Our span of life is divided into parts; it consists of large circles enclosing smaller. One circle embraces and bounds the rest; it reaches from birth to the last day of existence. The next circle limits the period of our young manhood. The third confines all of childhood in its circumference. Again, there is, in a class by itself, the year; it contains within itself all the divisions of time by the multiplication of which we get the total of life. The month is bounded by a narrower ring. The smallest circle of all is the day; but even a day has its beginning and its ending, its sunrise and its sunset. 7. Hence Heraclitus, whose obscure style gave him his surname, remarked: "One day is equal to every day." Different persons have interpreted the saying in different ways. Some hold that days are equal in number of hours, and this is true; for if by "day" we mean twenty-four hours' time, all days must be equal, inasmuch as the night acquires what the day loses. But others maintain that one day is equal to all days through resemblance, because the very longest space of time possesses no element which cannot be found in a single day, – namely, light and darkness, – and even to eternity day makes these alternations more numerous, not different when it is shorter and different again when it is longer. 8. Hence, every day ought to be regulated as if it closed the series, as if it rounded out and completed our existence.