between Metallic Masses having different Temperatures. 189 



cumulates much more at the point of contact in it, than it 

 could do in the latter metals, and produces an expansion in 

 that respect proportionally greater." 



54". I certainly approach with deference any opinion ex- 

 pressed 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, coidd 

 have induced me to spend my time in an investigation which 

 he considered decided upon some of the simplest principles 

 of physics. My dissatisfaction with the explanation increased 

 the more I thought of it, and the more closely I analysed the 

 natural process which he had traced out. I consider it essen- 

 tial to point out on what grounds I dissented from a theory 

 supported by two of the first names in British science, before 

 I proceed to give any opinion of my own, which may perhaps 

 be liable to equally strong objections, but the data of which are 

 not the less valuable as physical facts. 



55. Waving all minor objections, I conceive that the pro- 

 cess of the communication of heat, and consequently its effects, 

 would be very different from what has been stated in the pass- 

 age just quoted. Let fig. 9. represent on an exaggerated scale 

 the presumed state of the ap- 

 paratus in the middle of an 

 oscillation : the hot bar A, 

 whilst performing its vibra- 

 tion upon one of the solid an- 

 gles a, has expanded a por- 

 tion of the cold block BC 

 into a hillock at d: when 

 the semi- vibration is com- 

 pleted, the angle b of the bar will touch the block, and raise 

 a new hillock at the corresponding point c, whilst the ele- 

 vation at d subsides; and so on alternately. Let us con- 

 ceive that de is the finite depth to which heat is communi- 

 cated in the minute portion of time occupied by a semi-vibra- 

 tion, a depth so small as to be inappreciable by the senses, 

 and insignificant compared to the distances between the points 

 of impact dc. The elevation or height of the hillock da is 

 the amount of expansion of the element de, by the accession 

 of temperature received during a semi-vibration : the question 

 is, what relation will this expansion, or acquired vantage- 

 ground for the commencement of a new vibration, bear to the 

 nature of the block BC, considering the nature and tempera- 

 ture of the bar A, and the initial temperature of the block, to 

 be constant? It surely requires no elaborate demonstration to 

 prove that the amount of caloric which passes into the block 



