1846.] Agricultural Geology of Onondaga County. 167 



The plaster beds in this formation have been well described by 

 Mr. Vanuxem and Mr. James Hall. Their value is no where 

 0%'errated. We deem it unnecessary to describe them in this 

 place. 



We now pass to the water limes, where we find a change in 

 the mechanical condition of the layers; they are still thin, but 

 less subject to decomposition. The process, however, goes on, as 

 is shown in the changes of color of the weathered surfaces, the 

 softened state of the exposed edges, and the accumulation of 

 earth between the beds and upon the projecting parts. The rock 

 is usually gray, sometimes dark, but when exposed it passes into 

 a drab color. The thin layers are below, the thick above, where 

 we find the masses which are used for hydraulic lime, of which 

 there are two; each of which are from two to four feet thick. 

 The firmness of some of the upper layers fits them for tolerable 

 flag stones. The position of this upper rock is usually well indi- 

 cated by a steep escarpment, where the out-cropping edges are 

 well exposed and defined. 



The composition of the water lime series, though considerable 

 difference occurs at different places, is given by Drs. Beck and 

 Jackson, as follows: 



Beck. Jackson. 



Carbonic acid, - - - 39.80 Water, ----- 1.182 



Lime, 25.24 Silicic acid, - - - 10.087 



Magnesia, - - - - 18.80 Carbonic acid, - - 41.200 



Silica and alumina, - 13.50 Sulphuric acid, - - 0.606 



