CH. xxxi. SIR JOHN HERSCHEL. 295 



So true is the law of gravitation that two men sitting at 

 home in their studies were enabled, from slight irregularities 

 in the motion of Uranus to predict the existence and place 

 of a disturbing body, rolling on through space ! This new 

 planet is called Neptune, and is a little larger than Uranus; 

 it has certainly one moon, discovered by M. Lassell, and 

 Herr Struve thinks he has seen a second. 



Sir John Herschel's work in Astronomy. While these 

 different discoveries were being made in the observatories of 

 Europe, Sir John Herschel was carrying on the work his 

 father had begun of gauging or measuring the brilliancy of 

 the stars. Born at Slough, close to his father's observatory, 

 in 1792, the young John Herschel spent his early life with 

 his father and aunt, and saw them always busy night and 

 day studying the heavens. In 1813 he was Senior Wrangler 

 at Cambridge, and after that he turned his attention to 

 double stars, and in 1828 completed a list of no less than 

 2,000 of these wonderful double and sometimes treble suns 

 which revolve round each other. When he had completed 

 the survey of the whole of our northern skies, he went in 

 1833 to the Cape of Good Hope, where an observatory 

 had been built in 1820, and there he spent four years 

 gauging the stars of the southern hemisphere and classing 

 them according to their brilliancy, as his father had classed 

 those of the northern hemisphere. He was thus the first 

 astronomer who swept his telescope over the whole of the 

 heavens which are visible from our planet, and who saw 

 with his own eyes every star, planet, and nebula then 

 visible in the sky. Among the remarkable appearances 

 which he examined were those cloudy masses of light called 

 the Magellanic Clouds y which are the Milky Way of the 

 southern hemisphere, and he found them to be made up of 



