ON THE VARIATION OF THE SPECIFIC HEAT OF WATER. 



35 



were given in a preliminary note communicated to Section A at the 

 Dover Meeting. 1 The final results were communicated to the Royal 

 Society in June 1900,^ and are now in course of publication in the ' Phil. 

 Trans.' The object of the following note is to discuss one or two minor 

 corrections and reductions which have been suggested. 



Values below 20°. , 



At the Dover Meeting of the British Association it was stated that 

 the observations agreed very perfectly on the average with Rowland's 

 from 5° to 35°, but indicated a slightly more rapid change near the 

 freezing-point. This change required further verification, and was not 

 included in the formultB then suggested. Subsequent observations have 

 confirmed this effect, which may be represented within the limits of 

 probable error by the addition of another term to the formula below 

 20° C. The formula given in 1899 for the specific heat s at any tempera- 

 ture t between 0° and 60° was as follows : — 



s=-9982 + -0000045 («-40)2 . . . (1) 



Below 20° the formula should read : 



s=-9982 + -0000045 (<-40)'-- -0000005 (f- 20)3 . (2) 



This formula agrees with the curve and with the correction to the total 

 heat h of the liquid given in the note in the ' British Association Report,' 

 1899. Values calculated by these formulae are given in Table II. in the 

 column headed B.A. 1899. 



The quantity actually observed by Rowland was the total heat of 

 the liquid from the starting-point of each experiment. The following 

 table shows the close agreement of his results with this formula : — 



Table I.— Values of Total Heat of Water, 5°-35°. 



Results above 60°. 



In the 'British Association Report,' 1899, Regnault's formula was 

 adopted for the variation above 60°, modified by subtracting a constant 

 quantity -0056, to make it fit with formula (1) at 60°, and to reconcile 

 liis results with those of Reynolds and Moorby. We thus obtain 



5=0-9944 -f0-00004< + -0000009<'^ ... (3) 

 Subsequently to the Dover Meeting Dr. Barnes succeeded in obtaining 



B.A. Be])., 1899. 



» Proc. U.S., 1900. 



D2 



