34 PROCEEDINGS OF THE PRINCETON MEETING 



been established, yet the observations indicate that the negative wave is gen- 

 erally the precurser of the destructive positive wave. On the western coast 

 of South America, where there is a long record of tsunamis, the people are 

 accustomed to rush inland when the sea vrithdraws suddenly. 



Prof. D. W. Johnson asked whether the facts advanced by Professor Reid 

 might possibly be explained by the fact that ix)sitive waves travel more rapidly 

 than negative waves in the same depth of water. Thus an earthquake may 

 give rise to a negative wave which is followed by a positive wave of greater 

 velocity. On some coasts the negative wave arrives first, on others the posi- 

 tive. If waves of one phase overtake or are overtaken by waves of the 

 opposite phase, the smaller wave is extinguished and the surplus of the larger 

 wave propagated independently, as shown by G. Scott Russell. This might 

 further explain the lack of uniformity in the direction of water movement at 

 different ports. 



Brief reply was made by Professor Reid. 



RECENT EARTHQUAKES IN PANAMA AND THEIR CAUSES* 

 BY DONALD F. MAC DONALD ^ 



Presented by title in the absence of the author. 



CRITICISM OF THE HATFORDIAN CONCEPTION OF I80STASY REGARDED 

 FROM THE STANDPOINT OF GEOLOGY 



BY W. H. HOBBS 



{Abstract) 



An attempt to show that the facts from which Hayford's deductions have 

 been drawn are open to an alternative interpretation more in harmony with 

 the facts of geology. 



Eead in full from manuscript. 



EARTH-MOVEMENTS IN THE MINNESOTA PORTION OF THE LAKE AGASSIZ 

 BASIN DURING AND SINCE THE LAKE OCCUPANCY 



BY FRANK LEVEEETT 



(Abstract) 



As a result of somewhat detailed investigation of each of the successive 

 shorelines of Lake Agassiz, the present season data sufficient for determining 

 the progress of the northward differential uplift during the life of Lake 

 Agassiz have been obtained. These results extend along the highest shore 

 beyond the limits of work by Warren Upham, presented in his monograph on 



* The papers which were passed over at the first call and not i-ead at a later session 

 have been entered "by title" in their original position in the program. 

 5 Introduced by E. O. Hovey. 



