208 II. L. FAIECHILD POST-GLACIAL UPLIFT OF X. E. AMERICA 



water plane on some of the larger deltas. In some cases instead of a defi- 

 nite figure the two figures for the vertical range within which the plane 

 lies are given. 



While more intensive stud}- will change some of these figures, the 

 WTiter is confident that the future will confirm tlie general accuracy of 

 the figures in the column of theoretic altitudes. 



It will be noted that the figaires are usualh- in multiples of 5. It is 

 not now practicable to make the theoretic figures more refined, although 

 it may be so eventually, and for the measured altitudes it is unnecessary 

 to take time and give labor to secure precision to the foot when there 

 is so much variation in the height of shore feature, as previously de- 

 scribed. 



HUDSOX-CHAMPLAIX VALLEY 



The altitudes of the shore features on the marine plane in Xew York, 

 including Long Island, have been partially given in previous papers, 

 listed in the appended bibliography as numbers 81-85. The detailed 

 description of the closing Pleistocene of Xew York State, giving altitudes 

 of the features in the Hudson, Champlain, Saint Lawrence, and Ontario 

 valleys, is awaiting publication. The shore features on the Vermont side 

 of the Champlain Valley are described in paper number 83. 



WESTERN NEW ENGLAND 



For the State of Connecticut, verified altitudes are limited to the Con- 

 necticut Eiver Valley. 



For Massachusetts, the figures given by Emerson (64, 65) for the static 

 water levels ("Connecticut Lakes'') in the Connecticut Valley are re- 

 garded as precise. Some of them have been personally verified, especially 

 for the 400-foot isobase. 



The streams tributary to the Connecticut Eiver afford interesting op- 

 portunity for this study, care being taken to discriminate the sealevel 

 deltas from the glacial water deposits. An example is found at Shelburne 

 Falls, on the Deerfield Eiver. Lender the village and northward are 

 handsome gravel plains rising to 428 feet, but the isobase of the locality 

 is about 375 feet. Some of this superior altitude might be attributed to 

 aggradation above the static water plane; but more probably these high 

 plains represent glacial ponding, by the lobation of tlie ice-margin in the 

 Connecticut Valley. The marine delta has probably been destroved by 

 the river erosion in the narrow valley, although some remnants should 

 1)6 found. The true plane of the ocean-level waters may be determined 

 by careful study of the sides of the Deerfield Valley below Shelburne 

 Falls. 



