56 [Assembly 



upper portion is generally a gray slaty rock, with layers of 

 impure limestone, well seen along the Auburn and Syracuse rail- 

 road. The important Salt Springs of Salina being situated in 

 these rocks, they have received the name of the 



ONONDAGA-SALT GROUP. 



The salt has not hitherto been found in solid masses, though the 

 gray part of the rock in some places shows impressions of the 

 peculiar " hopper-formed " crystals of this mineral, proving that 

 it once existed there in small quantities. It is probable that it 

 is diffused in small proportion through large extents of these 

 strata, through which (as they are very permeable to water) the 

 rains percolate, and bear the salt in solution to the deep basin at 

 Salina. This is found by boring to be several hundred feet in 

 depth, filled with gravel and sand, in which the salt water seems 

 to lie as in a reservoir, and from which it is raised by the pumps 

 for the supply of the evaporating works. The Onondaga lake, 

 which is a comparatively shallow body of fresh water, lies over 

 this deep mass of gravel, but has a water-tight bottom of marl 

 which keeps its waters separate from those below. Such is the 

 generally accepted explanation of the Onondaga salines ; yet the 

 question as to their sources is somewhat obscure. 



The upper drab or gray slates of this, group contain great 

 quantities of gypsum, which is quarried extensively from Madison 

 county westward. The rock over the masses of gypsum often 

 seems arched, as if this mineral, in forming, had exerted an 

 upward pressure, lifting the overlying masses. 



The whole group is remarkably destitute of organic remains; 

 not a single fossil having been found in the lower part or red 

 shale, and but a small number in a few localities of the upper 

 portion. The most remarkable of these is the Eurypterus, a 

 very curious crustacean, with a semicircular head, a long jointed 

 body and spinous tail ; having several antenna or " feelers " about 

 the mouth, and one of its pairs of feet flattened into broad blades 

 like oars or paddles, doubtless used in swimming. It is a rare 

 fossil, found as yet only at Williamsville in Erie county, and 

 near Waterville in Oneida county and Litchfield in Herkimer 

 county ; but there is no doubt that more general search will yet 

 discover specimens in many other places. It is found in the 

 upper part of the Salt group, in the thin layers not far below the 

 base of the succeeding Waterlime group. 



