SILICON. 175 



If we take the mean of the first three analyses 

 which contain an excess of lime, we get 48*694 

 for the quantity of lime united with 53^ silica. 

 And taking the mean of this quantity, and of 

 45-086, the lime united to the silica, according 

 to BonsdorfFs analysis, we get 46 '89 for the 

 lirne. This gives us table spar composed of 



Silica 53-333* or 3'936 

 Lime 46-890 - 3-5 



By this constitution (which is as near the truth 

 as the accuracy of the analysis will admit) two 

 atoms of silica weigh 3*936, and consequently, 

 the weight of one atom is 1*968. 



2. SILICATE OF ALUMINA, OR BUCHOLZITE. 



Some years ago, a mineral was found in the 

 Tyrol, to which Weiss gave the name ofjibrous 

 quartz, but Brandes, who analyzed it, distin- 

 guished it by the appellation of buchohite. It 

 has a white colour, interspersed with black spots ; 

 its texture is fibrous, and it has never been met 

 with in crystals. Its constituents, according to 

 the analysis of Brandes, are as follows : 



Silica 46 



Alumina 50 



Oxide of iron 2-5 

 Potash 1-5 



100-0* 

 * Schweigger's Jour. XXV. 125. 



