Royal Astronomical Society, 1 37 



Our knowledge of the sidereal heavens is yet in its infancy. That 

 every thing must he in motion, in accordance with the laws of gra- 

 vitation, may indeed be looked upon as demonstrated ; but, except 

 the broad notion that our system is moving towards some point of 

 the present apparent heavens, the knowledge of the approximate 

 distances of two stars, certainly of 61 Cygni and probably of a Cen- 

 tauri, nothing is accurately known of the things which must become 

 data before the velocity and direction of motion of the centre of gra- 

 vity of our system can be determined. The late Astronomer Royal, 

 Mr. Pond, was of opinion, and his judgement has recently been con- 

 firmed by our illustrious associate Bessel, that a variation in the 

 proper motions of some stars has been detected by observation, and 

 if this be confirmed, the first step is made*. But the exceeding 

 minuteness of the difference of motions, which themselves require 

 many years to rise to an appreciable amount, presents a difficulty 

 only to be overcome by immense labour and the most scrupulous 

 accuracy. For each star there are required, at least, three different 

 and well-defined epochs ; and where are we, as yet, to look for such 

 data? 



The Council cannot but mention what is one of the most remark- 

 able astronomical events of the year, though perhaps no one of the 

 parties concerned in it gave our science a thought. They allude to 

 the repeal of the excise duty on glass, which might be called with 

 perfect truth an astronomical window-tax. Every person here pre- 

 sent must be aware that the nature of the regulations under which 

 it was found or thought necessary to place the manufacture of this 

 important article, rendered experiments for the improvement of op- 

 tical glass almost impracticable and a great deal too expensive. It 

 may now be confidently hoped, that in a few years our country will 

 not be obliged to admit that we are surpassed by foreigners in this 

 particular. But it must be remembered that it is not likely that the 

 object will be attained, unless systematic attention be directed to- 

 wards it. The Council hope, therefore, that those who feel inter- 

 ested in astronomy, and who have directed their attention to the 

 chemistry of manufactures, will not forget to keep their thoughts 

 fixed upon the great importance of procuring good optical glass in 

 large quantities. The end to be gained is not merely the acquisi- 

 tion of large object-glasses in greater numbers. The want of suffi- 

 cient supply, easily obtained, is found in regard to smaller lenses, 



* It may be worth consideration whether a complete recomputation of 

 all Bradley's observations of stars might not be advantageous. The Fun- 

 damenta, as edited by Bessel, does not include all the observations, and 

 the epoch of the observations is not given. This most important element 

 was first added by the present Astronomer Royal, and the yearly partial 

 catalogues which appear in the annals of our observatories are exceedingly 

 valuable from supplying the date. In making the above suggestion we do 

 not forget what we owe to Bessel's Fundamental nor how much of the rea- 

 sonableness of our expecting yet more benefit from Bradley's observations 

 lies in the consequences of the impulse which the publication of that mighty 

 work gave to accurate astronomy, and the means which it supplies for still 

 further improvement. 



