Our task is now to make clear the nature of these discontinuous and _pars pro toto_ time-indications, since from them proceeds, as order is ever evolved out of chaos, the continuous time-reckoning, the calendar. CHAPTER I. THE DAY. For primitive man the day is the simplest and most obvious unit of time. The variations of day and night, light and darkness, sleeping and waking penetrate at least as deeply into life as the changes following upon the course of the year, such as heat and cold, drought and rainy seasons, periods of famine and plenty. But for the primitive intellect the year is a very long period, and it is only with difficulty and at a later stage that it can be conceived and surveyed as a whole. Day and night, on the other hand, are short units which immediately become obvious. Their fusion into a single unit, the day of 24 hours, did not take place till later, for this unit as we employ it is abstract and numerical: the primitive intellect proceeds upon immediate perceptions and regards day and night separately. Evidence for this fact is furnished by most languages, which are as a rule without any proper term for day and night together, the circle of 24 hours. In writing English one sadly misses the Swedish _dygn_, which has exactly the required significance. The German _Volltag_ is an artificial and not very happy compound. The Greeks also formed a learned and rare (though good) compound, νυχθήμερον. The usual method is to make use of a term according to the _pars pro toto_ principle. This principle, which we meet here at the outset and shall come across more and more frequently in the course of the following pages, is of great importance for the development of time-reckoning since it shews how the original time-indication is discontinuously related to a concrete phenomenon, and only slowly and at a later period develops into a continuous numerical unit of time.