l>i. II. T. Kirnes. On the Capacity for Heat of 



suit;ible to select a thermal unit at a more convenient part of the 

 scale. The mean value of the mechanical equivalent of heat from 

 these measurements over the whole range is 4-18876 joules, which is 

 very nearly equal to the value at 16 C., which is 4*1883 joules. It 

 seems desirable to select a unit at a temperature which, if at the same 

 time at a convenient part of the scale, may be equal to the mean value 

 over the whole scale. The author has in consequence adopted a unit 

 at 16 C., and has expressed the specific heat of water in the following 

 table in terms of this unit : 



Variation of the Specific Heat of Water in Terms of a Thermal Unit 



at 16C. 



Temperature. Observed values. Calculated values. 



5 1-00530 



10 1-00230 



15 1-00030 



20 0-99895 



25 0-99806 



30 0-99759 



35 0-99735 



40 0-99735 



45 0-99760 



50 0-99800 



55 0-99850 



60 0-99910 



65 0-99970 



70 1-00035 



75 1-00100 



80 1-00166 



85 1-00237 



90 1-00305 



95 1-00370 



Mean... 1-00012 



1-00446 

 1-00206 

 1-00024 

 0-99894 

 0-99807 

 0-99757 

 0-99735 

 0-99735 

 0-99757 

 0-99807 

 0-99894 

 0-99910 

 0-99972 

 1-00036 

 1-00100 

 1-00166 

 1-00233 

 1-00301 

 1-00370 



In expressing the results in a formula it is impossible to fit any one 

 simple expression over the whole scale. It is seen that the curve falls 

 rapidly from 0, passes through a minimum point at 37-5, and in- 

 creases again less rapidly towards 100. Two formulae can be fitted 

 very accurately over the scale. Between 5 and 37-5 C. the following 

 expression in terms of a thermal unit at 16 is found to read, 



S = 0-99733 + 0-0000035 (37-5 -Q 2 + 0-00000010 (37 -5 -0 s . 

 The same formula holds between 37-5 and 55 by simply consider- 



