CAPACITY FOR HEAT OF METALS AT DIFFERENT TKMPKRATURES. 



147 



and 



de\ #,_ 



/ur 



JR(MS+ww) 



(E) 

 JR(MS+nw) 



-#)=(%} -(% 



\dtUt \dt 



Hence 



The table below shows the values of <r deduced from the two methods, and their 

 agreement affords strong evidence of the accuracy of the resulting correction. 



Hence, if 0, is the range below 6 a , corrected for radiation, and a the range above , 

 and 6, the " rise above " after correction for radiation, then 



n r E?t 

 JR 



Table II. (p. 148) represents a typical series of experiments by the "total heat" 

 method, the metal being copper at C., and the thermometers AB and CD. 



(2) The Intersection Method. 



The metal having been cooled a considerable distance beyond the limits of the 

 bridge, the current and potential balance were established from five to ten minutes 

 before the temperature came within the bridge range. This preliminary heating up 

 under the normal conditions of the experiment was essential, as it ensured a steady 

 state of gradient, lag, &c., being established before the commencement of the 

 observations. The time of transit of the temperature across each bridge wire division 

 was recorded on the chronograph tape, as in the " total heat " experiments. 



The current was switched off and the " rise above " taken in the usual way. 

 Similar experiments over the same range were performed with various values of n 

 (the number of standard cells balanced at the end of the heating coil). 



From these observations the value of SO/St at the centre of each scale unit of the 



u 2 



