FOEMER HEIGHT OF SEA. 481 



observations in Maine alone I have not felt justified in maintaining the subsi- 

 dence on our coast and that in the St. Lawrence Valley as contemporaneous. 

 Accepting the general conclusions of De Geer, I assume that the post- 

 glacial elevation of the land in the interior of Maine has been about three 

 times that of the coast. 



FORMER HEIGHT OF THE SEA. 



To determine the highest elevation of the sea in the valle3^s of the 

 interior of the State, we have to depend on the following means : 



i. The elevation of fossils. Possibly the time may come when this 

 method will be applicable, especially by means of microscopical examina- 

 tions. Thus far I have found no macroscopical fossils in large areas of the 

 marine clays, and do not find the absence of fossils in the glacial marine 

 sediments fatal to their being deposited in the sea. 



2. The elevation of raised beaches. On those portions of the coast 

 region where the hills were exposed directly to the surf, with few or no 

 protecting islands lying to seaward, we readily find such beaches. Even 

 near the coast the presence of hills toward the south that would form 

 islands has often so diminished the force of the waves that the beaches are 

 inconspicuous and are traceable with difficulty. At the time the sea stood 

 at its highest elevation the interior valleys contained landlocked bays or 

 fiords of the sea. In the Sebasticook and Penobscot and others of the 

 broader valleys it is possible that the waves had sufficient force to leave 

 traceable beaches, though I have not traced them. But these places are 

 not where the valley drift meets the marine beds. These two formations 

 meet in the valleys where the crooked fiords were usually less than 5 miles 

 in breadth and where we can not expect to find distinct beaches. 



3. The projection of lines of equal elevation. By projecting the eleva- 

 tions of the highest raised beaches on the exposed coasts, selecting points 

 at different distances from the outer coast line, we find the rate of differ- 

 ential subsidence. Assuming this rate to have been the same over the 

 interior as near the coast, we can then calculate the positions of the Ihies 

 of equal elevation. Following this method. Baron De Geer calculates that 

 the isobases, or lines of equal elevation, would take the following courses: 



* * * An isobase drawn through points which have been upheaved 300 feet 

 passes probably from near Niagara Falls, by Albany, i^ew York, and Augusta, Maine, 

 MON xxxiv 31 



