20 NEW YORK STATE MUSEUM 



eastward as far as Schoharie county. In field exploration it serves 

 as a very useful indicator, since the gypsum horizon lies just below, 

 in the shales. 



The limestone carries an eurypterid fauna which is also charac- 

 teristic of the Pittsford shale at the base of the Salina. The inter- 

 vening beds, however, are almost devoid of fossil remains, due 

 undoubtedly to the unfavorable conditions for life that prevailed in 

 the highly saline waters in which they were laid down. A common 

 physical feature of the limestone is conditioned by the presence of 

 numerous small cavities, which may so abound as to lend the ap- 

 pearance of a porous lava or slag. The cavities or cells are roumded 

 or irregular in shape, sometimes elongated like worm tubes, and 

 are frequently lined with a calcareous deposit. The structure was 

 coinsidered by some of the early writers to be of organic nature and 

 the limestone was commonly designated the A^erm.icular limerock. 

 This view of the origin of the cells was controverted by Vanuxem 

 who pointed out the fact that they are often accompanied by hopper- 

 shaped casts and impressions that have the clear outHnes of rock 

 salt crystals. There is little doubt but that they are due to the 

 former presence of rock salt deposited with the limestone and after- 

 ward dissolved away. 



The limestone possesses hydraulic properties and has been burned 

 for hydraulic cement.. The natural cement industry which was car- 

 ried on for many years at Buffalo' and Akron made use of this 

 limestone which was employed to some extent also by the plants 

 in Onondaga county. Its thickness varies from 60 feet in Canada 

 and 50 feet in Erie county to 10 feet or less in eastern New York. 



Camillus shale. Underneath the waterlime occurs a bed of soft 

 shale, containing intercalated layers of magnesian limestone. The 

 workable gypsum beds are found in this shale, at varying horizons, 

 but mainly near the top. The color of the shale is commonly drab 

 or gray with variations to olive-green and sometimes red. There 

 are no fossils, except one or two species found in the intercalated 

 limestones. 



The thickness of the shale, together with the gypsum beds, aver- 

 ages perhaps 300 feet in the central part. " Its outcrop is usually 

 found just north of the line of ridges (known as the Helderberg 

 escarpment in the eastern part of the State) formed by the great 

 beds of overlying limestone and spreads out as a flat more or less 

 swampy surface, physically continuous with the area of the Vernon 

 shales. In the central section the outcrop is .2 or 3 miles wide. 



The gypsum deposits are seamed more or less with shale which 



