124 MOHR AND REDWOOD'S PRACTICAL PHARMACY. 
plied. The circular opening C, in the top of the furnace, 
will receive a pan, small still, or other similar vessel. De- 
coctions may be boiled in flat-bottomed saucepans merely 
placed on the hot plate over the flue, a little further back 
than the opening C. The top of the boiler may be used 
for any process to which it is applicable, requiring the heat 
of boiling water. 
"The iron plate forming the top of the drying closet at 
X, will have only the slight heat which it acquires by con- 
duction from the fire. Processes involving the liberation 
of noxious vapours, may be conveniently conducted here, as 
the vapours will pass up the chimney. The gas-burner 
and flexible tube, as shown in the drawing, may be re- 
quired in some processes of this description, as also the gas- 
furnace (fig. 20,) which is placed over the gas-burner, and 
forms a support for a dish, flask, or other vessel. In some 
cases, however, the furnace-hood, (fig. 16,) will be found 
to form a better arrangement for getting rid of noxious 
vapours. It is made of tin-plate, and is placed, as repre- 
sented, on the top of the furnace over the circular opening 
C, while the vessel from which vapours are disengaged 
stands a little in front of the opening. 
" Under these circum- 
stances, the vapours arising 
from the dish will be 
drawn into the furnace as 
indicated by the arrow. If 
the furnace be well con- 
structed, this effect will be 
complete ; but, should 
there be any defect in the 
draught, it may be neces- 
sary to close the ash-pit 
door, in order to insure 
the desired result. 
