ix 



smaller specula. " The essential difference of these constructions," to 

 nse the words of Sir George Airy, " as regards the movements of the 

 grinder is this : that in Lord Rosse's apparatus every stroke is very 

 nearly straight, while in Mr. Lassell's apparatus there is no resem- 

 blance to a straight movement at any part of the stroke." This is not 

 the place to describe the many new contrivances in the mode of support 

 of the mirror, in the equatorial mounting, in the polishing machine, 

 and in the arrangements of the dome under which it was erected, 

 which enabled Mr. Lassell to bring his telescope to a high degree of 

 perfection. In this connexion it should be noticed, to use Sir John 

 Herschel's words, " that in Mr. Nasmyth he was fortunate to find a 

 mechanist capable of executing in the highest perfection all his concep- 

 tions, and prepared by his own love of astronomy and practical 

 acquaintance with astronomical observations, and with the construction 

 of specula, to give them their full effect." 



With this fine instrument he discovered the satellite of Neptune. 

 This minute body was seen on October 10th, 1846, but it was not until 

 the next year that it could be satisfactorily followed, and its existence 

 fully confirmed. The superiority of the telescope, and the vigilance 

 and skill of the observer were further shown by the discovery in 1848, 

 simultaneously with Professor Bond in America, of an eighth satellite 

 of Saturn, of extreme minuteness, which was named Hyperion. In 

 1851, after long and careful search, he discovered two additional 

 satellites of the planet Uranus (Umbriel and Ariel), interior to the 

 two discovered by Sir William Herschel in 1787. 



In the autumn of 1852, he took this twenty-foot telescope to 

 Malta, and observed with it there through the winter. A very care- 

 ful and detailed drawing of the nebula of Orion, and drawings of 

 several planetary nebulas made at Malta, will be found in vol. xxiii 

 of the " Memoirs of the Royal Astronomical Society." With respect 

 to the planets, his discoveries, to use his own words, " were rather 

 negative than otherwise," for he was satisfied, that without great 

 increase of optical power, no other satellite of Neptune could be 

 detected. With regard to Uranus, he says, " I am fully persuaded 

 that either he has no other satellites than the four, or if he has, they 

 remain yet to be discovered." 



Mr. Lassell's energy and zeal in the cause of science did not 

 permit him to remain content with this magnificent telescope. His 

 last work was a much larger telescope, four feet in aperture, and 

 thirty-seven feet focus, mounted equatorially, which was erected at 

 Malta, in 1861. The work done with it, with Mr. Marth's as- 

 sistance, during the next four years, is fully described, as well as the 

 instrument itself, in vol. xxxvi of the " Memoirs of the Royal Astro- 

 nomical Society." This work consists of numerous observations of 

 nebulas and planets, and a catalogue of the places of 600 new nebulas 



