446 JOURNAL OF THE WASHINGTON ACADEMY OF SCIENCES VOL. 11, NO. IS 



kopi pass with considerable interfingering into marine limestone. The Shina- 

 rump conglomerate and the Chinle formation maintain the same general 

 character though quite variable locally. There is a pronounced hiatus at 

 the base of the Moenkopi formation and another at the base of the Shinarump 

 conglomerate. The age assignment of the Redwall, Kaibab, and Moenkopi 

 formations is based on fossils ; the assignment of the other formations is based 

 on lithology and stratigraphic position only. W. T. Thom, Jr., Secretary. 



355th meeting 

 The 355th meeting was held in the lecture room of the Cosmos Club at 

 8 p.m. on Wednesday, February 9, 1921. 



Regular Program 

 H. S. Washington: The Deccan traps and other plateau basalts. 

 R. C. Wells: Utilization of some western salines and saline lakes. (Illus- 

 trated with lantern slides.) 



R. S. BasslER: Paleontological work at the National Museum. (Illustrated 

 with lantern slides.) 



Laurence LaForge, Secretary. 



356th meeting 

 The 356th meeting of the Society was held in the lecture room of the Cosmos 

 Club, at 8 p.m. on Wednesday, February 23, 1921. 



Informal Communications 

 Dr. R. C. Wells called attention to an inadvertent misstatement in his 

 paper given at the previous meeting, and corrected the same. 



Mr. Laurence LaForge gave a brief review of a paper by J. W. Gregory 

 on The eskers of Ireland and compared Professor Gregory's conclusions with 

 those derived by American glacialists from the study of American eskers. 



Regular Program 



F. E. Matthes : Torrent channels and torrent levees in the Yosemite Valley. 

 (Illustrated with lantern slides.) 



Sidney Paige : Structure of the Homestake ore body (illustrated with black- 

 board drawings and a wooden model). W. T. Thom, Jr., Secretary. 



357th meeting 

 The 357th meeting of the Society was held in the lecture room of the Cos- 

 mos Club at 8 p.m. on Wednesday, March 9, 1921. 



Regular Program 



G. R. Mansfield: Igneous geology of southeastern Idaho. (Illustrated 

 with lantern slides.) 



A. I. Jonas and E. Bliss Knopf: Stratigraphy of the metamorphic rocks of 

 southeastern Pennsylvania and Maryland. 



The oldest metamorphic rocks of the southeastern border of the Piedmont 

 Plateau are of pre-Cambrian age. The oldest formation is the Baltimore 

 gneiss which is a composite gneiss comprising a thoroughly recrystallized 

 biotite gneiss of undeterminate origin, possibly sedimentary, and a granitic 

 intrusion that has interpenetrated the biotite gneiss and produced in many 

 places an injection gneiss. The age of the granite has not yet been definitely 

 determined and it is probable that the Baltimore gneiss has been cut by several 

 granites of widely separated periods of intrusion. 



The Baltimore gneiss is overlain by a series of sediments that are tentatively 

 considered to be lower Cambrian. The base of this series is the Setters form- 



