264 Royal Irish Academy. 



with a green, or a blue, but the greater number with a red lustre ; 

 the former generally coupled together in binary or ternary groups, and 

 often exhibiting variety not only in tint, from time to time, but in 

 apparent magnitude also. Appearances so suggestive could not but 

 invite to scientific speculation. From a supposed analogy to some 

 phenomena arising out of the undulatory theory of sound, it was 

 thought that the change from green or blue to red in a variable star 

 might possibly indicate its approach to or retrogression from us in space 

 — a grand idea, which, if indeed a discovery, would have enabled 

 science to reach another arm's length into the unknown, and take note 

 not only of the transverse but of the direct motion of the non-planetary 

 celestial bodies. To these expectations was presently added the prospect 

 of a more definite means to the same end for all the stars, in spectro- 

 scopic observation. Each star yielded its own spectrum, and these also 

 had their variations, which might tell the same story of increasing 

 or diminishing direct distance, and also supply the means of measur- 

 ing it. Such, some fifteen or twenty years ago, were, and still are, 

 the exciting pursuits of Astronomic exploratory genius, stimulated by 

 constant additions to the number and characteristics of the coloured 

 classes furnished by the Observatories. You, Mr. Birmingham, from 

 your Yaldarno in the "West, where the feudal lords of Athenry and 

 Tuam used formerly to prosecute pursuits of so different a nature, in 

 contributing to these supplies, took your place as one of our leading- 

 Irish representatives in this walk of Science. You had already, on the 

 outburst of T. Coronae in 1866, been the first to observe that notable addi- 

 tion to the class then attracting so general an attention. It was at this 

 time, when your name was rising into distinction in the Observatories of 

 the world, that your Danish precursor, Schjellerup, published his list of 

 the Red Stars observed up to that time. It, for about ten years, was 

 the authoritative source for past observations ; but the growth of newly- 

 recorded phenomena, to which your own discoveries began materially 

 to contribute, ultimately called for a revised and supplemented Cata- 

 logue ; and in furnishing this to our Transactions, in 1876, you estab- 

 lished your claim to this, the highest scientific distinction the Academy 

 can bestow. In this Catalogue, which you are now revising and sup- 

 plementing down to the present time, you include every Coloured Star, 

 with its place-indication, and a digest, by date, of every observation 

 hitherto recorded of it by yourself or others. To this you have added 



