E. S. Holden~On supposed changes in Nebula M. 17. 359 



Star No. 1 brighter, but not much than 2. It precedes ,-V of 

 the nebulosity of the preceding hook of the horseslioe. The 

 line joining 1 and 10 is barely inside the nebulosity. The line 

 joining 10 and 3 is inside the nebulosity but not much. 11 is 

 just on following edge of the nebulosity, 34 follows the tvest 

 branch of horseshoe, about ^ the distance 2-7 [this is a rough 

 estimate only] and is clear of any nebulosity. The middle ^ 

 of the line 6-1 is in the dark. The line 6-85 is all in the neb- 

 ula. 8, 73, 11 about the same magnitude ; 73 is in faint neb- 

 ulosity, on the preceding edge of it. Between 11 and 73 very 

 faint nebulosity which joins these two stars. Line 3-13 is just 

 inside the nebula. — Star No. 1 certainly precedes y^ths of 

 west branch of horseshoe. Line 1-34 has its west /oths in 

 nebula. 34 seems to be in the dark. Certainly a connection 

 across 11-73 more distinct than in Naval Observatory drawing 

 — more definite. 



Line 10-11 is all inside nebulosity. 



" 10-13 runs through faiuter nebulosity. 

 13, 14, 10 are on following side of a bay which is filled with 

 very faint nebulosity. 43 brighter than 15. 44>42>15 but 

 the inequality is not great. 15 is the faintest star of 43, 44, 42 



The dark space within the horseshoe and bounded by 2, 7, 

 73, 11 is elliptic ; the largest diameter is perpendicular to the 

 line 8-14, and the diameters are as 6 to 4. It seems more reg- 

 ular in shape than in Naval Observatory sketch. Line 1-36 

 crosses fainter part of nebula about ^ of the way from 1 to 26 

 Preceding the line 1-10 is a darker space about 

 to the distance 1-6. Preceding that, the sky is 

 for 10' at least. [This requires confirmation.] There 



equal m width to the distance 1-6. Preceding that, the sky i 

 nebulous for 10' at least. [This requires confirmation.] Ther 

 is a faint prolongation from 6 towards south preceding. The shape 

 oF Herschel's resolvable knot is correctly laid down by Trou- 



3tly 1 

 velot. Two stars at its southern point and a 

 tion of the two prongs of this knot Sky more transparent than 

 I have ever seen it. Much annoyed by the forming of clouds." 

 It will be seen that it cannot be doubted that star No. 1 is now 

 in a position relative to the nebulosity quite different from that 

 laid down bv Lassell in 1862. Further, all the earlier drawings 

 except Hers'chel 1837, put star No. 1 well within the nebula, 

 and hence we are forced to the conclusion that the west half of 

 the horseshoe has moved with reference to this star. Trouve- 

 lot's drawing with his small telescope is the only one not show- 

 ing a similar and consistent motion with reference to the group 

 of stars 10, 11, 3, 13, 15, etc., and even here we find evidence 

 of changes in the same direction from the earlier drawings and 

 the conclusion of the motion of the west one-half of the horse- 



