PHILOSOPHY. 93

If she should rise later than the sun, we could
not see her.”

* Now, there’s one more way,” said Robert.

* Yes, mother,” said Lucy ; “ what is that?”

“ Sometimes it happens,” said her mother,
* that, while Venus, after having been behind the
sun, is passing round this side of it to go be-
fore it, that it goes exactly between us and the
sun, and so we can see it pass across his face.”

‘© How does it-look?” said Lucy.

“Tt looks like a little black spot,” said her
mother—— “a little, round, black spot, moving
across the face of the sun.”

“What makes it look so black?” said Lucy.

“ Why, it is only the side which is turned to-
wards the sun that is bright, and the part that is
turned towards us, when it passes between us and
the sun, will, of course, be dark. Besides,” she
continued, “ I suppose that, strictly speaking, we -
don’t really see Venus in that case at all. We
are only prevented from seeing a part of the sun.
Venus stops all the rays from that part of the sun
which is exactly opposite to her, from coming to
us ; and it causes the appearance of a small, round,
dark spot, moving along over the face of the sun.
That is called a transit of Venus. But a transit
of Venus happens very seldom.”