356 
[Assembly 
Mr. Mather to examine in the spring the whole of our common Hne, 
being desirous of obtaining an accordance of results, which could not 
be so well effected as by a conjoined examination. 
The subject matter of our report will consist of Lewis county, and 
an abstract or summary of all the rocks and groups of the district, pre- 
paratory to our next communication, which will be the final report of 
the district. 
It must not be supposed that we have given in this and in our former 
reports, all the useful matter collected, for this reason, that the term 
useful is too relative, and our reports, at least my own, have been made 
and given merely as reports of progress. 
LEWIS COUNTY. 
This is the only one of the northern counties of the third district not 
noticed in the former reports, its examination having been left to a late 
period of the survey, wishing to avail myself of whatever progress might 
have been made in the excavation of the Black River canal, and the 
quarrying of stone and other materials for the same. 
The Black river divides Lewis county into nearly two equal geogra- 
phical parts, draining the whole of its surface, with the exception of a 
small portion of the northeast and a similar portion of the southwest. 
No less important is this river in its hydrographical than in a statistical 
point of view, for it forms the boundary between the primary or the 
sparsely settled region to the east, and the transition of those rich 
limestone, slate and shale lands to the west, which in the early settle- 
ment of the county were well and far known under the name of the 
Black River lands. 
The geology of Lewis county, though it has many distinct rocks, yet 
from their regular geographical distribution and undisturbed position is 
quite simple. Its rocks are the primary, the Potsdam sandstone, the fuco- 
idal layers, the Mohawk limestone, the Trenton limestone, the black slate, 
the Frankfort slate, and the shales of Pulaski. All these rocks, with 
the exception of the Potsdam sandstone and the fucoidal layers, pur- 
sue a uniform north and south direction through the county. The 
whole of the primary lies to the east of Black river and along the mar- 
gin of the river, excepting at its entrance from Oneida. The Potsdam 
sandstone is only met with in the northeast part of the county, near to 
Jefferson and St. Lawrence, resting upon the primary, the two being 
unconformable to each other ; the primary showing in all places visi- 
