1895. | NEW YORK ACADEMY OF SCIENCES. 7 
action in North America, thus presenting certain features not 
found elsewhere. 
Character of the morainal material—To the student of gla- 
cial phenomena one of the most interesting features is the 
changes to be observed in the character of the morainal material 
in passing from place to place in an east or west direction. Thus 
on Staten Island it is largely of Triassic origin, but with De- 
vonian and Silurian erratics and some crystallines. On Long 
Island the crystalline rocks of New York and New England are 
the predominent features, with cretaceous clays and an occa- 
sional trail of Triassic sandstone from some limited area, while 
palzozoic rocks are rare. On Martha’s Vineyard clays, marls 
and sands of Cretaceous and Tertiary age, and New England 
erystallines, are practically all that are to be found. On Nan- 
tucket, in addition to quartzites and granites, we meet for the 
first time the igneous felsites and porphyries from eastern New 
England and occasional remains of Carboniferous rocks, pre- 
sumably from the Rhode Island area. 
In general structure the hills are strikingly like those of Long 
Island from Port Jefferson to Orient Point, that is to say the 
material of which they are composed is water worn, gravelly 
and sandy, with but little till and clay, the latter usually repre- 
senting limi! | local deposits, although the indications are tha 
near to and elow sea level clay strata of considerable extent 
occur, upon which the sand and gravel deposits rest. 
The only sections recently exposed and not previously de- 
scribed are to be seen along the cuts made for a new railroad 
across the hills from Nantucket City to Siasconsett. One of 
these cuts, about a mile from Nantucket City, at an elevation of 
sixty feet, is eight feet indepth. Here I found a lenticular mass 
of bluish-brown clay extending laterally for a distance of about 
one hundred and fifty feet, about three feet thick at the widest 
part, thinning out into a broken seam at each end and contain- 
ing numerous small pebbles. It was underlain by stratified 
gravel and sand and overlain by unstratified surface sand. In 
other cuts visited nothing of importance was noted. The ex- 
posures were mostly of stratified sand and gravel with little or 
no clay or till and few bowlders. 
Palzontology. The bluff which faces the ocean at Sankaty 
(spelled also Sankoty and Sancoti) Head is the locality which 
has received the largest share of attention from geologists, 
partly for the reason that the summit of the bluff is about 
eighty feet above tide level, the face affording the best exposure 
for studying the geological structure to be found anywhere on 
the island, and partly because fossiliferous beds of Post-Pliocene 
age occur there. 
