274 Correspondence of J. Nickles. 
of 1 part of nitric acid, 8 parts of distilled water and 2 of alcohol. We 
mention only these general facts, the details belonging more especially 
to the domain of technology. 
Theory of the Pile and the Aurora Borealis.—M. de la Rive, the 
celebrated physicist of Geneva, has presented to the Academy the first 
volume of a treatise on Theoretical and Applied Electricity, which he has 
published in London, and of which he is now preparing an edition in 
French. In explaining the plan of his work, M.de la Rive dwelt more 
Miscellaneous.—Among the various fa communicated to the 
Academy since my last communication, we mention the following. 
The transformation of tartaric acid into racemic, by M. Pasteur. 
work of considerable extent on the variations in chronometers, by 
the lubricating oil. M. Lieussou after explaining the causes, gives the 
methods of remedying the evils. 
A photographic apparatus by M. Quinzt, for producing at one and 
the same time two images for use in the stereoscope ; it is a modifica- 
hon of the binocular camera obscura of Brewster. 
_ A note of M. Gorcen, on the coloration of salts of manganese, tend- 
ing to show, that the salis are all colored, and that if M. Voelker bas 0 
tained colorless salts, it is owing to impurities, they including certain 
salts, which like those of cobalt, copper, &c., are not themselves color- 
less, but afford the complimentary color to that of manganese, so as by 
mixture to generate a white color. 
A letter of M. Dusarpin, calling attention anew to the method of 
using steam in extinguishing Jires. If one of the passengers of the 
n 
M. Fetix Bernarp has described a new photometer, and M. GavealN 
has announced a new electroscope with double condensation, which in- 
