PAN- 
AMERICAN GEOLOGIST 
VoL. XXXVIII Dece:mber, 1922 No. 5 
BRIDGING THE AGES OF ICE 
By Charles Keyes 
When, in the early eighties of the last century, W J McGee 
made known his now famous till-sections displaying the evidences 
of a possible dual, instead of a unal Glacial Epoch, the conception 
seems already to have begun in several quarters faintly to resolve 
itself upon the geological screen. McGee’s fundamental observa¬ 
tion is the actual finding of two distinct drift sheets widely separ¬ 
ated in the same section by a thick bed of loam or loess. Although 
he may not at the time grasp the full significance of his far-reach¬ 
ing discoveries, his results, nevertheless, stand as the first actual 
and unmistakable record of old and young till deposits exposed in 
the same vertical succession. 
Presence of an interglacial loam of great thickness is not the 
only line of critical evidence pointing to complexity of the Glacial 
Epoch. Peat beds, we now know, sometimes separate drift-sheets. 
But in the decade previous to McGee’s exploit buried peat deposits 
are not by any means the diagnostic features that they have since 
become. G. F. Wright ^ in particular emphasizes the inconclusive 
character of these early observations. Newberry, and his assistants 
on the Ohio Geological Survey, Orton,^ Winchell,^ and Gilbert,^ all 
describe buried soils associated with the Glacial tills of that state; 
1 Ice Age in North America, 5th ed., p. 592, 1911. 
2 Am. Jour. Sci., (2), Vol. L, p. 54, 1870. 
3 Ohio Geol. Surv., Vol. I, p. 591, 1873. 
4 Am. Jour. Sci., (3), Vol. I, p. 339, 1871. 
