Colours of Stars. 61 



that much difference will exist as to the inferior limit of percep- 

 tible colour in stars. Struve I. terminated his observations of 

 colour in the Dorpat Catalogue with the 9th out of the 12 mag- 

 nitudes of his scale, corresponding with the respective numbers 

 10 and 16 of Smyth. The latter observer carried his estimates 

 much lower, occasionally even down to his 16th magnitude, or 

 about 11 "2 of Struve' s scale, and was struck by the " strong 

 blue ray" emitted by some of the minutest points among the 

 double stars. We find as specimens of this a 15 mag. (e Vir- 

 ginis) of an intense blue — a very striking colour, he remarks, in 

 so small an object: — a 14 mag. (113 P. XX. Vulpeculce , R. A. 

 20h. 1 7m., D.N. 23° 39') "indigo, an intense colour to the averted 

 eye f 3 an instance the more remarkable, as no contrast could be 

 induced by the bluish white of the principal, an 8 mag. star : — 

 a 15 mag. (t Ceti) deep blue : — a 14 mag. (52 Piscium, R. A. 

 Oh. 25m., D. N. 19° 33') of the same tint. And though this 

 would seem to be the prevailing hue of minute components, yet 

 others are occasionally to be met with ; such as the orange of 

 the 13 mag. companions of 7. Camelopardi (R. A. 4h. 46m., 

 D. N. 53° 32-) and 2 Lacertce (R. A. 22h. 15m., D. N. 45° 51'), 

 the purple of the similar-sized attendants of k Pegasi and i Ursce- 

 Majoris, the emerald of the equivalent " comes "■ of 42 Piscium 

 (R. A. Oh. 15m., D. N. 12° 44'), and even the pale red of the 

 16th or smallest magnitude in the Bedford telescope (5* 9 inches 

 aperture), attached to 212 P. XIV. Librce (R. A: 14h. 49m., 

 D. S. 20° 47'). These, among other instances, will show how 

 far an originally delicate and finely- educated eye will push its 

 perceptions of colour. I have usually found my own sight at 

 fault with regard to very minute stars ; but not without excep- 

 tions; for example, 144 P. XIX. Aquilce (R. A. 19h. 24m., D.N. 

 2° 37'), the attendant of which, 11 mag. according to Smyth, 

 but as I thought large for that rating, being known to be green, 

 could be readily seen of that hue with 3^th inches of aperture. 

 Some further remarks have still to be postponed to a future 

 opportunity. 



