242 
I Assembly 
mass in one county, may in its prolongation, so thin out as to attract 
little notice in another county, producing this result, that should the 
examination be commenced in the latter and not the former one, it may 
be passed over with but slight attention, requiring, therefore, a re-exa- 
mination, before the whole series of the county can be completed. Of 
the truth of this remark, Western New-York furnishes some remarka- 
ble examples. 
The limestone of Niagara, Lockport and Rochester, estimated by 
Mr. Hall, at 150 feet thick, thins out in its progress east, so as to be 
but two or three feet in thickness near the Sauquoit in Oneida county. 
The mass which lies below the limestone, the " calciferous slate," is 
about 80 feet thick in the western part of the Fourth District, and 
seems to disappear before reaching Madison county, and reciprocally 
the " millstone grit,'' which is thirty and more feet in thickness in Her- 
kimer and Oneida, gradually attenuates in going westward, being from 
four to five feet at Rochester. The materials of which this rock is formed, 
gravel and sand, prove that their source was eastwardly. In Herkimer 
and in the eastern part of Oneida, the pebbles are larger and the mass 
thicker, the sand increasing going west, whilst the pebbles diminish in 
the same direction. Thus, in Cayuga the pebbles are rare, and I know 
not that they have been noticed in the " gray band" at Rochester, the 
continuation or equivalent of the " millstone grit." 
The counties principally examined were Madison, Onondaga and 
Cayuga. The whole boundary between the Third and Fourth Districts 
was likewise examined conjointly with Mr. Hall. Besides, many por- 
tions of the southern counties were visited preparatory to a more tho- 
rough exploration the coming season. In this report, we shall not treat 
each county separately, but connect the whole, in order to avoid repe- 
tition. 
Proceeding up the Mohawk valley, a rapid rise takes place to near 
Utica, from which point commences the long level of the Erie canal; no 
great change comparatively of level takes place thence proceeding w^est, 
and in a NNW direction, throughout the Third District. 
Though the general upper level is attained near Utica, yet we are not 
upon the top of the plane, until w^e are a little to the w^est of Rome; 
there the waters pass in opposite directions, some to reach the ocean by 
Lake Ontario, others by the Mohawk and Hudson. 
Where the bottom of the valley ceases to rise, its sides begin to re- 
cede from each other, and to the south and left in proceeding west 
