VIII
HERACLITUS
IF the astronomy of Xenophanes represents a decided set-back in comparison with the speculations of Anaximander and Anaxi-menes, this is still more the case with Heraclitus of Ephesus (fl. 504/0, and therefore born about 544/0 B.C.); he was indeed no astronomer, and he scarcely needs mention in a history of astronomy except as an illustration of the vicissitudes, the ups and downs, through which a science in its beginnings may have to pass. Hera-clitus’s astronomy, if it can be called such, is of the crudest description. He does not recognize daily rotation; he leaves all the apparent motions of the heavenly bodies to be explained by a continued interchange of matter between the earth and the heaven.1 His original element, fire, condenses into water, and water into earth; this is the downward course. The earth, on the other hand, may partly melt; this produces water, and water again vaporizes into air and fire; this is the upward course. There are two kinds of exhalations which arise from the earth and from the sea; the one kind is bright and pure, the other dark; night and day, the months, the seasons of the year, the years, the rains and the winds, &c, are all produced by the variations in the proportion between the two exhalations. In the heavens are certain basins or bowls 
turned with their concave sides towards us, which collect the bright exhalations or vaporizations, producing flames; these are the stars.2 The sun and the moon are bowl-shaped, like the stars, and they are similarly lit up.3 The flame of the sun is brightest and hottest; the other stars are further away from the earth and consequently they give out less light and warmth. The moon, although nearer the earth, moves in less pure air and is consequently dimmer than the sun; the sun itself moves in pure and transparent air and is at a moderate distance from us, so that it warms and illuminates more.4 ‘If there were no sun, it would be night for anything the other stars could do.’5 Both the sun and the moon are eclipsed when the bowls are turned upwards (i.e. so that the concave side faces upwards and the convex side faces in our direction); the changes in the form of the moon during the months are caused by gradual turning of the bowl.6
According to Heraclitus there is a new sun every day,7 by which is apparently meant that, on setting in the west, it is extinguished or spent,8 and then, on the morrow, it is produced afresh in the east by exhalation from the sea.9
The question arises, what happens to the bowl or basin supposed to contain the sun if the sun has to be re-created in this way each morning? Either a fresh envelope must be produced every day for the rising of the sun in the east or, if the envelope is supposed to be the same day after day, it must travel round from the west to the east, presumably in the encircling water, laterally.10 Diogenes Laertius (i. e. in this case Theophrastus) complains that Heraclitus gave no information as to the nature of these cups or basins. The idea, however, of the sun and moon being carried round in these 
reminds us forcibly of the Egyptian notion of the sun in his barque floating over the waters above, accompanied by a host of secondary gods, the planets and the fixed stars.11
Heraclitus held (as Epicurus did long afterwards) that the diameter of the sun is one foot,12 and that its actual size is the same as its apparent size.13 This in itself shows that Heraclitus was no mathematician; as Aristotle says, ‘it is too childish to suppose that each of the moving heavenly bodies is small in size because it appears so to us observing it from where we stand.’14
He called the arctic circle by the more poetical name of ‘the Bear’, saying that ‘the Bear represents the limits of morning and evening’ . . . whereas of course it is the arctic circle, not the Bear itself, which is the confine of setting and rising15 (i.e. the stars within the arctic circle never set).
According to Diogenes Laertius, Heraclitus said absolutely nothing about the nature of the earth;16 but we may judge that in his conception of the universe he was closer to Thales than to Anaximander; that is, he would regard the universe as a hemisphere rather than a sphere, and the base of the hemisphere as a plane containing the surface of the earth surrounded by the sea; if he recognized a subterranean region, under the name of Hades, he does not seem to have formed any idea with regard to it beyond what was contained in the current mythology.17
When he gave 10,800 solar years as the length of a Great Year,18 he meant no astronomical Great Year, but the period of duration of the world from its birth to its resolution again into fire and vice versa. He arrived at it, apparently, by taking a generation of 30 years as a day and multiplying it by 360 as the number of days in a year.19