All... must be built with due reference to durability, convenience, and beauty. Durability will be assured when foundations are carried down to the s… - Vitruvius

These are, of course, some things which, for utility's sake, must be made of the same size in a small theatre, and a large one: such as the steps, curved cross-aisles, their parapets, the passages, stairways, stages, tribunals, and any other things which occur that make it necessary to give up symmetry so as not to interfere with utility.

These rules for symmetry were established by Hermogenes, who was also the first to devise the principal of the pseudodipteral octastyle.

Travertine and all stone of that class can stand injury whether from a heavy load laid upon it or from the weather; exposure to fire, however, it cannot bear, but splits and cracks to pieces at once. This is because in its natural composition there is but little moisture and not much of the earthy, but a great deal of air and of fire. Therefore, it is not only without the earthy and watery elements, but when fire, expelling the air from it by the operation and force of heat, penetrates into its inmost parts and occupies the empty spaces of the fissures there comes a great glow and the stone is made to burn as fiercely as do the particles of fire itself.