Miscellanies. 405 
Whilst in the liquid state, its elastic force is under such energetic 
restraint that a gramme of this substance produces an explosion as 
great as the same weight of powder: this spring, in the solid state, 
is completely broken: the new body disappears insensibly by slow 
evaporation. 
A fact not less curious than the solidification of this gas, is, that it 
is effected by the sudden passage from the liquid to the gaseous 
state, and that the approach and coherence of the molecules which 
constitutes the solid state, is caused by the expansion of a liquid 
which instantly occupies a space 400 times greater than its primitive 
volume. 
A fragment of solid carbonic acid, slightly touched by the finger, 
glides rapidly over a polished surface, as if sustained by the gaseous 
atmosphere with which it is constantly surrounded until it is entirely 
dissipated. 
If we introduce a few Siete of this substance into a little 
flask, and stop it hermetically, the interior is filled with a thick va- 
por, and the stopper is soon driven out with violence. 
e€ vaporization of solid carbonic acid is complete. It leaves 
but rarely a slight humidity, which may be attributed to the action 
of the air on a cold body, whose temperature is much helag that of 
freezing mercur 
The influence “6 cooling upon liquid carbonic acid, whose e expan- 
sive force is thus found to be annihilated at about the hundredth de- 
gree (Cent.) below melting ice, begins to be manifest at a much 
higher temperature : this expansive force, which at zero is equal to 
36 atmospheres, is no more than 26 atmospheres at 20° below zero. 
It seems proper to add, that the term one hundred degrees below 
zero, which I assign to the solidification of the liquid acid, is not hy- 
pothetical. In the experiment which I made before the members 
of the committee, the alcoholic thermometer sunk to —87°; and 
by adding to these 6 degrees, which the fluid would have contracted 
if the whole thermometric column could have been subjected to the 
frigorific action, we shall have the actual temperature of 93° Cent. 
below 0°, and this number cannot have been the maximum of the 
effect of the blowpipe fed by liquid carbonic acid.—Jdem, 
6. ayrele of objects in Natural History. (Extract of a let- 
ter from Dr. H. G. Bronn, to Prof. Silliman, dated Heidelberg, 
Germany, 13th June, 1836.)—The museum of Natural History con- 
