3There are five species of courts; which receive their names from their forms. The Tuscan, Corinthian, the Tetrastylôn (with four columns), the Displuviatum (open at top), and the Testudinatum (roofed). The Tuscan cavædia are those in which the beams across the breadth of the court have trimmers (interpensivæ) to them, and valleys (colliquiæ) from the internal angles of the walls to the angles formed by the junctions of the beams and trimmers. Thus the rain falls into the middle of the court from the eaves of the rafters. In the Corinthian cavædium, the beams and uncovered middle of the court (compluvium) are as in the foregoing; but the beams around are detached from the walls, and rest on columns. The tetrastyle are those wherein columns are placed under the beams at the angles, which give strength and support to the beams; for thus they are not so liable to sag with their own weight, nor are they loaded by the trimmers.
3There 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.