296 
GEOLOGY OF THE FOURTH DISTRICT. 
plainly fractured, and the small fragments in the joint are crushed and partially ground to 
clay. The amount of lateral motion may have been greater than appears ; for an oblique 
fissure, extending from the vertical one to the left, was found to have the surfaces striated. 
Such a phenomenon could scarcely have resulted, unless from the moving of one surface 
over the other, by a lateral force. 
Beyond this point, in a southwest direction, the dip continues as uniform and gentle as on 
the northeast. 
Several other points along the lake present similar appearances. The following occurs a 
few miles northeast of the Pennsylvania line, in rocks of the Portage group. 
i 42. 
Elevation and fracture of the strata. Ripley , Chautauque county. 
The strata are mostly shales, or shaly sandstones, with a single thick bed of sandstone, 
which is broken at numerous points along the curve. The irregular fracture is strongly 
stained by decomposing pyrites; and there seems to have been injected mud, which has 
forced its way into all the fissures and between the shaly laminae, for several inches, and often 
for several feet. The laminae of slate and shaly sandstone are broken, and stand in the frac¬ 
ture at various angles, from nearly horizontal to vertical. 
The fracturing of the strata has rendered the mass much more destructible, and the waves 
have worn a deep, cavernous depression, which recedes fifteen or twenty feet beyond the 
general line of the cliff. Many of the indentations along the shore are produced in this man¬ 
ner, their commencement being the fracture in the strata. I have seen several where the 
amount of excavation is much greater than in this, but much of the same character. 
