And these parts or divisions are made in a similar manner in the year--in Spring, in Summer, in Autumn, and in Winter.

And it is the same in the day even to the third hour, and then even to the ninth, leaving the sixth in the middle of this part, or division, for the reason which is understood, and then even to vespers, and from vespers onwards.

And therefore the Gentiles said that the chariot of the Sun had four horses; they called the first Eoo, the second Piroi, the third Eton, the fourth Phlegon, even as Ovid writes in the second book of the Metamorphoses concerning the parts or divisions of the day.
And, briefly, it is to be known that, as it has been said above in the sixth chapter of the third treatise, the Church makes use of the hours temporal in the division of the day, which hours are twelve in each day, long or short according to the amount of sunlight; and because the sixth hour, that is, the midday, is the most noble of the whole day, and has in it the most virtue, the Offices of the Church are approximated thereto in each side, that is, from the prime, and thence onwards as much as possible; and therefore the Office of prime, that is, the tertius, is said at the end of that part, and that of the third part and of the fourth is said at the beginning; and therefore, before the clock strikes in a division of the day, it is termed half-third or mid-tertius; or mid-nones, when in that division the clock has struck, and thus mid-vespers.
And, therefore, let each one know that the right and lawful nones ought always to strike or sound at the beginning of the seventh hour of the day, and let this suffice to the present digression..