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



stants determined by special experiments of the nature of those 

 just detailed, and that their photometric use should then be 

 limited to the reduction of the light of bodies possessing a 

 small angular magnitude. 



Allegheny Observatory, July 13, 1885 



Art. XXYI1I. — Geological Relatioiis of the Gypsum Deposits in 

 Cayuga County, Y. Y. ; by S. Gr. Williams. 



It is well known to geologists that the strata containing the 

 gypsum deposits of New York, ranging from Madison County 

 westward, at the time of the State Geological Survey were all 

 assigned to the third of the four groups into which the Salina 

 Period was divided ; and that these gypsum deposits were de- 

 scribed as isolated masses of possibly concretionary character 

 contained in the enclosing beds. The gypsum beds a short 

 distance north of Union Springs, Caj^uga County, are much the 

 most extensive of these deposits, and as they afford a fertilizer 

 of approved quality, they have been largely laid open by work- 

 ings prosecuted during more than fifty years. A rock cutting 

 made by the Cayuga Lake Railroad, along the bank of the lake 

 within eighty rods of the largest quarries, has also laid open 

 the strata which underlie the gypsum beds. A recent examina- 

 tion of the gypsum beds and their enclosing strata, made with 

 these more recently afforded aids to investigation, and accom- 

 panied by fortunate discoveries of somewhat abundant though 

 often badly preserved fossils, has not only shown that the 

 gypsum in this locality exists in continuous beds of a considera- 

 ble degree of regularity, but has also afforded reasons for be- 

 lieving that this portion of the gypseous series belongs rather 

 with the Lower Helderberg than with the Salina. 



A section at this point eastward, and thus nearly in the line 

 of strike, from the level of Cayuga Lake to the top of the 

 Oriskany sandstone, is about 114 feet thick, and consists of the 

 following members, numbered upward from the lake level : 



No. 8. Oriskany sandstone in a single fossiliferous seam, 3 feet 8". 

 " V. Drab limestone, upper beds with thin undulating 



lamiiise: exposed, 10 feet. 



" 6. Limestone revealed only in occasional outcrops, 



leveled with Locke-level, about 46 " 



" 5. Thick-bedded blue limestone, containing Meristella 



Icevis, Orthis oblata, small form, Rhynchonella 



semiplicata, Strophodouta varistriata, etc., 10 " 



" 4. Drab limestone, holding a branching fucoid and 



Nucleospira ventricosa, 4 " 



