Jo~ty—On the Conservation of Mass. 37 
through in the 115 minutes, or 0:0043 calories persecond. This result is recorded 
as giving some idea of the value of the jacket as a non-conductor of heat; but it 
~ does not directly answer the question as to the interval elapsing after the mixing 
of the substances during which the alteration of temperature arising in the 
solution will not have sensibly altered the external temperature of the paper 
cylinder. 
Experiments on the rate of Propagation of a temperature change through the Cork- 
dust Jacket. 
One of the glass vessels used in the experiments presently to be given is 
charged with 25 grms. of CuSO in the lower bulb, and with 25 ces. of water in the 
upper bulb, and arranged within the cork-dust jacket and paper cylinder precisely 
as in the experiment. The weight of the cork-dust + paper cylinder is 16°3 grms. 
A second cylinder of cardboard surrounds the paper cylinder with an annular 
space of about 1 cm. intervening. In this annular space a sensitive thermometer 
is placed, and the upper opening of the annular space closed with cotton wool. 
The whole is placed in the zinc-lined box in the cells, the tube containing the 
fusible plug, and which controls the descent of the water, extending into the glazed 
cell in front of the box and above the platinum heater. Through this window the 
thermometer is observed by a lens. Twenty-four hours after setting up, the heater 
is used to melt the plug, and the observations of temperature made. 
Before contact the thermometer stood at 11°,03 steadily. For the first com- 
plete four minutes no change was detected. For the next two minutes there was 
uncertainty as to whether any movement was taking place, the temperature was 
at last entered as 11°.025 as attained at end of the sixth minute and the movement 
beginning during the fifth minute. During the seventh minute the thermometer 
fell to 119-015; in the eighth minute to 11°01; in the ninth, 11°00. The experi- 
ment was then dismantled, and the thermometer inserted in the solution, when 
it read 9°-9. This was thirteen minutes after commencement. 
A second experiment, using a weight of cork-dust just 33 grammes greater than 
in the last experiment, 20 grammes of CuSO, and 20 ccs. of water, gave the 
folloWwing results :—The initial temperature in the annular space was 10°-95, steady 
as observed for ten minutes. After contact no change whatever was perceived for 
six minutes. In the course of the seventh minute, a fall of 0°-01 was determined 
by aid of the lens. Finally the complete experiment stood as follows :— 
Initial temperature, : . ; . . 10°:95 
In 63 minutes, . . 0 ; . . HOS 94: 
In 7 3 ‘ 5 : : : 3 10°°93 
fa8 5 j =. 2 . 10°92 
ice , . 10°91 
In 93 : . : . 10°90 
? 
