BOOK ONE

Walls made of squared stones original: "pietre quadrate" — this refers to opus quadratum, where precisely cut rectangular blocks are laid in regular courses without mortar are seen in Rome where the forum and the Temple of Augustus were located; in these, they bonded the smaller stones with certain courses of larger stones.

The filled method, which is also called "box-work" original: "a cassa", was made by the Ancients by using planks set on edge to create a space as wide as they wanted the thickness of the wall to be. They filled this space with mortar and stones of any kind mixed together, proceeding in this way course by course. Walls of this sort can be seen at Sirmione on Lake Garda.

The walls of Naples—that is, the ancient ones—can also be said to be of this manner. These have two walls of squared stone, four feet thick and six feet apart from each other. These walls are tied together by other transverse walls cross-walls providing structural stability, and the compartments original: "casse" that remain between these cross-walls and the exterior walls are six feet square, and are filled with stones and earth.

In short, these are the methods used by the Ancients, the remains of which are visible today. From these, we understand that in walls of any kind, certain courses must be made to act like nerves structural ligaments or ribs that bind the other parts together. This should especially be observed when walls are made of bricks pietre cotte: literally "baked stones," meaning terracotta bricks; so that as the structure settles over time...