It is no secret that the moon has no light of her own, but is, as it were, a mirror, receiving brightness from the influence of the sun.

Pytheos made a mistake by not observing that the arts are each composed of two things, the actual work and the theory of it. One of these, the doing of the work, is proper to men trained in the individual subject, while the other the theory is common to all scholars.

The stone in quarries is found to be of different and unlike qualities. In some it is soft, in others it is medium, in still others it is hard as in lava quarries. There are also numerous other kinds: for instance, in Campania, red and black tufas; in Umbria, Picenum, and Venetia, white tufa which can be cut with a toothed saw like wood.

Wind is a floating wave of air, whose undulation continually varies.

There are also half bricks. As the bricks are always laid so as to break joints, this lends strength and a not unattractive appearance to both sides of such walls.

In all matters but particularly in architecture, that which is signified is the subject of which we may be speaking and that which gives significance is a demonstration on scientific principles. One who professes himself an architect should be well versed in both directions.

Architecture depends on Order, Arrangement, Eurythmy, Symmetry , Propriety , and Economy.