HEAT OF EVAPORATION OF WATER. zi 
Appendix I.—Deratis or Stirring EXPERIMENTS WHEN THE CALORIMETER 
WAS FILLED WITH OIL. 
The tank temperature having become steady (at 6)), the calorimeter was raised to 
a temperature 6, slightly below 6. In order that the conditions should become 
steady, the stirring was allowed to proveed for half-an-hour to one hour, before 
observations were commenced. The battery key (f;, Plate 6, fig. 2) was kept 
continually oscillating and, as the temperature rose, the swings of the galvanometer 
diminished, until no motion was observed on reversing the battery circuit. The 
observer then pressed a key communicating with the chronograph, and thus the time 
was recorded. As before stated, the stirrer automatically registered its own revo- 
lutions. At the same moment that the observer at the galvanometer pressed his 
recording key,* a second observer took the readings on the mercury thermometer, 
which gave the temperature of the steel walls. 
As any change in the mercury thermometer was of great importance, this observa- 
tion was made with the micrometer eye-piece before referred to. 
Groups of five observations were taken about certain previously fixed bridge-wire 
readings, and each group of five was meaned to find the time of passing the given 
points. 
The following Table gives full particulars of a stirring experiment. It is by no 
means a good one, but I give it simply because it is the first one done aiter the 
introduction of the oil. The exterior temperature was unusually unsteady. 
* In the slower experiments, however, instead of using the chronograph, I called the transit, and my 
assistant recorded the time, as alsc the time of the revolutions, the stirrer ringing a bell at each 1000. 
