1849.] DESOR AND CABOT ON NANTUCKET. 341 



generally isolated, and the Balanus disintegrated and more or less 

 worn. There are besides no traces of dendritic (manganese) incrusta- 

 tions, which, as you will perceive, are very common on most shells of 

 the oyster-bank beneath. Above this stratum of loose shells there is 

 found a series of layers of sand and gravel, with a thickness of nearly 

 fifty feet, in which every variety of materials may be seen, from the 

 finest sand to the coarsest gravel. On the top of these sand layers 

 lies a stratum of dry peat (b), filled with trunks and roots of trees, 

 the remains of a peat bog that has been drained by the washing away 

 of the cliff. Finally there is seen, covering this peat deposit, a 

 stratum several feet thick of fine sand («), which has been deposited 

 by the wind, as is evident from its form, being everywhere bent ac- 

 cording to the outline of the hill, and likewise from the fact that 

 there is not a single stone to be found in it, but only such grains of 

 sand as are capable of being transported by the wind, thus affording 

 a striking instance of the action of wind in the formation of strati- 

 fied deposits. 



The strata thus enumerated seem at first horizontal, but in digging 

 along their edges, we soon ascertained that they all dipped to the 

 west, their inclination varying from fifteen to five degrees, the upper 

 beds being generally less inclined than the lower ones. The inferior 

 clay stratum, however, was found to differ considerably from the 

 others, its dip being nearly thirty degrees to the south-west, and in 

 some places even as much as forty degrees. 



This circumstance induced us to examine this lower clay stratum 

 more carefully. Having made out a spot where the overlying gravel 

 bed was seen in immediate contact with the top of the clay, we could 

 distinctly trace its unconformable deposition, the gravel being seen 

 dying out towards the more inclined clay-stratum, as shown in the 

 al)ove section, fig. 1, taken on the side of a gully in the cliffs. Such 

 differences in the inclination cannot be attributed merely to a differ- 

 ence in the mode of deposition. A considerable change of level must 

 have taken place between the deposition of the clay and that of the 

 gravel. And although no fossils have been found in this clay, yet its 

 great resemblance to the clay of Truro in Cape Cod, which Mr. 

 Hitchcock considers as tertiary, leads naturally to the idea that they 

 may be contemporaneous, and probably of the same epoch as the 

 clay of Gay Head, which you have proved to be miocene. Indeed 

 there may be seen below the red clay of Gay Head, several layers of 

 a brown sandy clay very similar to that of Sancati. Thus the ter- 

 tiary cliffs of Gay Head should no longer be looked upon as an 

 isolated fact, but the cliffs of Sancati may be considered as the op- 

 posite outcrop of a large tertiary basin, underlying the islands of 

 Nantucket and Martha's Vineyard, fig. 2, and extending to the south 

 below Long Island, and to the north as far as Truro, The edges of 

 this basin having thus been raised, became, at the time of the deposit 

 of the drift, a nucleus against which the tide-currents, according to 

 the theory of Capt. Davis, deposited the mud, sand and gravel 

 which they carried with them in their course along the eastern coast 

 of the United States, just as they do at present. We are even in- 



