THE COXNECTICUT ItlVEK LAKES. (31 1 



plants in the upper portion of the clays is in harmony with this state of 

 things, and the many kettle-holes in the high terrace of this age are in part 

 due to masses of ice covered deeply by the sands of unusual floods and 

 remaining for long periods in the frozen soil. We may be reasonably sure 

 also that no time elapsed between the disappearance of the ice and the full 

 occupancy of the valley by the flood waters. The frontal lobe of the ice 

 was buoyed up and floated away in the advancing waters. 



From the first disappearance of the ice the waters were never lower 

 than 180 feet above sea level in the central part of the State until after the 

 culmination of the flood i)eriod, when the waters began to settle to their 

 present level, because over the broad area where the clays have been left 

 undisturbed they are continuous from this level downward, and show no 

 intercalation of pebble or sand beds and no interruption of their regular 

 lamination, and they extend clear across the valley from the Pelham range 

 to Northampton. 



While these "Champlain" clays were being laid down over the broad 

 bottom of the valley its swollen triliutaries were bringing in coarse mate- 

 rial along its borders, and the Avaters of the lake itself were eating into its 

 banks, sweeping ofli" the loose glacial debris and wearing narrow shelves 

 in the rocks themselves, and especially cutting deep into the sides of the 

 great di'umlins which are so abundant on both sides of the valley, and 

 cai'rying- the material so gained out into deeper water. It is quite certain 

 that but a small portion of these shoreward deposits have been carried far 

 south Ijy the flooded river itself They are the confluent deltas of its trilj- 

 utaries. Where we can trace the layers of the clay and their delicate sand 

 partings shoreward, we find the latter growing coarser and thicker, and 

 passing continuously into the thick sand and gravel layers which foi"m the 

 " front set " beds of the deltas and bars. The fine flat clay layers continue 

 on unthickened up the delta fronts, more and more separated by the thick- 

 ened sand layers, and grade into fine sand or are prolonged only as the 

 partings between the tliick sand or gravel beds. Hence we may be sure 

 that the great body of the central clays is strictly contemporaneous with 

 the great body of the shoreward gravels, and that the whole has the 

 character of a lake deposit. 



We shall need all the light we can obtain in our attempt to reproduce 

 tlie history of the valley from the reestablishment of the drainage to the 

 subsidence of the waters. The stream may liave been at first like the body 



