580 
MR. R. W. STEWART ON THE ABSOLUTE THERMAL 
space in the centre of the heater in close proximity to the bulb of the thermometer, 
Th., which passes through a cork in the lid of the case. The silk thread passed through 
the glass tube, t, and was attached at the other end to a small hook in the end of the 
slide, S. The tube, t, was just long enough to be in contact with the piece of iron, so 
that when the slide, S, was withdrawn quickly the thread broke and the iron was 
free to fall through the holes in the double bottom of the case, between which the 
slide, previous to withdrawal, acted as a screen. When it was desired to make a 
determination the heater was lifted on to the lid of the calorimeter case and placed 
in a marked position, so that the holes in the bottom were direct!}^ over the mouth of 
a paper funnel, F, acting as a guide to the calorimeter tube, T. When placed in 
position, the thermometer was watched and the slide, S, withdrawn, when the 
required temperature was indicated. The iron at once fell straight into the calori¬ 
meter tube and the heater was then removed, the mouth of the funnel, F, closed 
Fig. 2. 
i 
i;! 
\Th'. 
T 
w 
with cotton wool, and the observation of the mercury-thread in the indicating-tube 
proceeded with. In the meanwhile, a second piece of iron was suspended in the 
heater so as to be ready for another determination. The cooling of the heater was so 
slow that there was no doubt about the temperature of the iron vdren dropped into 
the calorimeter, and the time of fall into the tube, T, was too small to admit of any 
appreciable cooling. Experiment also showed that placing the heater on the lid of 
the calorimeter case, even for a lonof time, had no effect on the calorimeter. 
In the reduction of the results obtained the latent Ijeat of water and the specific 
heat of ice were assumed to be correct as given by Bunsen. 
The rapid melting of the snow and some accidents wuth the calorimeter limited the 
time of working and prevented any extension of the results given. 
The principal data of two sets of experiments are given in the followung Table. 
