230 H. L. FAIRCHILD PLEISTOCENE MARINE SUBMERGENCE 



Appeal was then made to the depressed attitude of the land during the 

 ice waning, as shown by marine fossils. Taking the uplift at New 

 Haven as 15 to 25 feet; Middlebury, Vermont, at 403, and Montreal, 520 

 (page 196), he calculated a mean rate of uplift northward along th'3 

 Connecticut Valley at 1.25 feet per mile (page 198). From this Dana 

 calculates the water surface at the Middletown dam (?) as 137 feet; 

 Springfield, 135; South Vernon, 236; Windsor, 299, and Haverhill, 383 

 feet (page 199). This calculation reduced the gradient of the imaginary 

 river, but yet failed to harmonize the facts. After further discussion and 

 calculation, he says: 



"But it is not so evident what slope would harmonize the facts ; that is, 

 would cause a velocity sufficient to make or leave coarse valley deposits near 

 and at flood level, . . . and at the same time leave almost undisturbed beds 

 of sand or of fine pebbles along its bottom" . . . (page 200). 



The article ends with the difiQculty unsettled. But the difficulties all 

 disappear under the recognition of a Connecticut marine inlet instead of 

 a river. 



Amount. — The river theory involves difficulty when the volume of de- 

 tritus is considered. Both Dana and Upham thought that the valley had 

 been filled with alluvial material up to the level of the higher terraces, 

 and that the filling had been swept out by the river in its diminished flow 

 after the glacial flood. 



"In this way the Connecticut River . . . has excavated its ancient high 

 floodplain of the Champlain period to a depth of from 150 to 200 feet" . . . 

 (Upham, page 15). 



"The formation of the terraces has taken place by excavation of a vast de- 

 posit that filled the river valley with these upper plains" . . . (page 59). 



Upham gives the widths in the New Hampshire section of the valley 

 up to 2% miles and an average of fully 1 mile. If we take the greater 

 width at the summit of the deltas, it is over 4 miles. 



In Massachusetts and Connecticut the width of the valley between the 

 high terraces is from a few miles up to 12 or more. Detrital plains occur 

 in the very wide as well as in the narrow sections. If the volume of the 

 river, without dams, was great enough to occupy the wide sections of the 

 valley at Hartford and Springfield, it would have left no detritus in the 

 constricted sections. 



One condition seems not to have been recognized. The deposition of 

 detritus was not a process of down-stream migration or the eroding of an 

 upper section of the valley to supply material to fill a lower section. The 

 valley was opened by the recession of the ice-front from south to north, 



