144 
ONTARIO DIVISION. 
ridges : hence it is, so far as evenness is concerned, a good agricultural district. Streams 
which cross it, cut through the softer portions, and form impassable ravines or gorges ; but 
these are not so frequent as to interfere with farming operations. 
Reason why this rock should he studied. This rock forms an interesting chapter in the his¬ 
tory of the progress of geology in this State. It was considered by the early cultivators of 
this science as identical with the New Red Sandstone of Europe, which overlies the Coal 
measures, that embrace the rock salt of the district of Cheshire in England. Hence these 
opinions led to speculations and explorations both for salt and coal, underlaid by this rock. 
This erroneous view arose from placing too much reliance upon lithological characters ; 
for, in this particular, it closely resembles some portions of the New Red sandstone. Mr. 
Conrad and Mr. Vanuxem, however, were able, by the character of the fossils, to set this 
matter right in the first year of the survey. 
Springs originating in the Medina sandstone. Brine springs issue from the lower part of 
this sandstone, but the water is too impure for the manufacture of salt. The fact is im¬ 
portant in a geological point of view, as furnishing a high probability that it is from the 
chemical changes which the materials undergo, that salt is formed, the elements of which 
exist in the body of the rock. As in most instances of mineral springs in Western New- 
York, the chloride of sodium is adulterated with the chlorides of calcium and magnesium. 
Geological relations of the Medina sandstone. This rock is succeeded in the ascending 
order by the green shales of the Clinton group. Below, it reposes upon the gray sand¬ 
stone of Oswego county, which is equivalent to, and identical with, the gray thick-bedded 
sandstone of the Hudson-river series. It is wanting in the southeastern part of the State. 
In the vallies of the Hudson and Rondout, the Hudson-river series supports the shales of 
the Waterlime series (See PI. XXI. Sec. 1; and PI. XX. Sec. 3). 
§ 2. Clinton group. 
The most interesting feature in this group, consists in the rapid changes in the strata 
which enter into its formation, and which, taken together, constitute a most heterogeneous 
assemblage of materials : for this reason, the group was called, in an early stage of the 
survey, the Protean group. The formation consists of layers and beds, composed of green, 
blue, and brown sandy and argillaceous shales, alternating with greenish brown sand¬ 
stones and conglomerates, or pebbly beds, and oolitic iron ore. These different kinds of 
materials rapidly succeed each other. The late Mr. Eaton called this formation ferriferous 
slate , and ferriferous sandrock. 
The parts of this formation which are the most persistent, are the green shales ; whose 
color, however, inclines more to blue than green, where they have not been exposed to 
weathering. The sandstone, which is rather harsh, in consequence of the predominance 
of sharp angular grains, is also greenish, or greenish gray. The layers of this part of the 
rock are never thick-bedded, or massive ; and their lower surfaces are often covered with 
cylindrical bodies, varying in size from a barleycorn to that of the finger. These bodies 
