144 ONTARIO DIVISION. 



ridges : henco it is, so far as evenness is concerned, a good agricultural district. Streams 

 which cross it, cut througli the softer portions, and form impassable ravines or gorges ; but 

 these are not so frequent as to interfere with farming operations. 



Reason lohy this rock should be studied. This rock forms an interesting chapter in the his- 

 tory of tlie progress of geology in this State. It was considered by the early cultivators of 

 tliis 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, imderlaid bj^ 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 fust 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 tlie Medina sandstone. This rock is succeeded in (he 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 

 assemlilage 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 lirown sandy and argillaceous shales, alternating with greenish brown sand- 

 stones and conglomerates, or pelibly beds, and oolitic iron ore. Tiiese different kinds of 

 materials rapidly succeed each other. The late Mr. Eaton called this formation yerri/'eroMS 

 slate, and ferriferous sandrock. 



The parts of this formation wiiich 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. Tiie sandstone, which is rather harsh, in consequence of the predominance 

 of sharp angular grains, is also greenisii, or greenish gray. Tlie layers of this part of the 

 rock arc 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 



