46 Geological Reports on the State of New York. 



The compact portions are durable, but there are seams of argillaceous 

 matter, some of them scarcely perceptible, and others where this matter 

 has been removed ; all of these will absorb water, which, by expansion 

 in freezing, will finally split the stone. The effect of freezing water on 

 this stone, is illustrated in many of the locks in the vicinity of Syracuse, 

 where every stone in which the seam occurs is split. This objection is 

 a very serious one, and when a work of the magnitude of the Roches- 

 ter aqueduct is to be constructed, more care should be observed in se- 

 lecting the material." 



Cavity containing Water. — " At Barre, in digging a well, rock occur- 

 red at 24 feet; upon passing into the rock 17 feet, a cavity was found, 

 from which a copious supply of water issued, rose to the surface, and is 

 permanent." 



Fucoides and Ripple Marks. — " The surface of the layers at some 

 points, as at Medina, is covered with fossil stems of vegetables, chiefly 

 of the family of Fucoides. The most common species is the Fucoides 

 Harlani, (Conrad,) in the form of stems which branch and cross each 

 other, and which possess transverse striae, and other evidences of an or- 

 ganic nature. Another very pretty Fucoides occurs at the same localhy, 

 apparently consisting of short thick leaves, resembling a Cactus, and with 

 no apparent stems. The above are accompanied by other species of an 

 irregular form. The new genus instituted by Mr. Conrad, Dictuolites 

 Beckii, occurs in the uppermost layers, and has not yet been seen at 

 any depth in the sandstone. It occurs in the upper layers one mile 

 south of HoUey. About forty feet deep in the sandstone occur one or 

 two layers of about two feet in thickness, containing a new species of 

 Lingula, the L. cuneata, associated with fresh-water shells, viz. Unio 

 primigenius, Cyclostoma pervetusta, and Planorbis trilobatus, as descri- 

 bed by Mr. Conrad. Associated with the above shells, is a species of 

 Cytherina, very much resembling that which occurs in the bituminous 

 limestone of Wayne county. 



"At Medina can be seen, in great perfection, those appearances which 

 ^have been called ripple marks. They consist of parallel furrows, or de- 

 pressions on the surface of the layers, resembling exactly the tide or rip- 

 ple marks in the fine sand on the shores of rivers. They are slightly 

 waved, or serpentine, and sometimes run into each other. Near the cul- 

 vert at Medina, these furrows appear on both sides of the canal, without 

 any interruption, for about one hundred yards. They exist on the upper 

 surface of the upper layer of the sandstone, which is here gray, and Mery 

 siliceous, and contains the Dictuolites, or net-like Fucoides, which some- 

 times continue across the furrows, as if they had been inflexible. These 

 furrows are on several of the top layers, and occasionally we observed 

 the marks, not on the upper surface, but having a small portion of rock 

 above them." 



