238 MESSRS. W. R. BOUSFIELP AND W. ERIC BOUSFIELD 



be seen that ours corresponds much more nearly with the curves of LtJDm and 

 RBGNAULT than with BARNES' curve, except from C. to 15 C. In this portion of 

 the range our curve is very near the mean of the observers since REGNAULT, 

 and is almost identical with that of BABTOLI and STRACCIATI. 



TABLE XII Comparative Values of Specific Heat of Water, taking the 15 Calorie 



as Unity. 



As regards the absolute values of the mechanical equivalent of the water calorie at 

 various temperatures, the only figures available for a complete comparison over the 

 range of to 80 are those resulting from the researches of CALLENDAR and 

 BARNES. In addition to these there are others for a portion of the range or for 

 single points, the evaluation of which is rendered difficult for comparative purposes 

 by an incomplete knowledge of the electrical units and of the exact point in the scale 

 at which the mean calorie from to 100 is equivalent to other calories. Assuming, 

 however, that the mean calorie is approximately equal to the 15 calorie, and giving 

 the results in terms which take the E.M.F. of the standard Clark cell as being about 

 1*433 volt at 15, we have the following data : * 



The different values for the mechanical equivalent are considered and evaluated for purposes of 

 comparison in the following publications, where all the references to the original papers are to be found : 

 'Jahrbuch der Elektrochemie,' vol. 12, p. 6, 1909; 'Verb, der Deut. Phys. Ges.,' vol. 6, p. 589, 1908; 

 BARNES, 'Phil. Trans.,' Series A, vol. 199, p. 257, 1902; BARNES, 'Roy. Soc, Proc.,' Series A, vol. 82, 

 p. 393, 1909. 



