I 



on the Polarity of the Diamagnetic Force, 177 



From the position which it occupies in Mr. Faraday's list*, I 

 had also some hopes of proving the polarity of sulphide of car- 

 bon. The following results were obtained : — 



XVIL 



Cylinders of Bisulphide of Carbon. 

 Length 4 inches. Diameter 0*65. 



Current direct. Current reversed. 

 Position 1. 631 210 



Position 2. 629 213 



Position 3. 626 216 



As in the case of distilled water, we observe a deflection in one 

 directien when the current is " direct '^ and in the other when it 

 is " reversed/' the action in the first case, in passing from posi- 

 tion 1 to 3, amounting to five, and in the latter case to six divi- 

 sions of the scale. The polarity exhibited is that of diamagnetic 

 bodies. 



Deportment of Magnetic Bodies. 



Thus far we have confined our examination to diamagnetic 

 substances ; turn we now to the deportment of magnetic bodies 

 when submitted to the same conditions of experiment. Here 

 we must select the substances suitable for examination, for all 

 are not so. Cylinders of iron, for example, of the same size as 

 our diamagnetic cylinders, would, through the intensity of their 

 action, quite derange the apparatus ; so that we are obliged to 

 have recourse to bodies of smaller size or of feebler magnetic 

 capacity. Besides, the remarks of writers on this subject render 

 it of importance to examine whether bodies through which the 

 magnetic constituents are very sparingly distributed present a 

 veritable polarity the same as that exhibited by iron itself. 



Slate rock usually contains from eight to ten per cent, of oxide 

 of iron, and a fragment of the substance presented to the single 

 pole of an electro-magnet is attracted by the pole. A cylinder of 

 slate from the Penrhyn quarries near Bangor was first examined. 

 It was not found necessary to increase the effect by using two 

 cylinders, and the single one used was suspended in the right-hand 

 helLx H'E'. The deportment of the substance was as follows : — 



XVIII. 



Cylinder of Penrhyn Slate. 



Length 4 inches. Diameter 0*7. 



Current direct. Current reversed. 



Position 1. 620 280 



Position 2. 647 240 



Position 3. 667 198 



* Phil. Mag. March 1853, p. 222. 

 Phil Mag, S. 4. Vol. 12. No. 78. Sept, 1856. N 



