Intelligence and Miscellaneous Articles. 4<75 



great precision. Amongst other results obtained, I may refer to the 

 fact that the relation of the attraction exerted by a magnet upon 

 oxygen, to the repulsion which takes place with the same volume of 

 water, is in proportion to the density of the gas, and that it may be 

 represented by - 18 at a temperature of 53°"6 F. 



Since the publication of these researches, Faraday * has given for 

 the comparative action exerted upon oxygen and water, ascertained 

 by another method, a number similar to mine. M. Matteuccif has 

 also indicated a method by which he has succeeded in arriving at a 

 number which differs but little ; but M. PliickerJ has arrived at dif- 

 ferent results, by means of a balloon successively filled with oxygen 

 and empty, in contact with the armatures of an electro-magnet, 

 determining the weights necessary for the interruption of this con- 

 tact. If we reflect that the earth is surrounded by a mass of air 

 equivalent in weight to a stratum of mercury of 76 centimetres in 

 thickness, it is easy to understand that such a mass, subject to in- 

 cessant variations of temperature and pressure, must influence some 

 of the phenomena dependent upon terrestrial magnetism. Thus, if 

 we calculate the magnetic power of this gaseous mass, we shall find 

 that it is equivalent to an immense iron plate of a little more than 

 one-tenth of a millim. in thickness, which would cover the whole 

 surface of the globe. I have thought, therefore, that it would not 

 be uninteresting to examine afresh the action exerted upon oxygen, 

 air, and gases at different temperatures and at different pressures, so 

 as to determine their specific magnetism for different magnetic in- 

 tensities. 



As in my first researches I have referred all the determinations 

 to distilled water, and have determined by means of my delicate 

 balances the attractions and repulsions effected by a powerful electro- 

 magnet, of rather less power than that formerly employed ; I decided 

 upon this method, because M. Pliicker, having adopted an analogous 

 process, arrived at numbers differing from those given by me ; but I 

 avoided all contact between the bodies submitted to the action of the 

 magnets and the armatures, and I have reduced all the determina- 

 tions to the same temperature and pressure. 



In my previous experiments, I supposed in each case that the in- 

 tensity of the action exerted upon the substances examined varied 

 as the square of the intensity of the electrical current circulating 

 round the electro-magnet ; -but in these new researches, the action 

 exerted upon the bodies submitted to experiment being complicated 

 by that exercised upon the envelope, its adjuncts, &c, I preferred 

 the direct determination by experiment of the action exerted ««pon 

 each body at different magnetic intensities, varying the number of 

 couples employed from ten to sixty, and determining the intensity 

 of the current in each case by means of a tangent galvanometer ; it 

 was then possible by a very simple interpolation formula to find the 

 magnetic action exerted upon each substance, and at different deter- 

 minate and constant intensities. 



* Bibliotheejue Universelle de Geneve, 1853, p. 112. 



t Comptes Rendus, vol. xxxvi. p. 317- 



X Annates de Physique et de Chimie, vol. xxxiv. p. 342. 



