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LXVI. On the Law of Electric Discharge. By Dr. P. RiEss. 



To the Editors of the Philosophical Magazine and Journal. 

 Gentlemen, 



IN the May Number of your Magazine there is a paper of 

 twenty pages, entitled " On a General Law of Electric Dis- 

 charge, by Sir W. Snow Harris," which would, necessitate many 

 observations if all the errors contained in it were to be corrected. 

 As, however, this paper possesses rather a personal than a 

 scientific interest, I will confine myself to a very few remarks, 

 which may easily be added to by those familiar with the subject. 



The appearance of the above paper is not to be laid to my 

 charge. ^I. De la Rive, in his most recent English work, has 

 given in part to my investigations upon electrical heat that con- 

 sideration which they have long enjoyed in German works, and 

 has uot made use of Harris's labours upon the same subject. 

 That Sir W. Harris should gladly give importance to his own re- 

 searches is of course very natural ; but whether he has done it 

 in a proper manner others may judge. For my own part I have 

 only to observe, that it does not appear, to me to be altogether 

 just that he should make me answerable for statements which 

 are not derived from my original works, that he should ascribe 

 to me " a systematic disparagement " of his scientific labours, 

 and lastly, that he should allow himself (p. 359 at the bottom) 

 to express a suspicion regarding me. Against the two first pro- 

 ceedings I hereby remonstrate, and his suspicion I beg to say is 

 totally unwarranted. 



The subject which, according to the title, forms the principal 

 contents of the paper is easily dispatched, perhaps to the satis- 

 faction of the author. He has long since set up a law upon the 

 dependence of the electrical heat upon the charge of the battery. 

 I ascertained this law to be incorrect, and set another in its 

 place. Sir William Harris now seeks to bring the two laws 

 into agreement by the inadmissible process of giving a signifi- 



Q2 



cation to the symbol s in my formula T= — different from that 



given to it by me. He understands by it the resistance in the 

 circuit, although in the formula (which constitutes only a portion 

 of the general heat-formula) this ought not at all to be intro- 

 duced, as it is supposed to be constant. If the resistance in the 

 circuit is variable, not only this, but also the resistance in the 

 battery is expressed, which must have entirely escaped Sir W. 

 Harris, as he asserts (p. 354) that I had overlooked the latter 

 resistance. The question for him therefore is a simple one, 

 whether the formula referred to with the signification which I 

 attached to the symbol s be correct or false, and he may endea- 



