REVIEWS. 
The great Ice-dams of Lakes Maumee, Whittlesey and Warren. By 
FRANK BurRsLey TayLor, Fort Wayne, Ind. American 
Geologist, July 1899, Vol. XXIV, pp. 6-38, Pl. II and III. 
Two years ago Mr. Taylor contributed to Pleistocene geology a new 
working hypothesis.’ Pointing out that the recessional moraines left 
by certain lobes of the Laurentide ice sheet on plains or in broad 
smooth valleys were characterized by regularity of interval, he postulated 
that this regularity was caused by a definitive rhythm in the general 
conditions controlling the magnitude of the ice-field; whatever may 
have been the cause of the general wasting of the ice, its action was 
modified by a concurrent cause of a rhythmic nature, which alternately 
promoted and opposed the wasting. Under the joint action of the two 
causes the ice front first retreated with comparative rapidity, then 
halted, readvanced slowly over part of the abandoned territory, and 
finally halted a second time before beginning a second cycle ; and each 
recessional moraine marks the position of the ice front at the close of 
such a cycle. This hypothesis, if well founded, is of far reaching 
importance. It affords a basis for the correlation of moraines in widely 
separated districts, and for the mapping of the ice sheet at various stages 
of its final waning. It affords a regularly graduated chronologic 
scheme of classification. It leads to an estimate of the duration of a 
definite portion of geologic time, far superior to any based on phenom- 
ena of erosion. And it probably assists in the discussion of the cause 
of the ice age. 
When the hypothesis was first presented it was applied to the mak- 
ing of a time estimate. In the present paper it is applied to local 
geology, the correlation of moraines and associated phenomena in a 
district about Lakes Erie and Huron. After a general discussion of 
the function of the ice front as a dam to retain glacial lakes, and of the 
theoretic relations of successive positions of the dam to cols, and the 
™ Moraines of Recession and their Significance in Glacial Theory. JOUR. GEOL. 
Vol. V, 1897, pp. 421-465. 
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