532 



REPORT — 1902. 



following taUe for diffevent temperatures, calculated by the metLod already described 

 by one of tbe authors. 



The results are in terms of the nitrogen thermometer and are ruicorrected for 

 the temperature gradient in the flow tube as described by Professor Callendar. 



Since this coi'rection is small, and is partly balanced by the correction to the 

 standard hydrogen scale, the results will not be changed much by its application, 

 and the variation with temperature will remain practically unaft'ected. 



In fig, 1 is given a plot of the observations, the vertical scale being the value 



Js- 0-140 

 ■~"0-140" 



The preliminary results are also included. 



It will be seen that the specific heat decreases with rise in temperature, sug- 

 gesting that portion of the curve ibr water between 10° and 20°. 



Eesults over a wider interval of temperature could not be conveniently taken 

 with the present apparatus. We purpose continuing the work to much higher 

 temperatures immediately in order to trace the course of the curve as the boiling- 

 point of the mercury is reached. 



The equation representing the change of Js and shown by the curve in the 

 figure reads : 



Js, = Js. - 4-462 X lO-' t + -0157 x 10-^ f- 

 where 



Js, = ^140ir)4 



The value of the specific heat in terms of water has been calculated, taking 

 the value of J equal to 4-1891 for a tliermal unit at 15°-5, which was the tempera- 

 ture recommended by Griifiths at the Paris Congress in 1900, as being suitable for 

 the selections of the thermal unit. 



The temperature expression of the specific heat rends : 



S, = S„ - 1-074 X 10-'' t + -OOSSS X 10--^ t" 



or 





where 



^"3'. = - •000321 1 + •OOOOOllS t"- 



So = •033458. 



This gives for the temperature coefficient at any temperature t the expression 



f-f?^") = - -000321 + '00000230 i 

 and for the average change per degree at 50° the value - -OOOOOGO. 



