TWO TRADITIONAL ROMAN TYPES:
CHANNELED AND PILLARED
Since the history of the Roman hypocaust has been fully
documented elsewhere, we may confine ourselves here to
the most summary review.[260]
This heating system, developed
to perfection by the Romans, is found not only in their
baths but also in practically every Roman villa north of the
Alps. The Roman hypocaust was either of the channeled
or the pillared type.[261]
In the latter, a good example of which,
from the Roman camp Saalburg, is shown in fig. 379, the
floor of the room to be heated was raised by short columns,
usually two feet high, a shallow chamber thus being formed
below the floor level. The heat, generated in a furnace that
was built against one of the outer walls and serviced from
the outside, was dispersed into this chamber and rose from
there in vertical flues imbedded in the walls. In the other
type, hot air was taken from the furnace through a trench
beneath the floor to the center of the room and then diverted
radially to the four corners into a channel running all the
way around the room, at the bottom of the walls, from which
point it rose into the wall flues, as in the hypocaust from a
building in block II of the Romano-British city of Silchester
(fig. 380).[262]