POGGENDORFF ON CLOSED ELECTRO-MAGNETS. 295 



If the quotients obtained by dividing the differences of the 

 currents by the corresponding differences of the lifting powers 

 be compared, the above proposition will follow. 



Considering the great difficulty presented to the accurate 

 determination of the lifting power, the author does not intend 

 to claim a high degree of exactitude for the above numbers ; 

 neither does he believe that the numbers express a general law ; 

 for not only is the progression of the lifting power dependent 

 on the character of the magnet and its keeper, but also on the 

 absolute strength of the current, or rather the magnitude of the 

 galvanic moment*. But the convergence of the progression he 

 regards as placed beyond doubt by the above and other results 

 which he has obtained ; indeed, if such were not the case, it 

 would be possible to obtain infinitely great lifting powers, which 

 is not only very improbable, but also directly opposed to the 

 results established by J. Miiller, as also to the necessary limit- 

 ation of magnetization which follows from the theory of Am- 

 pere t» 



The great divergence of the lifting powers from the laws of 

 attraction at a distance, established by Lenz and Jacobi, is 

 strikingly exhibited. If the excitation of magnet and keeper 



* Under galvanic moment, the author understands the product of the 

 strength into the length of the current, multiplied by a coefficient which de- 

 pends upon the form and distance, which, however, like the length of the mag- 

 netizing current, remained constant throughout these experiments. 



f [This remark appears to us to put the disputed question of magnetic satu- 

 ration in a new and simple light. The author, if we understand him aright, 

 considers the act of magnetizing to consist in the setting of the molecular 

 currents of Ampere parallel to a common plane. With weak currents, this 

 parallelism is but partially established, and becomes more complete as the 

 strength of the current is augmented. When complete, further magnetization 

 is impossible, or, in other words, the point of saturation has been attained. 

 See Weber's investigation, Scien. Mem. Feb. 1853, p. 197. J. T.] 



