No. 275.] 
265 
sion below the surface of the area, and in the lower part of the salife- 
rous group of Onondaga. When we consider that Sodom lake is wholly 
unconnected with any of the present or ancient water courses, we should 
expect a less erosive action than where a connection with such existed. 
Onondaga lake is but the extension of the vally which lies south, and 
the Onondaga valley, like every valley north, is connected with a val- 
ley which lies south, and reciprocally every valley south has its north- 
ern valley, and w^hether you rise towards the point where the waters di- 
vide, either from the south or the north, you find that the sides of the val- 
ley lose but little of their elevation, thereby proving the existence of a 
more ancient valley, and anterior to the cause which formed the double 
plane which they present. This view is given to show that great and 
mighty changes, but simply wrought, have taken place upon the eleva- 
tions of the Third District, which should lessen our surprise for changes 
of a like kind upon a depression; when a cause of erosion existed upon 
those heights; one of which outlets was by Onondaga lake. 
Looking over the surface of Onondaga lake we find it encircled by a 
white margin, which when examined, shows that it is formed of lake 
marl, the part exposed to the air being in a state of aggregation, which 
gives it the appearance of tufa, but in gravel-like fragments. With the 
exception of the hills at Geddes, Salina and Liverpool, the margin of 
the lake lies very little below the general surface of the country.—- 
These hills show" by their composition that they are the remains of the 
ancient sides of the valley, being formed of the masses which belong to 
the saliferous group. 
The proof being ample, of the existence of a deep excavation where 
Onondaga lake is seated, and the same excavation being filled, in part, 
with alluvial materials containing salt water, nothing more is required 
ior a right understanding of this reservoir, than an impermeable cover- 
ing to prevent the union of the salt water of the alluvial with the fresh 
water of the lake. The salt water often rising in its reservoir and flow- 
ing over its limits to the lake. This covering is the lake marl; it is co- 
extensive with the whole border of the lake, extending inwards until 
lost to the eye, but met with in every sounding that was made, 
only sullied by vegetable or argillaceous matter in the deeper parts of 
the lake. In all the borings for salt water this marl is constantly tra- 
versed, unless the boring is in the original mass or rock. Its thickness 
is about six feet, and highly adhesive or tenacious in its character. No 
material for insulation could be better, end seems to me to fully explain 
f Asscm. No. 275.] 34 
