THE GAS-LIGHT APPARATUS. 647 
cistern for holding water may be attached to the top, the 
evaporation of which will prevent the heat from becomir.ff 
excessive. 
THE GAS-LIGHT APPARATUS. 
This apparatus consists of an iron retort, about three feet 
long, and two feet in diameter, open at one of its extremities, 
to which is screwed, by means of a flaunch, a door piece : 
to this the door is applied, and is shut close by a screw 
placed in the centre. The coals to produce the gas are shut 
u]i in the retort, and the whole heated to redness by a fire 
applied underneath, the retort being placed in a sort of oven 
or furnace, so that the heat surrounds every part, except 
that at which the coals are introduced. Around the space 
of this oven a flue leads from it to the chimney, the 
aperture of which is regulated by a small damper. A plate 
of cast iron preserves the retort from being injured by the 
intensity of the fire underneath it, and causes it to be heated 
more uniformly. A cast-iron pipe conveys all the volatile 
products of the coal to a refrigeratory of cast iron, in which 
the tar, &c. extracted from the coal are deposited, and 
whence they can be drawn off by means of a copper pipe. 
The gas is conveyed from the refrigeratory to the top of a 
cylindrical vessel or receiver, which is in that part air-tight : 
consov'iuently the gas displaces the water in this receiver, to 
a level with the small holes made round its inferior edges, 
where it is sutfered to escape, and rises in bubbles, through 
the water of the well, into the receptacle or gasometer. 
This gasometer is made of wrought-iron, and is capable of 
rising, or of sinking down nearly to a level with the top of 
tlie well which contains the water, when it will consequently 
ba nearly filled with that fluid ; but it rises gradually as the 
elastic gas enters it from the pipe, and displaces the water. 
^^'eights are suspended to balance and keep it steady j it is 
strengthened withinside by two sets of iron stays ; its seams 
•ire luted to make them air-tight j and it is well painted in- 
side and outside to preserve it from rust. 
I’he use of the gasometer is to equalize the emission of 
the gas, which issues from the retort more quickly at some 
times than at others. When this happens, the vessel rises 
Up to receive it; and when the stream from the retort 
