742 PLUCKER ON THE DETERMINATION OP THE 



The first column in the preceding table exhibits the repulsion 

 which the various substances, when inclosed in the watch-glass, 

 experience from the influence of the electro-magnet, expressed 

 in grammes. In the second column the diamagnetic repulsion 

 of the water is placed at 100, and that of the other substances 

 is calculated from it. These numbers have a general signifi- 

 cation, and are independent of the volume and the shape of 

 the substance tested ; so that when we place the various sub- 

 stances in any other given form, and withdraw this in a corre- 

 sponding manner fi'om the poles, the same numbers must be 

 found. In the case of the powdered substances these numbers 

 are neglected, because they have not a general signification. In 

 the third column, the diamagnetic repulsion which equal iveights 

 of the substances examined experience, is expressed in numbers, 

 the repulsion of water being placed at 100. Thus these num- 

 bers give the corresponding diamagnetic repulsions, when we 

 place equal weights of the various substances, uniformly distri- 

 buted, in the same given form. The numbers corresponding to 

 the different powders here also have a perfectly definite signifi- 

 cation. In each case they were at last pressed into the watch- 

 glass with tolerable force, and as uniformly as possible, by means 

 of the cover. Assuming that they were uniformly pressed in, 

 their greater or less density has no influence upon the numbers 

 of the third column. 



42. To the preceding table I shall append the following ex- 

 planations and remarks. 



The mercury examined was pure. The watch-glass was filled 

 with it, as with the other liquids ; but, assuming a convex form 

 at the margin, it elevated the cover, so that at that part most 

 remote fi'om the two halves of the keeper its form became some- 

 what changed. The diminution of the diamagnetic repulsion 

 arising from this cause is scarcely perceptible. 



Impure mercury may exhibit magnetic reactions (70.). 



43. The phosphorus was fused in water, poured into the watch- 

 glass, and wiped off with the cover. It then solidified within it. 

 With this same mass of phosphorus some preliminary experi- 

 ments were previously made. With a weak current (the mag- 

 netism being excited by only four Grove's cells) the intensities 

 of the diamagnetic repulsion of the phosphorus and of the water 

 were especially compared. The former was repelled with a force 

 of 0'14 grm., the latter with a force of 0-08 grm. ; hence the 



