380 PLUCKKR ON THE RELATION 



simple body react in this manner? I consider that a direct 

 answer to this question by means of experiment is at present 

 impossible, because we could not ensure certainty that those 

 simple bodies which exhibit slight magnetic and diamagnetic 

 properties, according to Faraday, are really chemically pure. 



8. When we conjoin the observations described in the present 

 treatise with those which I have detailed in the previous memoir, 

 it results, that of the threefold action emanating from the poles 

 of a magnet, viz. 



1st, the magnetic action in a strict sense; 



2nd, the diamagnetic action discovered by Faraday ; 



3rd, the action exerted upon the optic axes of the crystals (and 

 that producing the rotation of the plane of polarization, which 

 probably corresponds to it) * ; 



the second diminishes more with the distance than the first, and 

 the first more than the third. 



9. As I was looking through the above memoir, it occurred to 

 me (in which case the conclusion made at the end of paragraph 

 5 would retain its general correctness) that Faradaj^ might 

 have found charcoal magnetic, and T diamagnetic, because I 

 placed it so as to oscillate at a less, and he at a greater distance 

 from the poles. Moreover, it appeared to me desirable to con- 

 firm the general result in paragraph 6 by new experiments. I 

 therefore made the following experiments, in which I again pro- 

 ceeded in the manner described in the former memoir, but using 

 ten feebly-excited Gi'ove's elements instead of the former five. 



10. I at first fovmd my supposition completely confirmed. 

 I examined four dift'erent pieces of charcoal successively, all of 

 which were acted lapon in exactly the same way ; and, according 

 as the distance of the extremities of the poles was more or less, 

 arranged themselves magnetically or diamagnetically. I shall 

 only detail one experiment. One of these pieces of charcoal 

 (ordinary wood- charcoal) was cylindrical, about 14 millim. long 

 and 6 millim. thick. When the poles were 17 millim. apart, it 

 arranged itself equatqrially ; but when raised 24 millim. above 



* The appai'ently equal illumination of the eittire field by respectively equal 

 intensities of colour, after the rotation of the planes of polarization in Faraday's 

 expeiiments, proves that the action observed here does not diminish very 

 rapidly with the distance. 



