Intelligence and Miscellaneous Articles. 79 



the excellence of the mirror is the same as regards lustre and dura- 

 bility ; but it may sometimes happen that at a high temperature the 

 air contained in the water ascends in small bubbles and thus causes 

 fine holes in the mirror, which are not visible in reflected, but are so 

 in transmitted light; for this reason, when a high temperature is used, 

 it is convenient to raise nearly to boiling the alkaline solution of 

 gold before the addition of the reducing-liquid, and before bringing 

 it in connexion with the glass to be gilded. 



The mirror, when ready, is carefully washed with water, leaned 

 against the wall with the bottom resting on bibulous paper and the 

 coated side underneath, and dried in the air at the ordinary tempera- 

 ture ; it exhibits then a perfect polish. 



In preparing the glasses for gilding, it is in most cases sufficient 

 to clean the surface with soda-lye and alcohol. Care must be taken 

 not to use an acid for cleaning; the layer of gold in this case sub- 

 sequently becomes detached from the glass. — Poggendorff's Annalen, 

 January 1868. 



ON SOME SPECIAL ELECTROMAGNETIC PHENOMENA, AND ON WE- 

 ber/s HYPOTHESIS ON ELECTROMAGNETISM. BY E. VILLARI. 



The author has investigated the influence which the initial mag- 

 netic state of a bar of iron or of steel exerts on induced magneto- 

 electrical currents excited in an adjacent conductor by any modifica- 

 tion whatever, be it increase or diminution, in the magnetic condi- 

 tion of the bar. His object was to verify Weber's theory, which was 

 also proposed by De la Rive, and which is only a complement of 

 that of Ampere, according to which, molecular currents preexist in 

 magnetic- bodies, and are merely directed by the action of magneti- 

 zation, carrying along with them in this motion the particles of the 

 body. He thinks that if there is molecular motion, the rapidity 

 with which it is effected must depend on the initial magnetic con- 

 dition, like the magneto-electrical currents which result from it, 

 and which themselves depend oq the rapidity of the magnetic modi- 

 fication. 



The apparatus he used consisted of a bar of steel or iron, round 

 which were coiled two conducting wires ; through the outside one 

 a first current passed, which magnetized the bar, and then other 

 weaker ones, direct or inverse, which more or less modified the ori- 

 ginal magnetism ; in the other, the inside, which was connected with 

 a galvanometer, the breaking of the outside coil and the alteration 

 in the magnetism produced induced currents, which were to be 

 measured. 



The author himself gives the following summary of his researches, 

 which, in his view, fully confirm Weber's theory : — - 



(1) Magnetization and demagnetization are accompanied by mole- 

 cular movements. 



(2) The rapidity with which these molecular motions are effected 

 depends on the initial molecular condition of the iron or the steel. 



