Intelligence and Miscellaneous Articles, 485 



salts of iron submitted to the action of magnetism exert an action 

 opposite to that of the generality of transparent substances upon 

 polarized light. 



I shall propose to call the magnetic rotatory power of water, heavy 

 glass, sulphuret of carbon, and most transparent bodies direct, and 

 that of the salts of iron inverse. 



It was natural to inquire whether any other magnetic salts, besides 

 those of iron, would not present analogous phsenomena. I am not in 

 a position to give a certain opinion except upon the salts of nickel 

 and manganese ; of these I have examined a certain number, such 

 as the sulphate, nitrate, and chloride of nickel, and the sulphate and 

 chloride of manganese ; and I have ascertained that in solution they 

 possess a direct rotatory power, which is added to that of the water. 

 They present no difference therefore from the ordinary metallic salts. 

 I can say nothing certain as to the salts of chrome and cobalt : these 

 compounds have such a great colouring power that their solutions 

 must be very dilute if we wish to have them sufficiently transparent; 

 the influence of the dissolved salts is then very weak in comparison 

 with that of the solvent, and I have been unable to ascertain posi- 

 tively its direction, the apparatus at my command not being suffi- 

 ciently powerful. I need not point out the new difficulty which the 

 opposition of the optical properties of the salts of iron and nickel 

 presents to the establishment of any theory of the phsenomena. At 

 any rate it is impossible to say simply that the rotation of the plane 

 of polarization is weak in proportion as the magnetic capacity is 

 strong, since we find magnetic bodies presenting rotatory powers in 

 opposite directions. 



Lastly, I have examined the solution of nitrate of ammonia, which, 

 according to Bertin, possesses a magnetic rotatory power less than 

 that of water. The fact is perfectly correct, but it must be inter- 

 preted quite otherwise than in the case of the salts of iron. Nitrate 

 of ammonia is so soluble in water that we may easily prepare solu- 

 tions containing 60 to 66 per cent, of the salt. The magnetic rotation 

 of the plane of polarization produced by these solutions is weaker 

 than that of pure water, but it is much greater than that which 

 would be produced by the quantity of water alone which enters into 

 the solution. The experiment, therefore, merely proves that the 

 nitrate of ammonia gives the solution a rotatory power less than that 

 of water, but still in the same direction. — Comptes Rendus, Sept. 8, 

 1856, p. 529. 



ON THE POSSIBILITY OF THE SIMULTANEOUS EXISTENCE OF OP- 

 POSITE ELECTRICAL CURRENTS IN THE SAME CONDUCTING 

 WIRE. BY PROFESSOR G. BELLI. 



The author's object in this paper is to show that the galvanometer, 

 by means of which many physicists have endeavoured to solve the 

 above question, is not adapted to furnish its solution. This has 

 already been pointed out by M. Soret, in a particular case, upon the 

 foundation of some considerations exactly analogous to those now 

 put forward in a much more general manner by M. Belli. The 

 latter shows that, — 



