188 Mr. Phillips on the Crystalline Form 



or sub-families, be distinguished by the termination ina or 

 ana, as Papilioimia, Coliana, Paphiana, &c. This rule, so 

 generally adopted in other departments of natural history by 

 modern writers, will at once explain the station occupied by 

 these groups, in relation to those throughout nature. 

 Tittenhans^er Green, near St. Albans, 

 Feb. 1st, 1827. 



XXXVIII. On the Crystalline Form of the Hyalosiderite . 

 By William Phillips, Esq. F.G.S. Src* 



T^R. WALCHNER of Freiburg not long since described a 

 -*-^ new mineral, under the name of Hyalosiderite, in Schweig- 

 ger's Nerves Journal; and a translation of his communication 

 has appeared in the 63rd vol. of the Philosophical Magazine, 

 and also in the first vol. of the Edinburgh Journal of Science. 



Having lately obtained a specimen of that extremely cu- 

 rious mineral, affording several nearly perfect crystals, well 

 adapted for the use of the reflective goniometer, I was in- 

 duced to measure them by means of it, both because the in- 

 spection of them raised some doubts of the correctness of 

 Dr. Walchner's determination in attributing to this substance 

 an octohedron as the primary form of its crystals, and also 

 because he has himself observed, that his own determinations 

 of the measurements he has given, " cannot boast of very great 

 accuracy." But it is somewhat singular that Dr. Walchner 

 should believe his determinations will nevertheless " contribute 

 to adjust in some measure the determinations published in 

 Hausmaim's Spec. Cryst. Metall. relative to the crystals of iron 

 slags formed in various metallurgical processes ;" " for," says 

 Dr. W., " we find a corresponding similarity not only in the 

 forms in general, but also in the angles of inclination of the 

 planes :" and he then observes, that the angles given by Haus- 

 man " could not but be very imperfect, on account of the small 

 size" of the crystals. 



Dr. Walchner has not said by what means he obtained the 

 two measurements on which he has relied for the calculation 

 of all the others given by him : he says, " the inclination of the 

 planes d and d' [a^ on c or c' of the following figure) may be 

 determined most exactly, although on account of the small- 

 ness of these crystals, even these measurements remain imper- 

 fect;" and immediately adds, " the inclination on d on d' was 

 determined to be 141°, and the inclination on d' on a (c or c' 



* Communicated by the Author. 



