816 NEW YOKK STATE MUSEUM 



ried by Higley, Monty & Co., but, owing to its silicious natur©, it 

 has been used only for building stone. It analyzed 



Lime . . - 29 . 05 



Magnesia , 12 . 8 



Ferric oxid 1.02 



Alumina . 46 * 



Carbonic acid 38 . 6 



Insoluble residue 18 . 04 



The Trenton limestone is exposed about 14 miles east of the 

 canal, and the section is very similar to that found at Glens Falls, 

 the upper layers being somewhat impure and the lower layers 

 showing 8 feet of black limestone evidently of considerable 

 purity. 



Other quarries are at Saratoga Springs and South Glens Falls. 



Schenectady county^ 



This county is destitute of limestones except a small area of 

 Calciferous in its extreme northwestern corner, and a bit of 

 Lower Helderberg in the southwestern portion. Both are of small 

 extent. Limestone is quarried at Hoffmans. 



Schoharie county ^ 



This county exhibits a great thickness of Helderberg limestones, 

 which have been opened up at Schoharie, Howe Cave, Barnerville, 

 Cobleskill, Middleburg, Sharon Center, Sharon Springs and 

 Cherry Valley. The general section can be obtained from the ac- 

 count of the Helderberg limestone formation in another portion 

 of the report. 



At both Schoharie and Howe Cave there is a splendid develop- 

 ment of the lower Pentamerus and Tentaculite members. The 

 former beds, which are 60 to 70 feet thick, are hard, massively 

 bedded, vertically jointed limestones, of bluish gray color. . 



The Tentaculite beds, underlying the Pentamerus, are thin 

 bedded, dark blue limestones, whose layers vary from 2 to 3 

 inches. At Howe Cave and Schoharie their thickness is 40 feet. 



lYanuxem, Lardner. Geol. 3d dist. N. Y. 1842. 

 2 Mather, W. W. Geol. 1st dist. N. Y. 1843. 



