88 MEMOIR OF GALILEO. 



terward from Paris. To the consideration of this subject Le 

 immediately applied himself, and the first night after his re- 

 turn to Padua, he discovered what he sought in the doctrine 

 of refracting light. He fitted a spectacle-glass to each end of 

 a leaden tube, one of which was plano-convex, and the other 

 plano-concave, and on applying his eye to the concave glass, 

 he found that it magnified. Delighted with his discovery, 

 he carried his little instrument in triumph to Yenice, where 

 it created a most intense excitement, and for a month thou- 

 sands flocked to see it. He made a present of it to the Ve- 

 netian Senate, and received in return a perpetual grant of 

 the professorship at Padua, and an increase of salary from 

 520 to 1000 florins. It was shortly after this that he entered 

 the household of the Grand Duke of Tuscany. 



After disposing of his first instrument, which magnified 

 only three times, Galileo applied himself to the making of 

 another, which magnified eight times, and "at length," as he 

 says himself, " sparing neither labor nor expense," he con- 

 structed an instrument which magnified thirty times. With 

 this instrument he discovered the inequalities in the moon's 

 surface. " The dark and luminous spaces he regarded as in- 

 dicating seas and continents, which reflected in different de- 

 grees the incidental light of the sun ; and he ascribed the 

 phosphorescence, as it has been improperly called, or the sec- 

 ondary light which is seen on the dark limb of the moon in 

 her first and last quarters, to the reflection of the sun's light 

 from the earth." With the telescope he discovered a strik- 

 ing difference between the appearance of the fixed stars and 

 the planets. The latter exhibited round and well-defined 

 discs like the moon, while the former, even of the first mag- 

 nitude, appeared but as lucid points. He was likewise ena- 

 bled to resolve portions of nebulae and clusters, which appear- 

 ed to be hazy spots in the heavens, into distinct and numer- 

 ous stars. 



On the 7th of January, 1610, he discovered three of 



