208 The American Geologist. March, i897 
esker ridges which contain this gravel, another stream course 
is indicated by an esker, but in the extensive excavations 
which have been made into it, a half hour might be spent in 
searching for a single pebble of the Freeport gravel. Instead, 
it appears to be replaced by well-rounded pebbles of Galena 
limestone which constitute 90 per cent, of the coarser material. 
Now, the till or unstratified glacial drift of the immediate vi- 
cinity, or of any part of the district, while it contains a very 
large percentage of Galena chert and also a considerable 
amount of Galena limestone, lias comparatively little of the 
Freeport gravel, and not nearly a sutlicient amount of local 
limestone pebbles to supply them in the percentage found in 
this southern esker. The origin Of these pebbles in the strat- 
ified drift, however, is nicel}^ explained by the fact that the 
stream passed across a ridge of Galena limestone about a half 
mile east of the excavations noted. Moreover, this was the 
only rock ridge with which the esker stream came in contact 
within several miles, and its large percentage of Galena lime- 
stone must have been derived from this source. The streams 
farther north failed to reach the limestone ridge, but instead 
eroded a deposit of Freeport gravel, which they probably 
found at low levels and carried within a few miles to a hight 
of at least 90 feet. It is this great abundance of the Freeport 
gravel in certain knolls, and its almost total absence in others 
of the same system, which suppl}' the strongest proof of its 
local origin. 
In the Cedarville belt the method of gathering the coarser 
material is equally plain. It passes through a country in 
which the hills are higher and closer than in the southern por- 
tion of the district, and there was better opportunity for the 
streams to come in contact with the rock ridges. Consequent- 
ly we find many deposits of coarse gravel and cobbles in which 
95 percent, is Galena limestone, and one large deposit in which 
99 per cent, is of this material. An examination of the till in 
that portion of the district shows that on an average it does 
not contain 5 per cent, of pebbles of Galena limestone, and 
they are almost invarial)ly small. This statement is not made 
at random to support a theory, but it is the result of repeated 
examinations of the ordinary drift of that region. It is evi- 
dent that the major portion of the coarse pebbles and cobbles 
