468 
[Assembly 
the general deposition. In some of them there is an admixture of the 
black oxide of manganese. 
The rock is principally composed of white and yellowish quartz peb- 
bles and sand. The former vary in size, from a large grain of sand to 
that of a hen's egg. One measured three inches in length. The thick- 
ness of the whole strata is variable. South of Olean, it is generally 
less than twenty feet, while at Rock City near Great Valley, some 
blocks are thirty-five, and at Merritt's mills upon the Allegany, ten 
miles below the State line, the cliff is more than one hundred and fifty 
feet in height. 
> Quarries. 
From the abundance of timber in Cattaraugus, little need of good 
building stone has hitherto been felt, and, consequently, little explora- 
tion has been made for valuable quarries. Of those opened in different 
parts of the county, nearly every one will be found noticed in the list 
which follows. 
The quarries against Olean, contain micaceous sandstone, and an 
olive shale, which is concretionary. The stone at the lower quarry are 
coarse, while at the one some fifty feet above, they are of a finer grain. 
The underpinnings and cellar walls of many buildings in Olean, have 
been obtained from them. 
A quarry owned by Mr. Pratt, in a small alluvial hill, an hundred 
rods down the river, from the quarries above noticed, is nearly ex- 
hausted. 
In a ravine which is entered just south of Pratt's quarry, there are 
found masses of a coarse sandstone, like that alternating with the con- 
glomerate which is seen a few miles south. These masses are strewn 
along the ravine its entire length. In the hope of finding the rock in 
place, an expedition, in company with several gentlemen of the town,* 
was made to the summit of the mountain. All the way from the base, 
in following Pratt's ravine, to within a dozen yards of the very highest 
point, masses of the rock, coarse grained, micaceous and characterized 
by vertical facoides, varying in magnitude from blocks of a cubic foot 
to those of several cubic yards, were found indiscriminately scattered 
about. So angular were they, so frequent, and so wholly above the 
* Messrs. McMartin, Penfield, Richardson and others. 
