1871.] 



President's Address. 



51 



cote, when Secretary of State for India), and the Mauritius Observatory, 

 under Mr. Meldrum (that establishment itself, as well as its magnetographs, 

 being mainly due to the action of Sir Henry Barkly, F.R.S., when Governor 

 of that colony). 



The care of our Foreign Secretary in watching scientific proceedings in 

 other countries has recently called our attention to the investigation of a 

 new feature in the cosmical connexions of terrestrial magnetism, in a paper 

 by Professor Hornstein, of Prague, entitled, " On the dependence of the 

 Earth's Magnetism on the Rotation of the Sun" *. From an examination 

 of the magnetic records at Prague and Vienna, Professor Hornstein infers 

 the existence of a periodic magnetic disturbance in very close accord with 

 the synodic period of the rotation of the sun-spots in the sun's equator. 



As the existence of the Great Melbourne Telescope is in no small degree 

 owing to the exertions of Members of this Society, and to their influence, 

 you will be glad to hear that it is now in regular and successful work, 

 after several difficulties and misadventures, such as often occur in the 

 early trials of uncommon instruments or new sorts of observations. Some 

 of these will be found in the volume of correspondence which your Council 

 has thought it desirable to publish, both as containing a complete history 

 of this great work from its first conception to its complete execution, and 

 also as presenting a collection of the opinions of persons whose know- 

 ledge of large telescopes must make these opinions specially valuable 

 to any who may hereafter be engaged in similar undertakings. In parti- 

 cular one matter, about which considerable apprehension was entertained, 

 the repolishing the specula at Melbourne, has been well performed. The 

 speculum, described as A in the correspondence, which had become tar- 

 nished (under circumstances described there), has been repolished, and 

 Mr. Ellery reports that "its performance is highly satisfactory." In a 

 subsequent part of his last Eeport, he thus summarizes his estimate of 

 the instrument : — " Further experience with the Great Telescope, and of 

 " the conditions which affect its performance, have very much enhanced 

 " our opinion of it ; and the drawings and other results obtained unmis- 

 " takably show that excellent work can be done with it. On really 

 " favourable occasions the performance, even with very high powers, is 

 " exceedingly good. It is evident, however, that a telescope of such 

 " large dimensions requires a very long practice before it can be fairly or 

 " successfully used. The mechanical arrangements are all in perfect order ; 

 u and the moving and setting the telescope from one object to another is 

 " performed almost as quickly and easily as with a five-feet equatorial. 

 " The clock has worked well and with great regularity from the first." 

 This is in full accordance with the Eeports of the Telescope Committee 

 and of Mr. Lassell : the chief remaining difficulty is how the results 

 * Vide supra, p. 31. 



