Notes on Foreign Geology and Mineralogy. ad 
lomite, as Mr. Fischer supposed from its blow-pipe reactions and spe- 
cific gravity. This species was originally described by Professor 
Shepard. Its specific gravity is 3-745 according to Claus (3°80 ac- 
cording to others), and it has given him the following composition :— 
DLlCANe. , : : . 5 29°55 
Titanic acid. 2 : é : 21:18 
Peroxide of iron. : : : 18-08 
Lime .. ; : ’ : : 25°13 
Magnesia : : 5 1:2 
Soda and potassa . : . : 4:22 
99°38 
This corresponds tolerably with the analysis of Whitney, Rammels- 
berg, and Crosseley, made with this mineral from Arkansas (Ozark 
Mountains). 
Professor Pisani, of Paris, has made a very interesting discovery 
as regards the rare mineral Pollux from the Island of Elba.* We 
have hitherto only one analysis, by Plattner, of this mineral, and the 
addition of the analysis did not make up 100 parts, but only 92-75, 
although it was made with the greatest care. M. Pisani has found 
that this is due to the mineral containing the rare oxide of cesium in 
place of potassa. ‘This is the first mineral in which oxide of cesium 
has been detected ; the metal, it will be remembered, was dis- 
covered by Professor Bunsen, in certain mineral waters, where 
its presence was ascertained by specirum-analysis. According to 
M. Pisani’s analysis, Pollux contains about 34 per cent. of oxide of 
cesium, and merely a trace of potassa. The result was as follows : 
ULCay new. : : ; : : 44-05 
Alumina. 5 : : : : 15:97 
Oxide of iron . ; : 4 : 0-68 
Lime : : 0:68 
Oxide of cesium (traces of potash). 34:07 
Soda (with a little ee : F 3°88 
Water . A é é - 2°40 
101-71 
In calculating Plattner’s analysis for cesium instead of potassium, 
the addition comes up to 100 parts. The specimen of Pollux of 
which the above is the composition was transparent like quartz, its 
breakage conchoidal, lustre vitreous; colourless; exterior worn, as if 
decayed, and having an aspect like gum ; hardness about 6:5 ; specific 
gravity = 2-901. Heated it loses its transparency ; and when heated 
on a platinum wire with fluoride of ammonium, and then moistened 
with hydrochloric acid, it shows in the spectroscope the two blue 
lines which are characteristic of the metal cesium. Pollux is met 
with at the Island of Elba in granite, along with beryl, tourmaline, 
quartz, &c. It crystallizes in the Ist (cubic) system, and conse- 
quently exercises no action upon polarized light. 
The Density of the Earth appears to be in as unsettled a state as 
our distance from the Sun. I will not discuss here the different 
* Comptes Rendus de l’Acad. des Sciences, lviii. No. 16. 
