M. Pouillet on the Recent Researches of Prof. Faraday. 333 



The chloride of sodium has an action very analogous to that 

 of the flint-glass. 



I have also subjected to experiment some transparent or 

 coloured liquids ; these experiments were made in a trough 

 formed of parallel glasses, having a length of thirteen centi- 

 metres, equal to the distance of the axes of the electro-mag- 

 nets, a breadth of three centimetres, and a depth of five centi- 

 metres. The trough being empty, and the electro-magnets 

 being in action, no sensible effect was produced by the pa- 

 rallel glasses which formed the extremities. 



The intensity of all these liquids is very nearly equal to 

 that of the crown-glass; the most energetic however ap- 

 peared to me to be olive oil, distilled water, concentrated 

 ammonia, and pure nitric acid ; and the less energetic, acetic 

 acid, sulphuric acid, ferrocyanide of potassium, and ferrocya- 

 nate of magnesia. It appeared to me certain that several 

 bodies dissolved in distilled water weakened its effects. 



Mr. Faraday states that manganese, chromium, and cerium 

 are magnetic after the manner of iron, and that all the com- 

 pounds of these bodies preserve this property more or less. 

 I had long ago proved the first fact for manganese, and in 

 the course of last summer I proved it for very pure chromium 

 obtained by the battery, both from chromic acid and from 

 sulphate of chromium. With regard to the magnetic com- 

 pounds, I have studied them recently by a very simple and 

 very easy process, which consists in arranging a powerful 

 electro-magnet, with its poles at top, forming a horizontal 

 plane ; a thin paper is stretched over each pole, in contact 

 with the iron itself, and it is then only requisite to throw 

 upon this paper some very fine particles of the substance to 

 be examined, and to give the paper some slight vibrations, 

 which put them in motion. The particles arrange and fix 

 themselves on the circle which corresponds to the terminal 

 bar of the iron of the electro-magnet, and describe the circle 

 with great precision. By this means I have ascertained that 

 almost all the compounds of magnetic metals are, in fact, 

 more or less magnetic ; prussian blue and the sesquichloride 

 of chromium (of M. Peligot) are so in a remarkable manner. 

 There are some compounds however which are exceptions to 

 this rule ; such, for example, are the double cyanide of iron 

 and of potassium, the chromate of silver, and the bichromate 

 of potass. 



Other metals, as platina sponge and arsenic, exhibit a per- 

 ceptible action ; but it would require to be verified on per- 

 fectly pure specimens. 



Bismuth presents other phenomena; instead of forming a 



