GEOLOGY. 253 



materials of Cape Cod, Nantucket, and Long Island, as could not have 

 been taken from the mainland by marine agencies, must have been car- 

 ried by glacial agency, and consequently the intervening basins must 

 have been above the sea level. The passage of the glacial sheet 

 across the basin of Lake Superior presents some difficulties, which 

 are diminished by the theory of elevation. The bottom of this basin is 

 now, at least, one hundred and sixty-five feet beneath the sea level. 

 Without elevation, drainage would have been impossible. 



It is easy to ascertain approximately the amount of submergence 

 which closed the glacial period. Submergence to a depth of not less 

 than two thousand feet below the present level effected the dissolution 

 of the glaciers, and introduced the pliocene period. 1. The general 

 proof of such submergence is the present existence of altered drift at a 

 corresponding elevation. 2. Special proof is found in the existence of 

 osars at great elevations. A semicircular one, well characterized, oc- 

 curs in the town of Peru, Vt, at an elevation of between one and two 

 thousand feet. 3. Other special proof may be found in the lines of an- 

 cient sea margins, which are much more rare than the fluviatile terra- 

 ces of a later date. Such a margin was found by President Hitchcock 

 in Pelham, Mass., at an elevation of one thousand two hundred feet. 

 4. The most forcible argument is derived from the existence of regular 

 stratified deposits of fine sand and clay at the summit level of longitu- 

 dinal valleys. 



ON THE SUBSIDENCE OF THE ISLAND OF NEWFOUNDLAND. 



AT the Boston Natural History Society, December, Mr. Perley, 

 Government Commissioner for New Brunswick and Canada, in reply to 

 a question, stated that it was a well-known fact that the harbours on the 

 south and east side of Newfoundland are deepening, while on the up- 

 per shore they are growing shallow ; harbours which twenty years ago 

 were deep enough for large vessels now hardly answering for shal- 

 lops. On the south side of the island of Grand Manan, there was 

 formerly a marsh covered with trees, which were cut down by persons 

 now living. The marsh has sunk so much, that the stumps of those 

 trees may now be seen eight or nine feet under w 7 ater at low tide. Mr. 

 Desor quoted from recollection a statement in Poggendorff's Annalen 

 for 1849, that the shores of Newfoundland, in the vicinity of Concep- 

 tion Bay, are in the process of elevation. It was interesting to know- 

 that a corresponding process of depression is going on, as it would give 

 confirmation to Mr. Dana's views with regard to the changes of level 

 in the Pacific ; he having stated that a rise in one place is always at- 

 tended by a subsidence in another. Mr. Desor also referred to a state- 

 ment which had been made formerly by Dr. C. T. Jackson, that the 

 inhabitants on the coast of Maine believe that the rocks on the sea- 

 shore are growing. Prof. Wyman remarked that, while on a visit to 

 Labrador two years since, he had noticed on the shores of Great Maca- 

 taney, shingle, pebbles, and rounded rocks, for a long distance, far 

 above high-water-mark. He had noticed the same thing at Bras d'Or 

 and Red Bay. At Red Bay is a large accumulation of the remains of 



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