No. 50.] 
367 
Upper rocks of Lewis county. In proceeding west after leaving the 
terrace or level of the Trenton limestone, we ascend the black slate, then 
its successor the Frankfort slate, and finally the Pulaski shales. On 
these latter the waters divide, going east and west. Those of the west 
descend over rock, which though holding a higher geological level, yet 
are geographically lower, exhibiting the same phenomenon observed on 
the south side of the Mohawk valley, after attaining the height of the 
elevation, or the point from whence the waters divide, showing that the 
uplifting cause has operated upon the south and west side of the prima- 
ry nucleus, in an uniform manner. 
Having communicated all the information that we wish to give in this 
report of Lewis county, our next subject is a summary of all the rocks 
and groups of rocks which compose the third district, with such other 
matter or information which may seem necessary, since some of the 
counties of the third district have not been noticed in the reports that 
have been made. In this summary we shall commence with the low- 
est rock or mass, then the next in succession, terminating with the last 
one in the district. 
Primary rocks. Granite and gneiss constitute the base or substratum 
of the third district, having occasionally for associates combinations of one 
or more of their mineral elements, with amphibole or hornblende forming 
sienite, granito-sienite and hornblende rock ; likewise some aggregates 
of which granular carbonate of lime is the base, and other more rare in 
which we find pyroxene and table or tabular spar. It is with horn- 
blende rock, granite and gneiss, that magnetic ore is usually associated. 
All these rocks and aggregates are designated as primary ones, mean- 
ing thereby, that their origin was anterior to all known organic bodies, 
and that their mineral particles or their parts, are the result of crystal- 
lization. 
The primary rocks form the northern part of Herkimer and Fulton 
counties, the northeastern part of Oneida, and the whole of Lewis coun- 
ty east of Black river, being the south and west part of that immense 
nucleus, which from a height, according to Prof. Emmons, of nearly 
6,000 feet, descends with grearirregularity, and disappears under the 
less ancient rocks which border the St. Lawrence, the Champlain, the 
Mohawk and the Black river, appearing again west in the Ozark moun- 
tains of Arkansas and the iron mountain of Missouri. 
