110 NEW YORK STATE MUSEUM 



fore with niarlj strata surrounding and inclosing them, they 

 are not associated with any " vermicular lime rock " within 

 them, nor with anything answering to the 4th or Magnesian 

 division of the Salina lying above them. In one point only do 

 they bear a superficial resemblance to the deposits elsewhere: 

 they occur in two " ranges,'' or rather beds, separated from each 

 other, however, not by shaly or vesicular lime rock, but by a 

 l>ed called slate by the quarrymen, made up of thin seams of 

 gypsum, interlaminated with other layers of shale. 



The gypseous series here has a very uniform character, con- 

 sisting as it does of three persistent and tolerably regular mem- 

 bers. First occurs the lower seam of gypsum highly laminated 

 and separating into several distinct layers, somewhat harder 

 than the upper seam, and of a usual thickness of 7 feet, vary- 

 ing but little in this respect. Second, upon this rests a stratum 

 about 3 feet thick called slate by the quarrymen, consisting of 

 alternating laminae of gypsum and shaly matter, and said to be 

 gypseous enough in the northernmost quarries (which are now 

 little worked) to be ground for plaster. Third, the upper gypsum 

 bed which closes the series, varies much in thickness, from noth- 

 ing to upwards of 20 feet, averaging possibly 15 feet. Its 

 variability in thickness is probably due mostly to denudation, 

 since it is capped by yellow drift clay in nearly every place 

 where it is laid open by workings. The upper gypsum bed shows 

 little disposition to separate into distinct layers save in the 

 northern quarries, and is softer and somewhat less dense than 

 the 7 foot bed. It was thought to be of better quality until 

 analysis showed it to be nowise superior. All the members of 

 the series show occasionally small spots and thin, scalelike 

 laminae of sulfur, more specially on dirt seams. The upper 

 bed, I am told, contains more of the sulfur than the lower, and 

 the slate seam more than either. The gypsum of both seams 

 varies from a light to a somewhat dark gray. 



The gypseous series here shows, therefore, no tendency to 

 form isolated masses, save where denudation may give it that 

 appearance, in which case it is enveloped in drift clay. Two 

 proprietors of long experience, however, inform me that the 

 entire set of beds is occasionally cut across by what are called 

 *' mud seams " from 1 to 5 feet wide, that the mud seams are 

 often of a thin laminated structure and sometimes contain a 

 little gypsum and selenite, and that the gypsum beds abut 

 against them regularly on both sides. The only example of this 

 kind of replacement that has come under my notice was in the 

 edge of one of the quarries, where, at the time of my last visit, 

 the lower gj-psum bed and the slate, the only members there 



