APRIL, 1900. BRUNCKEN— PHYSIOjGRAPHICAL NOTES. 
97 
being beach deposits. They are very distinctly stratified, but 
show the cross-bedding characteristic of beaches. The material 
is usually composed of alternating strata of sand, varying in fine- 
ness up to the size of a pea, and gravel consisting of flat, well- 
worn pebbles. The fact that these deposits occur on all sides of 
hills, and that their strike and dip is in all sorts of directions, pre- 
clude the idea that they indicate a continuous coast line. For the 
same reason they cannot be identified with the various beach form- 
ations indicated along the present shore of Lake Michigan by the 
Geological Survey. The only alternative seems to be that they 
were formed around islands, while the clay was deposited in the 
deeper portions of the straits throughout the archipelago. 
Some caution is necessary in identifying quaternary deposits 
in this region. As a general rule, we may classify all formations 
showing distinct stratification as Champlain rather than Glacial. 
But this does not always hold true. It is well known that the 
Till not rarely shows limited areas of pure clay, without pebbles 
or boulders, or of sand and gravel. Not rarely, also, there is an 
imperfect stratification visible. AVhere the exposure is large, 
mistakes are not likely to happen because such areas are usually 
small and surrounded on all sides by unmistakeable boulder clay. 
But in small exposures it is sometimes impossible to come to a 
positive conclusion. Among the tests must be, aside from the 
general topographical relation of the area, the character of the 
pebbles, which in the Till are subangular, but in the beach deposit 
worn more or less flat. In the lacustrine clay, the pebbles may 
be of either kind, according to their history. The stratification 
within the Till is usually irregular, often crumpled, while the 
strata of the lacustrine clay are regular and approximately 
horizontal. 
These accumulations on the sides of the boulder clay hills have 
of course materially changed the outlines of the latter. It is 
noticeable that the farther southwest one goes within the town- 
ship the more distinctly drumloid the hills appear. In the eastern 
portion they are often broad, while towards the west they are 
often elongated beyond the typical drumloid form. The western 
half of the township offers less favorable opportunities for study- 
ing the quaternary formations, because there are not so many 
cuts and other artificial exposures ^s in the portions nearer the 
city. It is not at present practicable to say precisely how far west 
the archipelago extended. The mainland must, of course, be held 
to have begun where the boulder clay commences to be the con- 
tinuous surface deposit of the hills as well as the depressions, 
which, according to the map, is somewhere near the county line. 
