552 PROCEEDINGS OF THE WASHINGTON MEETING 



mulated, probably thorough a change in climatic conditions, and sediments having 

 a thickness of several thousand feet were laid down. In these lake beds are the 

 great deposits of salt, gypsum, soda, and borax which have made the region 

 famous. Following this period of sedimentation came one of movement along 

 the north-south axis, which lifted and tilted the surface into immense mountain 

 ranges trending parallel with the new axes. Panamint, Death, and Amargosa 

 valleys were thus formed, and Funeral and Panamint mountains were raised up 

 between them. Lakes formed in the new valleys and received sediments similar 

 to those of the preceding period. 



The age of the second lake forming period is vaguely referred to late Tertiary. 

 From structural and stratigraphic evidence the beds are younger than the lake 

 sediments of Death valley, and they are certainly older than the gravel deposits 

 which mark the Pleistocene period in this region ; therefore they are provision- 

 ally classed as Miocene and younger. 



The subject of the three papers, " Basin Range Structure," was dis- 

 cussed b}" C. R. Van Hise, S. F. Emmons, and Doctor Gilbert. 



Doctor White asked Professor H. S. Williams to take the chair, and 

 the fourth paper read was 



IXSTRUMENTS FOE OBSERVATION OF DISTURBANCES CAUSED BY DISTANT 



EARTHQUAKES 



BY H. FIELDING KEID 



The fifth paper was read by title, the author placing on the table for 

 distribution copies of a similar paper published in the Transactions of 

 the American Institute of Mining Engineers. 



STRUCTURAL SECTION ACROSS THE SIERRA MADRE OF MEXICO 

 BY W. H. WEED 



The sixth paper was received from the Section E list : 



HIGHLY VISCOUS ERUPTION OF RHYOLITE 

 BY G. K. GILBERT 



Remarks were made by A. C. Lane. 

 ' The following four papers were read b}^ title : 



RELATION BETWEEN THE KEEWATIN AND LA UR EN TIDE ICE SHEETS 



BY A. n. ELFTMAN 



POST-GLACIAL TIME 



BY A. H. ELFTMAN 



