310 
SELECTED ARTICLES. 
sets of experiments, is truly surprising. By mine, 73. S5 
parts raised from 32° to 74°, or 42°, become 93 parts, and 
gain 19.15 parts, while the same bulk of the gases acquires in 
the same range of temperature only 6.46 parts, or the liquid 
is expanded very nearly three times as much as its own or any 
other gas. According to Thillorier, sixty parts gain twenty- 
three parts by an elevation of 54°, while the same bulk of air 
would, under like circumstances, be augmented only by 6.75 
parts ; or the liquid is nearly four times as expansive as the 
gases. 
As below 32°, or at reduced pressures, the augmentation of 
temperature is productive of much less expansive influence, 
we may infer that, under the weight of a few atmospheres, as 
when near to its freezing point, liquid carbonic acid is scarcely 
more dilatable by heat than water. Between — 4° and -f 32°, 
its expansion is 0.053, while that of air is 0.069. These facts 
suggest the inquiry, how far water, zivery high temperature 
and pressure, may be obedient to the same expansive influence, 
and thus, by suddenly filling the whole interior of a boiler, 
sometimes cause explosions. 
The pressure of carbonic acid gas, when placed over its 
liquid, is given by Thillorier at 32° and 86°, as thirty-six and 
seventy-three atmospheres respectively. By means of the 
gauge S, M, R, I found the pressure as follows : 
32° 36 atmospheres. 
45° 45 " 
66° 60 " 
86° 72 " 
The principle of the gauge renders it capable of registering 
the pressure with great accuracy :— for as one tube, M, begins 
to mark the pressure from the commencement of an experi- 
ment, and the mercury in the other, R, does not reach a 
visible point until the first has shown a pressure of several 
atmospheres, the second tube is equivalent in effect to one of 
several times its length. The first determines the amount of 
