been previously subjected to a pressure of a hundred and fifty atmos- 
pheres, and as carbonic acid liquefies below one third of this pressure, 
the instrument was perfectly safe. A sheet of wrought iron, not more 
than the sixteenth of an inch thick, rolled into form and carefully 
welded, is the substitute for the massive cast iron mortars that were 
formerly used. 
The following references to the diagrams which I send you, will 
readily explain the manner of using it. 
as was permitted to accumulate in the gasometer to the amount 
of about a gallon and a half, and then by the forcing pump driven into 
the cylinder. When this volume had been repeatedly forced into the 
3 
Ridzgstings “eee ceed 2 1 feet. Scale for figs: 1 and 2. 
EAA EP COP : sg Petts eter © itt Byat and 6, 
1. Side view of the instrument, with apparatus and connections for supplying 
earbonic acid._2. End view of the same.—a. Evolution flask containing 2Co2+- 
Na0+S0,.—b. Gasometer.—c. Ceca tube.—d. Caouichoue tube about four feet 
for condensing the gas.—4. Apparatus for solidification, made of sheet iron tin- 
ned.—5. Inner view of one half.—6. , 
gas into 47, Valve controlled by coiled wire spring at the other extreme of the 
cylinder 3.—g. Tube fitting upon f.—h. Apertures for the escape of gas in the pro- 
cess of solidification.—i i. Double cylinder to prevent the cold from affecting the 
hands of the operator. , 
