300 



SCIENCE 



[N. S. Vol. XXXIII. No. 843 



DISCUSSION AND CORRESPONDENCE 



BOTANICAL EVIDENCE OF COASTAL SUBSIDENCE 



In a recent number of Science' Mr. H. H. 

 Bartlett, writing under the above title, criti- 

 cizes an earlier paper of my own concerning 

 " The Supposed Recent Subsidence of the 

 Massachusetts and New Jersey Coasts," " on 

 the ground that it represents hasty conclu- 

 sions based on the examination of one locality 

 where conditions are far from typical. Mr. 

 Bartlett is of the opinion that the hypothesis 

 there advanced to account for the appearances 

 of recent subsidence along- the coasts in ques- 

 tion has " as a matter of fact ... no bearing 

 whatever on most of the evidence which has 

 been offered." 



Inasmuch as the brevity of my paper may 

 be responsible for Mr. Bartlett's failure fully 

 to understand it, perhaps a few words as to 

 the development of the hypothesis presented 

 in that paper may serve to make the hypoth- 

 esis itself clearer. The writer's active interest 

 in the problem of subsidence began a number 

 of years ago when he was retained by counsel 

 for the commonwealth of Massachusetts, in a 

 case involving title to lands now below high 

 tide level, to determine if possible the nature 

 and extent of the recent subsidence along the 

 Massachusetts coast. He entered upon this 

 investigation with the belief that recent 

 coastal subsidence in this district was a fact, 

 well established by the studies of various 

 students of shoreline phenomena ; and his 

 efforts were mainly directed toward ascertain- 

 ing whether the subsidence was continuous in 

 time and regular in rate, or whether it was 

 intermittent and at varying rates. In con- 

 nection with this investigation examination 

 was made of numerous publications on recent 

 changes of level in the United States and 

 Canada, and many foreign reports on the same 

 topic; and so fair familiarity with the litera- 

 ture of the subject was gained. 



Even before undertaking the above investi- 

 gation, certain geologically recent changes in 

 the form of the shorelines about Boston had 

 attracted the writer's attention; and in the 



' Science, N. S., XXXIII., 1911, 29-31. 



= Science, M. S., XXXII., 1910, 721-723. 



succeeding years more or less consideration 

 has been given to this subject. Several of his 

 students have made special studies of selected 

 areas along the coast, in each case giving at- 

 tention to the problem of coastal subsidence. 

 Their observations and his own, supplemented 

 by studies of maps of certain areas not vis- 

 ited, led the writer to conclude that the coast 

 had remained essentially stable for a long 

 period of years; and that if any considerable 

 subsidence had taken place, it must have oc- 

 curred long ago. 



The botanical evidence of recent subsidence 

 was still a puzzle. Manifestly, the upper- 

 most layers of the Spartina turf, and the 

 stumps of cedars and other trees exposed in 

 the marshes, could not be due to a remote sub- 

 sidence, even if the lower layers of turf and 

 the more deeply buried stumps had been de- 

 pressed long ago. Careful attention has been 

 given to this phase of the problem, and in this 

 connection let me express my great indebted- 

 ness to Dr. Charles A. Davis, who gave me 

 the opportunity to accompany him on several 

 of his field excursions, and who took the time 

 to visit with me two or three localities where 

 I had studied the physiographic features of 

 the shoreline. On these excursions I became 

 fairly familiar with the botanical evidence of 

 subsidence, and with the interesting methods 

 of investigation which Dr. Davis has devel- 

 oped for the study of salt marsh deposits. By 

 means of the ingenious peat sampler devised 

 by Dr. Davis, the writer has endeavored to 

 increase his knowledge of the structure of 

 several of our marshes; and one of his stu- 

 dents has made a detailed series of sections 

 across the marshes at the mouth of the Ne- 

 ponset River, which will be referred to in a 

 future publication. 



As a result of these studies, it seemed to the 

 writer that while the lower portions of the 

 marsh deposits might indicate subsidence in 

 times long past, the upper portions (the por- 

 tions which furnish supposed evidence of re- 

 cent subsidence) might be explained in either 

 one of two ways: they might represent a 

 resumption of the downward movement of the 

 coastal region in recent times, after a long 



