MEDINA SANDSTONE. 
73 
It is again seen at Squire Parks’ mill dam, to the east of Amboy centre, with some small 
accretions of shale which look like rounded fragments ; these, by decomposition and removal, 
produce cavities in the sandstone. Yellow spots of hydrate of iron are also observable upon 
the sandstone. 
At Petrick’s mill, half a mile to the east of Colosse, the red sandstone appears in the bottom 
of the creek under the bridge. It is of the harder variety ; and like all the sandstone of this 
mass in the district, it appears to resist the destructive action of atmospheric agents much 
better than the same mass in the fourth district, being less mixed with argillaceous materials. 
Loose masses or fragments of the sandstone are very abundant around the village, being used 
for field enclosures. 
On the same creek, about four miles below, it forms the low fall at Mexicoville, being one 
of its extreme north points. About three sand layers are there exposed, with some streaks of 
grey, the layers about fourteen or more inches thick. From the small exposure here and in 
most other places, the dip of the rock was difficult to determine, appearing to be horizontal. 
The greatest exposition of the red sandstone in Oswego county is at Fulton, on both sides 
of Oswego river, forming the banks and the falls. The upper layers are covered with Fucoides 
harlanii, some in admirable preservation and of gigantic dimensions, intermixed with the smaller 
and more common variety. In some of their parts the fucoids have been replaced by small 
pebbles, showing a peculiar organization and material which could admit of such replacement, 
the form being well preserved. 
The upper layer of the falls is a hard, light-colored, variegated red sandstone ; the next below 
it, is a mixture of sandstone and slate, more or less friable, and of a dark red color ; the third, 
a red and grey sandstone, and of intermediate shades, which is quarried for buildings, hearth 
stones, etc. ; and a fourth, same as the third, with the color more general. Each of these 
layers is about two feet thick. 
The sandstone is seen for half a mile below the falls, by the side of the canal path. A 
considerable part shows the water lines of deposition, being formed of wedge-shaped masses 
of unequal dimensions as to length, and either curved or straight. These are again subdivided, 
the parts being disposed at various angles to each other, and generally arranged between pa¬ 
rallel lines, conformably with the other layers with which they are associated, the whole being 
nearly horizontal. Along the bank this structure extends to two or three layers, but at the 
falls it is confined to the one below the upper rock. 
These oblique lines of structure are seen to greater advantage in the red sandstone of the 
Clinton group in Herkimer county, and are highly characteristic of the grey sandstone of the 
Catskill group as it appears in Otsego, Chenango and Broome counties. It is the common 
structure of the roofing slate of the Hudson group, and is also seen in a hill of sand through 
which the Camden and Amboy railroad in New Jersey passes. 
Three causes present themselves in explanation of this structure ; 1, oblique depositions by 
water or wind; 2, infiltration of water, carrying and depositing the finer particles in an oblique 
Geol. 3d Dist. 
10 
