S. G. Williams — Gypsum Deposits in New York. 215 



liar porous or vesicular lime rock, or by shaly limestones, hold- 

 ing indications in hopper-shaped accretions of the action of 

 saline waters. It was natural, therefore, in the absence of any 

 evidence to the contrary, that the occurrence of gypsum in any 

 additional locality not obviously removed from its usual horizon, 

 should lead to the reference of both gypsum and the accompany- 

 ing strata to that usual horizon. A brief description of the 

 gypseous series here however will show, I think, that its struct- 

 ure bears no very close resemblance to that of the gypsum of 

 the Salina Period ; that its character is intimately related with 

 that of the accompanying limestones ; and that both character 

 and structure tend to indicate for it a different geological 

 horizon, if not a different origin, from that of most of the other 

 gypsum deposits. 



It may be said at the outset that the gypsum deposits of this 

 region are not irregular masses : they have no relations there- 

 fore with marly strata surrounding and enclosing 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 else- 

 where : they occur in two " ranges," or rather beds, separated 

 from each other, however, not by shaly or vesicular lime rock, 

 but by a bed called slate by the quarrymen, made up of thin 

 seams of gypsum, interlaminated with other layers of shale. 



The gypseous series here, as revealed by workings mostly 

 confined to the vicinity of the lake, but extended northeast- 

 ward nearly three miles by occasional pits, from Yawger's 

 Quarry on the south, the bottom of which is 25 feet below the 

 lake level, to the northernmost ones of Mr. Fitch and others 

 which are more than 100 feet above the lake, has a very uni- 

 form character, consisting as it does of three persistent and 

 tolerably regular members. First occurs the lower seam of 

 gypsum, highly laminated and separating into several distinct 

 layers, somewhat harder than the upper seam, and of an usual 

 thickness of seven feet, varying but little in this respect. The 

 existence of this seam appears, from the statement of the 

 owner of most of the quarries, not to have been suspected 

 forty years ago. Second: upon this rests a stratum usually 

 about three 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 up- 

 per gypsum bed which closes the series, varies much in thick- 

 ness, from nothing 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 



