238 The American Geologist April, iso? 
about tliis eiiglacial and siiperglacial drift: 1. Its total 
amount (excluding clay and fine sand which have been largely 
removed by subsequent erosion) would not make a uniform 
layer over the entire district exceeding one inch in thickness. 
To remove ail element of uncertainty in the statement, I will 
replace it by five inches. 2. Among this material exceeding 
one inch in diameter, Galena limestone does not make up a 
tenth part of one per cent. During several years' residence 
in this district, and in repeatedly traversing it, I have found 
several hundred erratics of Niagara limestone, but less than a 
score of boulders of Galena limestone, which could clearly be 
traced to the en glacial drift. 
Having satisfactorily determined that the greater portion 
of the coarser material in the esker ridges was derived nei- 
ther from the engiacial drift nor the ground moraine, but by 
direct erosion of the stream from the rock ridges, let us see 
to what this conclusion leads us. Some of the coarse gravel 
knolls reach an altitude greater than any hills within miles 
of them and overlof)k all the surrounding country. While this 
is not generally the case, there are quite a number of places 
where the origin of the coarse cobbles and small boulders can 
be determined with some certainty, and in a large proportion 
of these cases the gravel is now higher than the point from 
which it was eroded. In the case of the knolls containing 
Freeport gravel, it was probably raised to a hight of at least 
90 feet, but we cannot tell in how short a distance this was 
accomplished. A careful study of the entire district, how- 
ever, will convince ar.yone that the streams sometimes raised 
coarse gravel to a hight of 100 feet within two miles; or, to 
be within the limits of absolute certainty, we may reduce this 
to 25 feet per mile. Now it is obvious that the esker stream 
flowed with a strong current from the place where it eroded 
the material to the place of its deposition; and therefore, if 
in an ordinary channel, it flowed down grade. This would 
require a most remarkable amount of tilting of the district to 
account for the raising of the gravel. Were this a geologic 
province subject to profound orogenic movements, we might 
seriously entertain this hypothesis; but there is absolutely no 
correlative evidence of it. On the contrary, if we may judge 
by analogy with later glacial epochs, our district was at the 
