Book 16
17
WE had been told that the ager Vaticanus, or Vatican region, and the presiding deity of the same place, took their names from the vaticinia, or prophecies, which were wont to be made in that region through the power and inspiration of that god. But in addition to that reason Marcus Varro, in his Antiquities of the Gods, states Frag. 20b, Agahd. that there is another explanation of the name: For, says he, just as Aius was called a god and the altar was erected in his honour which stands at the bottom of the Nova Via, because in that place a voice from heaven was heard, so that god was called Vaticanus who controls the beginnings of human speech, since children, as soon as they are born, first utter the sound which forms the first syllable of Vaticanus; hence the word vagire ('cry'), which represents the sound of a new-born infant's voice.
18
Some interesting and instructive remarks about that part of Geometry which is called Optics; of another part called Harmony, and also of a third called Metric.
18
A PART of Geometry which relates to the sight is called o)ptikh/ or Optics, another part, relating to the ears, is known as kanonikh/ or Harmony, which musicians make use of as the foundation of their art. These are concerned respectively with the spaces and the intervals between lines and with the theory of musical numbers.
