DETERMINATION OF THE SPECIFIC HEAT OF WATER. 455 
(A) in the meantime had changed f; from a to b, k, being still at b. The circuit is now 
seen to be such that the small battery A, sends a current through the magnetostatic 
meter M and the calorimeter coil. In this final period (B) observed the thermometer 
and the magnetostatic meter, and also made observations on the auxiliary thermo- 
meters placed near the stem of the Baudin, in order to introduce the stem correction. 
(A) once more compared the Clarks. 
The Results. 
We divide our experiments into three series, but only attach any value to the 
third, as during the first two sets the thermometer was falling in the last period. 
We had hoped, at first, to be able to apply a small correction, to eliminate the error 
which is due to the fact that a falling thermometer will read too high, and we made 
a large number of experiments to determine the correction. We arrived, however, at 
the result that the indications of a falling thermometer are so irregular that no 
correction is possible. Consequently in our third series the thermometer was rising 
during the whole course of each experiment. 
We think it worth while to put on record an impression that the behaviour of our 
Baudin thermometer has altered since we received it from the maker. As soon as it 
came some preliminary experiments were made, to see if we could work with the ther- 
mometer while it was falling, and the observations seemed to show that the fall was 
sufficiently uniform. Our first three experiments gave results which were very con- 
sistent, and a minute after the current was broken the temperature seemed to fall 
already in a perfectly regular manner. But as we continued our work, the behaviour 
of the instrument seemed to deteriorate. Thus in our experiment of March 8th the 
thermometer had hardly fallen three minutes after the current had stopped. It is 
possible that this was due to accidental circumstances, for it is well known that 
different places in the bore of a capillary tube behave very differently. We wish 
therefore to express no opinion at present as to the probability of an actual change 
in the behaviour of the thermometer, but only to draw the attention of other 
experimenters to this point which seems worth keeping in mind. 
The results of the first three experiments which constitute the first series are con- 
sistent, but no value is attached to the equivalent as deduced from them, owing to 
the uncertainty of the water equivalent. The coil, as has been mentioned, was then 
wound on an ivory frame. When Mr. HApiey, who then assisted in the work, began 
to experiment on the specific heat of ivory, he met with serious difficulties. The 
ivory contained water to begin with, as was shown by the diminution in the weight 
of fresh ivory when heated up ; it absorbed again when placed in water ; the results 
were consequently not to be trusted. Even when coated with shellac, the substance 
did not behave in a consistent manner. There were other imperfections in our 
calorimeter at that time which make it impossible for us to know the water equivalent 
with sufficient accuracy. 
