Mr Haidinger's Description of Erinite. 93 



u He then adds some observations on the contrasted colours 

 so frequently observed in double stars, and regards them as 

 (at least) in many cases referable to the laws of vision ; in vir- 

 tue of which, a strong light having an excess of the less re- 

 frangible rays, will cause a feebler one, in which no such ex- 

 cess exists, to appear of the complementary hue ; instances of 

 which, in artificial lights, are adduced. He notices especially 

 the extremely intense red colour of a star of the eighth magni- 

 tude, R. A. 4 h 41 m . N.P.D. 61° 47 (1828.) 



" These prefatory remarks are terminated by some obser- 

 vations of the fifth star in trapexio nebulce Orionis, pointed 

 out by M. Struve. The author adduces evidence, which he 

 considers as satisfactory, that no such star existed in that si- 

 tuation on the 13th March 1826. It was observed, however, 

 by M. Struve to be conspicuous on the 11th November of that 

 year. It is now readily seen in the Slough telescope ; and at 

 the time of drawing up the present paper, it was so bright as 

 not to be overlooked with the most ordinary degree of atten- 

 tion. He considers it, therefore, if not as a new star, at least 

 as a variable one of very singular character. 



" The catalogue which follows is arranged in all respects 

 like the preceding ones published in the Memoirs of this So- 

 ciety, and is followed by a list of about 200 double stars, for 

 the most part found in the same sweeps with the others ; but 

 which, occurring in M. Struve's catalogue, cannot now be re- 

 garded as new double stars. Their observed places, and esti 7 

 mated angles of position, distances, and magnitudes, are, how- 

 ever given, in order to afford ground of comparison between 

 the two catalogues, of which comparison the results are stated.'* 



Art. XIII. — Description of Erinite, a New Mineral Species. 

 By William Haidtnger, Esq. F. R. S. E., &c. Commu- 

 nicated by the Author. 



.Mineralogy is indebted to Count Bournon for the esta- 

 blishment as distinct species, of several of those minerals which 

 contain arsenic acid and copper, some of which are found ex- 



* Read at the Royal Society of Edinburgh, April 21, 1828. 



