282 
GEOLOGY OF THE THIRD DISTRICT. 
made, and the materials which fill it, that the two cannot be confounded, so perfect is the 
identity of the latter even in boring. The present depth attained in the excavation is 265 
feet; the strength of the brine at that depth being about 20° greater by the salometer there 
in use, than that of the other wells or borings. The excavation therefore forms a drain and 
reservoir, in which the saline waters exist; and these must have originally been surface 
waters, which have acquired their saline materials in passing through the group, being connected 
directly with none other. The deeper the borings which have been made in the excavation, 
the stronger has been the brine ; a fact of great importance to the people, since 21° are yet 
required to obtain saturated brine. Were this attained, and the reservoir should be as here¬ 
tofore a never failing one, it would be of far more value to the State than the discovery of 
rock salt; as this would have to be extracted or dissolved in place for purification, the labor 
and expense of which would greatly exceed the making of salt from saturated brine, even 
with its soluble impurities, so easy are they to be gotten rid of when the natural process is 
imitated. 
The real depth of the ancient Onondaga valley cannot but be matter of conjecture : its 
present known depth shows that its outlet has been covered up by alluvion. It probably falls 
very short of the depth of Lake Ontario, which must have received its waters ; and from the 
rather solid character of the Lockport limestone upon which the red shale is based, the south¬ 
west dip of that rock constantly increasing, would, as at the Falls of Niagara, with its lime¬ 
stone constantly increase the difficulty of excavation. 
In the Report of 1839, the facts in relation to the reservoir and the source of its brine were 
made known, with the cause which separated the waters of the reservoir from those of the 
lake ; a covering of lake marl forming the insulating medium. In the same report, the ex¬ 
istence of salt in the group and the part which it occupied, were distinctly asserted, having 
given origin to the hopper cavities ; and that it also existed in the cavities of the porous rocks, 
inclining at that time to attribute their origin to a cause which is not required for their expla¬ 
nation. The discovery of hopper cavities in the porous mass shows that salt existed therein; 
and there is no difficulty in believing that the pores were formed of the same mineral, espe¬ 
cially as instances of porous rocks of like origin are already known. In that report, also, it 
was asserted, that from the permeable nature of the gypseous hills, no salt could be expected 
to be found above the level of the drains of the country ; that it must be sought below their 
level, and in that part of the group where the salt had been known to exist; and from the dip 
of the rock to the south and west, it must be to the south and not north of Syracuse. 
From the fact of hopper cavities existing in the porous rock, there is no objection to consi¬ 
der salt as having given origin to the pores, and there is no other mineral in the group to 
which they might be referred. From the size of the hopper cavities, and from the cubic 
arrangement of the greater number of them, it follows that the crystallization of the salt took 
place in the mass where they exist; which, with the previous fact, is favorable to the exis¬ 
tence of rock salt in the group ; the quantity of salt where these forms are found having been 
too small, and too much diffused, to overcome the resistance of the inert medium in which its 
particles were placed, its very soluble character favoring the diffusion. 
