416 Of the Propagation of Heat 



As it might possibly be objected to the conclusions 

 drawn from these experiments that, notwithstanding all 

 the care that was taken in the construction of the two 

 instruments made use of that they should be perfectly 

 alike, yet they might in reality be so far different, either 

 in shape or size, as to occasion a very sensible error in 

 the result of the experiments ; to remove these doubts 

 I made the following experiments: 



In the morning towards eleven o'clock, the weather 

 being remarkably fine, the mercury in the barometer 

 standing at 27 inches n lines, Reaumur's thermometer 

 at 15, and the hygrometer at 47, I repeated the experi- 

 ment Np. 3 (of heating the thermometer No. i in 

 boiling water, &c.), and immediately afterwards opened 

 the cylinder containing the thermometer at its upper 

 end, where it had .been sealed, and letting the air into 

 it, I resealed it hermetically, and repeated the experi- 

 ment again with the same instrument, the thermometer 

 being now surrounded with air, like the thermometer 

 No. 2. 



The result of these experiments, which may be seen 

 in the following table, shews evidently that the error 

 arising from the difference of the shapes or dimensions 

 of the two instruments in question was inconsiderable, 

 if not totally imperceptible. 





