116 The Limestones, and Lime. [March, 



solidation of the lower limestones is not objectionable in a general 

 system. 



Composition of the Calciferous Sandstone of JVew-York. 

 Jinalysis. 



Insoluble matter (silica), - - - 6.20 



Alumina and per oxide of iron, - - 4.50 



Carbonate of lime, - - - 58.86 



Carbonate of magnesia, - - 27.20 



Water, 8.04 



99.50 

 This rock invariably furnishes a large amount of magnesia; 

 and when the silicious matter is not in excess, it may be used as 

 a hydraulic lime. The specimen, the analysis of which is given, 

 was from Galway, Saratoga county. Its color is gray. Those 

 layers which form the best cement, weather to a light or yellow- 

 ish drab. 



The best localities known of this variety of limestone, are in 

 the neighborhood of Plattsburgh. A belt of the rock extends 

 into Canada; and in many places the purer beds are highly 

 charged with interesting fossils. In the valleys of the Mohawk 

 and Black river, localities of a pure limestone abound. The 

 rock skirts the St. Lawrence river from Ogdensburgh to Canada; 

 and in places it is the lowest rock of the New-Yoik system, and 

 rests immediately upon the primary, or upon theTaconic slates. 

 Interesting relations sometimes appear, especially when this rock 

 is found in the vicinity of the primary limestone. In these places 

 we find sufficient cause for rejecting the opinion of some geolo- 

 gists, that the primary is only an altered limestone of the New- 

 York system. Both rocks, however, sometimes exist in a short 

 distance of each other; one associated with granite, the other re- 

 posing upon the Potsdam sandstone. 



Composition of the Chazy Limestone of JYew-York. 



.flnalysis. 



Insolul)le matter, .... 27.62 



Alumina and per oxide of iron, - - 18.03 



Carbonate of lime, - - - 49.00 



Carbonate of magnesia, ... 3.00 



Water, 1.74 



99.89 

 This limestone is usually too impure to be used for agricultural 

 purposes. The specimen, however, exhibits an extreme of im- 

 purity — some layers furnishing quite a pure limestone. Indeed, 



