378 PLUCKER ON THE RELATION 



5. It appeared to me to be hazardous to form general conclu- 

 sions upon magnetism and diamagnetism from the experiment 

 detailed in the last paragraph, which I had made even before 

 writing my former treatise, inasmuch as it was to be feared that, 

 with the complicated structure and chemical properties of the 

 substance used, some unknown extraneous cause might have 

 produced the phaenomenon observed. Further experiments must 

 decide whether all substances, which at a certain distance from 

 the pole become placed (with slight force) magnetically, when 

 moved nearer to the pole react diamagnetically ; and the next 

 problem was, to find more simple substances which were mag- 

 netic in the slightest possible degree. For this purpose, I took 

 tinfoil, which was magnetic (probably from its containing iron), 

 and fused it with some bismuth. With the proper proportions 

 in this alloy (more bismuth than tin), which I poured out 

 upon paper into a thin bar of about 15 millira. in length, I 

 obtained my object. The bar was affected in exactly the same 

 manner as the piece of cherry-tree bark, i. e. it became axial or 

 equatorial, according as the apices of the poles were more or less 

 distant from each other. From this I draw the conclusion, that 

 it forms a general law, and not merely an isolated phaeno- 

 menon. A similar one has already been observed by De la Rive 

 in charcoal*. I may remark here, that whilst Faraday found 

 charcoal magnetic, I found common wood-charcoal, as also box- 

 wood charcoal prepared for electrical experiments, diamagnetic, 

 which cannot surprise us, because the smallest quantity of iron 

 mixed with it, which may even arise from the body, must 

 make charcoal magnetic; and thus, among the specimens of 

 charcoal examined by Faraday and myself, there would be some 

 which are affected in the same manner as the above alloy. 



6. I therefore adhere to the following hypothesis, which at 

 present has the best foundation, that the magnetic and dia- 



* The part of the Bibliothcque Universdle for June, p. 171, contains my first 

 notice upon the relation of magnetism to the optic axes, as published in the 

 Compfes Rendiis, from a letter to M. Arago, dated June 14th, to which the 

 following note is appended by M. De la Rive: — 



Like M. Plikker, I have made a great many experiments upon the action of 

 the magnet upon different bodies. I shall mention one here which has yielded a 

 similar result to those obtained by M. Pliicker ; it relates to the action of the 

 electro-magnet upon charcoal, a substance which I have sometimes found mag- 

 netic, sometimes diamagnetic, according to its molecular stale, and sometimes 

 also according to its distance from the poles of the magnet. 



It was in consequence of this note that in the present short essay I treat of 

 an object which it was my intention to discuss subsequently in connexion with 

 some others. 



