296 proceedings: geological society 



The course of these moraines throughout exhibits an independence 

 of the trough edge, suggesting strongly that the formation of the trough 

 was not the work wholly of the ice invasion represented by the moraines 

 in question. The trough evidently existed previous to the advent of 

 the later ice and was onlj^ modified by the latter. In this regard, the 

 inchcations of the moraines of the Little Yosemite Valley are similar 

 to those in other localities in the Yosemite region. Accordingly valley 

 troughs hewn one within the other are not to be correlated with separate 

 ice invasions, but appear to have been traversed and enlarged by each 

 of these in succession. 



Moraine Dome is of interest, further, in that it affords approximate 

 measures of the depth of denudation suffered by its mass since the 

 later as well as the earlier ice epochs. Old surface shells preserved 

 from disintegration by the uppermost moraine of the later ice, and re- 

 cently uncovered by rain wash, show that since the moraine was de- 

 posited a thickness of about 3 feet of granite has disappeared from the 

 surface of the dome. 



On the crown of Moraine Dome a vertical dike of aplite has weath- 

 ered out in the form of a little wall, eight feet high. Several large 

 erratics near by, composed of a coarsely porphyritic granite from the 

 crestal portion of the Sierra Nevada, one of them mounted on a pedestal 

 about 4 feet high, show bej^ond doubt that the dome was overridden 

 by the earlier ice. It is clear, therefore, that the aplite dike has weath- 

 ered out since the retreat of the earlier ice, and that its height may be 

 taken as an approximate measure of the depth to which the dome has 

 been denuded since that date. 



The occurrence of carnotite in eastern. Pennsylvania: Edgar T. 

 Wherry. Carnotite occurs near Mauch Chunk, Carbon County, Penn- 

 sylvania, as an impregnation in a conglomerate. Analysis shows it to be 

 high in potassium and low in calcium, the uranium and vanadium show- 

 ing the usual 1 :1 ratio. The features of the rock indicate that the last 

 two metals have accumulated by local concentration of minerals con- 

 taining them during sedimentation, rather than by precipitation from 

 solution, which has been thought to account best for the features of the 

 Colorado and Utah deposits. Investigation of the commercial value 

 of the deposit is now in progress. 



The 283rd meeting was held at the Cosmos Club, April 8, 1914. 



INFORMAL COMMUNICATIONS 



Correlation of the Hawthorn formation: T. Wayland Vaughan and 

 C. Wythe Cooke, presented by Mr. Vaughan. (See this Journal, 4: 

 250. May 19, 1914.) 



Occurrence of the mineral hisengerite in central Idaho: D. F. Hewett. 



REGULAR PROGRAM 



Petrographic evidence on the origin of the Catahoula sandstone: M. I. 

 Goldman. The object of the study was to find what lines of evidence 

 are available for throwing light on the origin of a quartz sandstone 

 with no striking peculiarities. Most of the determinations depended 



