ONONDAGA-SALT GROUP. 161 



series, the thin shiily beds, which in Oiioiulagii county contain gypsum and the liopper- 

 form cavities, are certainly wanting, and they have not been recognized in this part of the 

 State. They ought not, it is true, to be found at llie falls of tiie Rondoul, if the series 

 consists only of the Clinton and Niagara groups ; tlie former comprising the shales, green, 

 red and mottled, and the ten feet of sandstone ; and the latter, the limestone at the head 

 of the falls, which is (juarried for cement. The plaster beds in this case ought to be found 

 above the falls, resting upon the cement rock or the Niagara limestone. 



The waterlimes are also exposed on the eastern outcrop of the Ilelderberg, on a rano-e 

 not far west of the Hudson river, near the villages of Kingston, Saugerties, Catskill, 

 Leeds, Coxsackie, Coeymans, New-Baltimore, and also on the cast side of Hudson river 

 at Becraft's mountain. At all these localities, the upper beds arc the ones wliich are 

 exposed, and which arc ranked rather as thin-bcddcd limestones than as sliales, the latter 

 being always disposed to disintegrate rapidly, and pass into tlic condition of soil. 



Otlier parts of the Hclderberg range also furnish important points of exposure : thus, 

 about one and a half or two miles east of New-Scotland in Albany county, the same series 

 of beds appear ; and these may be traced around on the northern outcrop, or rather ter- 

 minus of the Helderberg range, as far as Schoharie. Still onwards through Carlisle, 

 Cherry-valley, Springfield, Warren, and through Oneida and Herkimer counties, they 

 maiiUain much the same character. In Onondaga county, the lower part, and that which 

 crops out in the village of JVIanlius, is shaly, and green or drab-colored, with cavities lined 

 with crystals of lime. This part can not be distinguished from that at the falls of the Ron- 

 dout, of which I have expressed some doubts whether it is to be regarded as belonging to 

 the Waterlime series or the Clinton group. 



In Onondaga county, the scries terminates abruptly above ; a fact of considerable im- 

 portance in fixing the limits of the series, as the circmnstanccs show that an important 

 change took place in the condition of the seas in which these rocks were in the progress of 

 formation. 



At Manlius, the exposed rocks are as follow : 



1. Greenish shales with imperfect geodes, fragile, and rapidly decomposing; exposed in the road above 



the village. 



2. Thin-bedded limestone, which becomes of a drab color on exposure to the weather. 



3. Compact black thick-bedded limestone, much broken, in thin beds, from eight to ten feet thick. 



4. This is succeeded by a lighter colored limestone, eight feet : this last supports a few feet of the 



Pcntamerus limestone, which is quite concretionary. 



The mass which is burnt and used for hydraulic cement, is the upper four feet of the drab- 

 colored No. 2, and just beneath the black compact limestone. It is a mass thicker bedded 

 than the lower part of the same tier, from which it is not very easy to distinguish it. 



At Auburn, the quarries north from the town give nearly the same series. The black 

 rock, with a small univalve, occurs in great abundance at both places. 



In Monroe county, Mr. Hall gives a section at Wcst-Mendon, consisting of the Onon- 

 daga salt group, twenty-five feet, in thin courses of light drab or ashen hue, succeeded 

 [Agricultural Report.] 21 



