PROPERTIES OF MATTER IN THE GASEOUS STATE. 
759 
According to Law III., when the density of the gas is sufficient, the differences of 
pressure should be inversely proportional to the density. 
Hence, according to this law, the product of the pressure into the difference of 
pressure should approximate to a constant quantity as the density increases. 
In the case of stucco Ho. 2, we have, adding the two tables of logarithms, sub¬ 
tracting '684 —l = log. '483, and taking out the numbers 
Pressure. 
Pressure x difference 
of pressure-^'483. 
30-25 
1 
30-05 
1-004 
28-05 
- 964 
27-25 
■957 
25-85 
•940 
24-90 
•927 
2315 
•933 
This sufficiently shows that the approximation is very close and according to Law III. 
Coming now to the lower pressures, it will at once be seen that in all cases there is a 
tendency towards constancy. This is best seen in Plate 49, where the curves not only 
converge towards the left but turn towards the horizontal. 
It is clear, however, from these curves, that the limit had not been reached, nor is 
it possible to say simply from the shape of the curves how far it might be off. 
The following comparison, how T ever, will show that the indication is in favour of 
Law IV., viz.: that the ultimate ratio which the difference of pressure bears to the mean 
pressure should be as the ratio which the difference of the square roots of the absolute 
temperature bears to the square root of the mean absolute temperature. According to 
this, we should have in the case of the meerschaum plate the ratio of the difference of 
pressure to the mean pressure equal 
A /212 + 46l- v /63 + 461 _f 
^/T37"5+461 S’ 
whereas, supposing that there was a difference of 20° between the surfaces ol the 
meerschaum and the opposite tin plates 
v/192 4 461 - -v/83 + 461 _ A 
-v/137'5 +461 IP 
between which values it is probable that the actual ratio lies. 
The highest ratio of the difference of pressure to the mean pressure obtained is 1 to 
13, and this may well be considered as an approximation to 1 to 11. 
Thus, not only in their general features, but in the approximation towards definite 
limits, the experimental results show a close agreement with the laws as deduced from 
the theory. 
MDCCCLXXIX. 
O E 
