756 ABSTRACTS OF PAPERS 



erosion of their outlet gorges? Is it not probable that the gorge cutting may 

 have accompanied the uplift of the highlands; or, in case the lake basins 

 occupy weak structures, that the erosion of the basins has been accomplished 

 in the same period of time as the erosion of the gorges? Hercegovina shows 

 similar features without any indication of overflowing lakes. 



Prof. D. W. Johnson : I wish to report the occurrence, in eastern West 

 Virginia, of a small valley from which the stream has been recently diverted 

 to an underground course through limestone caverns, the stream reentering 

 the valley farther down its course. Thus we have a continuous stream-carved 

 valley, one section of which is no longer occupied by a stream. If this condi- 

 tion prevails for some time, the upper part of the valley might be reduced 

 slightly below the level of the deserted portion. Obstruction of the opening 

 into the caverns through which the stream disappears would produce a lake 

 which might overflow at times through the deserted section of the valley. 

 Possibly a similar condition may explain the lakes and deserted outlet gorges 

 mentioned by Doctor Huntington. 



Prof. Joseph Barbell: Small rhythmic fluctuations of climate, of which 

 the longest well established cycle is 35 years, have become generally accepted, 

 but are regarded by most meteorologists as of small magnitude and not lead- 

 ing toward larger and more permanent climatic changes. Doctor Huntington, 

 in his work, however, has brought together a mass of data and develops con- 

 clusions of very different import. Climatic changes of pronounced character 

 and enduring for centuries are seen to have taken place within historic times — 

 changes of such magnitude that they are recognizable from their geologic 

 records. The question arises as to how these climatic changes are related to 

 the geologic past. Are they parts of a cycle some thousands of years in length 

 which has consequently not yet become completed within historic times, and is 

 such a cycle, if it exists, one which in rising and falling series has run through 

 geologic times? 



As Lyell showed that the present is the key to the past in the crustal history 

 of the earth, similarly the key to the climatic history is to be found in the 

 study of the present climates and their fluctuations. It is seen from Hunting- 

 ton's work that the recent changes are not dependent on the precession cycle 

 of about 21,000 years, and this may go far toward clearing up several difficul- 

 ties. F. B. Taylor,* for instance, in his study of the moraines of recession 

 south of the Great Lakes finds fifteen of the first order between Cincinnati 

 and Mackinac. 



At the time, in 1896, it seemed necessary to correlate these changes with the 

 precession cycle, but this gives an excessive duration for the retreat of the ice- 

 sheet, and Taylor remarks that a period of between 5,000 and 10,000 years 

 would seem to accord more closely with the phenomena. 



Further, in 1893, Gilbert ^ called attention to a rhythmic alternation of argil- 

 laceous and calcareous beds in a portion of the upper Cretaceous of Colorado 

 running through 3,900 feet of strata, a single rhythm averaging 4 feet. He con- 

 siders the alternations to be of climatic origin and, because no other competent 



1 Moraines of recession and their significance In glacial theory. Journal of Geology, 

 vol. V, 1897, pp. 421-465. 



a Sedimentary measurement of Cretaceous time. Journal of Geology, vol. Ill, pp. 121- 

 127. 



