hers.
When Mr. Clark found his son trying to make a telescope out of the
pieces of a bell, he became interested in telescopes. He studied all
about them in order to help the boy with his work. He helped his son
grind the metal disc into a concave mirror; that is, a mirror that is a
little dish-shaped. With this they made a telescope with which they
could see the rings of Saturn, and the little moons that revolve round
Jupiter.
After Mr. Clark had made this little telescope, he made larger
reflecting telescopes that were very powerful. But he found that no
telescope with a mirror in it could be very good.
He now said to his son that they would make a refracting telescope;
that is, one in which no mirror is used, but which brings the distant
stars to the sight by the light shining through lenses. Lenses are
large glasses that are regularly thicker in one part than in another.
The glasses you see in spectacles are small lenses.
George Clark, the son, told his father that the books said that the
grinding of such glasses was very difficult. Mr. Clark would not give
it up because it was hard. He liked to do hard things. He had already
spent a great part of his money trying to make good reflecting
telescopes; but he made up his mind to give them up, and try to make a
better kind. He first looked through the great telescope just put up
for Harvard College. The large lens in this telescope was not perfect,
and Mr. Clark's eye was so good that he could see what the small fault
was. When he heard that twelve thousand dollars had been paid for this
glass, he was encouraged to try to make such lenses. But there was
nobody in this country who could show him how to do it.
He first got some poor lenses out of old telescopes. These he worked
over, and made them better. By this means he learned how to do it. Then
he got some discs of glass and made some new lenses. These were the
best ever made in this country. But he was not satisfied. He kept on
making better and larger lenses. With one of these he discovered two
double stars, as they are called. These had never been seen to be
double before.
But nobody in America would believe that some of the best telescopes in
the world were made in this country, for even the English astronomers
had to get their telescopes in Germany.
With one of his telescopes, larger than any he had made before, Mr.
Clark now made a new discovery. He wrote about this to an English
astronomer named
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