Luther — Economic Geology of Onondaga County. 2(57 



E. B. Alvord & Co., Jamesville, buy and grind 2,000 tons. A. E. Alvord, 

 Syracuse, buys and grinds 3,500 tons. 



There are a number of small quarries in Manlius and Dewitt, besides 

 these mentioned, but their product is sold to the mill owners and dealers, and 

 the output is included in the amount stated. 



Mr. A. E. Alvord opened a quarry near Brighton, two and one-half miles 

 south of Syracuse, but is not operating it at present. None of the quarries in 

 Camillus are now worked. L. D. Sherman, at Marcellus falls, grinds about 

 300 tons annually ; quarries near the Marcellus station. 



So far as known, the bed of gypsum quarried by F. M. Severance on the 

 Heard farm is the thickest in the county, measuring sixty-five feet including 

 some thin intercalated beds of shale. A few feet of dolomitic limestones at 

 the top of the Salina group have very obscure lines of deposition, but split 

 easily into thin slabs with a somewhat conchoidal fracture. These are pro- 

 fusely scattered over the surface of the ground in the regions of the outcrop 

 of this horizon, and are utilized as material for farm fences, etc. The needle 

 cavities are very common in them, but fossils, except Leper ditia alia, are 

 wanting, or at least very rare. 



Lower Helderberg Group. 



The hydraulic limestone beds of Onondaga county, provisionally referred 

 to the Lower Helderberg group, are composed almost entirely of even 

 courses of very dark blue, fine-grained limestones, from one to five feet thick. 

 Exposure changes the color to a medium light, dull, bluish grey, and makes 

 the lines of bedding very distinct. With two or three exceptions, all of 

 the beds are composed mainly of calcic carbonate and contain but a small 

 amount of magnesian, or clayey matter, as compared with the "Magnesian 

 deposit" below. They are known as the blue lime beds, and from them 

 almost the entire outpuc of quicklime of the region is taken. A few courses 

 contain too much impurity for use in the manufacture of quicklime, and are 

 utilized as building stone. The rock splits easily along the lines of depo- 

 sition, and breaks across them with a straight, even fracture. In some 

 localities, masses of Stromatopora occur, and the rock loses its regular struc- 

 ture. The two beds of hydraulic limestone which give the name to this 

 group, lie near the top of it, separated from each other by one to four feet of 

 impure, blue limestone. The upper layer is a little more than four feet 

 thick at the eastern boundary of the county, becoming thinner till it pinches 

 out entirely in the Split Rock quarries, but reappearing near Marcellus falls 



