1825.] Royal Society. 63 



Endowed in so high a degree with une of the essential charac- 

 ters of an accomplished astronomer, his various and later com- 

 munications to the Royal Society show that Dr. Brinkley is 

 equally distinguished as a laborious, acute and accurate 

 observer. 



After stating the several subjects of Dr. Brinkley's seven 

 communications to the Royal Society, published in the Philoso- 

 phical Transactions, and justly eulogizing their extraordinary 

 merit. Sir Humphry Davy proceeded to notice the two great 

 leading questions of astronomy, concerning which the Astrono- 

 mer Royal and Dr. Brinkley are at issue ; namely, 1. The sensi- 

 ble parallax of some of the fixed stars ; and, 2. The apparent 

 southern motion or declination of parts of the sidereal system. 



It is well known that sensil)le parallax is denied by Mr. Pond, 

 and believed to exist by Dr. Brinkley ; whilst, on the contrary, 

 southern declination is denied by Dr. Brinkley, and believed to 

 exist by Mr. Pond. I mentioned, the President continued, in 

 announcing the award of the medal last year, that the Council 

 of the Royal Society had no intention of giving its sanction to 

 the opinions of the Astronomer Royal, or of attempting to decide 

 on these important and difficult questions. I again feel it my 

 duty to make the same observation on this occasion, and to 

 state that the general labours of Dr. Brinkley in the most diffi- 

 cult parts of astronomy, and the approximation that he has made 

 to the solution of a great problem, and the high merits of his 

 philosophical inquiries, are the sole grounds on which the Cop- 

 leian medal has been bestowed. 



. When Copernicus first developed that sublime system of the 

 planetary worlds, which has since been called after his name, 

 he was obliged to suppose the fixed stars at an almost infinite 

 distance, and the astronomical instruments of that day offered 

 no means even of attempting the discovery of their parallax. 



The importance of such a discovery was, however, imme- 

 diately felt ; as a demonstration of it would in fact become like- 

 wise an absolute demonstration of the Copernican system of the 

 imiverse. 



Gallilaeo seems to have suggested the method of inquiring for 

 parallax, by examining the relative position of double stars, one 

 of large, and the other of small magnitude, at the two extremities 

 of the earth's orbit; a method founded on the supposition that 

 the stars do not greatly differ in absolute size. This method, 

 which was likewise strongly recommended by Dr. Wallis, was 

 first, I believe, said the President, practised, and pursued with 

 great sagacity and industry, and with instruments of extraordi- 

 nary magnitude and perfection, by the late Sir William Herschell, 

 and, in following his path, by Mr. Herschell and Mr. South. 

 Though it has afforded many important results M'ith respect to 

 the proper motions of the stars and the arrangement and groups 



