ON THE SOLIDIFICATION OF CARBONIC ACID. 303 
ruble and excessively cold. Because, surrounded by an at- 
mosphere of gas which is constantly escaping from it, a frag- 
ment of it touched lightly by the finger glides rapidly over a 
plane surface. 
Its evaporation is so complete as to leave no other trace of 
moisture than that which is caused by the coldness and con- 
sequent atmospheric humectation. 
The force of its gasefaction is alleged to be equal to, but 
not so sudden as, that of gunpowder. 
The temperature at which the solidification took place was 
presumed to be about — 148 C F; although the experiments be- 
fore the committee of the Academy showed — 124.° 
Such is, in substance, the account by M. Thillorier of his no- 
vel and curious discovery, reported in the Annates de Chimie. 
No description of the method of procedure, or of the appara- 
tus used, is annexed; and we are left to conjecture, and to the 
imperfect description of travellers, for any farther knowledge 
of either. 
Having repeated the experiments of Thillorier, I deem it 
not useless to subjoin a draught of the instrument with which, 
aided by the suggestions of an intelligent pupil in France, and 
the assistance of friends here, I was enabled successfully to 
repeat most of the experiments of Thillorier and to verify 
some, and correct other, of his results. 
The apparatus consists of a generator of cast iron, A, sup- 
ported by a wooden stand, B, a receiver, F, also of cast iron, 
connected to the generator by a brass tube, and fastened firmly 
to it by the stirrup screw, K, — H, I, J, are stop cocks, G the 
nozle of a pipe, L a glass level-gauge, and S, M, R, a pres- 
sure-gauge. 
The generator is 20 inches long and 6 inches in diameter 
exteriorly. Its cavity is 16 inches deep, and 3 inches, nearly, 
in diameter, so that it will hold about 4 pints. The walls 
are, of course, \h inches in thickness. At the top an aperture 
of 2 inches in diameter is closed by a strong wrought-iron 
screw, the shoulder of which is let in about a quarter of an 
inch. The collar is of block tin turned to the size of the 
