CH. xix. H ALLEY'S COMET. 163 



tions. He was the first astronomer who foretold the return 

 of a comet. Before his time it was thought that they went 

 away and never came back again ; but when the comet of 

 1682 appeared, Halley began to search for former records 

 of comets and found that one had been seen about every 

 seventy-six years, reckoning backwards from 1682. There- 

 fore he thought these must all be the same comet, and he 

 foretold its return in 1758. It came as predicted, and has 

 ever since been called * Halley's comet.' Halley died in 

 1742, and with him ends the astronomy of the seventeenth 

 century. 



Chief Works consulted. Proctor's ' Transits of Venus j ' Herschel's 

 ' Astronomy ; ' Denison's ' Astronomy without Mathematics ; ' Airy's 

 ' Popular Astronomy.' 



