Proceedings of the British Association. 389 



particular clay to be designated by the London Council. The Rev. J. 

 Peacock, Dean of Ely, was elected President of the next meeting. 



Section A. Mathematical and Physical Science. 



Rev. Dr. Robinson presented a Report, by Mr. Baily, from the 

 Committee appointed to prepare the British Association Catalogue of 

 Stars, from which it appeared that the reduction was complete. He 

 proceeded to explain the value of this catalogue by stating, that among 

 the heavenly bodies the stars are generally considered as motionless, 

 and were used as points of comparison for their more erratic compan- 

 ions. In this respect, an accurate determination of their places is of 

 high importance ; but it becomes still more interesting from the fact, 

 that we know many of them to be in motion, so that it is difficult to find 

 one absolutely fixed, and the research of their proper motions becomes 

 matter of great interest. This is effected by comparing their places 

 observed now, with those accurately determined at a former epoch. 

 To do this, is not so simple as might at first sight appear. In the first 

 place, we do not see the star in its true place ; the motion of light 

 makes it to be observed in advance of that, as the earth moves. Sec- 

 ondly, it is referred to the pole or equinox : these points ai'e not fixed 

 in space ; the one is influenced by the action of the sun and moon — the 

 other moves with irregular precessions by the same force, and that of 

 some of the planets. The observed place must therefore be corrected 

 for aberration, mutations, &c. before it is of any use, and the mean of 

 several such mean places, gives the desired result. This is very trouble- 

 some, and was often loosely performed, till Mr. Baily published the 

 Catalogue called by the name of the Astronomical Society, containing 

 about 2800 stars, and which changed the history of Stellar Astronomy. 

 Formerly from 30 to 40 stars, called standard, were observed, and the 

 rest overlooked ; so that in an emergency of a comet, or an occultation, 

 there was often no reference possible, and direct observations of the in- 

 dividual object were requisite. Its great advantage is — the system of 

 logarithms computed for each star gives, with extreme facility, the cor- 

 rections above described. But their numbers change with the changes 

 of the stars' places, so that already they require an alteration. The 

 advantages of this work were such, that the Association thought no 

 greater service could be rendered to astronomy than the extension of 

 Mr. Baily's catalogue. It now contains nearly 10,000 stars, and the 

 secular changes of the constants are given with them. Besides, in 

 the places of the stars there is an important improvement ; the places 

 in the former catalogue were derived from a comparison of those 

 given by Bradley for 1745, and Piazzi for 1800 : whatever error was 

 in either of these, was multiplied by the mode of computation when 

 brought up to 1830 ; but this fault was, in the present instance, corrected. 



