350 E. S. Holdcn — On siipposed changes in Nebula M. 17. 



Washington for the purpose of making drawings of nebulae, 

 etc., by means of the twentj-six-inch Clark refractor. By the 

 courtesy, of Admiral Davis I am able to give a drawing of the 

 Horseshoe Nebula as delineated by M. Trouvelot from obser- 

 vations made jointly by him and myself. 



Pretty much the' same method was adopted in this drawing 

 as in tig. 6, but the vastly more complex structure of the 

 nebula itself is what might have been expected from an in- 

 crease of eighteen times in the light, over M. Trouvelot's six- 

 inch telescope. 



It may be said of the drawing from which fig. 7 was copied, 

 that nothing is there laid down about which the slightest doubt 

 is entertained; and although, in some respects, it was made in 

 greater haste than is desirable, yet it is sufficiently accurate to 

 found an argument on, for or against variation in tbe shape of 

 any of the brighter portions of the nebula. The fainter portions 

 of' fig. 7 are too well defined and too bold, but it is. in general, 

 a good representation. 



