We have already seen that single columns may be used to carry arcades of
two or more orders, either by breaking their abaci into receding angles,
to fit them to the orders of the arches, or by making round or
octagonal abaci large enough to receive them; and such single columns
may be alternated with clustered piers. There is, however, another
extensive variety of pillar compounded of the two.
[Illustration: Fig. 300.