454 Prof. FORBES on the Vibrations which take place 



52. This more difficult task was undertaken by Mr FARA- 

 DAY ; and in a lecture on the subject which I was fortunate 

 enough to hear at the Royal Institution in April 1831, he freed 

 the subject (as we have already seen) from many of the difficul- 

 ties with which it had been surrounded, and illustrated the 

 theory which he supported, in that happy style for which he is 

 so remarkable. 



53. The principle which he adopted was fundamentally the 

 same as that of Sir JOHN LESLIE, but he added an explanation 

 of the influence of the properties of different metals upon the 

 phenomena. According to his view, the hot metal should have 

 a higher conducting power, and a smaller expansion by heat, 

 than the cold one, and the arrangements of the metals as vibra- 

 tors depend, according to him, upon this principle. To employ 

 the official statement of his views contained in the Royal Insti- 

 tution Journal *, " the superiority of lead, as the cold metal was 

 referred to its great expansive force by heat, combined with its 

 deficient conducting power, which is not a fifth of that of cop- 

 per, silver, or gold ; so that the heat accumulates much more 

 at the point of contact in it, than it could do in the latter 

 metals, and produces an expansion in that respect proportional- 

 ly greater." 



54. I certainly approach with deference any opinion express- 

 ed by a philosopher of the reputation and acuteness of Mr 

 FARADAY, and nothing but a strong conviction, entertained 

 chiefly upon the general grounds already alluded to, could have 

 induced me to spend my time in an investigation, which he con- 

 sidered decided upon some of the simplest principles pf physics. 

 My dissatisfaction with the explanation increased the more I 

 thought of it, and the more closely I analyzed the natural pro- 



New Series, No. IV. p. 119, 122. 



