342 R. S. TARR LAKE CAYUGA A ROCK BASIN. 



From the margin of the delta, lake Cayuga extends northward, with 

 a slightl}' HuxuouB course, for a distance of nearly forty miles, and with 

 a width varying from one mile near Ithaca and Ludlowville to more 

 than three miles opposite Aurora. The enclosing hills, which near the 

 southern end are high though gently sloping, gradually decrease in ele- 

 vation and angle of slope toward the north, and near the northern end 

 have practically disappeared. At this end the outlet is through an 

 extensive swamp. On both shores of the lake there are high cliffs, but 

 they are particularly well developed on the eastern shore, .indicating 

 that waves had a share in their formation. 



The surface of the lake is 378 feet* above sealevel, but at the deepest 

 point, near the middle of the lake, there is a depth of 435 feet. For a 

 distance considerably more than half its length tjie bottom of the lake 

 is below sealevel, and at the deepest point the bottom is 57 feet below' 

 tide-mark. The lake is distinctly deeper at its southern end, or at least 

 in its southern half. For nine miles from the northern end the depth 

 does not exceed 100 feet at any point, while at the southern end a depth 

 of 200 feet is found at a distance of one and one-half miles from the 

 delta, and at a distance of three miles the depth is 300 feet. 



Seneca Lake and Valley. — The valley of Seneca lake exhibits very nearly 

 the same features, but the lake is about five miles shorter, the surface is 

 440 feet above sealevel and the greatest depth is 618 feet, or 178 feet 

 below sealevel. Almost everywhere the lake is over 300 feet deep, and 

 more than half the lake bottom, the southern half, is over 500 feet below 

 the surface, or distinctly below sealevel. 



Professor Brighamf points out that these two lakes are situated with 

 their northern ends in the comparatively hard Helderberg rocks, the 

 lakes themselves being in the soft Marcellus and Hamilton shales, while 

 in the region of the divide to the south the strata are harder and more 

 sandy. This, taken in connection with the gentle southerly dip of the 

 strata and the greater depth of the lakes in their southern ends, has an 

 important bearing upon the question of the origin of the lakes. 



Review of Opinions of previous Writers.J 



It is not surprising that a region so peculiar as the Finger lake dis- 

 trict should have attracted Avidespread attention, but it seems extremely 

 strange that until within a A^ear or two no one should have seen the very 



*The facts concei-ning the lake bottom are obtained from the very excellent maps prepared by 

 tlie Civil Engineering Department of Cornell University. 



t Bull. Am. Geograph. Soc, vol. xxv, no. 2, 1893, p. 17. 



J This does not pretend to be an exhaustive statement, but discusses all the papers which the 

 author has been able to find. 



