220 A SHORT HISTORY OF SCIENCE 



Venice, in order to see sails and shipping that were so far off that it 

 was two hours before they were seen, without my spy-glass, steering 

 full sail into the harbour ; for the effect of my instrument is such that 

 it makes an object 50 miles off appear as large as if it were only 

 five.' 



' But the greatest marvel of all is the discovery of four new planets. 

 I have observed then* motions proper to themselves and in relation 

 to each other, and wherein they differ from the motions of the other 

 planets. These new bodies move round another very great star, in 

 the same way as Mercury and Venus, and, peradventure, the other 

 known planets, move round the sun. As soon as my tract is printed, 

 which I intend sending as an advertisement to all philosophers and 

 mathematicians, I shall send a copy to his Highness, the Grand Duke, 

 together with an excellent spy-glass, which will enable him to judge 

 for himself of the truth of these novelties.' Fahie. 



Galileo's discoveries on the surface of the moon were ill received 

 by the followers of Aristotle. According to their preconceived opin- 

 ions, the moon was perfectly spherical and absolutely smooth ; and to 

 cover it with mountains and scoop it out into valleys was an act of 

 impiety which defaced the regular forms which Nature herself had 

 imprinted. It was in vain that Galileo appealed to the evidence 

 of observation and to the actual surface of our own globe. The very 

 irregularities on the moon were, in his opinion, a proof of divine wisdom ; 

 and had its surface been absolutely smooth, it would have been ' but 

 a vast unblessed desert, void of animals, of plants, of cities, and men 

 the abode of silence and inaction senseless, lifeless, soulless, and 

 stripped of all those ornaments which now render it so varied and so 

 beautiful.' 



In examining the fixed stars and comparing them with the planets, 

 Galileo observed a remarkable difference in the appearance of their 

 discs. All the planets appeared with round globular discs like the 

 moon; whereas the fixed stars never exhibited any disc at all but 

 resembled lucid points sending forth twinkling rays. Stars of all 

 magnitudes he found to have the same appearance; those of the 

 fifth and sixth magnitude having the same character, when seen 

 through a telescope, as Sirius, the largest of the stars, when seen by 

 the naked eye. 



Important and interesting as these discoveries were, they were 

 thrown into the shade by those to which he was led during a careful 



