378 Of the Propagation of Heat 



of that Heat — extreme in its intensity, or degree, but 

 small in regard to its quantity, or to the space it occu- 

 pies — which is generated in the particle of amber in the 

 experiment under consideration. 



As this Heat must first exist where it is generated, it 

 is evident that it must exist at the surface of the particle 

 of amber ; and as all solid bodies are, in a greater or 

 less degree, conductors of Heat, a part of this Heat will 

 penetrate the substance of the solid particle, while 

 another part of it will be carried off by the cold particles 

 of water in contact with the surface thus heated by the 

 light. 



It remains, therefore, to be determined what the effects 

 are which this Heat — so absorbed, on the one hand, by 

 the solid particle of amber, and communicated to the wa- 

 ter, on the other — ought necessarily to produce. And 

 first, if the dispersion of the Heat by both these means 

 should be sufficiently rapid to prevent its accumulation to 

 such a degree as to melt the amber, it is evident that no 

 visible effects by which its existence could be discovered 

 would be produced in that substance ; and this event 

 (the fusion of the amber) will depend on three circum- 

 stances, namely, — First, on the temperature at which 

 amber melts ; Secondly, on the facility with which Heat 

 expands and is dispersed in a solid mass of that sub- 

 stance, or on its conducting power ; and Thirdly, on the 

 rapidity with which the Heat generated at the surface of 

 the amber is carried off by the cold Fluid in which it is 

 immersed. 



Though I do not think there would be any reason for 

 surprise, even admitting the existence of the supposed in- 

 tense Heat, should the amber be found not to be melted 

 under the circumstances described, yet it appears to me 



