To describe the period of 24 hours, regarded as a single unit for purposes of calculation, most modern and also the ancient tongues employ the term that denotes its light part, i. e. ‘day’ etc. Primitive peoples have no term to express this idea and must describe the period by means of expressions equivalent to ‘day and night’, e. g. ‘sun-darkness’ (Malay Archipelago)[2], ‘light and darkness’ (Yukaghir in N. E. Asia)[3]. The day is sometimes described by the concrete phenomenon which it brings, namely the sun. The Bontoc Igorot of north Luzon have the same word for sun as for day, _a-qu_, and the time is reckoned in suns[4]. The Comanche Indians reckon the days in ‘suns’[5], and in an Indian hieroglyph from the northern shores of Lake Superior the duration of a three days’ journey described is expressed by three circles, i. e. three suns[6]. The western tribe of the Torres Straits reckons time in ‘suns’, i. e. days[7]. We may compare the well-known primitive idea that the sun originates afresh for every new day. The same thing is found in the language of signs. La Billardière in the year 1800 relates of the very low Tasmanians, now long since extinct, that they had some idea of regulating time by the apparent motion of the sun. In order to inform him that they would make a journey in two days, they indicated with their hands the diurnal motion of the sun and expressed the number two by as many of their fingers. This, he asserts, is the only reference that can be found to any knowledge of the movements of the heavenly bodies[8]. So also according to Homfray the natives of the Andamans describe a day by making a circle with the right arm, i. e. a revolution of the sun. We may compare the indication of the time of day by pointing with the hand to the position of the sun, with which we shall shortly have to deal. It is not improbable that the designation of the day by means of an indication of the course of the sun arose in the first place from the indication of the position of that planet. The same method of expression is found in the classical languages as a poetic or hierarchical archaism[9], and also in medieval Latin. But ἥλιος, _sol_, is also used to denote the yearly revolution of the sun, i. e. a year, and the year is denoted by φάος, _lux_. Still more striking and more significant for the discontinuous method of reckoning is the Homeric use of ἠώς, ‘dawn’, instead of day, e. g. “this is the twelfth dawn since I came to Ilion”,[10] “this is the twelfth dawn he lies so”,[11] and elsewhere. Aratus follows the Homeric use[12]. The nature of this _pars pro toto_ reckoning will be further explained in the chapter dealing with the year.