866 



of this substaiife only bv cooling very small quantities of the oom- 

 poLind. The cristallized liquid consists of long, opaque, porcelain-like 

 looking needles, which show a principal and very complete cleavage 

 in the direction of their elongation; heavier individuals therefore 

 w^ill decay very easily in a number of thin, felty needles, showing 

 normally orientated extinction. In the zone of the longer axis we 

 could measure some angles between 59° and 61°; this form of the 

 silicate seems to be the same as that, described by Hautefeuille and 

 Margottet as rhombic, with pseudo-hexagonal symmetry. Doubtless 

 the silicate is biaxial, and probably raonoclinic ; the plane of the 

 optical axes parallel to the elongation of the needles, and perhaps 

 almost perpendicular to the formes |100| or jOOlj. 



The silicate used was the 

 same, as formerly described by 

 oue of us ^). Its analysis gay e 

 the following values : 



Sio, 66.6ü7o 



Fig. 2. 



Lilhiummetasilicale (Enlargement 50 X) 

 {immersed in a liquid). 



99.967„ 

 There is thus about 0.87„ 

 LiJ) too little. The metasilicate 

 is decomposed by water, how- 

 ever much more slowly than the 

 ortho-silicate. Finallv however 



the water shows some alkaline reaction. The meltingpoint was determi- 

 ned with Sosman's element C at 11954 M.V., corresponding with 

 1201°.8 C. ; Day and Sosman determined 1200°.6 C. Another pre- 

 pai-ation, (Crenshaw), whose analysis gave the following numbei-s : 



SiO, 65.897, 



LiO^_ 32.837„ 



FeO 0.057„ 



H,0 1.2 7„ 



99.977„ 



had a meltingpoint of 11930 M. V., or 1199,°8 C. ; with the ther- 

 moelements G and H of Sosman and Day. The meltingpoint of pure 



') F. M. JaecxEr, Joiirn. of Wash. Acad, of Sciences 1. 4 9. (1911). 



