210 ANNALS NEW YORK ACADEMY OF SCIENCES 



Summary of Papers. 



Mr. Condit's paper was read by Professor James F. Kemp. A very 

 large number of sands had been studied by Mr. Condit in considerable 

 detail, especially for type of grain and range in mineralogic composition. 

 It seems to establish that sands of the same origin or general source have 

 definite characteristics which distinguish them from others. Comparison 

 of these types of sands has led the author to conclude that the very 

 general absence of certain metamorphic mineral grains, such as garnet, 

 from the earlier sands may have a deeper significance. He suggests that 

 their absence may mean that the metamorphic products are of later date. 



Eemarks were made by Dr. Charles P. Berkey, bo which attention was 

 called to the sweeping nature of the conclusion suggested by Mr. Condit 

 and pointing out other possible reasons for such widespread failure of the 

 metamorphic grains. 



Dr. George F. Kunz remarked the wide range of specific gravities 

 represented in the list of minerals determined by Mr. Condit and drew 

 attention to the differences of behavior that this would bring about in the 

 processes of assorting and deposition. 



Professor A. W. Grabau called special attention to the part of the 

 paper dealing with size of grains and evidence of their wear and em- 

 phasized the work of wind in connection with the development of the 

 great sandstone formations. 



Dr. Berkey gave special attention to the results of recent studies in 

 the Moodna Valley and adjacenl ground. The great thrusi which passes 

 through Cornwall on the Hudson was classified, and some of the data 

 bearing upon its importance and the amount of displacement involved 

 were given. It is the author's opinion that a total displacement of 2,000 

 feet or more is indicated by conditions at this fault. Lantern slides of the 

 fault were shown. Eemarks were made by Professor J. F. Kemp. 



Professor Grabau described and illustrated the complex structure in- 

 cluding faults and folds as recently determined by him in the Helderberg 

 limestone strata near Catskill. Diagrams showing reconstructions of the 

 formational positions were shown. 



The Section then adjourned. 



Charles P. Berkey, 



Secretary. 



