Nebula?. 281 



\\° p Antares, a large but rather dim object. Sm. remarks 

 that it stands on the W. edge of a starless area. Our next is — 



39. Gen. Cat. 4173. M 80. Sm. calls it a compressed 

 globular cluster of very minute stars; a fine bright object with 

 a blazing centre,, like a comet.* Ijl styled it the richest and 

 most condensed mass in the heavens. It was all resolved by 

 H., at the Cape, into 14 and 15 mag. stars. A wonderful 

 instance in itself of the mysterious arrangements of creative 

 power, but deriving its chief interest from the fact that in the 

 same position is a marvellous variable star. Neither M., ^t> H., 

 Sm., Argelander, nor ~D' Arrest, had noted anything unusual 

 here. Auwers, the well-known observer of nebulae, had often 

 seen this cluster in its ordinary aspect, in the spring of 1 859, 

 and even as late as 1860, May 18. By May 21, with a rapidity 

 analogous to that of the variable in Corona Borealis (1866, 

 May 12), or that of the Great Star of 1572, there had broken 

 out in the place of the cluster a bright telescopic star, accord- 

 ing to Auwers of 7, to Luther of 6*5 mag. It was the same 

 the following night; by the 25th both found it rather smaller; 

 and Pogson saw it of 7 or 8 mag. on the 28th. June 10, 

 Pogson had lost it ; but thought the cluster unusually brilliant 

 and condensed. Auwers did not quite lose sight of it, and 

 perceived that it was not central. It is barely conceivable 

 that such an outburst should take place in the heart of a cluster, 

 and leave it as before ; and it is more natural to suppose that 

 the objects are merely optically coincident ; but the progress 

 of discovery may well teach us caution in our deductions. In 

 the same field with this cluster, f, a little n, are two undoubted 

 variables, R and S Scorpii, discovered by Chacornac in 1853 

 and 1 854, changing from about 9 to less than 14 mag., or in- 

 visibility ; the former with a probable period of about 648 ; 

 the latter, 364£d. BaxendelFs remark, that these marvellous 

 objects are apt to occur in groups, is strikingly exemplified 

 here. 



We shall readily find this cluster half way between Antares 

 and ft Scorpii, 2 mag., the brightest star of the group n p 

 Antares. 



40. Gen. Cat. 4261. M 62. Sm. calls this a fine large 

 resolvable nebula, running up to a central blaze. H., at the 

 Cape, who terms it superb, resolved it all into 14 — 16 mag. 

 stars. We may find it from S Scorpii, 3 mag;, the most s star 

 of the group n p Antares, by running a line back to Antares, 



* The assertion of this usually most accurate astronomer, that it lies on the W. 

 edge of a vast obscure opening without stars, 4° broad, may, perhaps, have arisen 

 from some confusion with its neighbour, M 4. On two occasions I have seen, with 

 only 3i 7 (j inches, many minute stars E. of it. 



