384 APPENDIX. 



perhaps two hundred feet above its bed, horizontal water-marks, 

 deeply impressed upon the face of the rocks, as if the waters had 

 formerly stood at that level ; and it is impossible to resist the con- 

 viction, in travelling over this rugged district of country, that 

 it has not been totally submerged by waters, which have been 

 suddenly drawn off, but by gradual or periodical exhaustions, 

 standing for many ages at different levels. 



Slate Eocks. — These were, not inaptly, denominated "brittle 

 slate," by Dr. Mitchell, in 1809. Brittleness is their pervading 

 character; and it is owing to this quality, in a formation of great 

 thickness, that the action of the water at Niagara Falls is of so 

 very striking a character. There is no portion of the Niagara 

 slate solid enough to be used for building stone. It is uniformly 

 shelly, and exhibits, even in hand specimens, its reproduced cha- 

 racter.* Those portions of the general formation which are solid 

 constitute silicious slate. A locality of this variety may be seen 

 at the Halfway House, eight miles east of Canandaigua. 



Seneca Lake. — This clear and picturesque lake has its bed in 

 the secondary formations, and may be referred to as exhibiting 

 localities of them. Its upper parts afford the compact limestone 

 in quadrangular blocks. Large portions of its margin consist, 

 of the brittle carbonaceous slate. The shores, from the vicinity 

 of Rose's Farm to Appletown, are little else but a continuous bank 

 of the slate. On the opposite coast, it is also visible at various 

 localities below the Crooked Lake inlet. Cashong Creek may be 

 particularly referred to. A short ascent of its valley brings the 

 spectator into a scene where the walled masses of slaty rock as- 

 sume a character of grandeur. Among the recent portions which 

 have been thrown into the valley, may be seen masses having 

 large species of the stem-like organic remains, which indicate its 

 newness as a formation. Here are also disclosed orbicular masses, 

 and pebbles of other rocks, imbedded in the slate. These prove 

 it to be — what its texture would, in other places, indicate — a se- 

 condary slate. 



The order of position on the banks of this lake is the same as 

 at Niagara ; but the sandstone is not apparent above the water 

 line. Its existence, in the bed of the lake, may be satisfactorily 



■* Appropriately pronounced a "secondary graywacke slate," by JMr. Eaton. 



