290 Transactions of the Geological Society of France. 
the atmosphere take place in the regions of the magnetic poles, un- 
der the form of the Aurora borealis, for the reason that the ferrugi- 
nous particles arrange themselves about the pole in an order similar 
to that of iron filings around a magnetic bar. Future observations 
upon terrestrial magnetism will aid in explaining the anomalies of this 
phenomenon. 
The vaporization of all solid and fluid bodies goes on under every 
degree of temperature. When the maximum of density in the va- 
por is passed, a precipitate occurs, and clouds, cirri, or mists are form- 
ed, which rest upon the earth, or a concretionary formation takes place. 
The latter case happens partly from the condensation of clouds, 
sometimes under a clear sky, sometimes without electric explosion 
(aerolites,) or with the phenomena of electricity (fire balls); finally, 
the fall of these bodies takes place in small particles, or agglomerated 
into masses of a larger size, and analogous to hail. 
If such are the phenomena beyond the polar regions; near the 
magnetic poles, the precipitates being attracted, would continually 
_ be undergoing an arrangement in a circular series, and thus produce 
the aurora borealis. 
This kind of precipitation might take place cotemporaneously with 
aqueous precipitation, in which case there would oceur rains attend- 
ed by foreign mixtures. 
Professor Grurruutsenis occupied with the origin of aerolites and 
shooting stars; and he has proved by mathematical calculations foun- 
ded upon physics, that these bodies must necessarily be formed be- 
yond our atmosphere, in the interplanetary space, where the metals 
and the metalloids, he says, are still held in solution by means of 
hydrogen, and where they exist continually for the formation of these 
opake bodies. 
According to Herscwenn, the observation of the shooting stars 
may be useful for the determination of longitude. The height of 
the meteors seen by M. Qurrexer, is estimated at from ten to 
eighteen leagues from the earth, and their motion at from five to 
eight Atarics per second ; results which correspond with those of 
Branpes eel other German philosophers. 
CHEMICAL MINERALOGY. 
M. Fenty has discovered an interesting repository of salts in a 
cavern upon the Bosjesman river at the Cape of Good Hope. They 
occur in beds, the upper one of which is composed of a siliceous 
