Page:Historical eclipses.djvu/28

 Eclipse of Sardis.

I pass over the total eclipse of the Sun which is said by Herodotus to have been seen when the army of Xerxes had left Sardis. All that I wish to say about it is that, like four of the Chinese eclipses, it didn't happen.

Eclipse of Thucydides.

The next eclipse to which I would invite your attention is recorded in the second book of Thucydides and took place in B.C. 431 August 3. Thucydides describes it as follows:

'During the same summer at the beginning of a lunar month (the only time, it seems, when such an occurrence is possible) the sun was eclipsed after midday; it assumed the shape of a crescent (literally "became moon-shaped") and became full again, and during the eclipse some stars became visible.'

The statement that stars were visible during this eclipse has led to interesting discussions. My elements of the motion of Sun and Moon would give the eclipse at its greatest phase a magnitude of 10&middot;50 digits at Athens; as 12 digits constitute totality, this would mean that seven-eighths of the Sun's diameter were eclipsed. Ginzel makes it 10&middot;03 at Athens, uncovering about a third as much again as I do. The difference is not unimportant. It is generally supposed that no star except Venus is visible except when an eclipse verges on totality, and it has therefore seemed necessary to make one of three assumptions:

(1) That the plural 'some stars' is an exaggeration. I regret that in my paper published in the Monthly Notices of the Royal Astronomical Society for last December I adhered to this view.