536 
BUIvLETiN OF THE BUREAU OF FISHERIES. 
above the lakes. Since the lakes extend to the north ends of their respective valleys, 
where they open into the valley of the Clyde-Seneca River, the altitude of the ridges is 
in general lower at the northern end, where the valleys are also wider and the slopes of 
their sides are less steep. (See fig. 2.) To the south the valleys narrow, their sides be- 
come steeper, and the height of intervening ridges increases. These characters are most 
marked in the valleys of the larger lakes, perhaps most conspicuous of all in Cayuga 
Lake, which at one end extends deep into the highlands at the south and at the other 
reaches farthest into the valley of the Seneca River, so far, indeed, that it is continued 
to the north by the extensive marshes that bound its outlet. 
The immediate shores of the lakes are smooth and regular. They have a steep 
slope, which toward the south may rise above the lake to a height of 100 to 150 meters 
(300 to 400 feet) or more. Above this altitude this slope rises more gradually to the 
general level of the plateau, and then comes a steeper rise to the higher elevations. 
The tributary valleys on the upland slopes are broad, and the lower and steeper slopes 
are trenched by innumerable narrow gorges. These range in size from gullies which serve 
to carry off the rains, but are usually dry, to picturesque gorges, cut deep into the rocks 
and occupied by considerable streams. Of these last the most famous are Watkins Glen 
at the south end of Seneca Lake and the several gorges at the south end of Cayuga Lake. 
The smoothly outlined shores of these lakes show few irregularities or decided 
projections except where the axis of the lake bends on account of the course of the 
original valley. Long Point on Seneca Lake is an instance of such a structural pro- 
jection. Cayuga Lake has a broad expanse of shallow water at the north end, and 
here there are several points and one small island (the only island in the series of lakes) 
which represent irregularities of the original shore. The maps show similar conditions 
in less marked degree at the north end of other lakes. In general, however, the irregu- 
larities of the water line are small and are due to flat deltas and spits built by the 
tributary streams and by the waves. These constitute a characteristic and very beautiful 
feature of the shores of the lakes. They vary greatly in size according to the drainage 
basin of the stream that produced them. The maps of the lakes show numerous examples 
of such points ; Myers Point on Cayuga Lake is perhaps the largest ; and the flat on the 
west side of Seneca Lake on which the town of Dresden is situated was built in similar 
fashion by the outlet of Keuka Lake. In Conesus Lake (fig. 3) two such points opposite 
each other near the middle of the lake have nearly divided it. 
The form of the lakes and their steep banks have so directed the course of the 
winds that very little work has been done by the waves along their sides. As a result, 
the wave-cut shelf is very narrow and the water deepens close to the shore and very 
rapidly. Few large tributaries enter the lakes by their sides; most of the larger streams 
enter at the south end. (See fig. i.) 
The larger lakes of the Seneca Basin take in and give out during the year an amount 
of heat whose aggregate is enormous. It has been computed that this is equal to the 
heat generated by the combustion of nearly 150,000 tons of coal for each square mile 
of the surface of the lake. The total amount of heat from Seneca Lake would equal 
that from nearly 10,000,000 tons of coal. This heat is absorbed by the water in the 
