18 TRANSACTIONS OF THE [ocr. 28, 
acter and position is entirely analogous to that at Glen 
Cove, L. I. 
South of Great Pond is the larger and more elevated portion 
of the island. It is quite similar in structure and material to 
the northern part, already described. The lignitic clay, however, 
forms a more important feature in the formation and in the 
bluffs at the southeastern extremity attains its greatest develop- 
ment. From the breakwater southward and westward very ex- 
tensive sections are displayed. Here again the stratified beds 
are upheaved, the’ axes of the folds having the same northeast- 
erly trend. About 200 yards south of the breakwater the banks 
are about 30 feet high and consist of surface drift, finely lami- 
nated sand and lignitic clay. The latter varies from four to six 
feet in thickness and in many places is mingled with sand. The 
lignite is in quite small pieces and has nodules of pyrites asso- 
ciated with it. A section taken about one-fourth mile east of 
the south light was as follows: 
Dark sandy-clay with pebbles... 0.00... 2. sas eee 10 ft. 
Pinesoray sand. lata ce tee see eee ee 2 
Dark clay with pebbles and thin layers of sand....... Loves 
Mereucimous: Sandls-. in elo cele ale os satiate oat Sn 
Dark iblue-sand ‘Clay... c)Atne feo. se. co eS) oe ia en Leva 
Pine compaciz yellowish sand so) 0.4.1. v.42 cece eee ES 
Dark prmepbastic clays. ).). cic. aie ated a teed ale Siete Levins 
Yellow stratified gravel with cobble stones........... 20<% 
Wo. Che beg cli ye es sya eicstve <teparerareral essa 4) olab ie a ye 5QL & 
At the south light house the cliffs are about 152 feet high and 
consist chiefly of dark stratified sandy clay, sand and gravel, 
which have been eroded into deep gullies separated by project- 
ing ridges and pinnacles which present a most picturesque 
aspect. 
West of the lighthouse the dark clays become less promi- - 
nent and the cliffs are chiefly composed of stratified sand and 
gravel. ‘The surface drift of the island nowhere attains any 
great thickness but contains many large boulders. 
A study of these deposits reveals the fact that Block Island 
consists of Post-pliocene stratified beds underlaid by white 
clays and sands which may be of Cretaceous age. These strata 
at intervals during the deposition of the former have been sub- 
jected to glacial action which has folded and contorted them, 
and finally in the Champlain period the ice has dropped upon 
their surface whatever boulders or débris were imbedded in its 
