INTENSITY OF MAGNETIC AND DIAMAGNETIC FORCES. 723 



By the inductive action of the two portions upon each other, 

 the attraction is here also increased. 



14. Our views allow of our determining the interfering effects 

 of induction in each of the present cases. 



For the purpose of measuring the more powerful attractions, 

 I had a brass cup made of the shape of a watch-glass, and its 

 upper margin was ground, so that it might be filled with liquids 

 and powders, exactly like the above-described watch-glass. A 

 massive piece of iron accurately fitted its cavity : this could be 

 removed and replaced by other substances; for the present pur- 

 pose these were finely-divided iron, and a fatty mixture consisting 

 of twenty-five parts of lard to one part of the iron-filings, 'ihe 

 adjustment was as before, the distance of the heavy rounded 

 keepers 6 millim. ; the only difference w^as that the cup was not 

 immediately laid upon the keepers ; but to diminish the force, a 

 glass plate 4 millim. in thickness was first placed upon the keepers, 

 and the attraction at this point measured. The magnetism was 

 excited by one Grove's element with nitric acid which had been 

 once used. The following are the results : — 



grms. 

 I. Weight of the iron in the cup . . . 81*0 



Its attraction 2187'5 



II. Weight of iron-fihngs in the cup . . 32*85 



Its attraction 996*0 



III. Weight of the fatty mixture in the cup 10*00 

 Its attraction 12*80 



The attraction of the cup itself with the glass cover, which 

 amounted to 8*36 grms., has been deducted throughout. 



Hence, when we calculate the attraction which one gramme 

 of iron experiences in the three separate weighings, we find — 



grms. 

 I. for the massive piece of iron .... 27*00 



II. for the iron-fihngs 30*32 



III. for the same in the fatty mixture . . . 33*28 



It is thus seen that the disturbing action of induction dimi- 

 nishes the total attraction of the molecule of iron. If we admit 

 that this disturbing action vanishes in the case of the fatty 

 mixture, which is at least approximatively correct, the attrac- 

 tion of the piece of iron and of the iron powder, independently 

 of the disturbing effect of the induction, as it immediately arises 



