Anniversary Meeting. 



[Nov. 30, 



that these strange bodies were masses of vapour, gradually condensing 

 by radiation of beat and tbe action of gravity, and tbat (according to 

 Laplace) in condensing they threw off rings which shrunk up into planets, 

 satellites, and comets, was long in favour with Cosmogonists. Lord 

 Bosse's discovery, that many of them which were cited as evidences of 

 this, were in truth mere clusters of stars ; that many more, though not 

 totally resolvable, were yet dotted over with lucid points, produced a re- 

 action which led to doubt the existence of any but stellar materials in 

 the remote heavens. But here we have a totally different view opened. 

 Mr. Huggins began with the planetary nebulae, so called from present- 

 ing well-defined luminous disks (which, however. Lord Eosse has found 

 in all that he examined to be complicated ring and spiral formations). 

 To Mr. Huggins's great surprise he found them to be totally different 

 from the stars ; instead of continuous spectra interrupted by a multi- 

 tude of dark lines, he found (which made it possible to observe them at 

 all) that their light consisted entirely of three bright lines ; the faintest 

 indicating the presence of hydrogen, the next some unknown element, 

 and the third a line which coincides with the brightest of nitrogen, but 

 which he hesitates to refer to that body because no others of its bright 

 lines are present. In some of them a very faint star-spectrum is also 

 visible, due of course to the small stars which are found in many ne- 

 bulae, often in such numbers that their presence can scarcely be merely 

 optical. Some nebulae, and all the clusters which in ordinary telescopes 

 look like them, do not show the distinctive three lines, but merely star- 

 spectra. The importance of this new view, this new " Explorator Abyssi," 

 to borrow a phrase of Hooke, cannot be rated too highly ; and you will I 

 am sure join me in expressing our hopes that these gentlemen will press 

 onward in the bright path which they have opened, and perhaps with 

 even higher instrumental powers. 



One who has not taken part in this kind of observation mast speak 

 with reserve; but I cannot refrain from expressing a wish that their 

 telescope were of much greater aperture — as two or three feet. The 

 object of the telescope is in this case mere concentration of ligbt, and it 

 will probably be attained without anything of that perfect finish which 

 is required for exact definition. If so, a mirror of silvered glass, or even 

 copper, and of comparatively short focus, or one of Presnel's Light- 

 house lenses, might be a powerful auxiliary. 



The remarks which I ventured to make in my Address at the last 

 Anniversary, on the expediency of combining Pendulum Experiments 

 with the Astronomical and Greodesical operations of the Grreat Indian 

 Arc, have given occasion to a correspondence between Colonel Walker, 

 the Superintendent of the Indian Trigonometrical Survey, and myself, 

 which has been subsequently augmented by letters from several Eellows 

 of the Eoyal Society conversant with such subjects, written in reply to 



