364 Air, Levy on the Tungstate of Lead, [Nov. 



Article X. 



On the Tungstate of Lead, By A. Levy, Esq. FGS. &c. 

 (To the Editors of the Annals of Philosophy.) 

 GENTLEMEN, 

 If you think the following short notice respecting tungstate 

 of lead worth insertion in the Annals of Philosophy y you will 

 oblige me by sparing a little room for it in the ensuing number. 

 One of the specimens of tungstate of lead in Mr. Turner's 

 collection offered me very distinct crystals of the form repre- 

 sented by fig, 1. They are much lengthened in the direction of 



Fig.l. 



the axis, whitish and translucent ; they cleave easily parallel to 

 the planes marked b% as well as in a direction perpendicular to 

 the axis. The incidences, easily obtained by means of the 

 reflective goniometer, either on natural planes, or planes of 

 cleavage, were as follow : 



b/, V = 99° 43' h\ h' = 13P 30' m, V = 155^ 45' 



fl, a« = 106 47 a% a* = 65 m, a" = 126 37 



b^, b^=z 92 46 b^, b^ = 154 36 m, 6^ = 167 18 



In some of the crystals, the planes of the modification b^ are 

 wanting ; whilst others are composed of this modification alone, 

 and present the form of very acute octahedrons, most of which 

 are cuneiform. I also found that the very small white crystals, 

 mentioned by Boumon, and which sometimes accompany the 



