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[1] At that same time, throughout the regions of the East the heaven was seen to be overcast with dark mist, through which the stars were visible continually from the first break of day until noon. It was an additional cause of terror when the light of heaven was hidden and its orb removed utterly from the sight of the world, that the timorous minds of men thought that the darkening of the sun lasted too long;
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but it thinned out at first into the form of the crescent moon, then growing to the shape of the half-moon, and was finally fully restored.
[2] This phenomenon never takes place so clearly as when the moon, after its shifting courses,
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brings back its monthly journey to the same starting-point after fixed intervals of time; that is to say, when the entire moon,
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in the abode of the same sign of the zodiac, is found in a perfectly straight line directly under the sun, and for a brief time stands still in the minute points which the science of geometry calls parts of parts.
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[3] And although the revolutions and movements of both heavenly bodies, as the searchers
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for intelligible causes had observed, after the course of the moon is completed,
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meet at one and the same point always at the same distance from each other,
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yet the sun is not always eclipsed at such times, but only when the moon (by a kind of fiery plumb-line)
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is directly opposite the sun and interposed between its orb and our vision.
[4] In short, the sun is hidden and his brightness suppressed, when he himself and the orb of the moon, the lowest of all the heavenly bodies, accompanying each other and each keeping its proper course, maintaining the relation of height between them and being in conjunction, as Ptolemy wisely and elegantly expresses it
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have come to the points which in Greek we call
ἀναβιβάζοντας and
καταβιβάζοντας
ἐκλειπτικοὶ σύνδεσμοι
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(that is, eclipse nodes). And if they merely graze the spaces adjacent to these nodes, the eclipse will be partial.
[5] If, on the other hand, they stand in the nodes themselves which closely unite the ascent and the descent, the heaven will be overcast with thicker darkness, so that because of the density of the air we cannot see even objects which are near and close at hand.
[6] Now it is thought that two suns are seen, if a cloud, raised higher than common and shining brightly from its nearness to the eternal fires,
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reflects a second brilliant orb, as if from a very clear mirror.
[7] Let us now turn to the moon. Then only does she suffer a clear and evident eclipse, when, rounded out with her full light and opposite the sun, she is distant from its orb by 180 degrees (i.e. is in the seventh sign).
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But although this happens at every full moon, yet there is not always an eclipse.
[8] But since the moon is situated near the movement of the earth, and is the most remote from heaven of all that celestial beauty,
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she sometimes puts herself directly under the disc
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that strikes upon her, and is overshadowed and hidden for a time by the interposition of the goal of darkness ending in a narrow cone;
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and then she is wrapped in masses of darkness, when the sun, as if encompassed by the curve of the lower sphere, cannot light her with its rays, since the mass of the earth is between them; for that she has no light of her own has been assumed on various grounds.
[9] And when under the same sign she meets the sun in a straight line, she is obscured (as was said) and her brightness is wholly dimmed; and this in Greek is called the moon’s
σύνοδος.
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[10] Now she is thought to be born,
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when she has the sun above her with a slight deviation from the plumbline, so to speak. But her rising, which is still very slender, first appears to mortals when she has left the sun and advanced to the second sign. Then having progressed farther and now having abundant light, she appears with horns and is called
μηνοειδής.
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But when she begins to be separated from the sun by a long distance and has arrived at the fourth sign and the sun’s rays are turned towards her, she gains greater brilliance, and is called in the Greek tongue
διχόμηνις,
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a form which shows a half-circle
[11] Then, proceeding to the greatest distance and attaining the fifth sign, she shows the figure called amphicyrtos,
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and has humps on both sides. But when she has taken a place directly opposite the sun she will gleam with full light, making her home in the seventh sign; and still keeping her place in that same sign, but advancing a little she grows smaller, the process which we call
ἀπόκρουσις
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; and she repeats the same forms as she grows old,
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and it is maintained by the unanimous learning of many men that the moon is never seen in eclipse except at the time of her mid-course.
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[12] But when we said that the sun had its course now in the ether and now in the world below,
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it must be understood that the heavenly bodies (so far as the universe is concerned) neither set nor rise, but that they seem to do so to an eyesight whose fixed situation is on the earth; this is kept hanging in space by some inner force and in its relation to the universe is like a tiny point; and that now we seem to see the stars, whose order is eternal, fixed in the sky, and often through the imperfection of human vision we think that they leave their places. But let us now return to our subject.
Res Gestae. Ammianus Marcellinus. John C. Rolfe (Translator). Cambridge, MA. 1935-1940.
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