ON THE SPECIFIC HEAT OF WATER. 223 



experiments (Nos. 67 and 68) gave respectively P 0018 C. and 0'0022 C. rise of 

 temperature per minute, which, on the weight of water contained in the calorimeter, 

 is equivalent to a mean heating effect of 0'43 watts a very high figure, which 

 would import a possihle error of 1 in 2000 into the results of the first two series of 

 experiments. 



In the third series of continuous-flow experiments the amount of the correction is 

 reduced to about 0'15 watts, and the resulting uncertainty is of an order of less than 

 1 in 4000. The correction for each experiment was obtained by olwerving the rise of 

 temperature during 60 minutes after the conclusion of the main run, and the results 

 ;ire given iii the third table in Appendix C in joules per minute. The figures of one 

 experiment are given in Appendix B. 



8. Continuous-flow Experiments. The special arrangement of the calorimeter for 

 these experiments has been already described with reference to figs. 1, '2, and 3. 

 There were three series of these experiments. In the first two the watt balance as 

 well as the ampere balance was in series with the calorimeter, the resistance of the 

 watt balance being in parallel with the calorimeter heater as shown in fig. 4. Before 

 the third series of experiments the watt balance had been disconnected, it having 

 been found that whilst the corrected readings of the ampere balance could be relied 

 on as a check to an accuracy of 1 part in 5000 the accuracy of the watt balance was 

 considerably less. The abandonment of the watt balance simplified the arrangement 

 and the calculations. 



In Appendix A (p. 244) are set out the notes of one experiment in the first two 

 series of experiments, and in Appendix 3 the notes of one of the third series. We 

 will describe the course of a continuous-flow experiment by reference to the notes in 

 Appendix B, which only differs from the earlier ones in the absence of the watt 

 balance and the introduction of the rubber-cap </, over the end of the inflow tul>e as 

 shown in fig. 3. In this experiment (No. 164) the continuous-flow run lasted only 

 three hours, as steady conditions were practically attained soon after the end of the 



first hour. 



Water from the mains flowed continuously into a cistern, where it was brought to 

 the required temperature (as described in Section 2), and thence flowed through the 

 pipe Q to the calorimeter. 



The outflow water passed into the flask X which stood upon a block, upon the 

 removal of which the flask could be lowered and withdrawn laterally. By inclining 

 two flasks until the mouths touched, it was easy to substitute one flask for another 

 by a lateral tipping at the exact instant indicated by the chronometer ticks without 

 loss of any water. The space between the tube and the neck of the flask X was 

 tilled by a cotton wool plug. Careful experiments showed that there was no 

 appreciable loss of water owing to vaporization with this method of stoppering. 

 The plug was weighed with the bottle and dried after each use before being used 

 again. 



