330 Economy of Fuel. 
ney, and insert a pipe connected with a proper air chamber, or drum, 
of sheet iron through which the gas might be made to pass and again 
be returned to the flue above the intercepting partition. The plan 
actually adopted, as the most simple, was to cover the top of the flue 
from which the gas originally escaped, with a board laid in mortar 
over the top of the chimney, and when the hot air had.traversed the 
drum, to turn it into another flue which remained open at the top, but 
closed at bottom, except a single aperture for the admission of a pipe 
from the drum. The arrangement is seen in the accompanying fig- 
ure, where F is the flue coming from the basement; E is the six inch 
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pipe which receives the gas; D is the drum ‘three feet wad nine 
inches high by two feet in diameter, from which proceeds the pipé 
e for the exit of the gas, into the chimney at P, through the brick 
wall with which the fire place has been closed.  F’ is the flue 
through which the gas finally makes its escape into the open air; ¢ 
is a thermometer with its bulb descending through a hole perforated 
in the sheet iron, to the center of the pipe, and near where it comes 
out of the flue. This is intended to mark’ the temperature of the — 
entering gas.’ is another thermometer similarly inserted into the 
pipe where it leaves the drum, and ¢” is a third one, serving to note 
the final temperature of the gas at its exit. The drum supports 00 
its top broad shallow dish containing water to be evaporated. The 
meter which marked the temperature of the room stood with- 
in one foot of the upper end of the drum. ‘The several thermome- 
ters Tepresented, were designed not only to show the temperature at 
which the gas entered and left the apartment, but also the relative 
portions abstracte by the main body of the drum, and by the pipe 
respectively » and the extent of variation eee the proportions 
