between Metallic Masses having different Temperatures. 17 



cessive hypotheses. The real difficulty of the subject, and 

 the singular conclusions deducible from several of my experi- 

 ments, led me to delay putting together the facts which I had 

 accumulated, into the form of a paper. Nearly two years 

 having now elapsed since the commencement of my experi- 

 ments (which were almost all made in the summer of 1831), 

 and no one else having taken up the investigation, I have re- 

 solved to publish the conclusions at which I have arrived, 

 though such as are purely theoretical I offer with all the dif- 

 fidence which a speculation connected with some of the most 

 unexplained processes in natural science requires. 



3. I propose to divide this paper into three sections, — first, 

 on the Phaenomena of Sound, as those which earliest pre- 

 sented themselves, and the consideration of which will pave 

 the way to further inquiries ; second, on the Phaenomena ot 

 Vibration ; and, third, on the Theory of these Phaenomena. 



I. Phaenomena of Sound. 



4. Musical sounds do not always accompany the vibrations 

 above described. There is one condition or modification of 

 the apparatus which generally ensures their production. If a 

 groove be made either in the bar or block, as shown in the 

 sections, fig. 2, in the direction of the axis of the bar, and se- 

 parating the points of contact with the 



block, upon which the bar oscillates, we Fig. 2. 



shall rarely fail in producing the sound. p"— ~ ~~" 

 These sounds generally commence with Wi, j 



a deep base note, which rises as the ex- ^^B 

 periment proceeds, and as the equili- fj| 

 brium of temperature of the two metals ^ "y0W 



approaches ; sometimes rising suddenly 

 an octave in the most fitful manner, and 

 occasionally redescending. Mr. Trevel- 

 yan, in his paper just alluded to, has 

 treated of the sounds thus produced, and 

 seems to consider the phaenomena intro- 

 duced by the condiion of the groove, of 

 an essentially different class from the 

 others. He assumes that the only effect of the groove is, that 

 it may allow a current of heated air to pass through it ; yet 

 he admits that this current is not sufficient alone to produce 

 musical notes, because no such occur when vibrations do not 

 take place; nor yet, according to him, do the vibrations suf- 

 fice, since they require the supposed current of air introduced 

 by the groove to complete the effect. In his enumeration of 

 the sources of musical notes, Mr. Trevelyan has omitted to 

 Third Series. Vol. 4. No. 19. Jan. 1834. D 



