Johann Kepler, who was born in Germany in 1571, contributed several important facts to astronomy. He studied the motions and laws of the celestial bodies. Copernicus taught that the planets revolved around the sun in circular orbits, but Kepler discovered that their paths are ellipses. He also found that the nearer the planets are to the sun the faster they travel. Kepler's discoveries were embodied in three great laws of astronomy known as Kepler's laws. These furnished the foundation for Newton's discoveries and are the basis of modern astronomy. Kepler died in November, 1630. Many of the wonderful discoveries that have been made in the field of astronomy could not have been possible without the telescope, the most important instrument used by astronomers. The first part of the word is the same Greek adverb meaning "afar," found in _telegraph_ and _telephone_; the last part is derived from a Greek verb meaning "to see." The telescope, therefore, is an instrument for seeing objects that are far off. It is a long tube With lenses so arranged as to make objects appear much larger than they would to the naked eye. The telescope was invented by a Dutch optician named Hans Lippershey about three hundred years ago. The Italian scientist Galileo, who was born at Pisa in February, 1564, heard of the invention, began studying the principles upon which it depends, and greatly improved it. Galileo was the first to use the telescope for astronomical purposes. With it he discovered the satellites of Jupiter, the spots on the sun, and the hills and valleys of the moon. [Illustration: GALILEO] At the present time the largest telescopes in the world are made and owned in America. The largest is the Yerkes telescope, belonging to the University of Chicago and located on the shores of Lake Geneva, Wisconsin. Microscopes, opera glasses, and other magnifying instruments depend upon the same principles as the telescope. One of the most astounding of man's tools is the spectroscope, an instrument used for analyzing light. Through a knowledge of chemistry scientists can establish scientific relations between different substances and the light which they emit. By analyzing the light from the heavenly bodies with the aid of the spectroscope, and comparing this result with the light sent out from different known kinds of matter, man can stand on this little flying speck of matter we call the earth and discover of what substances the stars are made.