130 LIGHT SCIENCE FOR LEISURE HOURS. 



distance. At length, setting aside all these measures, 

 and considering only the movements of the stranger, 

 Professor Saron was led to the belief that it was no 

 comet, but a member of the solar system. It was 

 eventually proved, chiefly by the labours of Lexell, 

 Lalande, and the great mathematician Laplace, that 

 this theory fully explained all the observed motions of 

 the newly-discovered body, and before long (so complete 

 is the mastery which the Newtonian system gives astro- 

 nomers over the motions of the heavenly bodies) all the 

 circumstances of the new planet's real motions became 

 very accurately known. It was now possible, not only 

 to predict the future movements of the stranger, but 

 to calculate his motions during former years. This last 

 process was quickly applied to the planet, with the 

 object of determining whether among the records of 

 observations made on stars, any might be detected 

 which related in reality to the newly-discovered body. 

 The result will appear at first sight somewhat surpris- 

 ing. The new planet had actually been observed no 

 less than nineteen times before that night when Herschel 

 first showed that it was not a fixed star, and those 

 observations were made by astronomers no less eminent 

 than Flamstead, Bradley, Mayer, and Lemonnier. 

 Flamstead had seen the planet five several times, each 

 time cataloguing it as a star of the sixth magnitude, so 

 that five such stars had to be dismissed from Flam- 

 stead's lists. But the case of Lemonnier was even more 

 singular ; for he had actually observed the planet no 

 less than twelve times, several of his observations having 



