GREAT REFRACTING TELESCOPE AT ELGHIES, IN MORAYSHIRE. 417 



In Position and Distance, the tabular results of observations for each star-group 

 so often giving a mean between distinguished but conflicting observers, as in 

 Nos. 1, 35 Piscium; 4, ^Pisciuni; 11, a Herculis; and some others, will prove 

 that useful results have been recorded ; though their degree of merit will only be 

 capable of being fully judged at some future day, when impartial computers 

 may, or may not, employ them in orbital calculations. And finally in Character, 

 much is believed to have been cleared up for many of the stars, either by the 

 above measures, or the "Proper Motion" test as now applied; in some instances 

 too with singular success, of which Nos. 13, 95 Herculis; 21, ^ Sagittse; and 

 22, a Aquilse, may serve for example. 



In conclusion, then, I trust that these pages have now shown that the Elchies 



But when we pursue our inquiries further still, and beyond the limits of sensible stellar parallax, 

 and merely employ the broad assumption that the smaller that stars do appear, the further off they 

 must be on the whole, — then arises the anti-terrestrial result, that the greater the depth of the distant 

 medium through which stars are seen, the bluer they become ; for all very small stars are bluish. 

 The smaller members also of most double stars, whether optical or physical, and of unknown 

 distance from us, are, as a whole, bluer than the larger members ; appearing thereby to imply, 

 though there may be other concurring causes to be mentioned, that the medium filling the more 

 distant realms of space is in a positively different physical condition from that in which we are 

 moving at present under the control and guardianship of our sun. 



It is even possible that there are more restricted regions of speciality still, and that floating cos- 

 mical motes may exist in interstellar space, capable of playing very peculiar parts on the light trans- 

 mitted through them from more distant bodies. Cosmical clouds have been suggested by both the 

 Herschels to explain observed changes in telescopic stars and nebula ; and such clouds, not very far 

 too from our own system, may be sti-ongly suspected, some might even be inclined to say are found, 

 to exist, from the many variable stars whose periods have been ascertained to be almost exactly 365 

 days. (See Spec. Hart., p. 269.) 



On the other hand, our case of 95 Herculis, even if there had not been any thing else of the same 

 order, establishes the point, of colours and changes of colours pecvdiar to, or arising in, the stars them- 

 selves. That instance forms an extreme case ; but the forces at work there are probably in exist- 

 ence elsewhere as well, and not improbably in our own sun, and even in our own earth. Let me 

 explain the hasty generalisation, which, in the absence of almost anything else, may at least incite to 

 further observation. The changing tints of the members of 95 Herculis are eminently auroral, i.e. 

 of the character of an Aurora Borealis when its displays are intense, such as we see them in the 

 northern sky once in half a century only, and when fiery pink and vivid green streamers alarm tlie 

 country ; and they are auroral also in their indications of fitful flashes and pulses, like the changes 

 of lustre in periods of a few seconds noticed by Mr Norman Pogson in the star U Geminorum (^Spec. 

 Hart. p. 107). Again, the pink prominences seen at total eclipses around our own sun, and at 

 times or in parts varying to other bluish colours, as established by Otto Steuve, with the appro- 

 bation of Mr Airy in 1860, have likewise been analogised by Mr Balfour Stuart to terrestrial 

 auroras. Something then of the same character that produces the immense eflPects observed on 

 the orbs of 95 Herculis, may, and apparently does, exist on the surface of our own sun; following 

 too, in its luminous and coloured manifestations, such active and impetuous changes of short period 

 (for the eclipse red prominences have never been seen twice alike), that some notable maxima, from 

 the occurrence of secular periods, capable of reacting on the climate of our earth, may at times be 

 looked for. 



Thus the subject of the colours of the stars becomes one, not only of great astronomical, but also 

 . of terrestrial, interest and extraordinary complication ; and it is possible that spectrum analysis 

 combined with eye estimations, may enable us to separate the colour produced by transmission 

 through intervening cosmical clouds from the colour of the star itself, by reason of the small differ- 

 ence in the dark lines of the spectrum effected by any colouring material at a low temperature. 



