hmy of its effect. I must now tell how this may be brought about,
and first I will speak of the proper construction of a cavaedium.

CHAPTER III

PROPORTIONS OF THE PRINCIPAL ROOMS

1. There are five different styles of cavaedium, termed according to
their construction as follows: Tuscan, Corinthian, tetrastyle,
displuviate, and testudinate.

In the Tuscan, the girders that cross the breadth of the atrium have
crossbeams on them, and valleys sloping in and running from the angles
of the walls to the angles formed by the beams, and the rainwater falls
down along the rafters to the roof-opening (compluvium) in the middle.

In the Corinthian, the girders and roof-opening are constructed on these
same principles, but the girders run in from the side walls, and are
supported all round on columns.

In the tetrastyle, the girders are supported at the angles by columns,
an arrangement which relieves and strengthens the girders; for thus they
have themselves no great span to support, and they are not loaded down
by the crossbeams.

[Illustration: _From Mau_

THE HOUSE OF THE SURGEON, POMPEII

Illustrating the Tuscan Atrium

1. Fauces
2, 3. Shops
4. Storage
5. Atrium
6. Chambers
7. Tablinum
8. Alae
9, 10. Dining rooms
13. Kitchen, _a_, hearth
14. Rear Entrance
16. Portico
18. Stairs to rooms over the rear of the house
20. Garden

]

[Illustration: _From Mau_

HOUSE OF EPIDIUS RUFUS AT POMPEII

Illustrating Corinthian Atrium]

2. In the displuviate, there are beams which slope outwards, supporting
the roof and throwing the rainwater off. This style is suitable chiefly
in winter residences, for its roof-opening, being high up, is not an
obstruction to the light of the dining rooms. It is, however, very
troublesome to keep in repair, because the pipes, which are intended to
hold the water that comes dripping down the walls all round, cannot take
it quickly enough as it runs down from the channels, but get too full
and run over, thus spoiling the woodwork and the walls of houses of this
style.

[Illustration: _From Mau_

HOUSE OF THE SILVER WEDDING AT POMPEII

Illustrating the Tetrastyle Atrium

_a._ fauces
_d._ tetrastyle atrium
_n._ dining room
_o._ tablinum
_p._ andron
_r._ peristyle
_w._ summer dining room

]

The testudinate is employed where the span is not great, and where large
rooms are provided in upper stories.

3. In width and length, atriums are designed according to t