Chemical Science. 377 
cess of stearine in it, for it was ascertained that elaine conducted 
electricity much better than stearine. ‘The fat of an animal dimi- 
nishes in conducting power with the age of the animal. ‘The same 
apparatus also marks a nectable difference between resin, gum lac, 
and sulphur, the most insulating of all bodies known, and also be- 
tween silk, flint-glass, and common glass. 
As to alcoholic or aqueous fluids, acids, alkalies, §c., the time 
required was too short to be adopted as a measure, but a modification 
of the apparatus would enable it to measure the conducting power of 
allof them. It is remarked also in the report, that ‘* it would be 
equally possible and very curious to make trial of the two electricities 
on various substances, for it would be suflicient for that purpose to 
put the poles of the pile alternately in communication with the earth, 
Itis probable, according to the results formerly obtained by Erman, 
that differences would be found with certain substances.—Ann. 
de Chim. xxv. 373. 
5. Distinction of Positive and Negative Electricity.—Positive and 
negative electricity may be readily distinguished by the taste, on mak= 
ing the electric current pass by means of a point on to the tongue. 
The taste of the positive electricity is acid, that of the negative elec- 
tricity is more caustic and, as it were, alkaline —Berzelius. 
6. Electricity produced by Congelation of Water.—When water is 
frozen rapidly in a Leyden jar, the outside coating not being insulated 
the jar receives a feeble electrical charge, the inside being positive, 
the outside negative. If thisice be rapidly thawed, an inverse result 
is obtained, the interior becomes negative, and the outside positive.— 
Grothus. 
7. Hare’s Single Gold-leaf Electrometer.—This instrument consists 
of a glass vessel, fixed by a foot on to a wooden stand, and haying an 
aperture at the top and also another at one side. ‘The top is closed by 
a metal cap, finished externally by a horizontal zinc disc, six inches 
in diameter, and connected internally with a single leaf of gold cut 
into an acute triangular form, and hanging in the centre of the instru- 
ment with the point downward. Opposite to the lower end of this 
leaf of gold is a ball attached to a horizontal wire, and which 
passing through a screw cap fixed in the lateral opening of the glass 
vessel, can be made to approach to, or recede from, the leaf at 
pleasure, the distance being estimated by a graduation on the screw 
into +4oth parts of aninch. A plate of copper six inches in dia- 
meter, and furnished witha glass handle, generally accompanies the 
instrument. 
*« The electricity produced by the contact of copper and zinc is ren- 
dered sensible in the following manner: Place the disc of copper 
on the disc of zinc, take the micrometerescrew in one hand, touch 
