342 Of the Propagation of Heat 



As the oil was very transparent, and the jar placed in 

 a favourable light, the conical projection of ice was per- 

 fectly visible, even after the hot cylinder was introduced 

 into the jar; and had any Heat descended through the 

 thin stratum of fluid oil which remained interposed be- 

 tween the hot surface of the iron and the pointed pro- 

 jection of ice which was under it, there is no doubt but 

 this Heat must have been apparent, by the melting of 

 the ice ; which event would have been discovered, either 

 by the diminution of the height of this projection, or 

 by an alteration of its form. But this was not the case : 

 the ice did not appear in the smallest degree diminished, 

 or otherwise affected by the vicinity of the hot iron. 



My reader will naturally suppose, without my men- 

 tioning the circumstance, that due care was taken, in in- 

 troducing the cylinder into the jar, to do it in the most 

 gentle manner possible, to prevent the oil from being 

 thrown into undulatory motions ; and that proper means 

 were used for confining the cylinder, motionless, in its 

 place, when it had arrived there. 



As this experiment appears to me to be unexception- 

 able, and its result unequivocal and decisive, in order 

 that a perfect idea may the more easily be formed of it, 

 I have added the Figure 4, where a section of the whole 

 of the apparatus used in making it may be seen, ex- 

 pressed in a clear and distinct manner. 



If the general result of the experiments, of which an 

 account has been given in the two first Chapters of this 

 Essay, aff"orded reason to conclude that water is a non- 

 conductor of Heat, the result of that here described cer- 

 tainly proves, in a manner quite as satisfactory, that oil 

 is also a non-conductor ; and serves to give an additional 

 degree of probability to the conjecture, that all Fluids 

 are necessarily non-conductors of heat. 



