1879. | The Formation of Cape Cod. 557 
south shore of Massachusetts bay. None of the streams of this 
region can be supposed to have aided in the accumulation of 
these materials, instead of which they are evidently carrying 
away small portions as they gradually deepen and extend their 
channels. The origin of these plains seems to be due, like the 
kames of Plymouth, to floods and detritus supplied by the melt- 
ing ice-sheet which sloped from both sides toward this area. The 
deposits made in the lower part of the channels of these glacial 
rivers, between walls of ice, remain as kames, or ridges and hills, 
composed mainly of coarse gravel, while the portion carried for- 
ward and spread beyond the retreating ice-margin forms the 
nearly level plains. 
The only fossils found upon this area are within about a mile 
south-west from South Marshfield, and were encountered many 
years ago in digging wells at the houses of Messrs. Kent, 
Chandler, Wadsworth and Sprague, which succeed each other 
along a distance of one-third of a mile, the last being in the edge 
of Duxbury. All these wells showed a surface of modified drift 
ten to twenty feet deep, enclosing occasional boulders, underlain 
by a hard ferruginous stratum, six inches to a foot thick, below 
which were muddy silt, sand and fine gravel, containing succes- 
Sive fossiliferous layers, those at Mr. Chandler’s well being four 
in number, twenty to thirty-five feet below the surface, at heights 
twenty-five to forty feet above the sea. The fossils include casts 
of the quohog, long and razor clams (Venus mercenaria, Mya 
arenaria and Ensatella americana), and numerous fragments of 
lignite. The iron-rusted stratum, varying in height from thirty 
to fifty feet above the sea, and extending continuously at least a 
third of a mile, seems to represent the depth to which the pre- 
glacial deposits were eroded by the ice-sheet, and the lower beds 
were probably contemporaneous with those at the base of Sankaty 
Head. 
The extreme portion of Cape Cod, north from Orleans to High 
Head, consists entirely of modified drift. Boulders are very 
rare, but in two places seem worthy of notice; one of these is, 
about a mile south-west from Nausett Lights, in Eastham, where 
an enormous boulder, called Enoch’s or Great Rock, lies appa- 
rently half buried in the sand. The portion in sight is thirty- 
three feet long, twenty-five feet wide and fifteen feet high. Only 
two or three other boulders were seen here, none of them exceed- 
