173 GLACIAL GRAVELS OF MAmE. 



join tlie main •\- alley in this part of its course. A well-marked instance is 

 found on tlie west side of the Kennebec about 3 miles north of Solon Vil- 

 lage, where a valley covered by ordinary till Qomes from the northwest into 

 the main valley. The Kennebec alluvial plain rises 8 feet or more above 

 the lateral valley, and once formed a dam across it, but shows no tendency 

 to extend back into the valley. This valley would have formed a lateral 

 bay of the main river at the time the alluvial plain was being deposited if 

 it was not covered by ice. Near the mouth of the Pleasant River — a small 

 stream forming the outlet of Pleasant Pond, in Carratunk — there is an abrupt 

 enlargement of the valley of the Kennebec toward the east, and. the coarser 

 sand and gravel plain found near the river does not expand to fill the broad 

 valley, but is bordered by an area of silt and clay on the east side. This 

 clay extends for some distance up the lateral valley. I see no reason why 

 all the lateral valleys would not be covered by such a clay at least to the 

 height of the higher Kennebec terrace, if the water were free to flow back 

 into them at the time the terraces were being deposited. The fact that sonne 

 of the lateral valleys are not covered by such sediments, though they are 

 not so high as the higher terraces, favors the hypothesis that the ice still 

 lingered in them after it had disappeared in the main valley. 



Directly after the melting of the ice in the valley the currents flowed 

 gently, and the underclay was now laid down in the bottom of the valley, 

 flanking the previously deposited osar-plain. Finally there came a time of 

 swifter floods, when the clays were covered by coarse sediments over the 

 whole of the vallej^ (up to 3 miles broad). Much of this sand and gravel 

 and cobbles was probably derived from the central osar-plain, which ^Yas 

 now in part eroded and spread laterally over the whole valley. At this 

 time the river was pouring its mighty volume of waters into the sea in 

 Anson and Madison or northward, while estuarine conditions prevailed for 

 some miles above that point. Subsequently the sea retreated to its present 

 position, but at this time the Kennebec had become much reduced in vol- 

 ume, and the change in level must also have been quite rapid, or a delta- 

 plain of sand would have been left over all the lower part of the valley. 

 As it is, the delta sands of the Kennebec poured into the sea can not be 

 traced south of Waterville. Below that place the whole of the broad area 

 ■occupied bv the sea is covered by clays, and these were rather deep-water 

 deposits, formed some considerable distance from where the Kennebec River 



