212 TRANSACTIONS OF THE [18^2 



examined by the writer, do they present upturned ends 

 overspread by succeeding formations. The woodcut illus- 

 tration, given by Prof. Edward Hitchcock, in his Report of 

 1841, although rough, sufficiently outlines the Gay Head 

 cliffs. It shows that marine erosion was one of the chief 

 factors in opening the beds vertically. Since then, diagonal 

 dislocations and slides have given the positions of the sea- 

 ward ends as they now exist. 



The Raritan formation, defined by the writer, in pre- 

 vious papers, as the upper member of the Albirupean 

 formation, and designated as the Alternate Clay-Sand 

 Series, has, by reason of later investigations in ISTew Jer- 

 sey and on Martha's Vineyard, proved to be well sepa- 

 rated from the contiguous formations. It is in fact more 

 sharply separated by broken lines in the underlying de- 

 posits, and by a change to marine sediments in the over- 

 lying beds, than we have found to exist between the 

 Miocene and Eocene, or the Eocene and Greensand Cre- 

 taceous formations in the adjacent tracts of country. 



If the Raritan once formed a part of the Amboy Clay 

 Series, we might expect to find evidences of direct contin- 

 uity between it and the underlying clays. Such, however, 

 appears not to be the case. Instead of continuity we see 

 an erosion interval. There is no agreement with other 

 series in the extension of the strata ; and there is such 

 agreement of plan throughout its whole long stretch that 

 it forms a consistent unit of structure. The fact is evi- 

 dent, also, that this formation has suffered greatly by 

 denudation and erosion. Large tracts of its mass have 

 been carried from its surface, and bayed-out excavations 

 extend to near its base level in terranes such as may be 

 seen at Bordentown and Kincora in New Jersey, and on 

 the Severn, Magothy and Elk rivers in Maryland. 



