Then if that be it, the sun must appear to cross the equator twice in the year.
It does so on the 21st of March and 23rd September. These are the vernal or spring equinox, and the autumnal equinox. March is the vernal equinox of London, or equal day and night in spring; but it is the Australian autumnal equinox. In September the Australias have the spring equinox, and the English the autumnal. The sun is seen overhead to the furthest north on the 21st of June, and to the furthest south on the 21st of December.
Why, the first is the summer of England, and the last the winter. Then I suppose that is the reason why in summer the sun looks so high up at noon. Then in winter, as it is shining more over parts south of the equator, the north would neither see nor feel so much of him.
That is correct. You now see why the Australian summer is at the time of the English winter.
Yes, father; because they are on opposite sides of the equator. But you know that the sun does not really move about like this. I want to know what does move.
The earth, to be sure.
I understand that; but neither the rotundity nor motion seems to explain this mystery of the Zodiac. But let me see. When the world swings round the master light, is it obliged to keep bolt upright—north pole up and south pole down?
How would your equator then be, James?
Right opposite the sun. But that will not do, for it is not always opposite to the sun. Perhaps the world goes waddling along like a duck, first on one side a little bit, and then on the other. This would bring the sun opposite to either place.
It would be a very regular waddle. We will try your scheme. Pick up that round wooden ball there. Carry it round the capstan, and see whether by twisting it from one side to the other you can keep the south pole shone upon for six months, and the north pole shone upon for the other six months.”