236 Intelligence and Miscellaneous Articles. 
When the acidulated water is replaced by common water, the 
current of a pile of fifty elements is incapable of producing the deto- 
nation of the mixture; but the slow recomposition becomes very 
energetic, and the liquid is seen to oscillate in the bell-glass in con- 
sequence of the unstable equilibrium which is established between 
the decomposition of the gases which takes place at the lower part 
of the electrodes, and the recomposition which is effected at their 
upper part. 
These phenomena are manifested with platinum plates supported 
below by platinum wires to which they are soldered, whether the 
surface of the platinum be naked or platinized.—Comptes Rendus, 
June 15, 1857, p. 12738. 
ON THE OPTICAL PROPERTIES OF MAGNETIC BODIES.—SECOND 
NOTE. BY M. VERDET. 
In his previous note* the author stated that the compounds of 
manganese acquired a positive rotatory power under the influence 
of magnetism. He has since found a compound of that metal, the 
double cyanide ef manganese and potassium (corresponding in its 
composition with the red ferrocyanide of potassium), the magnetic 
rotatory power of which is negative. Thus manganese represents 
to a certain extent the connexion between the two classes established 
by the author amongst the magnetic metals; that which is the rule 
for compounds of iron is the exception for those of manganese, and 
vice versd. 
The corresponding double cyanides of cobalt and chromium both 
possess a positive magnetic rotatory power. The double cyanide 
of cobalt and potassium is even diamagnetic. 
The author has now no doubt as to the negative magnetic rotatory 
power of the salts of cerium. A sufficiently concentrated aqueous 
solution of chloride of cerium, under the action of magnetism, exerts 
upon polarized light an action opposite to that of water; it is easily 
ascertained in consequence of the perfect limpidity of the liquid. 
The compounds of uranium and lanthanium have a negative mag- 
netic rotatory power. Nitrate of uranium in a state of purity is 
diamagnetic; but the red and black oxides of uranium, which may 
be extracted therefrom by the action of heat, are both magnetic. 
Uranium must therefore be classed amongst the magnetic metals. 
On dissolving nitrate of uranium in water, zther or alcohol, liquids 
are obtained, the action of which upon polarized light is less than 
that of the proportion of solvent contained in them. The negative 
action of the dissolved salt is therefore indisputable. 
Perfectly pure carbonate of lanthanium is strongly magnetic. The 
solution of chloride of lanthanium obtained by treating this carbonate 
with pure muriatic acid, when submitted to the action of magnetism, 
exerts a less action upon polarized light than water. The magnetic 
rotatory power of chloride of lanthanium is therefore to be regarded 
as negative. 
* See Phil. Mag. July 1857, p. 78. 
