Dr Turner on Haidingerite, a new Mineral Species. 317 



and decreasing gradation of intensity reckoning from the 

 centre, but at regular intervals, following, so to speak, a law 

 analogous to that of interference. At the negative pole, where 

 the electro -positive substances appear, we observe the same 

 phenomenon, namely an alternation of circles of oxide and of 

 pure metal. This alternation constitutes the second result 

 which I have announced. May we suppose that the radia- 

 tion of electric currents follows a law of interference ? There 

 exists, without doubt, certain alternations, but new experi- 

 ments are necessary to discover their true origin. 

 Reggio, November 20, 1826. 



Art. XXX I IT. — On Haidingerite, a new Mineral Species. 

 By Edward Turner, M. D. F. R. S. E. Lecturer on Che- 

 mistry, and Fellow of the Royal College of Physicians, 

 Edinburgh. Communicated by the Author. 



In an account of the analysis of two newly discovered minerals 

 described by Mr Haidinger in the third volume of this Jour- 

 nal, it was my intention to have proposed for the second spe- 

 cies, the Diatomous Gypsum-Haloide, the name of Haidin- 

 gerite, in honour of the distinguished mineralogist who first 

 noticed its existence. In this wish I had the pleasure to con- 

 cur with Mr Ferguson of Raith, in whose cabinet the mine- 

 rals were discovered ; but as Mr Haidinger was not at that 

 time in Britain, it was thought advisable to make no allusion 

 to the subject until after his return. Having now gained his 

 assent, I propose to employ the name of Haidingerite to de- 

 signate the species above-mentioned, and have no doubt that 

 this proposition will be favourably received by mineralogists. 

 In a recent scientific tour through the continent, made in 

 company with Mr Robert Allan, Mr Haidinger hoped to meet 

 with specimens of Haidingerite, and ascertain its locality. But 

 in this he was unsuccessful. He could not discover it in 

 any of the cabinets which he had an opportunity of inspect- 

 ing, not even at Carlsruhe, among the numerous and superb 

 specimens of the arseniates of lime and other products of the 

 mines of Wittichen in the Black Forest, collected by the Ber- 



