FISSURES AND CAVES AND KETTLE-FORM DEPRESSIONS. 179 
seen to originate along these veins where they are exposed to the air by 
the removal of the vein matter. After the calcite or aragonite is removed 
to some depth the rock itself is dissolved by the rain water which stands 
in the depression thus formed, and thus the fissure widens somewhat as 
it deepens. Some experiments made with a view to ascertaining the 
solubility of the rock in ordinary rain water showed that in two months’ 
time a very slight but distinctly appreciable per cent of the rock had 
passed into solution.”* 
Locally and at varying distances below the surface the fissures are 
found to widen, their walls retreating until a small chamber is formed, 
and it is thought that the caves which are not uncommon in the Lower 
Helderberg limestone of this region have been mainly made in this man- 
ner. At considerable depths below the surface, as shown at the foot of 
the west wall of Jamesville lake, the work of waters percolating down 
through these fissures is evidenced by the redeposition of stalactitic ma- 
terial on the walls of the fissure and on the roof of overhanging parts of 
its wall where it expands into a room. 
KETTLE-FORM DEPRESSIONS 
Jamesville lake is situated in a large, symmetrical, bowl-like depres- 
sion about 400 feet wide and 500 feet long. It is 160 feet down to the 
lake surface, and the water itself is about 60 feet in depth. Perpen- 
dicular walls enclose the lake on three sides, the east side being open. 
They sweep around the lake in a curve of remarkable regularity and 
beauty from the southeast around the south, west, and north to the north- 
east side of the lake. The bottom of this natural bowl is occupied by a _ 
sheet of water of regular, broadly elliptical outline. While this is the 
most striking natural feature of this region, it is not the only one of its 
kind. The depression in which Jamesville lake lies js in fact only one 
of a number of similar kettles which are scattered all about this inter- 
esting neighborhood, and which apparently are to be distinguished from 
the Jamesville lake depression chiefly in point of size. 
Two hundred feet west of the wall enclosing Jamesville lake, for in- 
stance, is a notable depression, with rock walls rising 75 to 100 feet above 
its lowest point, on the south, west, and north sides. The east side opens 
toward Jamesville lake. Again, not more than 100 feet north of the wall 
enclosing Jamesville lake on the north side, we come upon the edge of 
another depression, which consists really of two pit-like excavations lying 
so close together that they partially merge into one another. The larger 
one, to the southwest, is about 130 feet deep and 175 feet across. The 
*The quantitative measurements were kindly undertaken by Professor E. N. Pattee, of the De- 
partment of Chemistry, Syracuse University. 
