368 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



Plotting the values found for the rate of dissipation of heat as abscissas 

 and the corresponding values of the temperature as ordinates, the curve 

 /y, Fig. 3, is obtained. 



Determination of the Change in the Rate of Dissipation of Heat hy Radia- 

 tion and Convection on Reversal of the Heating Current. 



From the h curve, described in the last paragraph, and the curve of 

 distribution of temj^erature along -the bar, the condition of any section 

 of the bar as regards temperature and rate of dissipation of heat can 

 be obtained. If now the temperature of a section be slightly changed, 

 the corresponding change in the rate of dissipation of heat can be de- 

 termined by simple proportion, since the h curve is nearly a straight 

 line. The change of temperature on reversal of the heating current 

 has been already determined for all the sections of the part of the bar 

 under consideration ; so it is a very simple matter to calculate the 

 change in the rate of dissipation of heat, on reversal of the current, for 

 any section of the bar. 



Column IX., page 369, gives the mean temperature of every section of 

 the part of the bar under consideration. Column X. gives the corre- 

 sponding rate of dissipation of heat from the surface of the bar, as 

 obtained from the h curve. The change in the rate of dissipation for 

 the several sections is tabulated in column XI. From this column the 

 quantity H^ — ZT, see page 369, can be at once obtained for any part of 

 the bar consisting of a whole number of sections. 



