Constituents of various Minerals. 261 



nation with the 43.368 gr. of silica, to about 24 grains. This 

 approaches pretty nearly the ratio of 55.2 to 34.284, found by 

 Mr MITCHELL in my specimen. 



In my specimen there is a slight deficiency, and in HISINGER'S 

 a slight excess of silica. It is obvious, from a comparison of the 

 two analyses, that the other constituents are accidental. The 

 mineral is CS 3 , or a compound of 



3 atoms silica, . . 6 

 1 atom lime, . . 3.5 



9.5 



My specimen of tersilicate of lime was accompanied by a snow- 

 white, amorphous, soft matter, bearing a good deal of resem- 

 blance to the tersilicate, but entirely without the radiated struc- 

 ture. Its specific gravity was found to be 2.839. Mr MITCHELL 

 analysed it at my request, and found it composed of 



Silica, 56.67 



Lime, 39.00 



Alumina, .... 2.355 slightly tinged with iron. 



98.025 



There is a slight increase of the lime ; but it is obviously the 

 same mineral with the tersilicate of lime, making allowance for 

 the alteration produced on its texture by the action of the wea- 

 ther. 



L! 2 



