242 Mr. Levy on a neio Mineral. [April, 



planes is 137° 5' ', and that of the base on one of the lateral 

 planes 94° 3'. Sphene presents in the series of its secondary 

 forms many oblique rhombic prisms, the lateral planes of which 

 are produced by modifications either on the lateral edges, two 

 of the sides of the base, or the lateral angles ; and the base is, 

 either the base of the primary or some secondary plane produced 

 by a decrement on the angles a or o. None of these secondary 

 oblique rhombic prisms that I have observed, nor any of those 

 mentioned by Mr. Rose in the excellent paper on sphene, he has 

 published at Berlin, have their planes inclined at the same 

 angles as those of the primary of the substance I am describing. 

 The secondary oblique prisms of this substance do not either 

 in their measurements correspond with any of the oblique rhom- 

 bic prisms of sphene. I have also tried whether I could not 

 deduce by some law of decrement, the form of this new sub- 

 stance from the primary of sphene, and I have found it was not 

 possible without assuming very complicated laws. I believe, 

 therefore, I am entitled to consider it as a new species. Mr. 

 Heuland has proposed to me to call it Turneiile, from the name 

 of the gentleman in whose collection it was first noticed as a 

 distinct species. This tribute is certainly well due to Mr. Tur- 

 ner, who has undertaken with so much readiness and liberality 

 the publication of a detailed description of his most valuable 

 collection. This new substance is very scarce, and besides the 

 specimen where I have observed it, Mr. Heuland knows but one 

 more in England. I could only detach a single crystal of it, and, 

 therefore, could not attempt to determine its specific gravity, or 

 to have it analysed. I hope the observations I have made may 

 induce some others to examine the physical and chemical pro- 

 perties of this substance, should they be able to procure it, and 

 it is partly for this motive I publish them now. 

 The form of the crys- 



Fig.2. 



tal I have examined is 

 represented, fig. 2 ; its 

 planes were sufficiently 

 brilliant to measure the 

 incidences of any two 

 of them. The reasons 

 for which I took the 

 planes m, m, in prefer- * 

 ence to the planes mark- 

 ed b , for the lateral 

 planes of the primary 

 form, are obviously, that 

 in the hypothesis I have 

 made, the planes g 3 , h 3 , 

 are the result of simple decrements on the lateral edges of the 

 primary, and that in the other supposition, they would have 



