Employment of Potatoes in Steam Engine boilers, &c. 193 
fluids, that he has readily frozen mercury, by surrounding 
it with a frigorific mixture of ice and salt, in the apparatus 
in which aqueous vapour is produced and absorbed by the 
process of Mr. Leslie, and he has_no doubt that with analo- 
gous means and very volatile liquids, a degree of cold might 
em below that produced by mixtures.—Annales de 
ime. { 
20. New Electro-Magnetic experiments.—T he followingis a 
Varvnr - SP a: J } . Pe = rs oi kK 
7 v r c Pa 
Dr. Sebeck of Berlin. ‘Take a bar ofantimony, about eight 
inches long, and half an inch thick; connect its extrem- 
ties by twisting a piece of brass wire round them so as to 
form a loop, each end of the bar having several coils of the 
wire. If one of the extremities be heated for a short time 
with a spirit lamp, electro-magnetic phenomena may be 
exhibited in every part of it-—4nn, Phil. iv, 318. We 
have repeated this experiment with every success. 
brass is in that state which would be produced by connect- 
ing its heated end with the negative pole of a voltaic batte- 
ry, and its cold end with the positive pole.——Editor. 
Electrical Effect.—The following effect is. attributed 
by Mr. Fox, who observed it, to electricity. A piece of 
Iron pyrites was fastened with a piece of brass wire ina 
moss house, the moss being damp, On the following day, 
wire was found broken and excessively brittle, and in 
those parts in contact with the pyrites much corroded. On 
One occasion, after the brass wire had been fastened once 
or twice round a piece of iron pyrites, and had remained 
for some days enveloped in damp linen, the constituents of 
the wire were separated, and it was converted into 
Copper wire, coated with zinc.—An. Phil. iv. 449. 
