468 



SCIENCE. 



[N. S. Vol. XXIV. No. 615. 



quartz and granitic pebbles, the latter being 

 especially numerous in the borings of western 

 Long Island, where the deposit seems to ap- 

 proach a till in character. Elsewhere the 

 formation is often sandy and is to be regarded 

 as an outwash from the second, probably the 

 Kansan, glacier. The formation is known as 

 the Jaraeco. 



4. Deposition of Red and Blade Clays. — 

 These clays, known as the Gardiner, overlie 

 the Jameco with an abrupt line of demarca- 

 tion on Long Island, Fisher's Island and Block 

 Island, and on Martha's Vineyard, Cape Cod 

 and the Massachusetts coast to Boston. They 

 carry a shell fauna, characteristic of a some- 

 what colder climate than at present. The 

 maximum thickness is about 100 feet. In 

 some places the clay occurs as a single bed, 

 while at other localities it is split up into a 

 series of clays interbedded with sands. The 

 color varies from red, through gray and brown, 

 to black. li is correlated tentatively with the 

 Yarmouth interglacial deposits of the central 

 states. 



5. Deposition of Fine Sand. — Following the 

 Gardiner clay a thickness of ten to thirty feet 

 of fine sand, often almost quartz flour, was 

 deposited. This has been designated the 

 Jacob sand and is regarded as a transition be- 

 tween the Gardiner clay and the Herod gravel. 

 It is the equivalent in part of the Sankaty 

 beds of Nantucket, in which locality it is 

 abundantly fossiliferous. 



6. Deposition of Granitic Gravels. — These 

 gravels, known as the Herod, reach a maxi- 

 mum thickness of 100 feet or more, and con- 

 sist of layers of quartz and granitic pebbles 

 alternating with beds of sand. They are 

 thought to mark the beginning of a third ice 

 invasion, possibly the Illinoisan. They occur 

 at nearly all points from Long Island to Bos- 

 ton, at which locality they have been recog- 

 nized beneath the till of the drumlins. 



1. Deposition of the Principal Till of New 

 England and Erosion hy Ice. — This till, which 

 on Long Island and Fisher's Island and Cape 

 Cod has been called the Montauk drift, is a 

 hard, compact, dark gray, often partly ce- 

 mented till, having a maximum thickness of 



perhaps 75 feet on Long Island, but reaching 

 more than double this thickness in the drum- 

 lins about Boston, which, with few, if any, 

 exceptions, belong to this stage. It is usually 

 oxidized to a depth of ten to twenty feet and 

 is regarded as pro"bably Illinoisan in age. In 

 places the ice by which it was deposited cut 

 deeply into the underlying formations, and the 

 till may rest directly upon any of the older 

 deposits. In such instances the drift often 

 departs widely from its normal character, par- 

 taking of the nature of the local beds from 

 which its materials were derived. It marks 

 an actual invasion of the ice. 



8. Deposition of Granitic Gravels. — These 

 gravels, together with their included beds of 

 sand and an occasional layer of brownish clay, 

 resemble the Jameco and Herod formations 

 and are regarded as marking the close of the 

 third, probably the Illinoisan, stage. They 

 may be seen at many points on Long Island 

 and between that island and Cape Cod. 



9. Great Erosion Interval: Possihle Deposi- 

 tion of Clay. — Clays have been recognized 

 above the Montauk drift in the vicinity of 

 Plymouth, and appear to overlie the drumlins 

 near Boston. These underlie the latest drift 

 and may possibly belong to the lowan stage. 

 It may be said, however, that in the region 

 south of Boston but little reliable evidence 

 has yet been obtained of the existence of drift 

 of this stage, although it is not improbable 

 that it may be present. Deposition, at the 

 best, appears to have been a minor feature in 

 the interval between the gravels last men- 

 tioned and the latest till, the interval being 

 characterized rather by extensive erosion, such 

 a:s might be expected to mark a long period 

 like the Sangamon-Iowan-Peorian interval 

 rather than the Peorian interval alone, in 

 which, judging from the evidences in the cen- 

 tral United States, relatively little erosion was 

 accomplished. 



10. Deposition of Thin Till— This till is 

 usually from two to twenty feet in thickness 

 and is ordinarily loose and bouldery rather 

 than clayey, and is oxidized to a depth of only 

 two to five feet. It constitutes the surface 

 deposit over most of southeastern Massachu- 



