192 Mr. J. Napier on Copper Smelting. 



exposing an alcoholic solution to spontaneous evaporation in a 

 test-tube ; around the edge of the liquid a thin radiating plu- 

 mose crop is produced, being more distinctly acicular than the 

 disulphate. It is therefore not quinidine (/S-quiuine), but as- 

 similates probably to that variety of quinine recently called 

 7-quinuie, a mouohydi-ate of the organic radicle C-° H^^ NO", of 

 which a-quiuine is the tri-hydrate, and /3-quinine the bi-hydrate. 

 However, further researches are necessary to establish this fact ; 

 for the present we are justified, from the reproduction of the 

 polarizing ciystals from the alkaloid separated from the green 

 polarizing compound, in considering that the alkaloid quinine 

 enters into the composition of the crystals, but in the character of 

 an iodo-base; not a substitution base, as has been previously showii, 

 but a compoimd analogous in its constitution to iodo-codeine, 

 dicyauo-codeine, cyaniliue, cyano-toluidiue and cyano-cumidine, 

 all of which are compounds not belonging to the series of sub- 

 stitution products : this, if correct, is a remarkable fact, and 

 woi-thy of verification by a more elaborate investigation. 



It is necessary to correct an error into which I inadvertently 

 fell in my last communication, in reference to the optical pro- 

 perties of the disulphate of cinchonine, fig. 11. PI. IV.; this 

 should have been disulphate of the alkaloid qiiinidine (/3-quinine). 

 Since the publication of my last communication, I have suc- 

 ceeded in producing and mounting an artificial tourmaline, large 

 enough to surmount the eye-piece of the microscope, so that at 

 the present moment I am perfectly independent of the tourma- 

 line or Nichors prism in all my experiments upon polarized 

 light ; and the brilliancy of the colours is much more intense 

 with the artificial crystals than when employing the natural 

 tourmaline; as an analyser above the eye-piece, it offers some 

 advantages over the NichoFs prism employed in the same posi- 

 tion, for it gives a perfectly uniform tint of colour over a much 

 more extensive field than can be had with the prism. 



32 Old Market Street, Bristol. 

 June 11,1852. 



XXVIII. On Copper Smelting. By James Napier, i^.C.-S.* 

 [Continued from p. 59.] 

 Assaying of the Ores. 



THE first object of the assayer, like that of the smelter, is to 

 separate the earthy matters contained in the ore fi'om the 

 metallic portion. But experience has taught, that if the copper 



* Communicated by the Author, who reserves to himself the copjiight, 

 any infringement whereof will invoke legal proceedings. — Eds. 



