110 M. Scheerer's Observations on Elceolith and Nepheline. 



having been sublimed into the fissures and cracks of the do- 

 lomite. The specific gravity of this nepheline I found to be 

 2*56. It has been analysed by Arfvedson, who found its com- 

 position as follows: — 



Alumina (with some iron and manganese) . . 33*73 



Soda ; 20*46 



Water 0*62 



Silica 44-11 



98*92 

 As it is very difficult to obtain the crystals of nepheline 

 quite pure, without portions of the other minerals with which 

 it is accompanied being mixed with them, I had the precau- 

 tion to take a separate quantity of the crystals for each analy- 

 sis without previously pulverizing the whole together. Now, 

 if the result of the analysis was influenced by foreign mine- 

 rals, this influence must at least vary in the different analyses, 

 and consequently produce discordant results. Two analyses 

 gave 



10. 11. 



Silica. .... 44*03 44-29 



Alumina. . . . 33*28 33*04 



Peroxide of iron . 0*65 0*39 



Lime 1*77 1*82 



Soda 15*44 14*93 



Potash .... 4-94 4'72 



Water .... 0*21 0*21 



100-32 99-40 



The amount of water, from want of material, was determi- 

 ned only in one experiment. In both analyses, notwithstanding 

 the great precaution taken in choosing the fragments of the cry- 

 stals, it was impossible to prevent a quantity of foreign minerals 

 getting into the analysis, which was, however, not decompo- 

 sable by hydrochloric acid. In the first analysis this mixture 

 amounted to about 3 per cent ; in the second to about 5 per 

 cent. As from this cause, notwithstanding the near agreement 

 of the results, doubts might arise as to their perfect correctness, 

 I analysed a third portion of nepheline. Through the great 

 kindness of Prof. G. Rose I received from him for this pur- 

 pose a very fine crystalline geode in pure dolomite, containing 

 crystals perfectly free from all foreign minerals, with a por- 

 tion of vesuvian which was easily removable. I found this 

 to be composed of 



