106 PROCEEDINGS OF THE PHILADELPHIA MEETING 



clitions in the eastern United States and certain deductions drawn as to the 

 point in the time scale at wliich the first general uplift occurred. 



Presented in abstract extemporaneously, 



RELATION OF PHYSIOGRAPHIC (JHAXGES TO ORE ALTERATIONS 



BY WAU^CE W. ATWOOD 



(Abstract) 



While a land-mass is being dissected, the ground water table is slowly 

 lowered through that mass until, at the peneplain and baselevel stages, the 

 ground water table remains almost stationary for long periods of time. During 

 successive cycles of erosion the position of the baselevel of erosion in the land- 

 mass being dissected must change, and, if climatic conditions remain constant, 

 such changes are necessarily accompanied by changes in the position of the 

 ground water table. If the land-mass is elevated, the baselevel will be lowered 

 through the land, and the ground water table will be slowly lowered. When 

 it land-mass is depressed the baselevel of erosion and the ground water table 

 are elevated throughout that land-mass. Moist climates will raise the ground 

 \Aater table and dry periods lower that table. As the ground water table is 

 raised or lowered, the zones in which the chemical changes associated with 

 the secondary alteration of ore deposits take place are varied in thickness. 



These facts indicate that physiographic studies may be profitably applied 

 in the study of ore alterations, and conversely that the record of ore altera- 

 tions may furnish important data bearing on the physiographic evolution of 

 the districts concerned. 



The study of secondary ores by various investigators has called for in- 

 tensive physiographic studies. During the past season field-work was done in 

 the vicinity of Butte, Montana, and Bingham Canyon, Utah, to determine the 

 relationship of physiographic evolution to the secondary enrichment of ores 

 in those regions. In this paper the problem of the application of physiography 

 to the investigation of secondary ores was defined and some of the results of 

 the past season's field-work were presented. 



Presented in abstract extemporaneously. 



GRAPHIC PROJECTION OF PLEISTOCENE CLIMATIC OSCILLATIONS 



BY CHESTER A. REEDS 



(Abstract) 



Penck's curve, as presented on page 1168 of "Die Alpen im Eiszeitalter" 

 (1909), expresses graphically the climatic oscillations of the alpine district for 

 Pleistocene and post-Pleistocene time. Tlie key to the four glaciations and 

 the three interglacial stages indicated in the curve was found in the four out- 

 wash deposits of glacio-fluvial streams on the northern foreland of the Alps 

 in the vicinity of Ulm and Munich. Along tlie present stream valleys the 

 glacio-fluvial deposits are arranged in terraces, the oldest occupying the high- 

 est position and the youngest the lowest level. When the key was carried in 



