No. 200.J 
359 
or more, in thickness, and are generally wrought into proper shape and 
size with facility. This rock seems better adapted for building and 
other purposes, where durability is required, than any we have seen in 
Orleans county. It was employed for the upper facing, or coping, of 
the culvert at Medina, and appears to be unaffected, thus far, by expo- 
sure. 
Our acknowledgments are due to Judge Dixon and Judge Turner, of 
Medina; and to Rev. Mr. Beadle and Dr. Morgan, of Albion, for per- 
sonal attentions and assistance furnished us in the survey of Orleans 
county. 
LOCAL AND ECONOMICAL GEOLOGY. 
Niagara County. 
Surface of the Country — Streams ^fyc. 
The mountain ridge* is the most remarkable feature in the surface of 
this county. This ridge gradually rises to the westward, and at the 
Niagara river is about 350 feet above the level of Lake Ontario, and 250 
above the country on the north. At Lewiston, the whole descent to 
the north is made at one offset, but farther east it descends by two, ma- 
king two grand steps, or terraces. This double offset is produced by 
the unequal hardness of the rocks; a stratum of sandstone causing the 
lower one, while most of the rocks below and above it to the limestone 
are soft. In the eastern part of the county, this stratum of sandstone 
has so far declined that it dips beneath the general level of the country 
north. In this part of the county, the ascent from the north to the top 
of the ridge is from 80 to 100 feet. The mountain ridge passes through 
the towns of Lewiston, Cambria, Lockport, and Royalton. From the 
foot of this terrace the country declines gradually towards the lake, and 
the top of the terrace is the highest land in the county. From thence 
there is also a gradual slope south, to the Tonnewanda creek. A few 
of the streams flowing northward, rise south of the terrace; but these 
find their way to the north through gorges worn in the rocks by an im- 
mense body of water, covering the whole surface and flowing in that 
direction. With these exceptions, it will be perceived from the map, 
that streams rising south of the terrace flow into the Tonnewanda or the 
Niagara. The streams flowing to the lake have cut their channels 
deeply into the red marl and sandstone, and their great breadth and 
depth indicate a much greater quantity of w^ater at some previous time. 
* " Mountain ridge" and terrace have been used indiscriminately ; the former is the name 
commonly applied, though the latter is more appropriate. 
