loS HISTORY OF SCIENCE. 



from the writings of Fracastor, who died in 1533, and from those of 

 Baptista Porta and others, have been construed into indications of 

 an acquaintance with the telescope. It is tolerably certain that a 

 Dutch optician named Lipperhey accidentally hit upon an arrangement 

 of two convex lenses, which formed a telescope. The fact of this ar- 

 rangement being that which is now called the Astronomical Telescope, 

 is indicated by a circumstance expressly mentioned, namely, that the 

 weathercock of a church was seen through it, magnified, but inverted. 

 Iaj:6oQ Galileo, being at Venice, heard that an instrument had been 

 invented in Holland which caused distant objects to appear nearer. 

 When he had returned to Padua, he considered by what means this 

 effect must have been produced. He soon arrived at the conclusion 

 that two lenses, either concave or convex, must have been employed, 

 and proceeding to experiments, he found that the desired effect was 

 producible by placing at suitable distances a concave lens near the 

 eye and a convex towards the object. This is exactly the arrangement 

 which is adopted in the opera-glass ; but although after Galileo's dis- 

 coveries had made the telescope famous, telescopes were in the first 

 instance made on his plan, it has been found more advantageous to 

 adopt theprinciple involved in Lipperhey 's combination, and telescopes 

 are now always constructed with convex lenses. As soon as Galileo 

 had completed his first telescope, which magnified only three times. 

 he took it to Venice, where it made a great sensation, and Galileo's 

 quarters were daily besieged by a multitude of persons eager to satisfy 

 their curiosity concerning the new invention. It is said that Galileo 

 spent more than a month in exhibiting his instrument to the principal 

 inhabitants. The Doge caused a hint to be given to Galileo that the 

 Senate would be proud of the possession of so marvellous an instru- 

 ment, and Galileo, having taken the hint and presented the telescope 

 to his patrons, was rewarded by being appointed to the Padua profes- 

 sorship for life, and his salary was doubled. The public curiosity did 

 not subside for a long time, and instruments of a very inferior kind 

 were soon made and sold everywhere in great numbers as philoso- 

 phical toys. The instrument was not at first called a telescope, but 

 was known as Galileo's Tube, or the Perspective, or the Double Eye- 

 glass. 



Galileo proceeded to construct a second and more powerful instru- 

 ment, which gave him a magnifying power of eight, and immediately 

 directing it to the heavenly bodies, began with the moon that series 

 of splendid discoveries which will make his name immortal as long as 

 the human race remain to watch the planets which roll through the 

 sky. In the moon he recognized elevations and depressions like the 

 mountains and valleys which diversify the surface of our own globe. 

 The darker spaces he considered to be seas, the lighter continents. 

 The oft-quoted lines of Milton thus correctly describe Galileo's con- 

 clusions about the moon : 



