The Interval Between the Glacial Epochs. 
85 
If we pass to the upper Ohio and Allegheny valleys we find phenomena 
that fall into close correspondence with the foregoing. There are high 
shoulders and terraces at various points which bear upon themselves gla¬ 
cial river gravels. One of the most decisive is found in the vicinity of 
Parkers, and has been described by Mr. Chance and others. Here an old 
channel runs back from the present course, and curving around a group 
of hills, returns, forming an “ox bow.” In this old channel glacial river 
gravels are found, showing that it was occupied contemporaneously with 
some stage of the glacial period. This abandoned channel is about 200 
feet above the present Alleghany river. Mr. Chance tells us there is about 
fifty feet of drift in the present valley bottom. So between this upper river bed 
and the bottom of the present rock channel there is evidence of an erosion 
of 250 feet, 200 of which, m round numbers, are cut through Carboniferous 
strata. Similar and corroborative facts show themselves along the course 
of the river above and below and along the Monongohela and the upper 
Ohio. If we trace the old channel of the Alleghany northward by means of 
remnant shoulders and terraces we find that it lies considerably above the 
altitude of the terminal moraines of the later epoch; and also much above 
the gravel trains that head on the outer side of these moraines and run 
down through the trench above indicated. It therefore becomes a neces¬ 
sary inference that the trench was cut before the moraines were pushed 
across it and before the moraine derived gravels could be carried down 
into it. The trench therefore represents the interval between the earlier 
and the later glacial epochs. I have placed in manuscript elsewhere the 
fuller facts upon which these brief statements rest, and they will appear in 
print in time. 
If we pass over the Susquehanna valley we find like phenomena. These 
have been brought out by Mr. McGee and others and I need only to refer 
to them because of their connection with that which I have already pre¬ 
sented. Here we find old benches covered with rounded pebbles — some 
of which are glaciated — reaching to a similar height of about 250 feet 
above the present Susquehanna river. There are glaciated pebbles at high¬ 
er altitudes, but I have taken the more moderate figure because it is a safe 
one. Near Sunburg glaciated stones were found by Professor Salisbury 
about six hundred feet above the present river. Below these high terraces 
and in the valley excavated out of the plain from which they were de¬ 
rived, we find a lower terrace 60 or 70 feet in height of newer and dis¬ 
tinguished aspect. Above Berwick this lower terrace connects itself 
definitely with the terminal moraine which there crosses the river. The 
terrace rises rapidly as it joins this moraine, as is the habit of moraine¬ 
headed terraces, and reaches an altitude of 100 to 150 feet as it merges into 
the moraine. But it is still much below the old terraces from which it is 
sharply distinguished by its freshness and youth and by its constituent 
material. 
