254 



Of the Propagation of Heat 



In cooling the Thermometer ) 

 from the temperature of 200° V 

 to that of . . . . iSo ) 

 from iSo°to 160 

 160 to 140 

 120 

 100 

 So 

 60 

 40 

 Total time in cooling from 



o ^ o 

 200 to 40 



Times employed in cooling the | 

 instrument So degrees, viz. - 

 from 160° to 80° . . . ) 



Mean time in cooling it from "|_ 

 160° to 80° ) 



As the heating or cooling of the instrument goes on 

 very slowly when it approaches to the temperature of the 

 medium in which it is placed, while, on the other hand, 

 this process is very rapid when, the temperature of the 

 instrument being very different from that of the medi- 

 um, it is first plunged into it, both these circumstances 

 conspire to render the observations made at the ex- 

 tremities of the scale of the thermometer more subject 

 to error, and consequently less satisfactory, than those 

 made nearer the middle of it. In order that the general 

 conclusions drawn from the result of the experiments 

 might not be vitiated by the effects produced by these 

 unavoidable inaccuracies, instead of estimating the celer- 



