1875.] 4:UO [Frazer. 



quioxides, and the per cent, of the radicals of the sesquioxide bases 

 are somewhat less in the actual, than in the hypothetical analysis. 



In tabular form the proportions would stand as follows : 



HYPOTHETICAL BASIC 



IGNEOUS ROCK. WEST ROCK. 



Silicon I 24.96 24.92 



Oxygen) 27.00 27.02 



Aluminum \ "^ 13.50 10.03 



Iron (from peroxide) J > 



Oxygen ) 10.00 7.72 



Radicals of protoxide bases | 22.20 20.84 



Oxygen j 10.00 8.58 



A mean of 40 analyses of Labradoiite recorded in Dana's Mineralogy, 

 is as follows : 



PER CENT. 



Silica 53.09 



Alumina 27.96 



Ferric oxide 1.33 



Magnesia 0.93 



Lime 10.88 



Soda 4.09 



Potash 1 .08 



Water 0.84 



Total 99.39 



Or in the simple form : 



PER CENT. OXYGEN. OXYGEN RATIO. 



Silicon 25.48 27.61 27.61 



Aluminum 14.73 12.96 | 



Iron (from FeA) 0-93 0.40 ) 



Magnesium 0.24 0.151 



Calcium 7.77 3.11 j 



Sodium 3.03 1.06}. 



Potassium 0.98 0.19 



Hydrogen 0.09 0.75 J 



13.36 



5.26 



Mr. Hawes extracted enough crystals of pyroxene from one specimen 

 of Connecticut trap to enable him to determine its constitution. 



It bears the nearest resemblance to an Augite of the Rhone, analyzed 

 by Klaproth : 



