TITLES OF PAPERS. 11 



extensive are the examples furnished by the rivers which drain the area of the 

 secondary rocks in eastern England, of which I have given some account in the 

 (London) Geographical Journal for Februarj'', 1895. 



It is not, however, so much the result of these studies as the bearing of the result 

 upon the postulates on which they are based that I desire to bring before the So- 

 ciety, Certain assemblages of rivers and streams exist in nature. Their peculiar 

 correlations are for a long time not appreciated, if seen. Generally they are not 

 even seen. When at last they are detected and studied out it is found that they 

 find full explanation in accordance with the principles of uniformitarianism, prin- 

 ciples that were announced long before any such studies were attempted. The 

 deepening of a valley by its stream is a slow process ; the widening of the valley by 

 the wasting of its slopes is still slower ; the development of subsequent streams by 

 headwater erosion, the accompanying migration of divides, and the resulting re- 

 arrangement and adjustment of waterways are slowest of all. The deepening of a 

 canyon is a rapid process compared to the creeping of a divide. Even the widen- 

 ing of a mature, one-cycle valley is soon done compared to the accomplishment of 

 fully developed adjustments of {N -\- I) cycles. Here, if anywhere, the slow pro- 

 cesses of uniformitarianism are justified, and the hurried processes of catastrophism 

 are completely at fault. 



To attempt to substantiate principles so widely accepted as those of uniformitari- 

 anism may seem to some an unnecessary task. It might be compared to adducing 

 new evidence in support of the law of gravitation ; but, as the attempt involves the 

 extension of those principles into problems not contemplated by Hutton, Playfair 

 and Lyell and most of their disciples, it may deserve the little time and the few 

 pages that it occupies. 



The paper was discussed by B. K. Emerson, N. S. Shaler and W. M. 

 Davis. 



The second paper presented was — 



A NA L YSIS OF FOLDS 

 BY C. R, VAN HISE 



Remarks were made by W. N. Rice and the President. 



Professor Emerson made an announcement concerning a geological 

 excursion under his guidance in the afternoon. 



The President read the following paper : 



CONDITIONS AND EFFECTS OF THE EXPULSION OF GASES FROM THE EARTH 



BY N, S. SHALER 



It was voted that in calling for the papers which had been deferred or 

 carried over to the end of the program those papers whose authors were 

 absent should be presented only by title. 



