112 NEW YORK STATE MUSEUM 



a brecciated appearance. The Canadian geologists report the 

 presence of conglomerate bands in the synchronous graptolite 

 shale of Quebec ; and Mr Kummel and Dr Weller have discovered 

 a conglomerate bed at the base of the Trenton in New Jersey. 

 It is, however, more than doubtful that these occurrences have 

 any relation to the bed in Rensselaer county, specially as the 

 New Jersey conglomerate is considered a basal conglomerate, and 

 that of Rysedorph hill is evidently intraformational, containing 

 pebbles of the same epoch and intercalated in shales of the same 

 epoch. It has, however, been demonstrated that a continuous 

 stratum of conglomerate, over which, on a sinking coast, younger- 

 deposits creep, may belong to many successive horizons. This 

 has been most clearly pointed out by De la Becbe in the south- 

 west of England 1 . The New Jersey conglomerate may therefore 

 be only apparently basal and actually synchronous with the more 

 northern one. 



As the study of the conglomerate beds of various formations 

 and the investigation of the conditions along coasts where such 

 beds are formed, has furnished ample evidence that conglomer- 

 ates are the most inconsistent of all sedimentary formations, 

 usually sinking or swelling up suddenly, thinning out and reap- 

 pearing, it is also to be assumed a priori that the bed extending 

 from Ryeedorph hill to Schodack Landing is not of such a wide 

 extent as to allow its connection with the beds of Quebec or New 

 Jersey. 



However that may be, the Rysedorph hill conglomerate con- 

 tinues to be remarkable as an intraformational conglomerate. 

 A conglomerate, according to the experience of geologists, gen- 

 erally indicates a break in the continuity of the sedimentation, an 

 erosion of a preexisting formation and, therewith, an important 

 change in the physical conditions of the region. The writer feels 

 however that the presence of true intraformational conglomer- 

 ates in the Cambric and lowest lower Siluric of the Appalachian 

 region has been so distinctly and vividly set forth by Wal- 

 cott 2 that no reasonable doubt of the existence of this phe- 



i Geikie. Textbook of geology. 1893. p. 516. 

 » Geol. soc. Am. Bui. 1893. 5:181. 



