1S47.] 77^6 Limestones, and Lime. 1 19 



of the Hudson — the Helderbergh division resting upon the shales 

 and sandstones of Lorrain. Its position is well defined westward 

 and beyond Utica. It is the geodiferous rock of Eaton. 



Composition of the Helderbergh Limestones. 



The calcareous matter appears first in a series of shales which 

 lie at the base of the Helderbergh range. They effervesce 

 strongly with acids; but are too impure for any of the purposes 

 for which limestones are employed. Magnesia soon appears in 

 these beds, and finally forms a constituent part of the rock. 



The Manlius water-limes, as they have been called, were first 

 employed for cement. The best beds are only about six or eight 

 feet thick in Western New-York. In the valley of the Rondout 

 the Pentamerus limestone is the one which is so extensively used 

 for hydraulic lime. 



Analysis of the Hydraulic Limestone of the Rondout — by Jack- 

 son.* 



Water, I.ISI 



Silicic acid, 10.0S7 



Carbonic aciJ, .... 41.200 



Sulphuric acid, .... 0.606 



Lime, 25.0S7 



Alumina, 3.395 



Per oxide of iron, ... 3.274 



Magnesia, 12-800 



Oxide of manganese, ... 0.606 



Potash, 0.700 



Soda, 2.182 



101.158 



Limestone of Pennsylvania belonging to the same group as the 

 preceding. It is a rock eight miles east of Pine-Grove, Schuyl- 

 kill county. Color dull lead blue; texture somewhat coarse and 

 subcrystalline, sparry.f 



Analysis. 



Carbonate of lime, - - - 49.90 

 Carbonate of magnesia. - - -7.10 

 Alumina and oxide of iron, - . 6.30 



Insoluble matter, .... 36.30 

 Water, 0.40 



The limestones of this formation are not always magnesian, as 



• Jackson's analysis of the Ulster cement stone, in the Proceedings of the 

 American Geologists and Naturalists, 

 t Rodgers' Pennsylvania Report, p. 169. 



