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



circle, like the magnetic metals, it forms two concentric 

 circles, leaving thus a narrow white band, in the very place 

 where the other metals form a circle, as if it were repelled 

 by the more lively action of the iron armature of the magnet. 

 The effect is so marked, that on mixing, for example, some 

 sesquichloride of chromium very finely pulverized with some 

 bismuth, likewise in very fine powder, the violet circle of the 

 chloride is seen, and the two circles of the bismuth which are 

 separate from them, although very near. Amber seems to 

 give the same appearances as the bismuth, though in a much 

 weaker degree. 



No attractive or repulsive effect is observed by this means, 

 either on very pure antimony or on the other metals, binary 

 or other compounds (among the rare metals, I have only 

 experimented on tellurium and the uranium of M. Peligot), 

 nor on the alkalies, sulphur, iodine, charcoal, and diamond. 

 I regret that I had not at my disposal either cerium or any 

 of its compounds. 



These negative results cannot invalidate in the least the 

 general proposition of M. Faraday, who has doubtless ope- 

 rated with more delicate means or with more energetic mag- 

 nets. I merely mention them here to point out the easy pro- 

 cess which I have employed, and the limit of its sensibility. 



There is another process for investigating the magnetic 

 properties, — that which was employed by Coulomb when he 

 discovered that all bodies are subject to the influence of mag- 

 nets, and which has been since employed in the same view by 

 many experimentalists, and very recently by M. Ed. Becquerel 

 (Comptes Rendus, vol. xx. p. 1708). Mr. Faraday appears to 

 have employed it ; but doubtless, from the weakness of my 

 electro-magnets, although excited by a battery of 100 pairs, 

 I have not obtained the same results as he ; in my experi- 

 ments, bismuth and amber are the only two substances which 

 took a direction perpendicular to the line of the poles, and 

 without doubt the relation existing between this direction of 

 the bismuth and the effect of repulsion which the fine pow- 

 der of that body experiences from the part of the armature of 

 the magnet will appear highly remarkable. These two me- 

 chanical actions of magnetism upon bodies — the attraction 

 and repulsion of fine powders, placed almost in contact with 

 one of the poles, and the direction given to more considerable 

 masses, oscillating in the presence of the two poles — appear 

 therefore to be dependent one upon the other ; but in what 

 degree are they connected with the third action, the optical 

 action which Mr. Faraday has just discovered? 



Admitting with this philosopher that all the substances 



