236 
GEOLOGY OF THE FOURTH DISTRICT. 
This specimen is from Erie county, not far from the lake shore, and in the same locality 
numerous others were observed at different heights in the strata; some of them were much 
larger than those here represented. In two instances where I carefully noted the direction of 
these ridges, it was nearly E. and W. This is subject to a few degrees variation, but I have 
found the same general direction to prevail over wide areas.* In some instances the furrow 
appears to have been made in mud which w'as partially indurated, and the cast presents the 
same appearance of a tremulous motion in the body making the furrow, which is sometimes 
observed in the alluvial grooves. In many of these casts the angles are sharp, as if the 
grooves were made with a pointed or angular body ; in others they are round, as if the body 
Avere smooth, or the mud partially flowed together before the period of the succeeding de¬ 
position. 
In many instances the striae are not coarser than those of common alluvial or glacial origin. 
In Seneca county these striae occur upon the surface of a dark colored argillaceous sandstone, 
which rests upon a sandy shale of a blackish color. The shale is so friable that nothing is 
preserved in it, but the surface of the rock above is thus striated. This case is peculiar, 
and I think I have detected the same stratum similarly marked, at the distance of twenty 
miles. It appears in the ravine at Goodwin’s falls, on the eastern side of Seneca county, and 
on the western side of the county near the head of the lake is a similar stratum. The posi¬ 
tion of the two is almost or precisely the same, while in lithological character and the mark¬ 
ings no one can distinguish the difference. Thus it appears that, whatever may have been 
the cause, it operated very uniformly over large surfaces.! 
It will be recollected that there are no uplifts or disturbances which could refer these 
markings to the sliding of one stratum on another; and besides, they are always found at the 
junction of argillaceous with more arenaceous strata, the former of which could not make an 
impression in the harder stone. Many of them are so large, and their direction so uniform, 
that this cause could not have produced them, even allowing evidence of its operation, which 
does not exist. 
In some instances these ridges can be traced for a few feet in extent only, one end being 
large, and gradually disappearing as if the furrow was made by some heavy body striking the 
bottom for a short distance, and then lifted above it. Sometimes the furrows appear to have 
remained unfilled for a length of time, from the fact that they are then partially filled with 
drifted shells, of which the following is an example : 
* Some ridges of this kind have since been examined on Cayuga lake, which had a direction N.W. and S.E. It is often 
extremely difficult to ascertain with accuracy their direction ; for being on the lower side of the strata, it is only where we 
can find an overhanging rock that they can be examined, and we cannot always bo sure that it may not have been slightly 
moved in its bed. 
t In this instance, although large surfaces were examined, the striae have all a single uniform direction. 
