442 Lf. H. Mudge—Central Michigan and the 
Art. XLVUI.— Central Michigan and the Post-Glacial 
Submergence ; by E. H. Munee. 
FRom time to time during the past four or five years arti- 
cles from the pen of Dr. J. W. Spencer, in advocacy of the 
theory of a great depression and submergence of the great 
lake region at the close of the glacial epoch, have appeared in 
this Journal. Dr. Spencer’s conclusions are based principally 
upon the position and deformation of what he considers to be 
deserted high-level beaches in the vicinity of the great lakes. 
Whatever may be the value of the theory with reference to 
the eastern part of the lake region, I have been quite unable 
to harmonize it with certain phenqmena in central Michigan. 
While I have no desire to detract from the real value of Dr. 
Spencer’s labors, I wish to call attention to the conditions 
which here exist. , 
Across the Michigan peninsula, from the mouth of Grand 
river on the west to Saginaw bay on the east, there is a marked 
depression or valley. It is evidently the unfilled portion of a 
much deeper valley, eroded in pre-glacial times by Spencer’s 
Huronian river. The conditions to be considered are found in 
connection with a portion of this depression, extending from 
the watershed in Gratiot county to the vicinity of Grand — 
Rapids, a distance of about fifty miles. Through this entire 
distance, except near the watershed, the lowest part of this 
depression is occupied by a wide river valley, the dimensions 
of which are much greater, in proportion to the size of the 
stream occupying it, than those of any other river valley in 
the state. Its principal features must be noted. Its average 
width is perhaps two-thirds of a mile, and throughout its 
length, except where broken down by the entrance of tribu- 
taries, it is bordered by steep drift bluffs averaging fifty feet 
in height. The present flood plain is broad and flat, and a 
well-marked terrace is usually present above it. The condi- 
tions are such, in fact, that there can be no doubt that this 
valley was excavated in the drift by a stream much larger than 
that which now meanders through it. Whence came this 
greater stream ? 
Grand river, rising far to the south, enters the wide central 
vailey at a point in the eastern part of Ionia county. Above 
this point its valley is narrow and exceedingly crooked, with- 
out terraces—features denoting comparative newness, and in 
striking contrast with the greater valley which it here takes 
possession of. As the central valley, with its characteristic 
features as above described, extends far to the east of this 
