118 The Limestones, and Lime. [March, 



101.00 

 It is supposed by Messrs. Rodgers, that the property of har- 

 dening under water depends on the presence of magnesia. It has 

 not been shown, however, that the dolomites, or white granular 

 marbles, possess this property. The same view, however, of the 

 subject was previously maintained by M. Vicat of France. We 

 have already stated that magnesian limestones are favorable rocks 

 for agricultural purposes; and that it is only when caustic by 

 burning, that they become injurious, and then only before they 

 have lost their caustic state. These limestones, however, are un- 

 suitable for fiuxes in reducing iron ores, as will be found by 

 trial. 



The lower limestones of the New-York system, the composi- 

 tion of which we have just given, terminate with the Trenton, 

 after which a wide interval occurs before we reach another cal- 

 careous rock. The first in the ascending order is the Niagara 

 limestone, if we except a few calcareous bands immediately be- 

 low, one of which contains the Pentamerus oblongus, and which 

 is characteristic of the Caradoc sandstone of Murchison's Silurian 

 System. It is a dark colored limestone, often emitting a bitumi- 

 nous odor, when struck or heated. It is comparatively a thin 

 rock in New-York, but increases in thickness in its Western pro- 

 longation, and becomes in the Western states an important rock. 

 It is the upper member of the Ontario division. 



Analysis. 



Insoluble matter, - - - - O.OS 



Alumina and oxide of iron, - - 4.24 



Carbonate of lime. - - - 93.50 



Carbonate of magnesia, ... 0.20 



Water, 2.09 



101.11 

 The specimen examined was from Lockport, and its purity is 



above the average of the rock. 



This rock is continuous from a few miles southwest of Utica to 



Niagara Falls. It is absent in the New- York series in the valley 



