10 PROCEEDINGS OF ROCHESTER MEETING. 



emplify the physical law that " starting friction " is greater than " moving friction." 

 They should be looked for, not in the area of active glacial degradation, but about 

 the critical line at which deposition began, i e, the point of oscillation between 

 degradation and deposition. 



Mr Upham remarked — 



I musi continue to regard the isolation and strange distribution of drumlins as a 

 very singular, important and unexplained feature. 



The next paper was — 



THE EXTRA-MORAINIC DRIFT OF THE SUSQUEHANNA VALLEY 



BY G. FREDERICK WRIGHT 



Professor R. D. Salisbury and Mr W J McGee remarked upon the 

 matter of the paper, challenging the observations and inferences of the 

 author. 



The next paper was as follows : 



A NEW T.ENIOPTERID FERX AXD ITS ALLIES 

 BY DAVID WHITE 



Remarks w r ere made by Professor E. W. Clay pole and by the author. 

 The paper in full is printed in later pages of this volume. 



The tw r o following papers w ere read consecutively by the author : 



THE OVERTURN OF THE LOWER SILURIAN STRATA IN RENSSELAER 



COUNTY. N. Y 



BY A. S. TIFFANY 



ANCIENT WATERWAYS. 

 BY A. S. TIFFANY 



[Abstract] 



The writer gave a brief account of an ancient waterfall in a paper read before the 

 American Association for the Advancement of Science at Ann Arbor, and published 

 in pamphlet form in 1885. This waterfall eroded the hard, horizontally disposed 

 Corniferous limestone of what is now Rock island (Illinois) to a depth of 70 feel 

 and a width of 900 feet. The cavity was afterward filled with Coal Measure shales. 

 The boring of artesian wells in [llinois and Iowa has since developed a number <<\' 

 excavations of still greater depth filled with drift. 



\t Dixon, Illinois, at an altitude of ris feel above sea-level, a well drilled by Mr 

 Wilson ran through L50 feel of bowlder clay, though the < lalena and Trenton lime- 

 stones of the vicinity rise in cliffs many feet above the top of the well see Geol. 

 111., volume v. pages H'S-130). 



