54 
MR. FARADAY ON THE 
bars, the brickwork is carried on horizontally until close to the stack. The 
sides of this part are perpendicular, and 12 inches apart : they are continued 
upwards to the top of the brickwork 14 inches unbroken, except that at 5 
inches from the bottom they are thrown back ^rd of an inch so as to form a 
ledge there. This ledge is for the purpose of receiving the edges of certain fire- 
tiles, which, when put in, form the top of the flue and at the same time the 
bottom of the glass chamber ; but the whole is so constructed, that the tiles 
can be put in and taken out at pleasure without disturbing the rest of the 
work. The side or rather end of the chamber nearest the fire is constructed 
of a fire-tile, which terminates and faces the brick arch over the fire-place, and 
extends from the surface of the brickwork downwards 9 inches to the side ledges 
before described : the further end of the chamber is finished in a similar way, 
and beyond that the flue is carried in the most convenient and direct manner, 
but without any unnecessary contraction, into the stack or chimney. The 
length of this upper aperture, afterwards constituting the chamber, is 25 inches, 
its breadth 12f inches. When the bottom tiles are in their places, they leave 
a depth of 5 inches for that part of the furnace or flue beneath the chamber, 
which is also 38 inches from the fire to the end, and, with the exception of cer- 
tain supports in it, is 12 inches wide. 
These supports are built in with the bottom of the flue. They are essential 
to the permanency and regularity of the bottom of the glass chamber, and re- 
quire considerable nicety in their arrangement. They consist of fire-bricks 
placed up on end, so that their narrowest surfaces are towards the ends of the 
furnace, their sides or broadest exposed surfaces parallel with the sides of the 
furnace itself. They rise to the same height above the bottom of the flue as 
the ledges on the sides of the brickwork, or 5 inches, and with them, form the 
support for the bottom tiles. There are three of them in our furnace, placed 
in a line equidistant from the two sides of the flue; and being 2 \ inches thick, 
they leave spaces for the passage of flame and the reception of coke, which are 
\% inches in width. The first of these is two inches from the back edge of the 
fire, and in that direction extends 4 inches ; the second is 4 inches from the 
first ; and fl inches beyond that one is the third. 
During the action of the furnace, coke is supplied to this part, and arranged 
through two holes level with this space, and wrought in the side of the furnace 
