252 M. F. Reich on Diamagnetic Action. 



sities of the bundles by the deflection of a compass-needle placed 

 at a metre distance, and obtained as follows : — 



Nos. 1 to 8, a deflection of 1 1 3, intensity 1 

 ... 1 ...16, ... 15 45, ... 1-4442 



... 1 ...24, ... 21 42, ... 2-0378 



... 1 ...32, ... 27 3, ... 2-6148 



The relation of the squares of these intensities is therefore 

 expressed by 1 : 2-0857 : 4-1525 : 6-8369. The position of equi- 

 librium of the torsion balance was then observed : — 



Without magnet beginning 57-875 ^^^^ ^g.^^^Q 



By Nos. 1 to 8 beginning 55-125 p.. wnf-rj 



end 56-325 - ^^'^"^^^ 



... 1 ...16 beginning 51*975 ki.qqtk 



end 52-900 '•• ^^ ^»^^ 



... 1... 24 beginning 46-300 a^.^iok 



end 46-725 - ^^^^^^ 



... 1 ... 32 beginning 39-625 QQ.KryoK 



end 39-525 - ^^^^^^ 



From this we obtain the repulsion, — 



Nos. 1 to 8 3-1750 divisions =0-3709 millims. =1 



... 1 ... 16 6-9125 ... =0-8074 ... =2-1772 



... 1... 24 12-3875 ... =1-4470 ... =3-9016 



... 1 ... 32 19-3250 ... =2-2573 ... =60866 



This ratio of the repulsions does not diff'er more from that of 

 the squai-es of the magnetic strengths than may be referred to 

 the increase of distance with the repulsion ; for assuming for C 

 the not improbable value of 70 millims., we obtain the ratio of 

 the repelling forces to be — 



1 2-0857 4-1525 6-8369 



(70-3709)4 • (70-8074)4 ' (71-4470)^ ' (72-2573)" 

 = 1 : 2-0347 : 3-9080 : 6-1504, 

 which does not differ from the ratio of the observed repulsions 

 more than may be accounted for by the unavoidable errors of ob- 

 servation. 



Third experiment. — As the application of an electro-magnet 

 permitted us to hope for more exact results, because, while the 

 position of the magnet remains wholly unchanged, it is in our 

 power to change and measui-e its strength at pleasure, I placed 

 a round bar of iron, 32 millims. thick and 440 millims. long, 

 contained within a spiral of thick copper wire, horizontally near 

 the sphere of bismuth, so that its nearest end was 67 millims. 

 from the chamber of the torsion balance, and permitted a cur- 



