DR T. THOMSON'S Analysis of some Minerals. 457 



he analyzed, will appear from the following table, exhibiting the 

 constituents of a very fine specimen of chabasite from Kilma- 

 colm, which I subjected to a very careful analysis : 



Silica, V : '; j 'V 1 ;. ''. : - . 48.756 



Alumina, i 1 ;' 1 '^ . . . 17.440 



Lime, . . ': '.".' ; . 10.468 



Potash, V . /. . 1.548 



Water, ' V . ... 21.720 



99.932 



The potash was carefully examined for soda, but none was 

 found in it. It will appear from this analysis, that the Kilma- 

 colm chabasite, so far from containing no lime, contains in fact 

 a greater proportion of that substance than any other specimen 

 hitherto analyzed. Is it not possible that the Scottish specimen 

 analyzed by BERZELIUS may turn out to be a new species ? 



The formula for chabasite seems to be, 



3 A/ S 2 + C S 2 + 6 Kq. 

 Or it is composed of 



1 atom bisilicate of lime, with some potash, 

 3 atoms bisilicate of alumina, 

 6 atoms water. 



The excess of lime in the Kilmacolm chabasite, prevents this 

 formula from applying quite accurately to its constituents *. 



* Since this paper was read to the Society, I have analyzed a flesh-coloured cha- 

 basite from the north of Ireland, and found it composed of 



