Glacial History of Nezu England Islands. — Upham. 85 
Head, surpasses the wonderful results of glacial thrust on older 
beds in the islands of Moen and Riigen, in the southwest part 
of the Baltic sea. Professor Shaler invokes, however, along this 
whole marginal belt of glaciation, a development of deep faults 
or folds in the underlying hard rock formations, belonging to 
the same class as mountain-building movements, and yet find- 
ing expression at the surface in disturbances of the clay and 
sand strata upon narrow tracts, ranging in width from a few- 
rods to a mile, or at intervals across several miles. Except in 
the Gay Head section, the disturbance generally amounts to 
no more than a moderate tilting and arching of the beds near 
the surface or just under drift deposits, with infrequent in- 
stances of close folding, and it seems not to extend to great 
depths. Between these two explanations, I have no hesitation 
in accepting ice thrust as the disturbing agency in this entire 
region. 
We are led by this view to affirm an extension of the ice- 
sheet to Martha's Vineyard at an early stage of the Glacial 
period, long before the deposition of the chief mass of the ter- 
minal moraine and other drift there, since Shaler and Wood- 
worth have shown fiiat much erosion and land sculpturing en- 
sued, after the disturbance of the underlying beds, before that 
main stage of drift deposition. The ice front may in- 
deed have somewhat receded and readvanced, permitting ex- 
tensive subaerial erosion, previous to the Champlain depres- 
sion, final melting, and chief stage of drift deposition. In this 
connection, it is most important to note that Mr. Woodworth, 
in a recent letter, tells me that last April he found "glacially 
scratched pebbles in the boulder beds which occur at the base 
of the older Pleistocene on Gay Head." After the early tilting 
and folding, probably many thousands of years passed before 
the Champlain epoch of low altitude and final departure of the 
ice-sheet. Within that interval may be comprised the Kansan, 
Illinoian, lowan, and early Wisconsin stages of glaciation in 
the upper Mississippi basin. 
Deposits of Modified Drift. 
Granitic and gneissic rocks, yielding in decay or in glacial 
abrasion abundant quartz grains, occupy a very large propor- 
tion of New England, far exceeding any other part of the 
