No, 275. J 293 
reous matter, and the siaall admixture o/plastev, thus introduced, woulii 
be efficient in promoting vegetation. 
The water lime series is the upper member of the " Onondaga salift- 
rous group;" but at Seneca falls, the essential characters of this forma- 
tion are not developed. The soft marl is succeeded by a grayish blue 
limestone, very compact and brittle, breaking with a conchoidal fracture, 
and exhibiting numerous crystalline points. The rock in place is fissured 
into irregular masses by seams which traverse it in all directions. It 
possesses neither the colour nor mineral composition of the water lime. 
Throughout the whole series it is extremely variable; and though in 
many places possessing all the external characters of good hydraulic ce- 
ment, it burns into quick lime, or the product being too siliceous will 
not " set" under water. Depending, as this does, on a certain combination 
of the ingredients, it is not surprising, that a sedimentary rock, where the 
materials were transported from different directions, and subjected to the 
varying action of currents, should often be unfit for purposes where a 
constant mixture is required. This rock, at Seneca falls, passes into a 
compact coarse grained mass, and presenting often a geodal structure. 
The latter character may be seen at the large stone mill in the upper 
part of the village, where it has been quarried and used for building. 
The usual accompaniment of irregular or concretionary strata are not 
visible at this place; the rock passing by insensible gradations into the 
Onondaga limestone. A few strata of the latter rock are seen south 
of the falls, and at the quarries near Waterloo; but in general it is not 
as well marked as in other counties; while the succeeding rock attains 
a greater thickness, and is more exposed than in the counties westward. 
Seneca Limestone. South of Seneca falls, and covering the greater 
part of an area of five or six miles, occurs the limestone which succeeds 
the Onondaga. This limestone commences about two miles south of 
the falls, and extends a mile south of Cayuga village: its southern limit 
is in a line drawn from this point to Seneca outlet, two miles west of 
Waterloo. The rock is fine grained, compact, often brittle, and con- 
tains thin layers and nodules of hornstone, which have frequently stria- 
ted surfaces, and are covered with a deposition of carbonaceous matter. 
They present some analogy to the striated surfaces of portions of the 
water lime, and some other rocks, but probably cannot have had pre- 
cisely the same origin. Few species of fossil shells are found in this 
limestone; the most constant and characteristic one being the Stropho- 
mena lineata, a shell which I have not seen in any of the limestones, 
above or below, though it occurs in the sliale« above the Seneca lime- 
