70 GEOLOGICAL AND MINERALOGICAL NOTES. 



Assuming these soundings taken the past summer to be 

 even fairly correct there certainly appears to be a con- 

 siderably greater depth of water on all of these ledges 

 than there was ninety years ago. This also agrees with 

 the estimates of Professor McGee of two feet of subsid- 

 ence for the Century for the entire coast. 



The season at which these measurements were taken 

 (Aug. 30, 31, Sept. 1, 2, 1894,) was one of extremely 

 high tides and consequently correspondingly low water, 

 so that the figures used give as fair a comparison as it is 

 possible to niake with those of Dr. Bowditch. 



Second. The evidences of elevation in recent geoiogic 

 time along the coast line of the country are exceedingly 

 obscure. 



According to previously accepted theories the Quater- 

 nary period was one of great and widely extended os- 

 cillations of the earth's crust. It was divided into three 

 epochs: I. The Glacial. II. The Champlain. III. The 

 Terrace. During the Glacial epoch, in high latitudes, 

 the land became elevated until the continents were from 

 one to two thousand feet above their present height. The 

 Champlain epoch, on the contrary, was characterized by 

 a down ward motion of land surfaces in these sanie regions, 

 until the sea stood, relatively, froin five hundred to one 

 thousand feet above its present level. The Terrace epoch 

 was characterized by the gradual rising of the land until 

 the present conditions of the continents and their climate 

 were attained. 



But the study of the submerged f orests and the compar- 

 ison of soundings in our harbors indicate a diff erent story 

 for the later portion of the Terrace epoch, and necessitates 

 a probable modification of the theory, so far as it applies 

 to this region. 



In Essex County there are numerous examples of shore 



