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HELDERBERG DIVISION. 
3. A gray impure limestone, in which there are numerous small irregular-shaped cavities or cells, 
resembling those of lava or amygdaloid. These beds are associated with the above. 
4. Thin-bedded shaly limestone, passing upwards into a fine-grained one whose thickness has increased: 
this limestone emits a ringing sound when struck. These beds constitute the Manlius waterlime 
series of the Reports. 
It is proper to observe here in regard to this last division, which is a deviation from the 
reports, that there seems to be a gradual passage upwards, from the thin-bedded fragile 
shales and shaly limestones, to the thicker and firmer beds of the last division. There is 
no well marked line of divison between the lower and upper masses of the group, as defined 
above. The Pentamerus limestone, which succeeds the waterlimes, is clearly a different 
rock. Below, the Niagara limestone is a very distinct deposit in all respects ; but when we 
once pass into the Onondaga-salt group, no characteristic lines can be discovered, which 
seem to be suitable to the purpose of serving as lines of demarkation. Then again it is our 
wish to diminish the number of groups, as far as possible, without doing violence to ar¬ 
rangements founded in nature. 
I shall now proceed to speak in detail of the division which I have just proposed. 
1. Red shale. 
The ground color of this mass is a blood-red, upon which patches of green are common ; 
and sometimes or in some parts of it there are strata which are entirely green, a red shale 
alternating to a limited extent with green. The true character of these beds is so much 
concealed by their own debris, that it is often unnoticed. The rock is extremely fragile, 
and is constantly breaking down by the action of the weather : hence the surfaces exposed 
look more like a marl bed than a solid rock. The fracture is earthy, and the divisions 
which usually mark the strata are obscure, if not entirely absent. 
Localities where this rock is exposed. As has been stated in regard to the commencement 
of the Clinton group, this rock too does not appear east of Herkimer county. At Steel’s 
creek, at Cruger’s mill, and between Mohawk village and Dennison’s on the Sauquoit 
creek, on the north and west side of Paris hill, the red shale crops out, and appears under 
the characters which have been given above. Farther west, but still in Oneida county, 
the rock appears near Hamilton College ; from which place, it spreads out and extends 
into Madison county, in the eastern part of which it is cut through by the Erie canal. In 
its western prolongation into Onondaga and Cayuga counties, it forms a band to the north, 
but it runs nearly parallel with the Canal. Still farther west and in the vicinity of 
Genesee river at Rochester, the rock exists but obscurely. It was excavated in a well in 
Brighton, four miles south of Rochester. Mr. Hall expresses some doubts of its con¬ 
tinuance farther west than this river, unless indeed the character of the rock is changed. 
Thickness of the red shale. Mr. Vanuxem estimates its thickness in some places at five 
hundred feet, or as varying from one to five hundred feet. On the West branch of Steel’s 
creek, it forms a mass, in a precipice or perpendicular cliff, eighty feet thick. 
