The PresidenCs Address. 285 



practice, that the imperfect transparency of the earth's atmo- 

 sphere, and the unequal refraction which arises from differ- 

 ences of temperature, combine to set a limit to the use of 

 high magnifying powers in our telescopes. Hitherto, how- 

 ever, the application of such high powers was checked by the 

 imperfections of the instruments themselves ; and it is only 

 since the construction of Lord Rosse's telescope that astrono- 

 mers have found that, in our damp and variable climate, it is 

 only during a few days of the year that telescopes of such 

 magnitude can use successfully the high magnifying powers 

 which they are capable of bearing. Even in a cloudless sky, 

 when the stars are sparkling in the firmament, the astrono- 

 mer is baffled by influences which are invisible, and while 

 new planets and new satellites are being discovered by in- 

 struments comparatively small, the gigantic Polyphemus lies 

 slumbering in his cave, blinded by thermal currents, more 

 irresistible than the firebrand of Ulysses. As the astrono- 

 mer, however, cannot command a tempest to clear his atmo- 

 sphere, nor a thunder storm to purify it, his only alternative 

 is to remove his telescope to some southern climate, where 

 no clouds disturb the serenity of the firmament, and no 

 changes of temperature distract the emanations of the stars. 

 A fact has been recently mentioned, which intitles us to an- 

 ticipate great results from such a measure. The Marquis of 

 Ormonde is said to have seen from Mount Etna, with his 

 naked eye, the satellites of Jupiter. If this be true, what 

 discoveries may we not expect, even in Europe, from a large 

 reflector working above the grosser strata of our atmosphere. 

 This noble experiment of sending a large reflector to a 

 southern climate has been but once made in the history of 

 science. Sir John Herschel transported his telescopes and 

 his family to the south of Africa, and during a voluntary 

 exile of four years' duration, he enriched astronomy with 

 many splendid discoveries. Such a sacrifice, however, is not 

 likely to be made again ; and we must, therefore, look to the 

 aid of Government for the realization of a project which 

 every civilized people will applaud, and which, by adding to 

 the conquests of science, will add to the glory of our country. 

 At the Birmingham meeting of the Association, its attention 

 was called to this subject, and being convinced that great 



