1921] DACHNOWSKI—PEAT DEPOSITS rid 
up by strong winds, forming at first a surface coating upon the 
ice at the time the moraines were developing. The effect of 
possible meteorological changes over wide areas, such as PENCK 
and others have worked out, must be borne in mind. The shifting 
of all climatic zones southward (26), caused by the general lowering 
of the temperature during the Ice Age and the depression of sea- 
level, points to the probability of this area as part of a relatively 
windy arid belt. After the ice had melted back some distance, the 
inorganic material may thus have come to be contributed to the 
peat deposit. 
The basal layer of macerated peat is somewhat silty, and has 
a rather aged appearance. It is assumed, provisionally, to have 
been formed during the first or Shelbyville period of deglaciation. 
The layer of plant remains found overlying the basal peat has a 
much fresher aspect, but the organic débris in both of the lower 
layers of peat seems to fall short of reaching the greater variety 
of plant fragments which occurs in the succeeding layers. Further 
study of a microscopic nature, however, is necessary to establish 
fully the character of the plant remains from each of these glacial 
substages. The strongest evidence of an interval between the 
formation of the basal macerated peat and of the overlying layer 
of macerated plant remains is found perhaps in a comparison of 
the character and amount of the uppermost seam of clay. This 
clay seam is much more sharply terminated than the lower one, 
and it is also worth noting that the upper thickness of the clay 
stratum is compact and relatively free from plant remains. Whether 
or not the evidence thus far at hand favors the view that the seam 
of clay is derived from wind blown loess rather than from drift, 
or differences in the strength of the outwash, of considerably 
greater significance is the fact that the upper mineral layer consti- 
tutes a distinct break in peat formation. The cause of this break 
in the succession of peat materials must evidently have been a 
change from colder climatic conditions, from a more or less notable 
readvance, and a renewed aggression of the ice sheet. 
Apparently the climate was undergoing amelioration at the 
time, probably giving rise also to a lower water table. That such 
oscillations have occurred is evident from the work of LEVERETT 
