716 PLUCKER ON THE DETERMINATION OF THE 



My watch-glass and the brass ring in which it is suspended 

 are both magnetic ; therefore if I place any diamagnetic sub- 

 stance in the former, the attraction which we observe is the 

 excess of the magnetic attraction of the two former over the 

 diamagnetic repulsion of the latter. This attraction was stronger 

 than the diamagnetic repulsion of almost all the substances I 

 examined, so that the filled glass was always retained by the two 

 portions of the keeper, and could be pulled off like a magnetic 

 body. If then we subtract from the attraction of the empty 

 glass the smaller attraction of the glass filled with a diamagnetic 

 substance, we obtain the diamagnetic repulsion, which the latter 

 experiences by the electro-magnet. In this manner we are able 

 to compare the diamagnetism of different fluids of the same 

 form and volume, and of any bodies to which by fusion or 

 otherwise we can impart the form of the interior of the watch- 

 glass. 



7. To give the idea of the determination of a molecular mag- 

 netism laid down in paragraphs 2 to 4, and its relative intensity 

 in different substances a sure basis, we must first of all show 

 experimentally that when in the same volume having the same 

 boundaries in one case m times as many magnetic molecules of 

 the same substance are uniformly distributed as in any other case, 

 the resulting magnetic attraction in the one case is also m times 

 as great as in the other, so long at least as the magnetic particles 

 are not so close together that magnetic excitation of one portion 

 of the mass can exert a perceptible influence upon the magnetic 

 excitation of the other portion. 



8. I first took a somewhat concentrated solution ofprotochloride 

 of iron, and mixed one part of it with an equal volume of distilled 

 water, so that the mixture in the same volume contained only 

 half the original solution of the chloride ; hence also only half 

 the original quantity of the chloride and half only of the original 

 quantity of iron. This mixture was again diluted to twice its 

 bulk, and the solution thus obtained again diluted to two vo- 

 lumes. Hence in the four solutions which we shall denote by 

 I. II. III. and IV,, the quantities of the uniformly distributed 

 magnetic substance were in the following proportions : — 



8:4:2:1. 

 The watch-glass previously mentioned was first used in the 

 empty state, then filled with distilled water, and lastly with the 

 four solutions in succession ; the adjustment being the same as 



