TRENTON CONGLOMERATE OF RYSEDORPH HILL 111 



large area, as suggested by the relative thinness of the bed, and 

 the transportation of large boulders. It is a matter of repeated 

 observation that shingle, often of considerable size, is distrib- 

 uted widely along the coasts, when the two kinds of currents 

 mentioned above are able to display their full force. The 

 boulders and pebbles transported by such currents are reported 

 to be of different size, varying according to their relative hard- 

 ness. As the largest boulders in the conglomerate consist of 

 very hard Lowville limestone, and the smaller ones of more fri- 

 able sandstone or more brittle, black crystalline Trenton lime- 

 stone and of softer gray Trenton limestone, the common condi- 

 tions prevailing along the coast of an open sea seem to be suf- 

 ficient to explain the phenomena of the Rysedorph hill con- 

 glomerate. 



It has been lately urged by Gilbert van Ingen 1 that certain 

 unsorted deposits, observed by Ktimmel, Weller and himself 

 in New Jersey, should not be considered as of submarine origin, 

 but rather as flood plain deposits. The writer is convinced that 

 this view will greatly aid in understanding the barren measures 

 of several of our formations, but does not believe that it could 

 be applied to the explanation of the Rysedorph hill conglomerate, 

 for the following reasons : 



The matrix of the conglomerate has been found to contain 

 marine fossils, the bed is only relatively thin and intercalated in 

 distinctly marine deposits; and', the Rysedorph hill beds show 

 distinctly long strings of pebbles which indicate a certain assort- 

 ment of the material. In some places these pebbles are still 

 angular and appear as if belonging to a continuous bed broken 

 up and at once recemented. 



Other Trenton conglomerates 



The extension of this conglomerate bed north and south beyond 



the localities described will be a subject for farther investigation. 



Prof. Dana and Prof. Dwight have made known the presence of 



a Trenton limestone farther south which is described as having 



i N. Y. acad. sci. Oat. 15, 1900; Am. geol. Jan. 1901, p. 43. 



