176 OBSERVATIONS ON NEBULA 



classed among the Novse, although immediately contiguous to one of the most remarkable 

 and frequently observed nebulae in the heavens. 



jiug. 9. — Figured some half dozen of the stars of the trifid nebula. I see distinctly the 

 star near its centre triple, but a ray or burr of light from the larger star nearly obscures 

 the faint companion, so that I can scarcely tell whether the difficulty of the small star con- 

 sists in its closeness or faintness. Estimated distance of AB 10"; of AC 5", but the last may 

 easily be in error from the cause just mentioned. The triple star is certainly not central, but 

 involved in the skirts of the division marked A in the diagram, and also is north of the point 

 where the three clefts meet, being in the cleft y. The division B runs up at the junction 

 towards, or into the opposite cleft /3 a little way, shading ofl", at the same time, so gradually 

 that, at first sight, the rift a seems to proceed more directly from the triple star than it really 

 does. 



,^ug. 10. — Finished figuring the stars in Nebula Trifid. There is scarcely a visible star 

 in the nebula above the triple star. 



Figured the nebula. There is a peculiarity about the cleft a which had been suspected on 

 the night of the 9th. It shelves off suddenly to the north with a pretty well defined boun- 

 dary, which I can trace nearly up to the star (2;) if I mistake not, it divides in two, leaving 

 an extremely faint nebulosity, or fourth portion, isolated from the rest. Mr. S. saw the sud- 

 den turn of the cleft northwards, but could not satisfy himself as to its division into two, 

 which must therefore remain uncertain. 



Peculiarities of the lower nebula. — There is a large, but indistinct vacancy, or gap, north, 

 or below its central star, where the nebula is decidedly less bright, while, on the left hand 

 of this vacancy, is a small portion brighter than the rest of the nebula. " I think the va- 

 cancy runs up past the central star, though narrower there." — S. In my own observation, 

 I think it does not quite reach the central star, so that it remains doubtful whether the star 

 in the centre is not somewhat isolated from the surrounding nebula. I saw the same appear- 

 ance described by Mr. Smith, but considered it the efiect of the brightness of the star in 

 effacing the impression of the nebula in its immediate neighbourhood. Our estimates of the. 

 utmost extent of the lower nebula nearly agreed, although its boundary was very indefinite. 



Jiug. 14. — The nebula IV. 41 again examined; the moon at first troublesome, but setting. 

 I tried, this evening, a plan for better delineating this nebula by lines which represented 

 equal gradations of shade. I find it more convenient and direct, and, I believe, much more 

 accurate. I think I can thus take a copy of the nebula with as much exactness as I can see 

 it. To settle the angles of position of the triple star, lines were drawn on the star-chart, re- 

 pi'esenting their apparent directions as referred to other stars in the nebula. The nebula, as. 

 delineated by lines, was compared by Mr. Smith, and verified ; some slight alterations were 

 suggested by himself, nearly all of which a re-examination confirmed, and some others addedj, 

 which are better expressed in the drawing than by description. 



