Prof, Weber on the Theory of Diamagnetism. 409 



agree with you, but I only wish to convince you that this objec- 

 tion applies really to the theory of Ampere, and only applies to 

 mine in so far as it is built upon the former. (You may per- 

 haps find less ground for objecting to the speciality of such an 

 assumption, if you separate the simple fundamental conception, 

 which recommends itself particularly by a certain analogy of the 

 molecules to the heavenly bodies in space, from those additions 

 which Ampere was forced to make, in order to apply the mathe- 

 matical methods at his command, and to make the subject one 

 of strict calculation. He was necessitated to reduce the case to 

 that of linear currents, which necessarily demand channel-shaped 

 bounds, if every possibility of a lateral outspreading is to be 

 avoided.) 



To place my theory of diamagnetic polarity in a truer light, I 

 am anxious also to convince you that this theory is by no means 

 based upon new assumptions (hypotheses) ; but that it only rests 

 upon such conclusions as may be drawn from the theory of 

 Ampere, when the laws of voltaic induction discovered by Faraday, 

 and the laws of electric currents by Ohm, are suitably connected 

 with it. 1 affirm, that, even if Faraday had not discovered dia- 

 magnetism, by the combination of Ampere's theory with Fara- 

 day's laws of voltaic induction, and Ohm's laws of the electric 

 current, as shown in my memoir, the said discovery might 

 possibly have been made. 



In respect, however, to the artificiality of the theory of Ampere, 

 I hope that mathematical methods may be found whereby the 

 limitation before mentioned to the case of linear cuiTents may be 

 set aside, and with it the objection against channel-form beds. 

 All our molecular theories are still very artificial. T for my 

 part find less to object to in this respect in the theory of Ampere 

 than in other artificialities of our molecular theories j and for 

 this reason, that in Ampere's case the nature of the artificiality 

 is placed clearly in view, and hence also a way opened towards 

 its removal. 



To Mr. Faraday I beg of you to present my sincerest respect. 

 Believe me, dear Sir, 



Most sincerely yours, 



•WiLHELM Weber. 

 Professor Tyndall. 



The foregoing letter possesses more than a private interest, 

 and I have therefore laid it before the readers of the Philo- 

 sophical Magazine. On one ])oint in it only would I ask per- 

 mission to make a i-emark, and that is the proposition, that 

 the diminution of the excitement of a row of bismuth particles 



Phil. May. S. 4. Vol. 10. No. 68. Dec. 1855. 2 E 



