80 ECONOMICAL MINERALOGY, 



I. II. 



Carbonic acid, ... 39.33 38.65 



Lime, 25.00 27.35 



Magnesia, 17.83 16.70 



Silica, 11.76 8.95 



Alumina, 2.73 4-90 



Peroxide of iron, . 1.50 . 1.75 



Moisture, 1.50 Moisture, bituminous matter and loss, 1.70 



The composition of the calcined lime, in the state in which it is ordinarily used as a cement, 

 is as follows : 



Carbonic acid and moisture, 10. 90 



Lime, 39.50 



Magnesia, 22. 27 



Silica, 16.56 



Peroxide of iron and alumina, 10.77 



The proportion of carbonic acid, however, depends entirely upon the manner in which the 

 calcination is conducted, and it probably differs considerably in different specimens. 



The blue fetid limestone which is associated with the water limestone is a nearly pure 

 carbonate of lime, containing . 70 per cent, of insoluble matter, and a trace of oxide of iron 

 and bitumen, to which last is probably to be ascribed the odour which it gives out when struck 

 with a hammer. It contains no magnesia. 



I have also examined a specimen of the calciferous slate of Eaton, from the hill on the east 

 side of the village of Chittenango. The results are as follows : 



Carbonic acid, 40.95 



Lime 29.00 



Magnesia, 17.30 



Silica and alumina, 11. 00 



Peroxide of iron, 1.10 



Moisture and loss 0.65 



This composition, which I have reason to believe is quite constant, Avill satisfactorily ac- 

 count for the occurrence of sulphate of magnesia or Epsom salt, which is so often found in 

 efflorescences on this rock. It contains a sufficient amount of sulphuret of iron to furnish the 

 acid for this decomposition. 



Onondaga County. An important locality of water limestone occurs about a mile and a 

 half west of Manlius. The overlying rock is a blue limestone, similar to that found at Chit- 

 tenango. Some of the strata of water limestone are clouded or striped, while others are of a 

 uniform grey or drab colour. Through the upper layers there passes a thin seam of white 

 calcareous spar, in which are to be found small crystals of fluor of a dark purple colour. 



