38 Geological Reports on the State of New York, 



adds, that substances are in various places used as cement which 

 are inferior to common mortar ; and moreover, that one milHon 

 of dollars have been lost in the construction of the Erie canal 

 from the choice of bad materials. 



The geodiferous limestone of Prof Eaton " is well characterized at 

 Lockport and at Niagara falls : farther east it loses the geodiferous char- 

 acter, and diminishes in thickness. The rock is regularly stratified, 

 compact, of a gray, bluish gray or brownish gray color. It is sufficiently 

 distinguished from all other limestones by its finely granular texture, pre- 

 senting on fracture numerous shining points : the lustre is vitreous, or 

 resinous. The resinous lustre is produced by bitumen, which colors the 

 small crystalline lamiuce. The most striking feature of this rock, in the 

 localities referred to, is the numerous cavities, or geodes, many of them 

 filled with anhydrous gypsum, or lined with crystallized limestone or fluor 

 spar. The beautiful specimens of dog-tooth and rhomb spar, with sul- 

 phate of strontian and selenite from Lockport and Niagara falls, are from 

 cavities in this rock. Blende also occurs in the cavities with the minerals 

 mentioned. Many of these cavities present some partially decayed or- 

 ganic body. In some places the structure of the rock is very irregular, 

 presenting curved, contorted and concentric laminae, as if the mass had 

 been disturbed when partially indurated. The whole of this rock is bitu- 

 minous, particularly the upper portions; the odor is perceived on per- 

 cussion. 



"At the Niagara falls there are about eighty feet of this rock disclo- 

 sed; the lower portions are gray, becoming darker, and containing more 

 and larger geodes as we ascend. At the top of the falls it is of a brownish 

 gray color and resinous lustre, containing blende disseminated and in 

 geodes. Above this, there is a thickness of about one hundred feet, 

 which is less geodiferous, and inclining to a bluish color." 



Gypsum in the gypseous marls and slates. — " The gypsum in the lower 

 part of the formation, is limited to thin seams or nodules, but after the 

 commencement of the slaty limestones, it is found in large masses, or beds, 

 of a few feet thickness, and limited extent. These masses are of a flat- 

 tened spherical form, and are from a few pounds to fifty tons weight, com- 

 monly from five to twenty tons. The existence of these beds of gypsum 

 is indicated by appearances of the surface, which above the mass is raised 

 into a knoll or hillock. Sometimes the surface, to a considerable extent, 

 is covered with these hillocks, which resemble small mounds of earth. 

 When the soil is removed from one of these elevations, a corresponding 

 convex surface is presented by the limestone beneath, which is cracked 

 and broken in every direction, as if by some elevating force. On remo- 

 ving the stone, further evidence of such force is perceived. The layers 



