54 CALIFORNIA ACADEMY OF SCIENCES. 



produce double refraction. No microscopic reaction on 

 CI or SO3 could be obtained. 



A quantity of this isotropic mineral had been previousl}^ 

 isolated and analyzed (No. i) giving almost exactly the 

 composition and specific gravity of analcite. In order to 

 test the accuracy of this analysis a piece of the same rock 

 was again subjected to a separation by the Thoulet solu- 

 tion. The powder obtained was pure and with few excep- 

 tions composed of perfectly isotropic grains. The result 

 of this second analysis (No. 2) which Dr. W. H. Melville 

 of the U. S. Geol. Survey had the kindness to make for 

 me. is given below. The total substance for this analysis 

 only amounted to 0.3576 grm. ; to bases and siHca 0.2526 

 grm. was used, in which sulphur and chlorine were looked 

 for quantitatively, thus increasing the ordinary errors of 

 the separation of bases and siHca. For water and alkalies 

 0.1050 grm. was used. 



No. I, No. 2, 



49-87X' 



22.55 

 1-51 

 2.62 

 1.28 



10.92 

 2.66 



11.05 



102.46 



Sp. gravity: 2.24 

 No chlorine. Trace of chlorine. 



No sulphur. No sulphur. 



The oxygen ratio of this last analysis is nearly RiRs- 

 Si :H2= I : 3 : 7 • 2 whereas that of analcite would be 



