24 Hie American Geologist. January, 1895 
ing region. As we have endeavored to show, there is every 
reason for believing it continuous along the Mississippi bluff's 
and to some extent over the upland country to the Columbia 
in southern Illinois. 
In conclusion, there seems to me to be little doubt that the 
loess deposits of northwestern Illinois, including the Peca- 
tonica basin, are Columbia in age. Hence it seems to be rea- 
sonably inferred that the Columbia formation does not date 
from the time of the first glaciation of eastern North America 
represented by the ancient drift sheet adjoining the driftless 
area in northwestern Illinois and northeastern Iowa, but was 
contemporaneous with an intermediate stage of glacial ad- 
vance, which may probably have been closer to the end than 
to the beginning of the Pleistocene period. 
THE MUNUSCONG ISLANDS. 
By F. B. Taylor, Fort Wayne, hid. 
Since the autumn of 1891 excursions made in the vicinity 
of Mackinac island have added several new facts to those pre- 
sented in a previous paper relating to that region.* But these 
fragments have not found a suitable place of record in other 
papers recentl}' published, and they are therefore gathered to- 
gether and presented here. Following this article will be an- 
other in which the Nipissing beach will be traced in its south- 
ward extension, as far as now known, and the probable limits 
of the lake of that time will be defined. The accompanying 
map is made to cover the entire width of the ancient strait of 
Mackinac at the time of maximum submergence. It shows 
details which will be referred to in the next article as well as 
this, and shows also the principal shore lines described in the 
first paper on Mackinac. The large ancient island north of 
Little Traverse bay is here named Traverse island. 
The Munuscong Islands. 
From the lookout on the top of Mackinac island a long line 
of hills broken in two parts may be seen toward the north on 
the northern peninsula of Michigan. Without closer examin- 
*"The Highest Old Slioir Line on Mackinac Island." Am. .Tour. Sci., 
Ill, V..1. XLiii. March, 1892. 
