UPON GASES AND LIQUIDS. 5'jl 



after the excitation of the magnetism, an ellipse, the axes of 

 which were 33 milUms. and 26 millims. in length. 



42. In all the preceding experiments ten of Grove's cells were 

 set in action ; but a single cell only was sufficient to render the 

 effect perceptible. In the experiments upon flame, desci-ibed in 

 the earlier paragraphs of this memoir, tivo cells at least were 

 required for this purpose. To observe the effect with less power- 

 fully magnetic liquids,the halves of the keeper were usually placed 

 at a distance of 2 millims. to 4 millims. apart. The reflection of 

 the window in the liquid much facilitated the observation of the 

 magnetic action, especially in those cases where the expansion 

 and contraction of the fluid was only slight and difficult to be 

 perceived. A solution of commercial sulphate of copper afforded 

 an instance of a slightly magnetic fluid, probably in consequence 

 of its containing iron, as did likewise a solution of protosulphate 

 of iron in water, 1 part to 50 by weight. 



43. It was an important point to subject diamagnetic as well as 

 magnetic liquids to the same experiment; the results corre- 

 sponded to my anticipations. When the two halves of the 

 keeper were 2*5 millims. apart, the section in fig. 8 a correspond- 

 ing to the magnetic fluids became that represented in fig. 13. 

 [In this and the following figure the diamagnetic effect is repre- 

 sented as of greater intensity than really occurs with the above 

 intensity of the current.] The fluid was expanded in the axial, 

 whilst it was contracted in the longitudinal direction. Above 

 the centre between the two halves of the keeper, only a clepi'ession 

 contracted in the equatorial direction was formed, instead of the 

 former elevated ridge. When the two halves of the keeper were 

 15 millims. apart, instead of the section of the magnetic liquid 



"represented in PI. IV. fig. 10 c, a section of the form of fig. 14 

 '*was produced. The fluid expanded both in the axial and equa- 

 ''torial direction, forming in the equatorial plane an elevated ridge 

 ''^nd two depressions parallel with it, the perpendicular projec- 

 '^lions of which were in contact with the upper angles of the halves 

 of the keeper. 



44. It Mas always found, when the two halves of the keeper 

 were retained at a distance of from 2 to 4 millims, apart on account 



■'bf the greater magnetic tension, that no one of the various fluids 

 '•Vhich I examined was found to be indifferent. In this way, 

 •tlfnongst others, the following bodies were found to be diamag- 

 netic: — water, alcohol, sulphuric ether, sulphuric acid, nitric 



2 q2 



