ROUND TOWERS 219
overhead. Add successive ringlike courses and there is a Round
Tower, tapered for preference to give stability against big winds
and small earthquakes; it is easy to imagine the relative strengths
of a square, and of a round tower of the same wall-thickness, to
an attack by battering ram (Fig. 1c).
Another advantage of the circular section over the square is
that for the same amount of walling material, there is nearly a
third more floor-space, which may be valuable in emergency.
A structural advantage which may have been specially import-
ant in areas like East Anglia, where large building stones are
scarce, is that in a round tower, there are no quoins, or corners,
to be strengthened and no straight walls mutually at right-angles