Clusters and Nebulae. 211 



not, however, seem to have been increased. In the autumns 

 of 1850 and 1851 the positions of twenty-one stars were mea- 

 sured by his lordship's assistant, Mr. Bindon Stoney, and very 

 many more were distinctly seen, but not inserted in his sketch. 

 The powers employed were low, the number of stars visible 

 depending, he says, even more upon magnifying power and 

 distinctness than aperture. Several of those m his diagram lie, 

 as might be expected, much outside the extent of the nebula 

 in smaller instruments. 0. Struve had previously measured 

 twenty- five stars with a power of 207 in the great Poulkowa 

 refractor, possibly not exactly within the same limits. Six of 

 those fixed by Mr. Stoney are not found in Struve's list. Ex- 

 cepting one of 8 mag. (= 8i Sm.) the rest as given by Struve 

 range from 10 — -11 (about 12 to 14 Sm.) to 13 mag. (= 20 or 

 less) ; one only reaching 10 — 11, and two others 11 (=15). . Two 

 or three of these I was enabled to pick out with an 8-inch 

 silvered glass speculum, by Mr. With. They are admirable 

 tests for the light and definition of a superior telescope. 



Secchi, whose design is in some sense intermediate between 

 the two of Lord E-osse, and contains nearly as many stars, sees a 

 few of them steadily, but the rest by glimpses only, and it is 

 not surprising, therefore, that many of their positions are dif- 

 ferent. Besides these, he sees the bright lobes and their 

 uniting isthmus all dotted, and believes their composition to 

 be stellar. We have every reason, however, to suppose that 

 all the recognized starry points belong to the dense myriads 

 of the galaxy, since Mr. Huggins's analysis, instead of exhibit- 

 ing the continuous spectrum which would have resulted from 

 an aggregation of stars, brought out, from different parts of the 

 nebula alike, but one single bright line, which cc was ascertained, 

 by a simultaneous comparison with the spectrum of the [elec- 

 trical] induction spark, to agree in position with the brightest 

 of the lines of nitrogen/'' So that this gaseous wonder — for 

 all that can be proved to the contrary — may actually lie far on 

 this side those glimmering points, and at a comparatively small 

 distance from our own system. On this account, as changes 

 might possibly be detected in it, Secchi's measures become of 

 value. He gives, for the lesser diameter, Y ^"'4<4i ; for its 

 position 6° ; for that of the longer axis 97°. H. had found, 

 about twenty years previously, 31 0, 4 and 117°'l for these re- 

 spective angles ; but with a form so unmeasurable, and observed 

 with such different instruments, it is obvious that nothing could 

 be inferred excepting from a much wider discordance. 



Our next will be a much more intelligible, though less in- 

 teresting object — ! 



31. 71 M. {Sagittce). This will be found with little trouble 

 from 7 and B } as shown in the diagram. If we start from <y, an 



