Three great inventors in this country were portrait painters. Fulton, the builder of steamboats, was one of them; Morse, who planned our first electric telegraph, was another; and Alvan Clark, who found out a way of making the largest and finest telescopes in the world, was another.

Alvan Clark was the son of a farmer. When he was eighteen years old, he set to work to learn engraving and drawing. He had no teacher. After a while he began to draw portraits. Once he sent to Boston to get some brushes to paint with. When the brushes came, there was a piece of newspaper wrapped round them. In this bit of newspaper was an advertisement that engravers were wanted. He went to Boston, and found regular work as an engraver.

When he was not busy engraving, he was studying painting. After some years he became a painter of portraits and miniatures. He lived at Cambridgeport, near Boston.

While Mr. Clark was living at Cambridgeport, his son was at a boarding school. The young boy had become interested in telescopes. He learned that there were two kinds of these instruments. One brought the stars nearby showing them in a curved mirror. The other magnified by means of glasses that the light shone through. He had read that it was very hard to grind these glasses or lenses, as they are called, so that they would be correct. The telescope that used the mirror was not so good, but it was easier to make. So George Clark made up his mind that he would make a reflecting telescope; that is, one with a mirror in it.

The mirror in such a telescope is made of polished metal. One day somebody broke the dinner bell at the boarding school. George dark picked up the pieces of brass and took them home.

These pieces of brass he put into a retort. A retort is a vessel that will bear great heat, and that is used for melting metals and other substances. Young Clark put some tin into the retort with the brass. When the two metals were melted together, he poured the liquid into a mold. When it became cold, it was a round flat piece. Such a piece is called a disc.

Alvan Clark, the father, was a very ingenious man. He was a fine marksman. One reason that he could shoot so well was that his eye was so true. Another was that he made his own rifles, and made them better than others.

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 Dawes. Mr. Dawes thought that a telescope that could make such a discovery would be worth having, so he bought the large lens out of this new telescope. Then he bought other glasses from Mr. Clark, and sold them again to other astronomers. In this way Mr. Clark became famous in England.

Mr. Clark had given up painting. He put his whole heart into making the best telescopes in the world. He went to England and saw the great astronomers, and looked through their telescopes.

They were glad to see the man who made the best lenses in the world. His telescopes had helped them to find out many new things never seen before. By this time Mr. Clark was coming to be known in his own country. He got an order to make the largest glass ever made for a telescope in the whole world. This was to be put up in America. Nobody had ever dreamed of making so large and powerful a telescope.

After a long time the great glass for this telescope was ground. Mr. Clark set it up to try it. His younger son, Alvan, who was helping him, turned the telescope so as to look at the bright star Sirius. As soon as he had looked, he cried out in surprise, "Why, father, the star has a companion!" Sirius is a sun. It has a satellite, a dark star like our world revolving round it. Nobody had ever been able to see this dark star before. But this telescope was stronger than any that had ever been pointed at the sky.

Mr. Clark now looked through the tube himself. Sure enough, there was the companion of Sirius, never seen before by anybody on the earth. The large glass which had been a year in making had won its first victory. But Mr. Clark made much larger glasses even than that one. He had nobody to show him how. But by patient thought and hard work he had made the greatest telescopes in the world. Medals and other honors were sent to him from many countries.