464 Clusters and Nebulce. 



lence of green light among the stars of Orion. But what- 

 ever may become of this attempt at analogy — if such it may 

 be termed — the remark of H., already referred to, as to the 

 frequent occurrence of a ruddy star in the midst of a group 

 or cluster, will be full of additional significance when we com- 

 pare his account of another ornament of the southern skies, to , 

 be inserted here : — 



N n (ii.) The Great Cluster 47 ToucanL Gen. Cat. 52. E.A. Oh. 

 18m. D.S. 72° 52'; immediately^* the n part of the Nubecula 

 Minor. This, according to H., is u a most glorious globular 

 cluster — a stupendous object," the last outliers of which ex- 

 tend 2m. 16s. in R.A. from the centre. The stars are nearly 

 equal, 12 to 14 mag. ; immensely numerous, and compressed 

 in three distinct stages — being first very gradually, next pretty 

 suddenly, and finally very suddenly very much brighter up to a 

 central blaze, 13'5s. (R.A.) in diam., where they seem to run 

 together; and whose colour is ruddy or orange-yellow (in 

 another observation pale pinkish or rose-colour), contrasting 

 evidently with the white light of the rest — a phenomenon of 

 which he had do doubt. A double star, 11 mag., lies s jp the 

 centre, probably, as he thought, without any connection with 

 the cluster. The mass is completely insulated ; after it has 

 left the field, " the ground of the sky is perfectly black 

 throughout the whole breadth of the sweep." Ijl would have 

 seen here the result of a gradual agglomeration by the power 

 of gravity through the lapse of innumerable ages. Whatever 

 may be the value of the speculation, for which he supposed 

 there was ground in his visible heavens in the case of M 4, 

 and another cluster in Ophiuchus (^L VI. 40), the fact, at any 

 rate, ought not to escape notice. We have to remember that 

 the central blaze is not viewed by us separately, but as pro- 

 jected in perspective among a very considerable proportion of 

 exterior components in front of and behind it, and that its 

 peculiar tint must be consequently lowered by the admixture 

 of white ; which would not be the case with a single ruddy 

 star in that position. If the great reflector, which has been 

 so often spoken of as in contemplation for Melbourne, is ever 

 carried into effect, it is to be hoped that it wil] oe provided 

 with one of Browning's most powerful spectroscopes, as the E. 

 of Eosse's telescope has recently been. It is possible that the 

 central colour may not be out of the reach of its analysis ; at 

 any rate, very curious results may fairly be expected from its 

 employment in these unexplored regions. 



We will now return to our own skies, for a task requiring 

 some little patience at the hands of those not possessed of gradu- 

 ated instruments — the " fishing up" of a most curious planetary 

 nebula, discovered by Struve I., and therefore called — 



