60 PROCEEDINGS OF THE PRINCETON MEETING 



Prof. J. W. Spencer: In 1894, based on what proved to be erroneous data 

 on a map, I suggested the present continuance of earth movements in the 

 region of Lake Erie. This hypothesis was elaborated into a good monograph 

 (United States Geological Survey, number 18) by Dr. G. K. Gilbert by the use 

 of selected later levels. Since then I have taken all the daily fluctuations of 

 the Erie levels and find that since 1854 there have been no differential earth 

 movements, which result may be correlated with Doctor Johnson's results 

 relating to the Atlantic coast. 



Prof. Ellsworth Huntington : I should like to ask Doctor Johnson two 

 questions. As to the first, I may be laboring under some misapprehension. 

 His data seem to show conclusively that in his area there has been no differ- 

 ential movement during the last 25 years. Does this prove anything as to 

 general movements of the entire area? The whole region, covering a distance 

 of a hundred miles or more, might have been depressed 2 or 3 inches, but 

 measurements of the type here described would not show it, for all the points 

 of observation would sink equally. The second question relates to certain 

 recent discoveries reported from Boston. The newspapers state that a fish 

 weir has been discovered 18 feet below the present high-tide level and 12 feet 

 below low-tide level. How does this bear on the present conclusions? 



Dr. G. P. Merrill spoke of the gradual encroachment of the sea as illus- 

 trated by the undermining of stone walls and erosion of the soil on the north- 

 ern, western, and southern margins of a small island in Sheepscot Bay, Maine. 

 Of the three points of observation but one faced the open sea. He felt, there- 

 fore, that the erosion could not be due to temporary conditions, as a few sea- 

 sons of exceptional storms, and while not claiming that it Indicated an actual 

 sinking of the coast, felt that it unquestionably did indicate a change In con- 

 ditions over those existing at a period not more remote than 25 to 30 years. 



Prof. D. W. Johnson, replying to the points raised by the different speakers, 

 said that the evidence which he had just presented proved coastal stability 

 along one portion of the Atlantic coast for a quarter of a century only. The 

 evidence for coastal stability for a much greater period was abundant, and had 

 been presented in part at two previous meetings of the Society. It will not do 

 to assume that some parts of the coast are rising and others sinking, since 

 apparent indications of both elevation and depression occur at points on the 

 coast which can be shown to be stable, and any adequate theory must take all 

 these facts into consideration and satisfactorily explain them. The theory of 

 essential coastal stability, with local fluctuation In high-tide levels does. this. 

 The evidence furnished by the precise levels cannot be explained, as one 

 speaker suggests, by assuming general subsidence without warping, since it 

 was clearly proved that in addition to the absence of differential warping the 

 position of mean sealevel in New York harbor had not changed, with reference 

 to old benchmarks, in a quarter of a century. The fact that waves are erod- 

 ing the coast and destroying certain property does not appear to be significant, 

 since the same thing occurs on lakes where there is no change in the relative 

 level of land and water. Waves will continue to erode a shore indefinitely, 

 whether or not the coast subsides. 



