1909] Recent Results of Astronomical Research. 561 



WEEKLY EVENING MEETING, 

 Friday, March 26, 1909. 



His Grace the Duke of Northumberland, K.G. P.C. D.C.L. 

 D.Sc. F.R.S., President, in the Chair. 



Arthur Stanley Eddington, Esq., M.A. M.Sc. F.R.A.S., 

 Chief Assistant in the Royal Observatory, Greenwich. 



Some Recent Results of Astronomical Research. 



The object of this discourse is to give some account of two or three 

 of the principal points of interest that have come before astronomers 

 during the past year. It has seemed preferable to concentrate 

 attention on a few points rather than to make any survey of the 

 general progress of astronomy, and I have naturally selected that 

 work with which the Royal Observatory, Greenwich, was most 

 concerned, and which can best be illustrated with slides. That must 

 be the excuse for neglecting many important results which have been 

 obtained along other branches of the subject. 



The Eighth Satellite of Jupiter. 



The first result of which I have to speak is the discovery of an 

 eighth satellite of Jupiter. This body was discovered by Mr. Melotte 

 at the Royal Observatory, Greenwich, on February 28 last year. [A 

 shde was shown of part of the photograph on which the new satellite 

 was found.] If there are any here who are quite unfamiliar with 

 celestial photographs, I may explain that when a photograph is being 

 taken of any object such as a planet or satellite which is moving 

 relatively to the stars, it is necessary to keep the telescope pointing 

 continually on the object making proper allowance for its motion, 

 the stars being, as it were, left to take care of themselves. The 

 result is that the stars make little streaks on the plate. You see 

 these scattered about everywhere. Now, in this case the plate was 

 made to follow the motion of the planet Jupiter during an exposure 

 which lasted an hour and twenty minutes, and among these streaks 

 or trails were found three round images, which evidently belonged 

 to objects moving at nearly the same rate as Jupiter, and thus distin- 

 guished themselves from the fixed stars. It may be mentioned, however, 

 that they do not distinguish themselves from photographic defects so 

 readily. Two of the three images were of the objects for which the 

 photograph was taken, namely, the sixth and seventh satellites of 

 Jupiter discovered by Perrine at the Lick Observatory, Cahf ornia, in 



