350 
BRIDGING THE AGES OF ICE 
but Newberry merely designates such deposits “Forest Beds,” with¬ 
out further attempt to elucidate their possible meaning. Winchell,® 
in Minnesota, appears incidentally to notice at this early day that 
the relations of the till and loess in Mower County indicate a dif¬ 
ference of age of the associated drift deposits. Even McGee® 
describes a “Forest Bed” in the till deposits of northeastern Iowa. 
Chamberlin^ recognizes in the Kettle moraine of Wisconsin that the 
drift in front of the moraine must be older than that behind. As 
if to avoid all suggestion of possible duality of the Glacial Epoch 
he cautions: “It is evident that all evidences at correlation between 
superficial desposits on opposite sides of the moraine, should be 
attempted with much circumspection. ... If the evidence adduced 
to show that the Kettle moraine was due to an advance of the 
glacier be trustworthy, then, to that extent of that advance, 
whether much or little, the moraine marks a secondary period of 
glaciation, with an interval of deglaciation between it and the epoch 
of extreme advance. . . . The moraine, therefore, may be worthy 
of study in its bearings upon the interesting questions of glacial 
and interglacial periods.” It is likely that it was because of this 
very indecisiveness of final statement that Dana declined to print 
the article when offerd to the American Journal of Science; al¬ 
though in after years he ofifered that author his apologies for his 
mistake in believeing the paper to treat only on “local geology.” 
From the original conception of a single, simple Glacial Epoch 
the evolution to a complex, or multiple, one is a transformation 
painfully slow in its growth. Its adumbration is doubtless ascrib- 
able to no one particular mind, or to any single group of men, or 
to any particular nationality. Certain it is, that it was McGee’s 
exclusive privilege to give us the first clean-cut, unmistakable per¬ 
spective of the evidences of a dual Ice Age. Previously to his 
publication of the Iowa sections the idea of multiple glaciation is 
merely a fantastic dream. It is high above the clouds in the realm 
of speculative possibility. After his publication it is an accomp¬ 
lished reality. It leads to the establishment, not of a dual span of 
ice supremacy, but to an astounding resolution of a five-fold epoch. 
Upon this simple, unobtrusive observation and record rests one of 
5 Minnesota Geol. and Nat, Hist. Surv., 2nd Ann. Kept., p. 66, 1876. 
6 Am. Jour. Sci., (3), Vol. XV, p. 339, 1878. 
7 Trans. Wisconsin Acad. Arts and Sci,, Vol. IV, p. 201, 1878. 
