IV BULLETIX OF THE GEOLOGICAL SOCIETY OF AMERICA 



Page 

 Titles and abstracts of papers presented before the afternoon ses- 

 sion and discussions thereon 83 



Recent earthquakes of Porto Rico [abstract] ; by Haeky 

 Fielding Reid and Stephen Taber 83 



Structure of the Pacific ranges, California [abstract and dis- 

 cussion] ; by Bailey Willis 84 



Migration of geosynclines [abstract] ; bj' Amadeus W. 

 Gbabau 87 



Geotectonic adaptation through retardation of the earth's 

 rotation [abstract] ; by Chaeles R. Keyes 87 



Late Mississippian organic movements in North America [ab- 

 stract] ; by Feancis M. Van Tuyl and Raymond C. Moore. . 88 



Post-Glacial uplift of the New England coastal region [ab- 

 stract] ; by Herman L. Fairchild 89 



Topographic features of the Hudson Valley and the question 

 of post-Glacial marine waters in the Hudson-Champlain 

 Valley [abstract and discussion] ; by James H. Stollee. . 90 



Subterranean "chalk-streams" of northern France [abstract] ; 

 by Edward Mooee Burwash 91 



Relative efficiency of normative and modal classifications of 

 igneous rocks [abstract] ; by Edward B. Mathews 91 



Pegmatite, silexite, and aplite dikes of northern New York 

 [abstract] ; by William J. Miller 93 



Magnetic iron-ore deposits of Clinton County, New York [ab- 

 stract] ; by William J. Miller 93 



Session of Friday evening. December 27 94 



Cooperation in geological instruction [abstract] ; by Herbert 



E. Gregory 94 



Session of Saturday morning, December 28 95 



Report of the Auditing Committee 95 



Titles and abstracts of papers presented at the morning session 



and discussions thereon 95 



High-grade clays of the United States [abstract] ; by H. Ries 95 

 Occurrence and origin of white clays at Saylorsburg, Monroe 



County, Pennsylvania [abstract] ; by Frederick B. Peck.. 96 

 Oil geology in relation to valuation [abstract] : by Ralph 



Arnold 90 



Rock products and the war [abstract] ; by G. F. Loughlin. . 97 

 Manganese ore as a war mineral [abstract] : by D. F. Hewett 97 

 Economic limits to domestic independence in minerals [ab- 

 stract and discussion] ; by George O. Smith 98 



Imperial Mineral Resources Bureau. London; by Willet G. 



]Miller 100 



Some problems of international readjustment of mineral sup- 

 plies as indicated in recent foreign literature [abstract and 



discussion] ; by Eleanora F. Bliss 101 



War-time development of the optical industry [abstract] : by 



F. E. Wright 103 



Geologic and present climates : by Marsden Manson 103 



