f'dd Scientific Intelligence. 
trad-ion or a repulsion takes place, according to the direction of 
the galvanic current in the apparatus, and the magnetic current 
in the bar .—Bibl. Universelle. 
II. CHEMISTRY, 
SI. A New Fluid , with remarkable Physical Properties , dis- 
covered in the Cavities of Minerals. — A new fluid, of a very 
singular nature, has been recently discovered by Dr Brewster, 
in the Cavities of Minerals. It possesses the remarkable pro- 
perty of expanding about thirty times more than water ; and, 
by the heat of the hand, or between 75° and 83°, it always 
expands so as to fill the cavity which contains it. The vacuity 
which is thus filled up, is of course a perfect vacuum ; and at a 
temperature below that now mentioned, the new fluid contracts, 
and the vacuity reappears, frequently with a rapid effervescence. 
These phenomena take place instantaneously, in several hun- 
dred cavities, seen at the same time. 
The new fluid is also remarkable for its extreme volubility ; 
adhering very slightly to the sides of the cavities ; and is like- 
wise distinguished by its optical properties. It exists, how- 
ever, in quantities too small to be susceptible of chemical analy- 
sis. This new fluid is almost always accompanied with another 
fluid like water, with which it refuses to mix, and which does 
not perceptibly expand at the above-mentioned temperature. 
In a specimen of Cymophane or Chrysoberyl , Dr Brewster has 
discovered a stratum of these cavities, in which he has reckoned, 
in the space of ^th of an inch square, thirty thousand cavi- 
ties, each containing this new fluid ; a portion of the fluid like 
water, and a vacuity besides. All these vacuities simultaneous- 
ly disappear at a temperature of 83°. 
If such a fluid could be obtained in quantities, its utility in 
the construction of thermometers and levels would be incalcula- 
ble. There are many cavities in crystals, such as those opened 
by Sir Humphry Davy, which contain only water, and which, of 
course, never exhibit any of the properties above described. An 
account of these results was read before the Royal Society of 
Edinburgh, on the 3d and on the 17th March. 
£2. Pyro-citric Acid . — This new acid, discovered by M. J. 
Lassaigne, is produced by the distillation of citric acid. It is 
white, inodorous, and of a strongly acid taste, and generally oc- 
