380 Intelligence and Miscellaneous Articles, 



And putting 



w=Asin — 2rr, 



A. 



M = Bsinl27r, 



({*+») 



Csin 



we get for the determination of C and $ the following equations, 

 2tt 

 'T 



^QCsinS-W Ocosa = J A.. 



W CsinS+^QCcos3 = -^B, 

 from which follows 



^(J AQ-W B) 

 C sin 2 = — — — J - ., ■ ■> 



C cos 2= ■» ■ 2 i ■ ■. 



If the ratios be chosen (as can be done in various ways) so that 



J AQ-W B = 0, 



then a = 



and C=-J A. 



Thus the electrical conveyance will not introduce any alteration 

 either of the phase or in height or depth of tone.— -"Wiedemann's An- 

 nalen, 1879, No. 3, vL pp. 403-407. 

 Charlottenburg, December 1878. 



ON THE VARIATION OF THE THERMAL CONDUCTIVITY OF METALS 

 WITH TEMPERATURE. 

 To the Editors of the Philosophical Magazine and Journal. 

 Gentlemen, 

 Dr. Hopkinson has kindly pointed out to me, in my last paper 

 published in your recent issues (March and April), a slip of a fun- 

 damental character, which I am sorry to say renders the latter half 

 of that paper questionable, if not, as I fear, erroneous. I hope 

 shortly to be able to find time to go through the calculations again 

 and make the necessary modifications ; but in the meantime I must 

 beg your readers to treat the paper as if it had not yet appeared. 

 I am, Gentlemen, 



Tour obedient Servant, 

 April 7, 1879. Oliver J. Lodge. 



