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MESSRS. W. R. BOUSFIELD AND C. ELSPETH BOUSFIELD 
6. Correction for Stirring and Evaporation. —-These were estimated together. 
The temperature variations of viscosity and vapour pressure caused the correction to 
vary from a heat gain of about 55 joules per minute at 0° C. to a negative correction 
of about —30 joules at 40° C. Within this range the correction obeyed with 
sufficient approximation a straight-line law which for water is expressed by 
dQ/dt = 55 —2'2T d . 
This correction could also be taken for the KC1 solutions, the viscosity of which is 
little different from that of water. But for the NaCl solutions the higher viscosities 
rendered it necessary to observe the value of this correction for each solution. For 
the strongest NaCl solution its value was 
dQ/dt = 64 —2‘2T d . 
The observations for these corrections were made by observing the rise or fall of 
temperature in the calorimeter with stirring at the normal rate (350 revolutions per 
minute) at various temperatures between 0° C. and 40° C., keeping the temperature 
of the bath and obturator the same as that of the contents of the calorimeter. 
7. Obturator Heating.—For this correction the rise of temperature was observed 
for various excess temperatures of the obturator whilst keeping the bath at the same 
temperature as that of the calorimeter contents. The rise due to stirring was 
calculated from the preceding formula. The balance due to obturator heating was 
simply 
dQ/dt = 4‘85 (T ob —T d ). 
8. Radiation through Calorimeter Walls.— For this correction various excess 
temperatures of the bath were maintained whilst the obturator was kept slightly 
above the temperature of the contents of the calorimeter, and the rise due to this 
and to the stirring was calculated from the preceding formulae. The balance could 
be expressed as 
dQ/dt = (327 + 0’36T d ) (T b —T d ). 
It will be noted that the formula shows that the Dewar vessel was more 
diathermanous at higher temperatures. 
It may be observed that the above corrections are different from those given in 
the former paper. The Dewar vessel and mercury resistance thermometer formerly 
used had been broken. The fit of the obturator in the new Dewar vessel was not 
quite the same, which altered the correction for escape of vapour. The thickness of 
the walls of the Dewar vessel also turned out to be different and this necessitated 
the re-determination of its capacity. But as this has resulted in another series of 
experiments confirmatory of the former values of the specific heat of water between 
0° C. and 40° C. it may be regarded as a fortunate accident. 
