246 Of the Propagation of Heat 



to the cold sides of the tube in the same manner as I 

 have shown in another place that the particles of air give 

 off their Heat to other bodies^ I was led to conclude that 

 these, and probably all other liquids, are in fact non-con- 

 ductors of Heat, and I went to work immediately to con- 

 trive experiments to put the matter out of all doubt. 



On considering the subject attentively, it appeared to 

 me that if liquids were in fact non-conductors of Heat, or 

 if it be propagated in them only in consequence of the 

 internal motions of their particles, in that case every- 

 thing which tends to obstruct those motions ought cer- 

 tainly to retard the operation, and render the propagation 

 of the Heat slower and more difficult. I had found that 

 this is actually the case in respect to air, and though 

 (under the influence of a strong and deep-rooted preju- 

 dice) I had, from the result of one imperfect experiment, 

 too hastily concluded that it did not take place in regard 

 to water, yet I now found strong reasons to call in ques- 

 tion the result of that experiment, and to give the subject 

 a careful and thorough investigation. 



Thinking that the best mode of proceeding in this en- 

 quiry would be to adopt a method similar to that I had 

 pursued in my experiments on the conducting power of 

 Air, I prepared an apparatus suitable to that purpose. 

 The first object I had in view being to discover whether 

 the propagation of Heat through water was obstructed 

 or not, by rendering the internal motion among the par- 

 ticles of the water, occasioned by their change of tem- 

 perature, embarrassed and difficult, I contrived to make 

 a certain quantity of Heat pass through a certain quan- 

 tity of pure water confined in a certain space ; and, noting 

 the time employed in this operation, I repeated the ex- 

 periment again with the same apparatus, with this differ- 



