504 



accuracy, which, in the year 1819, there was no possibility of ex- 

 pecting.'* Now, it appears that these observations of 1855 fully 

 confirmed the fact of the acceleration of the comet's irfean motion, 

 so often observed before ; but they have done more than this, 

 for they have been so well made, that Encke was enabled by 

 their means to correct the elements of the orbit, and calculate an 

 ephemeris for the return of the comet this year, taking into account 

 the perturbations of Jupiter, with such consummate accuracy, that 

 on the first evening on which, through the absence of moonlight, 

 there was a hope of finding it, which was on the 7th of August, it 

 was actually detected during the first half-hour's search in the place 

 given by calculation, though presenting to the eye only a faint dif- 

 fused nebulous mass of about one minute in diameter. Now, if the 

 existence of this ether, or attenuated atmosphere, pervading the 

 planetary spaces, should be conclusively established, of which there is 

 now scarcely any doubt, it is a fact of the utmost physical importance. 

 We may not indeed in the present state of science be able to foresee 

 all the consequences which may flow from its establishment ; but we 

 know enough to perceive that the question has an important bearing 

 upon several interesting modern speculations. The suggestion of 

 this resisting medium is only one of many important services which 

 this diminutive but most interesting comet has rendered to astro- 

 nomical science, and will doubtless still continue to render. Mr. 

 Maclear's equatoreal will now be turned to profitable account in fol- 

 lowing up the fine comet of Donati, which has just escaped from 

 our view to present itself, but shorn of most of its former splendour, 

 to the expectant gaze of southern astronomers. Those who had the 

 good fortune to observe this comet on the night on which it ap- 

 proached Arcturus so nearly, will not easily forget the spectacle it 

 then presented. 



You are well aware that it was in our Colonies also that many of the 

 magnetical observatories were established, in which for several years 

 hourly observations were made of the three magnetical elements ; 

 and it may be confidently affirmed that from these observations most 

 valuable results have been deduced, to which, however, as they were 

 to some extent described by me on a former occasion, I will not 

 further allude, than to inform you that in the opinion of your 

 Council the time has now arrived, in which it is most expedient that 



