254 Scientific Intelligence. 
d of Zinc in the Porous Cup.—t connected four cups of 
Grove’ s ~~ <i charged in the common method by strong nitric acid 
in the porous cup and sulphuric acid diluted with twelve of water, so that 
the zinc of the fourth cup was connected by its platinum with the acid of 
the first botnns ae, so that there was a complete circle among the cups 
themselve action was strong and rapid; nitrous acid gas was 
thrown of ereety. while no hydrogen appeared in the zine cups. 
The process was suffered to go on till nearly all of both acids was con- 
sumed. After a while the porous cups began to fill with a white powder 
the liquid. This appears to show the advantage of using Glauber’s 
salt in the zinc cup in preventing the action of the nitric acid on the 
mercu O-B: 
Pabedan May, 1848. 
4. Selenium, (Acad. Berlin, Nov., 1847. )—The specific gravity of 
selenium has been determined by Fr. de Schaffgotsch as follows : 
For vitreous slenivm obtained .~ a rapid cooling from fusion,— 
4276 to 4:286 at 20° C.; the mean is 4°282. 
For fine- “Sapre selenium,—obtained from slow cooling after heating 
to 250° C.,—4°796 to 4'805 at 20° C.; mean 4801. This selenium had 
the aspect of ee and left traces on porcelain less red than the 
vitreous seleniu 
The red eaetjans precipitated cold, such as is obtained by the re- 
duction of selenic acid by sulphhydric ‘acid, and which becomes black 
when moderately heated, has the specific gravity 4:259 for the red, and 
4-264 for the black colored, which corresponds with that of the vitre- 
<7 selenium 
. Cause ae ieteate Colors on Minerals, (Soc, Sci. Gottingen ; L’In- 
siti, No. 750.)—From M. Hausmann’s valuable memoir on this branch 
optical Somion: we ety that the irised colors on minerals, like 
pa steel, is due to a thin film covering the s urface ; and that the 
etime 
iron is one of the most common of the substances that communicate 
irised hues. This compound results from the decomposition of pyrites, 
either forming first a carbonate which is common in many waters, and 
then by the evaporation of ~— water yielding the hydrate, or forming 
the hydrate direct. Thec on anthracite and specular iron often 
proceed from this source: an ae an exposure of the latter species to wa- 
ters ngs the carbonate, afforded Hausmann after a while, irised 
