13Divide the whole circle into sixteen parts. From the point E, at which the southern end of the meridian line touches the circle, set off at G and H to the right and left a distance equal to one of the said sixteen parts, and in the same manner on the north side, placing one foot of the compasses on the point F, mark on each side the points I and K, and with lines drawn through the centre of the circle join the points GK and HI, so that the space from G to H will be given to the south wind and its region; that from I to K to the north wind. The remaining spaces on the right and left are each to be divided into three equal parts; the extreme points of the dividing lines on the east sides, to be designated by the letters L and M; those on the west by the letters NO; from M to O and from L to N draw lines crossing each other: and thus the whole circumference will be divided into eight equal spaces for the winds. The figure thus described will be furnished with a letter at each angle of the octagon. Thus, beginning at the south, between the regions of Eurus and Auster, will be the letter G; between those of Auster and Africus, H; between Africus and Favonius, N; between that and Caurus, O; K between Caurus and Septentrio; between Septentrio and Aquilo, I; between Aquilo and Solanus, L; and between that and Eurus, M. Thus adjusted, let a bevel gauge be applied to the different angles of the octagon, to determine the directions of the different streets and lanes.
13Then find with the compasses a sixteenth part of the entire circumference; then centre the compasses on the point E where the line to the south touches the circumference, and set off the points G and H to the right and left of E. Likewise on the north side, centre the compasses on the circumference at the point F on the line to the north, and set off the points I and K to the right and left; then draw lines through the centre from G to K and from H to I. Thus the space from G to H will belong to Auster and the south, and the space from I to K will be that of Septentrio. The rest of the circumference is to be divided equally into three parts on the right and three on the left, those to the east at the points L and M, those to the west at the points N and O. Finally, intersecting lines are to be drawn from M to O and from L to N. Thus we shall have the circumference divided into eight equal spaces for the winds. The figure being finished, we shall have at the eight different divisions, beginning at the south, the letter G between Eurus and Auster, H between Auster and Africus, N between Africus and Favonius, O between Favonius and Caurus, K between Caurus and Septentrio, I between Septentrio and Aquilo, L between Aquilo and Solanus, and M between Solanus and Eurus. This done, apply a gnomon to these eight divisions and thus fix the directions of the different alleys.