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XVI. On the Repulsive Action of the Pole of a Magnet upon 

 Non-magnetic Bodies. By Professor Reich of Freiberg^. 



THE repulsion which takes place, according to Faraday's re- 

 cent observations, between the pole of a magnet and every 

 diamagnetic substance, apparently with the exception of the 

 atmosphere, is to my mind so new and surprising an exhibi- 

 tion of force, that probably some observations on the subject 

 will be considered worthy of attention, even though they 

 merely confirm what Faraday has found, if they exhibit this 

 repulsion in a more easy and direct manner. 



For these observations I employed a torsion- balance which 

 had been arranged to determine the mean density of the earth. 

 A horizontal wooden rod two metres in length is suspended by 

 means of a copper wire to a strong iron beam fastened into a 

 massive wall, and at each of its extremities a metallic ball is 

 suspended by a fine wire. The whole is inclosed in a wooden 

 case, which, however, is nowhere in contact with the torsion- 

 balance. The torsion-rod carries a mirror, in which the posi- 

 tion of the rod is observed with a telescope upon a distant scale. 

 The force required to deflect the rod a certain quantity from 

 its position of rest results from the following expressions, which 

 will likewise show the very great sensitiveness of the apparatus. 

 The mass of the whole moveable portion of the torsion-balance 

 reduced to the central point of one of the two balls is 

 ss^'s 1031 560 milligrammes. The distance of the central 

 point of either ball from the axis of rotation is = r = 10005 

 millimetres. The horizontal distance of the mirror from the 

 scale which is divided into millimetres is =]«. = 42827 milli- 

 metres ; if, therefore, we suppose the deflection of the ball from 

 its position of rest to be = A millimetres, and the number of 

 divisions of the scale corresponding to this deflection to be 

 = B millimetres, then 



A — ' R — ^^Q^^ R 



~ 2/Z ~ 85654- ' 



and the force which deflects the ball A millimetres from the 

 position of rest, with a time of vibration = N seconds, 



g-.A __ rg.B 



Wl ~2fi.W.l' 



I being the length of the seconds' pendulum in millimetres. 

 When the torsion-rod vibrates without any external action upon 

 the balls, N is very nearly = 350 seconds, which gives a de- 

 flecting force of 0*00098956 B milligrammes. But B may 



* From Poggendorff's Anruden, vol. Ixxiii. p. 60, 



