SEDIMENTAET DRIFT OF UPPEE KENNEBEC VALLEY. 175 



wide at Bingham, the clay broadens to 2 miles or more in Solon, Embden, 

 Anson, and Madison, while below that point the marine beds are several 

 miles in breadth. It is not probable that the clay covers the central parts 

 of the valley north of Solon Village. 



From Waterville northward to Norridgewock we find overlying the 

 sedimentary clay a stratum of sand rather horizontally stratified, except 

 where it has blown under the action of the wind. In Faii-field and Skow- 

 hegan this sand forms plains extending back from 1 to 3 miles from the 

 river, and it is plainly a marine formation, i. e., the fluviatile Kennebec 

 delta. In places it has been removed by the wind or by stream, and it is 

 difficult to trace its original distribution. Northward the sand becomes 

 coarser by degrees and in Madison passes into mixed sand and gravel, 

 while by the time Solon is reached cobbles and bowlderets are found more 

 than a foot in diameter along the central parts of the valley. From this 

 point to within three miles of the Forks well-rounded pebbles, cobbles, 

 bowlderets, and in places bowlders are found along the central part of the 

 valley, while at the sides of the valley the stones are not so large and are 

 less waterworn. At the sides of the valley this coarse stratum plainly 

 overlies the underclay. The sections observed by me did not show clay 

 beneath the gravel at the axis of the valley; yet this may be due to the 

 sliding down of the overlying gravel. Only at a few places did I find clay 

 in the banks of the river above Solon, and then it was uncertain whether it 

 was sediment of recent deposition or an uneroded portion of a stratum which 

 once covered the valley. It thus appears that there is little or no clay 

 beneath the coarse drift found along the axis of the valley. 



The so-called "horsebacks" are among the most interesting features of 

 the upper Kennebec Valley. From Solon to Bingham a nearly continuous 

 two-sided ridge is found along the west side of the river, and from that 

 point northward to within 3 miles of The Forks a similar ridge is found for 

 most of the way on the east side. These ridges rise 20 to 8U feet above 

 the alluvium at their sides. What is the cause of these ridges! 



Where they are broad enough to have a flat top, they have, by aneroid, 

 substantially the same height as the broadest of the alluvial terraces at the 

 sides of the valley, that which constitutes the main sedimentary plain. 

 Where they are narrow, they are usually lower than this terrace, and often 

 almost merge into an uneven or hummocky terrace many feet lower than 



