DiiEYKR — A Surrr// of flic Spiral Nehiila Memer 38. 



15 



the star + 30°-243 is perfectly round, its neighbour + 29°-265 is 

 slightly oval, while + 29*260 is round, but a little flattened on the 

 north-preceding quadrant. But the small and well-defined discs of 

 stars of about the 11-12 magnitudes can be bisected with great 

 comfort and apparent certainty; and as regards them I should be 

 disposed to think that the systematic errors, if existing, must be very 

 small indeed. I may here mention that when assigning these 

 magnitudes to the fainter objects, I do so on the assumption that the 

 faintest objects measured are of the 15th magnitude. Dr. Roberts 

 informs me that he has some justification for designating the faintest 

 stars on a plate exposed during 90"" on a clear night with the 20-inch 

 reflector as of the 16-17 mag." I have only used the ordinary mode 

 of designating brightness followed by observers of nebulae eF, vF^ F, 

 pF, B, and have assumed these to correspond approximately to 

 the magnitudes 15, 14, 13, 12, 11, 10. 



In addition to the nebula itself, the jSTew General Catalogue and 

 the Index Catalogue of Nebulae, found in the years 1888-94, contain 

 a number of objects more or less involved in it. Of these, I could 

 not identify I. C. 136, M. Bigourdan's No. 127, the place of which is 

 for 1860 l'^ 25"^ 34^ + 29° 45', described as eF, difficult,^nO np 3'. 

 The " S neb. or cluster, with 3 st in it, about 8' ssp a double star 

 11-11 mag.," found at Birr Castle, and catalogued as N. G. C. 603, is 

 outside the area covered by my measures ; but the double star is on 

 the plate close to the place indicated, and 6' s/;^; it an eeF star is 

 seen. M. Bigourdan's No. 125 is either an eeF star, or eeS nebula ; it 

 is 3' south of the star + 30°-240, and about 0'-6 following it. The 

 other objects catalogued correspond to the objects measured by me as 

 follows : — 



N. G. C. 588 



= No. 35 



„ 592 



No. 82 



Ind. Cat. (131) 



No. 88 



„ (132) 



No. 89 



„ (133) 



No. 92 



„ (135) 



No. 102 



N. G. C. 595 



No. 122 



Ind. Cat. (137) 



No. 147 



„ (139) 



No. 150 



(140) 



No. 157 



„ (142) 



No. 205 



(143) 



No. 242 



N. G. C. 604 



No. 287 



