496 
(GEOLOGY OF THE FOURTH DISTRICT'. 
surface of the rock below is level, it is scratched and worn smooth, evidently from the mate¬ 
rials having been moved along its surface. In one place near Portland harbor, in opening a 
quarry, a considerable quantity of this kind of material was removed; the larger masses fit 
for rough walls were left, and the finer thrown into the lake ; the quantity thus reserved was 
sufficient to have covered the whole surface, when packed closely, to the depth of four feet, 
though the original depth of the whole was only five or six feet. Numerous similar instances 
appear in the bluffs of gravel along the lake ; the moving force seems to have torn up the sur¬ 
face layers, and to have pressed them onward, accumulating in power and quantity, lifting the 
strata for great distances, bending and breaking the uplifted edges, and leaving them in all 
manner of contortions, with rounded gravel above and below. In some instances the gravel 
is forced under the uplifted edge of a stratum to the distance of many feet. 
The valleys are covered with a soil consisting of fine loam and gravel of rounded ma¬ 
terials, which has been derived from more northern rocks. Many of the lower valleys have 
evidently been overflowed with quiet water, from which the fine loamy deposits have been 
made. 
The small lakes, .Bear lake, Cassadaga lake and Mud lake, have once been much more ex¬ 
tensive ; and by successive drainage, they have left marks of their subsidence along the sloping 
hills around them. The valleys of the Cassadaga and Conewango creeks have evidently been 
extensive lakes, as would appear both from the nature of the materials in the bottom of these 
valleys, and from the evidences along the elevated grounds bordering them, as also from the 
narrow outlets worn through rocky strata. 
In the valley of the Chautauque lake, we find satisfactory evidence of its former greater 
elevation in ridges or terraces of gravel and sand ; these are particularly well defined upon the 
north side. On examinations about the outlet, the cause of this greater elevation is found to 
have been the obstruction of its former outlet, which was nearly in an easterly direction from 
the Cassadaga; whereas now, by the accumulation of large deposits of gravel, it is turned in 
a southerly direction, and only joins the Cassadaga valley by a channel excavated through the 
solid rock. This direction is seen very clearly by examining its course on a map, and the 
effects of the wearing action upon the rocks are still visible at Dexterville below Jamestown. 
At the time the original outlet was obstructed, the waters of the lake must have been raised 
to more than thirty feet above the present level, overflowing for a great distance the low 
valleys on its western side and its northern extremity, and which exhibit clearly the evidence 
of such condition from the almost level deposits of fine alluvium which cover them. 
Deposits of marl are less numerous in Chautauque county than in the counties farther east. 
The largest deposit of this kind is in Cassadaga lake and the marshes which nearly divide it 
into two portions. This marl has been used for several years for burning into lime, of which 
2000 bushels are annually made. There is a bed of marl and tufa at the southern extremity 
of Chautauque lake, near Dexterville. 
In many places, recourse is had to large boulders and transported fragments of limestone for 
burning into lime. One of these masses, found near Forrestville, yielded one hundred and fifty 
