234 Experiments on Diamagnetism. 



earth from a great height, applied to the discovery of diamagnetism 

 the observation, neglected by other philosophers, that the two poles 

 of the magnet employed together did not produce upon the body 

 a repulsion equal to the sum of the repulsions effected by each, 

 but equal to their difference ; to the end — that their united ef- 

 fect would be null when their forces are equal. At the same time 

 he made some experiments which seemed to indicate that the 

 pole repelling a diamagnetic body, produces in the adjoining 

 parts of another diamagnetic body a magnetic force like its own. 

 M. Wilhem Weber confirmed the idea of M., Reich by his learned 

 researches, and showed that diamagnetic bodies receive by the in- 

 fluence of an electro-magnet, a transversal magnetism having two 

 poles, but so disposed that each of them has the same sort of 

 magnetism as the nearest pole of the electro-magnet. M. Poggen- 

 dorff contrived other experiments of a decisive character that 

 have the advantage of proving the idea in an easy manner ; and 

 M. Plucker adds also a new experiment which increases if not 

 the certainty of the result at least the facility of arriving at it. 



These are the labors which served as a starting point for my 

 researches. I used for my experiments the great electro-magnet 

 of the Polytechnic School of Copenhagen, in the form of an U, 

 and capable of supporting 1,400 kilogrammes.* Meanwhile it may 

 be remarked that it was not necessary to put all its force in action 

 for these experiments; but we rarely used less than half of this 

 force, although the greater part of them could be executed with a 

 much more feeble power, even with one element. Each extremity 

 of the electro-magnet carried a piece of iron horizontally which 

 we call a polar-piece. These polar pieces serve to give to the 



action of the electro-magnet a horizontal direction. It is be- 

 tween the two perpendicular faces situated vis-a-vis to one an- 



• I here conform to the ordinary manner of indicating the force of a magnet; 

 although uncertain, U has heen proved upon this electro- magnet and communica- 

 ted to the Royal Society in their session of 17th Dec. 1847. In these experi- 

 ments the weight which the eiectro-magnet was , apable of supporting, was tried 

 when its poles were armed with different masses of iron. To certain limits tl 

 anpportinsr power increases very nearly in proportion to the mass of the armature. 

 But that which most merits our attention is that the force of the electro-magnet, 



*% *T r » ft* j- \ .. 4 jr* ** rf-J ■ arm *«* _**. * . *_ I _ »_ * ■ £* a Li *» 



expressed in weight, does m,t bear the same ratio to the electro-motive power ot the 

 galvanic machinery whilst the armature is in contact with the electro-magnet and 

 when at a distant from it. In contact, the mean power of each galvanic element 

 was 7U-o kil., hut two elements united gave only 72 the sum of power of each 

 element, three elements united gave only GMtf, eight 0-26, sixteen 0-125, the sum 

 of ( h power ; to the effect that nixteeo elements were only double the power of 

 one element. At the distance of 1 33 mm. the effect of one element was only 0-J/O 



of that of the san :<■ element, in the case of contact ; but the product increases qiiiW 

 differently with the number of the elements. Sixteen dements give here Jour 

 times the product of one alone. At the distance of 2-225 mm. the product or 



permit 



