18 
The American Geologist. 
January, 1896 
yield the veined structure of mountain glaciers and the 
admirable lamination of the frontal cliffs of the Greenland 
and Antarctic ice-sheets, reaching the conclusion that these 
features in both the valley and continental glaciers are due 
solely or principally to differential motion under pressure. 
The drawings by Deeley and Fletcher of glacier granulation 
are reproduced in plate II, and their explanation of the 
molecular conditions of flow and change of the granules is 
also reproduced in their own words. From these theoretic 
considerations of glacier motion, the reader is next asked to 
weigh certain other opinions concerning the erosion, trans¬ 
portation, and deposition of the glacial drift, the fluctuating 
stages of the oncoming, culmination, and wane of the Ice age, 
and especially the effect of the warm climate brought in its 
closing Champlain epoch. 
Stratification of Successive Snowfalls. 
In view of the demonstrative observations of Forbes and 
Tyndall on the origin of the veining of the Alpine glaciers, 
to he presently stated, we need not describe the undoubted, 
though probably mainly indistinct, stratification of the firn 
by its intermittent and seasonal additions of snow. No one 
has traversed any portion of the Antarctic ice-sheet, which 
perchance in its yawning crevasses may display the bedding 
of the recent snowfalls forming its surface. Referring to 
this condition of the firn covering the Greenland ice-sheet, 
and its possible relation to the well marked stratification of 
the vertical cliffs of its margin and outflowing glaciers, Prof. 
T. C. Chamberlin writes:* 
Beyond serious question, the general stratification had its initial 
stages in the original snowfalls. Whenever encrustment intervened 
between one fall and another, a layer of more or less definiteness result¬ 
ed. Whenever a succession of falls was followed by a period of en¬ 
crustment, a more complex and massive layer was formed. The seasons 
doubtless developed annual subdivisions, and possibly, at intervals of a 
few years, unusual summer effects bound the deposits of a succession of 
years into a great stratum. It is the testimony of Lieutenant Peary 
and his associates that the surface of the ice-cap, under the action of 
the great windstorms, becomes marble-like in solidity and texture, as 
well as in color. At the same time the erosion of the wind develops 
sastrugi, which further differentiates the accumulating snow. In view 
*Bulletin of the Geological Society of America, vol. vi, pp. 205, 206, 
Feb., 1895. 
