an aperture be left with a breadth of not less than one fourth nor more than one third the width of the atrium, and with a length proportionate to that of the atrium.
7. Peristyles, lying athwart, should be one third longer than they are deep, and their columns as high as the colonnades are wide. Intercolumniations of peristyles should be not less than three nor more than four times the thickness of the columns. If the columns of the peristyle are to be made in the Doric style, take the modules which I have given in the fourth book, on the Doric order, and arrange the columns with reference to these modules and to the scheme of the triglyphs.
PLAN OF THE HOUSE OF THE VETTII, POMPEII
8. Dining rooms ought to be twice as long as they are wide. The height of all oblong rooms should be calculated by adding together their measured length and width, taking one half of this total, and using the result for the height. But in the case of exedrae or square oeci, let the height be brought up to one and one half times the width. Picture galleries, like exedrae, should be constructed of generous dimensions. Corinthian and tetrastyle oeci, as well as those termed Egyptian, should have the same symmetrical proportions in width and length as the dining rooms described above, but, since they have columns in them, their dimensions should be ampler.
9. The following will be the distinction between Corinthian and Egyptian oeci: the Corinthian have single tiers of columns, set either on a podium or on the ground, with architraves over them and coronae either of woodwork or of stucco, and carved vaulted ceilings above the coronae. In the Egyptian there are architraves over the columns, and joists laid thereon from the architraves to the surrounding walls, with a floor in the upper
