Ld 
Chemical Reactions under High Pressure. 267 
without decomposition, by s of a high temperature (21° to 23° 
Wedgewoo The means he used were suggested by considerations 
published by Hutton, respecting the influence that pressure might exert 
on geological phenomena. Hall used a closed vessel under a pressure 
8 
To avoid accidents, the following are his arrangements. A square 
Structure or vat, A, of brick, divided into three unequal parts, one above 
the other, contains the furnace, b, B being the doors, ¢ the ash-pit, D the 
chimney ; a plate of iron separates this part from the oven of the up- 
aT et on. 
ing of the vat with a heavy plate of iron. The space containing the 
oil bath is thus closed on ail sides. we 
€ boiler is half filled with oil; and the temperature of the oil is 
oe by a thermometer, T, placed in a metallic tube which passes 
a 
Fer they are enclosed in iron tubes (s), solid at one end, and at the 
T closed b d 
other ¢ 
* This Journal, vol. xvi, p. 100. . saps aa ie 
