EXPLANATION OF THE MAP. 
301 
and in one or two patches to the north of St. Johnsville. Near Ephratah, it shows a patch 
at some distance on the south side of the village, and one of more extent to the northeast. 
Along the Mohawk, on the south side of the river, it caps the lower uplifted rocks, and extends 
to the east end of the Noses, visible in all places except where covered with soil or fallen 
materials. On the north side of the river, it appears in several places, coming out from under 
the Utica slate, between Mother creek and the calciferous of the Noses. It shows a patch at 
the quarries of Humphries, Sage and Reed, and at Stanton’s on the south side of the Mo¬ 
hawk. On the north side, it appears in small surface expositions near Fonda, Tripes hill, 
Amsterdam, Marcellus’ quarry, and the two insulated hills between the quarry and river. 
Finally, in the northern part of Montgomery, two patches occur in the town of Broadalbin, 
and one in Mayfield. 
The Utica slate, which succeeds to the preceding limestone masses, is colored of a dark 
shade of purple. It sheathes the lower rocks on all their southwestern border, but from up¬ 
lifts and denudations, it also appears to the north of lower masses. From the west end of 
East-Canada creek, it may be traced continuously to Jefferson county. East of that creek, 
from greater derangement and denudation, it is only a continuous mass on the south side of 
the river. 
The Hudson-river group. This group is colored of a lighter purple. It forms a range on 
the south side of the Mohawk river, and to the south side of the Utica slate, and continues 
thence to the west of Utica, where it appears also on the north side, increasing in breadth 
from Rome, where it begins to curve north; passes through Lewis county into Jefferson 
county, or the second district; and reappears again in the third district in Oswego county, 
making another curve. Its greatest breadth is in the northern part of Oneida and Lewis 
counties ; but its greatest thickness is at the east end, on the Mohawk. It appears in three 
large patches, one conjointly in Herkimer and Oneida, and two others in the latter county. 
Grey sandstone, colored of a shade of grey. This rock is only found in the counties of 
Oneida, Lewis and Oswego. It begins to show itself to the south of Rome, and covers a 
large area in the two latter counties. 
Medina sandstone, colored indian red. It must commence near Rome also, but is first 
distinctly seen in a branch of Fish creek. It forms the rock surface of a large area in Oswego 
county ; and but little is exposed in any one place, from the immense accumulation of drift 
or alluvion which covers the greater part of all that county. 
Clinton group, etc. The part which is colored of a yellow or pea green, is the Clinton 
group, including the Oneida conglomerate. These commence near the east extremity of the 
district, near the foot of the Helderberg cliff or range, and extend through the district. The 
Clinton group occurs on both sides of the lake, near the outlet of Oneida lake. The scale 
of the breadth of the lake being rather too great, gives a greater width to the group upon the 
map than it is quite entitled to. 
The Niagara group is colored with prussian blue, and consists of the limestone of Niagara 
falls, Lockport, &c. and the shale beneath that rock. It gradually diminishes from the west, 
and disappears towards the east end of Herkimer county . 
