stipposed Polarity of Diamagnetic Bodies. 9 3 



piece of bismuth or other body whose effects were to be ob- 

 served and compared. 



2653. A thin glass tube, of the given size (2643.), S\ by f 

 inches, was filled with a saturated solution of protosulphate of 

 iron, and employed as the experimental core: the velocity 

 given to the machine at this and all average times of experi- 

 ment was such as to cause five or six approaches and with- 

 drawals of the core in one second; yet the solution produced 

 no sensible indication at the galvanometer. A piece of mag- 

 netic glass tube (2354.), and a core of foolscap paper, magnetic 

 between the poles of the electro-magnet, were equally ineffi- 

 cient. A tube filled with small crystals of protosulphate of 

 iron caused the needle to move about 2°, and cores formed 

 out of single large crystals, or symmetric groups of crystals of 

 sulphate of iron, produced the same effect. Red oxide of 

 iron (colcothar) produced the least possible effect. Iron 

 scales and metallic iron (the latter as a thin wire) produced 

 large effects. 



2654. Whenever the needle moved, it was consistent in its 

 direction with the effect of a magnetic body ; but in many 

 cases, with known magnetic bodies, the motion was little or 

 none. This proves that such an arrangement is by no means 

 so good a test of magnetic polarity as the use of a simple or 

 an astatic needle. This deficiency of power in that respect 

 does not interfere with its ability to search into the nature of 

 the phenomena that appear in the experiments of Weber, 

 Reich and others. 



2655. Other metals than iron were now employed and with 

 perfect success. If they were magnetic, as nickel and cobalt, 

 the deflection was in the same direction as for iron, When 

 the metals were diamagnetic, the deflection was in the con- 

 trary direction ; and for some of the metals, as copper, silver 

 and gold, it amounted to 60° or 70°, which was permanently 

 sustained as long as the machine continued to work. But the 

 deflection was not the greatest for the most diamagnetic sub- 

 stances, as bismuth or antimony, or phosphorus; on the con- 

 trary, I have not been able to assure myself, up to this time, 

 that these three bodies can produce any effect. Thus far the 

 effect has been proportionate to the conducting power of the 

 substance for electricity. Gold, silver and copper have pro- 

 duced large deflections, lead and tin less. Platina very little. 

 Bismuth and antimony none. 



2656. Hence there was every reason to believe that the 

 effects were produced by the currents induced in the mass of 



