OF CUBICAL EXPANSION OF ICE. 
475 
filled with mercury and the top of the funnel thus completely sealed. The stopper 
was then unscrewed and a small vessel of hot recently boiled mercury was placed so 
that the hole o dipped beneath its surface. This caused the mercury in the tube 
to expand and to displace any air from about the orifice of the tube as the exuded 
mercury flowed through it. 
Tlie funnel was now levelled by adjusting the screws on which the bottom box 
rested, the level being placed with its legs on the top of the closing plate. The wii’e 
mooi-ino- the umbrella down then coincided vritli the axis of the tufje. In (U'der to 
find the buoyancy of the umbrella at 0° C., the vessel y was not used, hut the jar and 
the boxes ^rere filled with table ice, and the cases c placed round tlie appamtus. 
Clotlis were packed under the lower box, and the wh(fie was left ovei'iiight. 
When the equilibration was to he performed, the small mercury vessel into which 
C dipjjed was removed, the scale pan attached, and the weights adjusted so that 
equilibrium was attained when the wire projected 4 millims. from the hole. The 
reading having been taken, the jjan was removed and the hole was again closed with 
liot mercury. 
In order to get readings below 0° C., the ice was all removed, g was put in position 
filled with ice and salt, and the boxes were filled witli the same mixture. Then the 
thermometer was inserted so as to have its bulb in the mercury collar. 
The space round the funnel was clear of the freezing mixture, and the funnel thus 
changed in temperature so slowly that the thermometer readings coidd be relied on 
as giving tlie temperature of the funnel and its contents. All readings were taken 
witli the thermometer slowly rising. 
The thermometer used in these experiments was made liy Hicks, and liad the 
portion which projected aliove the cotton wool case graduated from 1° Ct to 10° C. in 
tenths of a degree. I tested its accuracy at 0° 0., and could find no error. The 
temperature lose (after the ap})aratus had been left a day or so) a])out a degree in 
three hours, and readings of the buoyancy could he ob¬ 
tained at intervals. 
Tlie results for the weights necessaiy to lie added to the 
pan, which itself weighed aliout 60 grammes, are set out in 
Table III., and sliown also in fig. 10. 
It will be seen that the last weicliino- taken after five 
otliers agrees closely with the first, showing that no air 
gained access to the umbrella in the process of equililiration. 
A new set of platinized weights by Oertling was used 
in these experiments. They were tested after the experi¬ 
ments, and were found to he consistent with themselves. 
Their absolute mass is not involved in the determination. 
TfMP. c. 
3 P 2 
