[149] From the spring equinox to the summer solstice, day receives an addition to its length, and night, on the other hand, submits to a diminution; until the longest day and the shortest night are both completed. And then after the summer solstice the sun, turning back again the same road, neither more quickly nor more slowly than he advanced, but always preserving the same difference in the same manner, having a constantly equal arrangement, proceeds on till the autumnal equinox; and then, having made day and night both equal, it begins to increase the length of the night, diminishing the day until the time of the winter solstice.