MINERAL CAVITIES AND THEIR CONTENTS. 
121 
an enormous pressure. The reasoning is of course applicable 
to all liquids. The presence of air was no obstacle to such 
change; it only rendered the dilatation of the liquid more 
regular, and the more easily observed in glass tubes up to the 
moment when it vanished completely. 
Although Gruyton de Morveau, towards the end of the last 
century, had liquefied ammonia gas by exposure to a temperature 
of— 48° C. ( — 54° # 4 F.), and Monge and Clonet had liquefied sul- 
phurous acid, yet their results appeared so incredible that doubt 
was cast upon them, on the supposition that the gases were not 
sufficiently dry. Northmore, in 1805-6, liquefied hydrochloric 
acid, sulphurous acid, and chlorine by pressure, but in such a 
manner that they were not obtained in a pure state. It is, there- 
fore, to Faraday that we owe our first and most trustworthy in- 
formation on the liquefaction of gases. His first paper appeared 
in 1823, and the second more complete publication in 1844. 
In this latter, when describing the properties of liquid carbonic 
acid, he says : “ I am inclined to think that at about 90° F. 
Cagniard de la Tour’s state comes on.” In other words, he 
believed that at the temperature of 90° F. (32°*2 C.) the car- 
bonic acid enclosed in sealed tubes ceased to be a liquid, and 
was resolved into a vapour. 
Mr. Greorge Gore, of Birmingham, has examined the solvent 
powers of many liquefied gases, and these are not at all such as 
one would expect. Thus the immiscibility of carbonic acid 
with water, and its power of dissolving iodine with a violet 
colour like that of the solution made with bisulphide of carbon, 
have been shown. Liquefied hydrochloric acid loses the chemi- 
cal activity its aqueous solution possesses ; for instance, it does 
not redden litmus paper, and it is quite inert in contact with a 
powerful base like caustic lime. 
The next point is the knowledge which Thilorier gave us 
concerning the properties of the liquid carbonic acid. He pre- 
pared it in large quantities and daringly sealed it up in glass 
tubes in a state of perfect purity ; in this way he was enabled to 
ascertain its tension at different temperatures, and its rate of 
expansion. 
Now Simmler in 1858, offering an interpretation of Brew- 
ster’s observations, pointed out that the new liquid, in some 
cases at least, was most probably liquefied carbonic acid. The 
most remarkable physical property of this liquid of Brewster’s 
was its enormous expansibility by heat, and on comparing Thilo- 
rier’s co-efficient of expansion for this liquid with that which 
Brewster estimated for the expansion of the liquid in crystals, 
he found them to be almost identical. This comparison was 
accomplished, however, in a much more satisfactory manner, in 
1869, by Messrs. Sorby and Butler, who published conjointly an 
NEW SERIES, VOL. I. — NO. II. K 
