ONONDAGA SALT GROUP. 
127 
The porous rock indicating a position between the two ranges of plaster beds, occurs on 
Grand island; and at a low stage of the river, fine specimens may be obtained. The group 
extends beyond the Niagara, and appears on the Grand river in Canada. 
In several places in Wayne and Monroe counties, imperfect hopper-form crystals and cavi¬ 
ties appear in this portion of the group, but I have rarely observed them in Genesee or Erie 
counties. The most perfect which I Have seen, are at Garbutt’s mill on Allen’s creek. These 
are, however, far from being as perfect as those of the Third District, figured in the report of 
Mr. Yanuxem, from which the following illustration is taken. 
50 . 
Hopper-shaped, crystals from the marl of Ike Onondaga sail group, town of Lenox, Madison county * 
The frequent occurrence of these forms in that portion of the group where the brine springs 
exist, and their disappearance in a westerly direction, is in accordance with the views enter¬ 
tained regarding their production. If the salines are dependant for their supply from the 
solution of salt once filling these cavities, it appears futile to expect important brine springs in 
situations where these do not occur in the strata. This might therefore furnish a guide to the 
proximity of salt water; but since the formation is often deeply covered with drift, the springs 
are usually more obvious than the hopper cavities. 
The small round or flattened pores before alluded to, usually occur in a layer above the 
lower range of plaster beds, but I have occasionally seen some of them in a higher situation. 
Report of Third Geological District, p. 102. 
