‹‹‹ Vitr. 2.9.10 | Table of Contents | Vitr. 2.9.12 ›››
11This is most evident at Ravenna, a city, the foundations of whose buildings, both public and private, are all built upon piles. The elm tree and the ash contain much water and but little air and fire, with a moderate portion of earth. They are therefore pliant, and being so full of water, and from want of stiffness, soon bend under a superincumbent weight. When, however, from proper keeping after being felled, or from being well dried while standing to discharge their natural moisture, they become much harder, and in framings are, from their pliability, capable of forming sound work.
11One can see this at its best in Ravenna; for there all the buildings, both public and private, have piles of this sort beneath their foundations. The elm and the ash contain a very great amount of moisture, a minimum of air and fire, and a moderate mixture of the earthy in their composition. When put in shape for use in buildings they are tough and, having no stiffness on account of the weight of moisture in them, soon bend. But when they become dry with age, or are allowed to lose their sap and die standing in the open, they get harder, and from their toughness supply a strong material for dowels to be used in joints and other articulations.