460 
GEOLOGY OF THE FOURTH DISTRICT. 
For a distance of two or three miles southeast of the village of Caledonia, thin flat masses 
of the drab limestone are scattered over the surface, in many places in sufficient quantities for 
enclosures; its outcropping edges often approach so near the surface as to be turned up by 
the plough. Three and a half miles southeast of Caledonia, it is quarried in large quantities 
for use on the Genesee valley canal. The quarry is owned by Mr. Wadsworth of Geneseo. 
There are about twenty feet in thickness of the rock exposed ; the lower part is in thin layers 
of a bluish color, striped with lighter bands. The succeeding courses are from two to two 
and a half feet thick, of a drab color, striped with darker. It is easily quarried, splitting into 
masses of any dimensions, and becomes very hard and brittle on exposure. The upper seven 
feet of the mass is often in one course, though generally divided into two; this portion, and 
a course of two feet below, contain numerous irregular cavities, often filled with greenish 
clay, gypsum, sulphate of strontian, blende, etc. In some of these cavities there are remains 
of some coralline fossils, the greater part having been dissolved out, probably by the action 
of sulphuric acid, which formed, with the lime, gypsum, and with strontian its sulphate. 
The same causes which here produced the small nodules of gypsum, were in operation 
over a large extent, to form the immense quantity which occupies a place in the rocks beneath 
the drab limestone. Owing to this circumstance only, we find no fossils in the gypseous rocks ; 
for none could exist in a sea where sulphuric acid was a free ingredient. 
The Onondaga limestone is but a thin mass in this county, scarcely appearing except in a 
few localities. The principal of these is at Caledonia, and extending for several miles north¬ 
west from the village. It abounds in its usual coralline fossils, but there are no places where 
it is sufficiently developed for quarrying. 
The Corniferous limestone succeeds the last described rock; it scarcely extends into the 
town of Lima, but forms the substratum of the northern portion of Avon, and in the river 
valley extends as far south as the centre of the town. This rock is quarried in the Conesus 
lake outlet, and on a small stream a short distance further east; at these places, only a few 
feet of the upper part of the mass are seen. It is easily quarried in blocks of large dimensions, 
and is nearly free from hornstone. The stone is wrought for use on the Genesee valley 
canal. The fossils at this place consist chiefly of Strojj/iomena rugosa, Atrypa affinis, Del- 
thyris, and some fragments of trilobites. The greater portion of this rock, on the east side 
of the river, is covered by a deep alluvium, which renders it difficult to trace its bearing and 
outcrop with extreme accuracy. 
On the west side of the river, this rock first makes its appearance in the southeast corner 
of Caledonia, near the town line. At this place a very extensive quarry has been opened, on 
the west bank of a small stream, on land of Mr. Christie. Large quantities of stone have 
been taken hence for the construction of locks, aqueducts, etc., for which purpose no 
better stone can be found. It is mostly free from seams, and is easily quarried and dressed. 
The whole thickness exposed does not exceed ten feet, the courses varying from one to two 
and a half feet. None of the layers are continuous of the same thickness : sometimes a thick 
one thins out entirely, and its place is taken by two thin ones; or a thin layer in one place 
