242 
DR. H. T. BARNES ON TIIE CAPACITY FOR HEAT OF WATER 
Summary of Results of Observations. 
The following table contains a summary of the observations arranged and 
abstracted by Professor Callendak. The original tables (abridged), giving details 
of corrections and calculations, are preserved for reference in the Archives of the 
Royal Society. 
The first column gives the number and date of the corresponding Abridged Table 
preserved in the Archives. The second column gives the temperature of the jacket 
water or inflow, taken by means of a mercury thermometer, and corrected to the 
nearest hundredth of a degree. The third column gives the mean difference of 
temperature, (W, between the inflow and outflow, observed to the ten-thousandth of a 
degree by means of a pair of differential platinum thermometers, and reduced by the 
parabolic difference formula, assuming the boiling-point of sulphur to be 444'53° C. 
The fourth column gives the flow of water, Q, through the calorimeter, in grammes 
per second, reduced to vacuum. The fifth column gives the value of the product, 
4'2 Q dd, for comparison with the power, EC in watts, given m the next column. 
The seventh column gives the difference, EC — 4'2 Q dd, of the numbers in the two 
previous columns divided by dd. This quotient is denoted by I), and is used in 
calculating the results given in the last column, by means of the difference equation 
EC /dO — 4 2 Q = D = 4-2 Q d + h, 
in which d expresses the fractional variation of the specific heat of water in terms of 
an arbitrary unit 4'200 joules, as defined by the relation J = 4'200 (1 -f- d), and 
the symbol h denotes the rate of heat-loss in watts per degree rise of temperature. 
The value of d is found by combining the observations for the two different flows Q' 
and Q", which give the relation 
d = (D' - D")/4-2 (Q' - Q"). 
The values of h and J follow immediately from that of d. The values of EC and J 
are calculated assuming the E.M.F. of the Clark cell at 15 c C. to be 1'4342 volts, 
but this does not affect the relative values. 
In cases where more than two different flows were taken at the same temperature, 
the values of d and h are calculated from the largest and smallest flow. These 
values of d and h are then assumed to calculate a value of D for the intermediate 
flow for comparison with the value of D deduced from the observations. 
