THE SUCCESSORS OF GALILEO 



new method of grinding and polishing, whereby they 

 overcame a great deal of the spherical and chromatic 

 aberration. With this new telescope a much clearer 

 field of vision was obtained, so much so that Huygens 

 was able to detect, among other things, a hitherto un- 

 known satellite of Saturn. It was these astronomical 

 researches that led him to apply the pendulum to 

 regulate the movements of clocks. The need for some 

 more exact method of measuring time in his observa- 

 tions of the stars was keenly felt by the young as- 

 tronomer, and after several experiments along dif- 

 ferent lines, Huygens hit upon the use of a swinging 

 weight; and in 1656 made his invention of the pen- 

 dulum clock. The year following, his clock was pre- 

 sented to the states-general. Accuracy as to time is 

 absolutely essential in astronomy, but until the in- 

 vention of Huygens's clock there was no precise, nor 

 even approximately precise, means of measuring short 

 intervals. 



Huygens was one of the first to adapt the micrometer 

 to the telescope a mechanical device on which all 

 the nice determination of minute distances depends. 

 He also took up the controversy against Hooke as to 

 the superiority of telescopic over plain sights to quad- 

 rants, Hooke contending in favor of the plain. In this 

 controversy, the subject of which attracted wide at- 

 tention, Huygens was completely victorious; and 

 Hooke, being unable to refute Huygens's arguments, 

 exhibited such irritability that he increased his already 

 general unpopularity. All of the arguments for and 

 against the telescope sight are too numerous to be 

 given here. In contending in its favor Huygens point - 



219 



