614 GEOLOGY OF OLD HAMPSHIRE COUNTY, MASS. 



The three great water areas mdicated akeady were sutfieiently broad 

 and sufficiently separated to justify one in calHng them lakes, and these two 

 terraces would then be called the lake-shore and the lake-bottom deposits 

 (1 s h and 1 b t). This is further justified by the lakelike mode of accumu- 

 lation of the sediments in these areas, and allows me to use the term "old 

 river bottoms" for the abandoned beds of streams in old oxliows. 



The second terrace or the old lake bottom, unlike the other terraces, is 

 a surface depending, not upon the level of the water at the time of its forma- 

 tion, but upon the water level and the amount of mateiial. The valley 

 widens southwardly, which has the same effect as if the supply of material 

 decreased in this direction. As a result, the lake-bottom level sinks gradu- 

 ally as one proceeds toM'ard the south relatively to the lake bench, m- the 

 deposition scarp which separates the two increases in height. The third 

 ten-ace, counting from the shore line, is generally the uppermost flood plain 

 of the normal Coimecticut River. 



This brings about the curious result that the second and third terraces 

 change places as we go south, the change taking place between the Mon- 

 tague and the Hadlej" lakes; that is, the Montague Lake was a filled-up 

 lake, and as we go inward from its shore line we pass by a slight scarp of 

 deposition to the remnant of the lake bottom at a level but little lower 

 than that of the bench itself. We descend next by a scarp of erosion to 

 a marked terrace (t^) that ci'osses the northern line of the State with a 

 height of 310 feet, which I have often called the intermediate terrace or 

 the Lily Pond ten-ace, formed during 'the early decline of the flood b)^ the 

 rocky barrier at the Lily Pond in Grill (see PI. XXII, p. 724). This is at 

 times broken into two or more tenaces. We descend then finally by an 

 erosion scarp to the group of terraces but little above the present flood 

 plain of the river, and still lower to the incomplete ten-aces which lie below 

 that level, both which groups have been formed by the river in its present 

 size and condition. The intermediate terrace (t*) was thus excavated in 

 the lake-bottom beds — that is, inside the lake bottom. 



Farther south, in the broader Hadley Lake, the filling had not pro- 

 gi-essed far enough to obliterate the lake, and the equivalent of this third 

 terrace (t^) is found as the first terrace below the bench, generally slightl}' 

 marked and excavated in the upper portion of the deposition scarp which 

 had connected the shore and deep-water deposits of the highest floods — that 



