Cotidie vero discedens cum pervenit ad diem septimum, distans a sole occidente circiter medias caeli regiones, dimidia luce, et eius quae ad solem pars spectat, ea est inluminata.
When in its daily departure it comes to the seventh day, being distant from the western sun about half the region of the sky, it has half its light and that part which looks towards the sun is illuminated.
final_alignments\Vitruvius_Architecture_Book_9.json