Chemistry and Physics. 427 
of no account, one of the sides of the rectangle is almost twice as long 
as the other. 
_{7.) The displacement does not occur in all the six positions of the 
parallelopiped, but only in the two positions in which the ray is perpen- 
dicular to the faces of the cube, 
(8.) On the contrary we observe displacements in all the six posi- 
tions when the parallelopiped has been cut perpendicularly to the octa- 
hedral faces of the crystal, but these displacements are of different 
“(9.) All these phenomena; the unequal optical compressibility as 
Well as the rotation of the optical ellipsoid, appear to have their origin 
in the permanent effects produced by tensions or pressures which take 
face in the act of crystallization ; we know that the mechanical or 
molecular elasticity is independent of the changes of form which the 
dody has previously undergone; but the optical elasticity preserves as 
it were the impression. ; 
(10.) An octahedron of fluor spar presented an example of a dis- 
placement of 45°, while cubic crystals of the same mineral offered no 
Wace of it; this fact evidently supports the hypothesis just expressed. 
(11) All the facts which we observe when we em loy compression 
lo'convert crystals of the regular system into repulsive doubly refract- 
ing crystals, are reproduced in a precisely similar manner which we 
use extension to convert them into positive crystals.—Comptes Rendus, 
XXXV 
3. On the Electrolytic Law.—Burr has taken up the consideration of 
Faraday’s law of electrolytic action, and has demonstrated by careful 
Studied the fermentation of citrate of lime both in the raw state, as pro- 
duced by saturating lemon juice with chalk, and as obtained by em- 
pring pure materials and adding yeast to bring on the fermentation. 
8a mixture of carbonic acid and hydrogen ; : 
We citrate of lime nae disappeared yields a white soluble lime salt, 
: Which, decomposed by nitrate of silver, gives crystalline silver salts 
