ch being
required for its strength only, not for its elevation. There is,
therefore, no reason why it should not be barred across by a horizontal
lintel, into which the valves may be fitted, and the triangular or
semicircular arched space above the lintel may then be permanently
closed, as we choose, either with bars, or glass, or stone.

This is the form of all good doors, without exception, over the whole
world and in all ages, and no other can ever be invented.

Sec. III. In the simplest doors the cross lintel is of wood only, and
glass or bars occupy the space above, a very frequent form in Venice.
In more elaborate doors the cross lintel is of stone, and the filling
sometimes of brick, sometimes of stone, very often a grand single stone
being used to close the entire space: the space thus filled is called the
Tympanum. In large doors the cross lintel is too long to bear the great
incumbent weight of this stone filling without support; it is, therefore,
carried by a pier in the centre; and two valves are used, fitted to the
rectangular spaces on each side of the pier. In the most elaborate
examples of this condition, each of these secondary doorways has an arch
heading, a cross lintel, and a triangular filling or tympanum of its
own, all subordinated to the main arch above.

Sec. IV. 2. Fillings of windows.

When windows are large, and to be filled with glass, the sheet of glass,
however constructed, whether of large panes or small fragments, requires
the support of bars of some kind, either of wood, metal, or stone. Wood
is inapplicable on a large scale, owing to its destructibility; very fit
for door-valves, which can be easily refitted, and in which weight would
be an inconvenience, but very unfit for window-bars, which, if they
decayed, might let the whole window be blown in before their decay was
observed, and in which weight would be an advantage, as offering more
resistance to the wind.

Iron is, however, fit for window-bars, and there seems no constructive
reason why we should not have iron traceries, as well as iron pillars,
iron churches, and iron steeples. But I have, in the "Seven Lamps,"
given reasons for not considering such structures as architecture at
all.

The window-bars must, therefore, be of stone, and of stone only.

Sec. V. The purpose of the window being always to let in as much light,
and command as much view, as possible, these bars of stone are to be made
as slender and as few as t