Employmetit of Potatoes in Steam Engine boilers, <^c. 193 



fluids, that he has readily frozen mercury, by surrounding 

 it with a fri^orific mixture of ice and salt, in the apparatus 

 in which aqueous vapour is produced and absorbed by the 

 process of Mr. Leshe, and he has^no doubt that with analo- 

 gous means and very volatile liquids, a degree of cold might 

 be produced below that produced by mixtures. — Annates de 

 Chimie. 



'2,0. Kezo Electro-Magnetic experiments. — The following is a 

 verycurious and simple electro-magnetic experiment made by 

 Dr. Sebeck of Berlin. Take a bar of antimony, about eight 

 inches long, and half an inch thick ; connect its extrem- 

 ities 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 — Ann. Phil, iv, 318. We 

 have repeated this experiment with every success. The 

 brass is in that state which would be produced by connect-- 

 ing its heated end with the negative pole of a voltaic batte- 

 ry, audits 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 in a 

 moss house, the moss being damp. On the following day, 

 the 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 brass wire were separated, and it was converted into 

 coppeT wire, coated with zinc—An. Phil. iv. 449, 



21. Employment of Potatoes in Steam Engine, and other 

 hoilers, to prevent the calcareous Incrustations on their bot- 

 toms and sides. — The practice of adding about one per cent, 

 of potatoes to the bulk of water contained in a Steam-Engine 

 boiler which has been long practised in this country, has 

 been recently introduced into France, and merits the enco- 

 mium which is bestowed on it by M. Payen, in a letter to 

 the Editor of the Jour, de Phar. Oct. 1822. He explains 

 the true cause of the beneficial agency of the root. The 

 Vol. VII. No. 1. 25 



