ONONDAGA SALT GROUP. 



96 



alluvial hills through the towns of Warren, Columbia and Litchfield in Herkimer county, 

 show the action of water upon the limestone terrace which covers the Onondaga salt group, 

 anterior to the excavation of the Mohawk valley, and also the greatness of that action at that 

 comparatively remote period. 



16. 



n- 



(O ^ /:} z^ <^ 



The above wood cut represents the order of Ibe different deposits of the group : — 

 No. 1. Red shale, with green spots. 



2. Alternate beds of red and green shale, etc. 



3. shows two ranges of plaster masses called beds, the lower in part arched ; also the hopper-shaped cavities, and the cavi- 



ties composed of six hoppors arranged with their apex inwards so as to form the cube. Above the cavities is the 

 bed of vermicular, or porous rock. 



4. Upper mass, with cavities formed by sulphate of magnesia. 



In the Report of 1839, the Onondaga salt group was divided into four deposits, as in the 

 annexed wood-cut, which divisions are still retained ; no improvement suggesting itself since 

 that report was presented. There are no well defined lines of division between the deposits ; 

 but for practical purposes, the divisions are sufficiently obvious. 



The first or lowest deposit is the red shale, showing green spots at the upper part of the 

 mass : it is No. 1 of the wood-cut. 2d, The lower gypseous shales, the lower part alternating 

 with the red shale, which ceases with this mass : they form No. 2 of the wood-cut. 3d, The 

 gypseous deposit, which embraces the great masses quarried for plaster, consisting of two 

 ranges, between which are the hopper-shaped cavities, the vermicular limerock of Eaton, and 

 other porous rocks : these products, represented in their order, form No. 3 of the wood-cut. 

 4th and lastly. Those rocks which show groups of needle-form cavities placed side by side, 

 caused by the crystallization of sulphate of magnesia, and which may from that circumstance 

 be called the magnesian deposit, being No. 4 of the wood-cut. 



The whole of these deposits are found between Oneida creek and Cayuga lake. To the 

 east of the creek, they do not all occur, as will subsequently be made known. They thin out 



