344 POPULAR SCIENCE MONTHLY. 



less new stars to light. In the belt and sword of Orion he sees eighty 

 stars where only seven were known before ; in the Pleiades forty instead 

 of six or*seven. The Milky Way is a multitude of faint stars clustered 

 together. The nebulas of Orion and Praesepe are formed of stars. 

 His discovery of the moons of Jupiter dates from January 7, 1610, 

 when three of them were seen. They describe circular orbits abont 

 their planet. Jupiter, like each of the planets, has an atmosphere, he 

 says. His telescope was not perfect enough to show this. It is a de- 

 duction from analogy. 



Xew discoveries soon followed in respect to Saturn (Dec, 1610) 

 and Venus (Jan., 1611), and they were announced in anagrams as 

 follows : 



Smaismrmilmepoetalevmibvnenvgttaviras. 



Altissimvm planetam tergeminvm observavi. 



(I have observed the highest planet — Saturn — to be tri-form.) 



HiEC immatura a me jam feustra leguntur. O. Y. 



Cynthia figuras aemulatur mater amorum. 



(The mother of the loves — Venus — emulates the figure of Cynthia — the Moon.) 



The latter discovery was of capital importance. If the planet Venus 

 revolved about the sun as Copernicus had said, it must show phases like 

 the moon. The phases, invisible to Copernicus, were revealed by the 

 telescope. They occurred at the precise times required to demonstrate 

 the truth of his theory. It was now no longer a theory. It was 

 proved. From this moment no competent witness could doubt the 

 truth of the Copernican system — Galileo less than any one. 



An opportunity unique in the history of the world was presented 

 to Galileo and he utilized it to the full. He went from triumph to 

 triumph. The phases of Venus, the mountains of the moon, the con- 

 stitution of the Milky Way, the tricorporate figure of Saturn, the solar 

 spots, the moons of Jupiter, were death-blows to the systems of Aris- 

 totle and of Ptolemy, and were skilfully utilized to establish the sys- 

 tem of Copernicus. That system rests, for us, not on the telescopic 

 discoveries of Galileo, but on the working out of its details by Kepler 

 and Newton. To the Italians of Galileo's day Kepler was all but un- 

 known; it is even doubtful whether Galileo appreciated Kepler's splen- 

 did discoveries; it is, at any rate, certain that he never publicly men- 

 tioned them with praise. 



The mere fact that the number of planets and satellites was in- 

 creased by Galileo's telescope from seven to eleven was another blow to 

 ancient superstitions. Seven was a mystic and magical number. It 

 had relations even to Christianity, so his contemporaries thought. The 

 seven golden candlesticks of Revelations were the seven planets. We 

 can form some idea of the hold of certain magical numbers on the im- 

 aginations of our ancestors by remembering that when Huyghens dis- 



