560 N. H. DARTON 
that the underground topography is very uneven and probably if all 
the details were brought to light much more irregularity of form 
would be seen. There are long basins and troughs, separated by 
irregular ridges and saddles, and numerous promontories project 
from the foot of the adjoming mountain slopes. The rocks are 
sandstones and shales of the coal measures and of course the excava- 
tion was effected by erosion prior to the filling of the valley. As 
shown on the map and section, the declivity of the underground 
valley is not like that of the present uniform river grade but there is 
a succession of irregular troughs. The deepest basin is near Ply- 
mouth from which to the southwestward there is a gradual rise of the 
rock floor as shown by many bore holes across the valley. Recent 
bore holes on the flats just east of Nanticoke show also that the rock 
comes to within less than too feet of the surface on the south side of 
the present stream, and as the rock outcrops on the north bank not 
far away from this group of holes there is no likelihood of a deep 
channel in the interval. Possibly it may be suggested that there is 
a narrow canyon cut moderately deep in the rocks here, but a feature 
of that sort would not be accordant with the topography of the 
buried channel farther upstream. As noted by previous observers, 
rock ledges cross the valley at no great distance downstream. The 
suggestion that some of the deeper basins in the valley are 
“potholes” is not tenable, for they are too greatly elongated to be 
in that category. 
Materials in the old channel.—The buried channel of the Susque- 
hanna is filled to the level of the present wide valley bottom with 
gravel, sand, and clay, which, as stated above, reaches a thickness 
of 309 feet at one place. In general the deposit varies from 100 to 
200 feet thick in the greater part of the area. Sand predominates 
but there is a large amount of silt, or mixed clay and sand, and 
admixture of gravel in various forms. Some of the gravel is in beds 
of considerable thickness and extent, but it is generally mixed with 
much sand. There are many beds of clay intercalated in the 
deposits, one of them underlying Kingston attaining a thickness of 
more than too feet and extending for some distance up and down 
the valley. No definite order of strata for any wide area could be 
determined from the bore-hole records and apparently there is great 
