WITH MAGNETISM AND ELECTRICITY. 195 



hence the hypothesis of Ampere, according to which the mole- 

 cules are the rotatory bearers of permanent molecular cun-ents, 

 and no proportionality between the magnetism and the magnet- 

 izing force exists, must be set in its place. This consequence 

 of the theory admits of being brought to the test of experiment, 

 and with reference to it the experiments of Miiller have been 

 already adduced. Other experiments have however been made, 

 particularly by Buff and Zamminer, which have led to dif- 

 ferent results. Before repeating these experiments it will be 

 first necessary to state the conditions upon which a certain de- 

 cision of the point depends. 



From Miiller's experiments, it appeared that the divergence 

 of the magnetism of iron from a proportionality with the mag- 

 netizing force exhibited itself at much smaller intensities of 

 the latter in the case of thin bars than when thick bars were 

 made use of. In the comparison of Miiller's experiments with 

 those of Buff and Zamminer, we must remember that the thin- 

 nest bar made use of by Miiller was only 6 millimetres thick, 

 while the thinnest of those used by Buff and Zamminer was 9 

 millimetres thick ; and this difference was rendered more in- 

 fluential by the relation of the length to the thickness ; Miil- 

 ler's thin bar was 330 millimetres long, while that of Buff 

 and Zamminer was only 200 millimetres. In the following ex- 

 periments a still thinner bar than that of Miiller was made use 

 of, namely, one 3*66 milUmetres in thickness, 100*2 in length, 

 and 8190 milligrammes in weight. The magnetism of such a 

 thin bar may be measured wuth great exactness by the deflection 

 which it is able to produce upon a small magnetometer, placed 

 at a distance, and observed by means of a telescope and mirror. 

 The only difficulty here is the proper separation of the action of 

 the magnetized iron from that of the galvanic current. It is 

 manifest that when the same galvanic spiral is applied to the 

 magnetization of thick and thin bars, as has been the case with 

 Miiller, Buff and Zamminer, the above separation admits of less 

 accuracy in the case of thin bars ; for here, inasmuch as the action 

 of the galvanic spiral remains the same, its comparative influence 

 will be greater than when thick bars are applied. In the fol- 

 lowing experiments, therefore, a spiral was made use of which 

 tightly embraced the thin bar ; and besides this, it was arranged 



