was 

 on the ' Origin of Yosemite Valley.' 



The rocks surrounding the Yosemite Valley 



are chiefly granites and gneisses. These rocks^ 

 originally all massive, have been subjected to- 

 stresses resulting in the development of sets of 

 partings, two of which are vertical, crossing: 

 each other at approximately right angles ; an- 

 other set horizontal, and two or more diagonal 

 sets. At no place are all of these partings, 

 which would be called by some a joint struc- 

 ture, equally developed. It is the rule that in 

 the neighborhood of the valley a set of vertical 

 partings running nearly parallel with the valley 

 are most prominently developed. These are- 

 seen particularly well on a spur at the west enA 

 of the valley, at Cathedral Spires and at Senti- 

 nel Rock. What is probably another set ex- 

 tends up the spur east of fhe valley, passing 

 just north of the Half Dome. At Yosemite 

 Falls likewise a set of nearly vertical partings- 

 may be noted, although these are not readily 

 seen from the valley below. Nearly all the 

 topographic forms about the valley are domi- 

 nated by these structure planes. To the verti- 

 cal partings are due the vertical walls, and to 

 the diagonal partings some of the inclined sur- 

 faces, like those of the Three Brothers. The 

 domes of the valley are considered as due to 

 exfoliation by weathering. Such exfoliation 

 only takes place where a mass of the granite is 

 not divided by joint structure. The vertical 

 north face of the Half Dome is believed to be 

 due to the vertical partings, the granite having 

 broken off in slabs from time to time as the base 

 was undermined by erosion, while the mass- 

 constituting the Half Dome, being comparatively 

 free from partings, has become rounded by ex- 

 foliation of successive shells of weathered rock. 

 The Yosemite Valley is regarded as a wid- 

 ened portion of a river canyon, the upper portion- 

 of which is now occupied by Tenaya Creek. It 

 is believed that river erosion had excavated a 

 canyon here before the valley was occupied by 

 a glacier. The small amount of debris in the 

 valley along the base of the vertical cliff's is due 

 to all the taleus having been removed by glacial 

 ice. It should be remembered, however, that 

 the exact form of the rock bottom of the valley 

 is not known, inasmuch as the glacier, when re- 

 treating, left moraines at the west side of the- 

 valley which acted as a barrier, causing a tem- 

 porary lake to form. The final result of this- 



