564 PROCEEDINGS OF THH PHILADELPHIA MEETING 



The' President called S. F. Emmons to the chair, and the next paper 

 was 



OVERLAP RELATIONS ALONG THE ROCKY MOUNTAIN FRONT RANGE 

 BY N. H. DARTON 



The following paper was presented by the same author : 



ZUNI SALT LAKE 

 BY N. H. DARTON 



[Abstract] 



Forty miles south of the Indian pueblo of Zuiii, there is, in the plain, a circular 

 depression about a mile in diameter, containing a salt lake and two cinder cones. 

 The depth of the depression is about 200 feet, and its walls are Cretaceous sand- 

 stone, capped on one side by a lava flow. All around the rim is a wide low ridge 

 of water-laid volcanic ejecta. The history of this remarkable feature is not clear, 

 but a hypothesis will be offered as to its origin. 



The paper was illustrated with lantern slides. It is printed in the 

 Journal of Geology, volume xiii, April-May, 1905. pages 185-193. 



The last paper of the day was 



EXPERIMENTAL INVESTIGATION OF THE COMPRESSIBILITY AND PLASTIC 

 DEFORMATION OF CERTAIN ROCKS 



BY FRANK D. ADAMS AND E. G. COKER 



[Abstract] 



The paper presents the results of an investigation into the cubic compressibility 

 of rocks and certain phases of rock flow, carried out at McGill University by the 

 aid of a grant from the Carnegie Institution. The apparatus employed and the 

 methods adopted are first described. The cubic compression of rocks is then con- 

 sidered. Seventeen (17) typical rocks have been selected and their cubic com- 

 pressibility determined. In these determinations an indirect method was em- 

 ployed which is believed to give as accurate results as any direct method known. 

 The following are the rocks examined : Carrara marble, Vermont marble, Tennessee 

 marble (pink), Belgian marble ("Noir Fin"), Montreal limestone (Trenton), 

 Baveno granite, Westerly granite, Quincy granite (gray), Lily Lake granite, Peter- 

 head granite, Stanstead granite, Montreal nepheline syenite, Mount Johnson 

 essexite, New Glasgow gabbro, New Glasgow anorthosite, Sudbury diabase, Cleve- 

 land sandstone. From the standpoint of their compressibility as well as of their 

 composition, these rocks fall into three main groups, as follows: 



Granites Value of D averages about 4,400,000 



Marbles " " " 4i " 6,300,000 



Basic plutonics " " " " " 8,800,000 



The sandstone, being porous, has a much higher compressibility. D is the modu- 

 lus of cubic compression, and is represented by a value the reciprocal of which is 

 the decrease in volume of a cubic inch of the rock for a pressure of one pound per 



