Apbil 1, 1910] 



SCIENCE 



519 



localities. On the coast, platinum is found in the 

 proportion of 2 to 1 of gold, near Surf, Santa 

 Barbara County, but other places in the same 

 region, including San Luis Obispo, show only 1 

 to 20 or 1 to 50 of gold. 



The next important group of accumulations is 

 found near Trinidad Head, Humboldt County, 

 Cal., another at Crescent City, Cal., at the mouth 

 of Smith River, Ore., and one on the South Fork 

 of Smith River. The most important group of all 

 extends from the mouth of Rogue River north to 

 Coquille River. At Cape Blanco an accumulation 

 of platinum has been found where that metal is 

 five times as abundant as the gold. On the west 

 coast of Washington platinum is comparatively 

 abundant in the proportion of 1 to 10 and 1 to 

 15 of gold. 

 The Half Dome of the Tosemite Valley: Mr. 



FEAwgois E. Matthes. 



The Half Dome, like the other domes of the 

 Yosemite region, represents a huge granite mono- 

 lith that has survived the reduction of the more 

 fissile rocks about it by virtue of the superior 

 resistance to disintegration of its undivided mass. 

 It is unique in that its dome form is a partial 

 or incomplete one, being abruptly trenched on the 

 northwest by a straight and sheer cliflf face 2,000 

 feet in height. The curving back and sides are 

 entirely normal, having evidently evolved through 

 progressive exfoliation, like the bulbous exteriors 

 of all domes. Their smooth, sweeping curves are 

 indicative of maturity; for it is only through long- 

 continued shelling that a monolith of irregular 

 shape is reduced to a continuously rounded mass. 

 At the same time, the prevailing flatness of the 

 back and its trend, parallel with the northeast- 

 southwest system of joints, prominent through- 

 out the region, are clearly inherited from the 

 structure planes that originally bounded the 

 monolith on that side. 



For the origin of the sheer front of the dome, 

 three alternative hypotheses have been advanced: 



1. The present mass is a true half dome — ^that 

 is, a remnant of a much larger monolith, the other 

 portion of which has caved off, perhaps owing to 

 glacial undercutting in the Tenaya trough. 



2. The monolith extended originally but little 

 farther to the northwest, and has suffered reduc- 

 tion on that side, as on the other sides, merely 

 through normal exfoliation. Only, the shells on 

 the northwest side were plane instead of curved, 

 because the initial bounding surface was plane. 



3. The present front coincides essentially with 

 the plane fissure that from the first constituted 



the boundary of the monolith, and has only com- 

 paratively recently been exposed through the rapid 

 scaling off of the thin plates of a zone of ver- 

 tically sheeted rock. 



The first hypothesis seems inadmissible, inas- 

 much as massive granites inherently break off by 

 conchoidal fractures and not by plane fractures 

 of the magnitude of the dome front. The second 

 hypothesis finds some support in the overhanging 

 shells on the top of the dome, for these plainly 

 indicate the former extension of the monolith for 

 a short distance to the northwest. The exist- 

 ence, however, of a great mass of plates clinging 

 to the northeast end of the cliff face in the form 

 of a conspicuous shoulder, together with the 

 strongly accentuated fracture that separates them 

 from the body of the monolith proper, is held to 

 demonstrate conclusively that the monolith never 

 did extend beyond its present front, but was 

 actually bounded there by a zone of thinly sheeted 

 rock. Only toward the top of the front has 

 exfoliation set in and commenced its rounding off 

 process (under the overhang), as is patent from 

 the profile view of the dome obtained from the 

 Quarter Domes. FBANgois E. Matthes, 



Secretary 



THE BIOLOGICAL SOCIETT OF WASHINGTOIT 



The 467th regular meeting of the society was 

 held March 5, 1910, in the west hall of Gfeorge 

 Washington University, President T. S. Palmer in 

 the chair. 



The following communications were presented: 

 Remarks on a Restoration of Basilosaurus cet- 



oides: J. W. Gidlet. 



Remains of this species were first discovered in 

 Alabama in 1834 and Harlan applied to it its 

 present generic name. Owen, in 1839, recognized 

 its mammalian character and renamed it Zeu- 

 glodon. The present restoration is based on por- 

 tions of two individuals, one of which furnishes 

 the anterior and the other the posterior part of 

 the animal. The restoration is almost complete. 

 This mammal is somewhat distantly related to the 

 whales. It has a total length of about 35 feet 

 and a skxill 5 feet long. 

 The Stridulations of some Katydids: H. A. Al- 



LAED. (Read by the recording secretary.) 



The author studied the stridulations of several 

 members of the Locustidse at Thompson's Mills, 

 Ga., and at Plummer's Island, on the Potomac, 

 above Washington City. The peculiar noises 

 made by the following species were studied: 



