ficulty to the reception of the Copernican doctrine.

[Illustration: FIG. 46.--Old drawings of Saturn by different observers,
with the imperfect instruments of that day. The first is Galileo's idea
of what he saw.]

Copernicus had predicted, indeed, a hundred years before, that, if ever
our powers of sight were sufficiently enhanced, Venus and Mercury would
be seen to have phases like the moon. And now Galileo with his
telescope verifies the prediction to the letter.

Here was a triumph for the grand old monk, and a bitter morsel for his
opponents.

Castelli writes: "This must now convince the most obstinate." But
Galileo, with more experience, replies:--"You almost make me laugh
by saying that these clear observations are sufficient to convince
the most obstinate; it seems you have yet to learn that long ago
the observations were enough to convince those who are capable of
reasoning, and those who wish to learn the truth; but that to
convince the obstinate, and those who care for nothing beyond the
vain applause of the senseless vulgar, not even the testimony of
the stars would suffice, were they to descend on earth to speak for
themselves. Let us, then, endeavour to procure some knowledge for
ourselves, and rest contented with this sole satisfaction; but of
advancing in popular opinion, or of gaining the assent of the
book-philosophers, let us abandon both the hope and the desire."

[Illustration: FIG. 47.--Phases of Venus. Showing also its apparent
variations in size by reason of its varying distance from the earth.
When fully illuminated it is necessarily most distant. It looks
brightest to us when a broad crescent.]

What a year's work it had been!

In twelve months observational astronomy had made such a bound as it has
never made before or since.

Why did not others make any of these observations? Because no one could
make telescopes like Galileo.

He gathered pupils round him however, and taught them how to work the
lenses, so that gradually these instruments penetrated Europe, and
astronomers everywhere verified his splendid discoveries.

But still he worked on, and by March in the very next year, he saw
something still more hateful to the Aristotelian philosophers, viz.
spots on the sun.

[Illustration: FIG. 48.]

If anything was pure and perfect it was the sun, they said. Was this
impostor going to blacken its face too?

Well, t