THE HORSESHOE NEBULA IN SAGITTARIUS. 277 



mature death is the more to be regretted, as he was, so far as I am aware, the 

 only other recent observer who has given himself with the assiduity which the 

 subject requires to the exact delineation of nebulae, and whose figures I find at 

 all satisfactory, expressly states that both the nebulous knots were well seen 

 by himself and his coadjutor Mr. Smith on August 1, 1839, i. e., two years subse- 

 quent to the date of my last drawing. Neither Mr. Mason, however, nor any 

 other observer, appears to have had the least suspicion of the existence of the 

 fainter horseshoe arc attached to the [eastern] extremity of Messier's streak. 

 Dr. Lamont has given a figure of this nebula, accompanied by a description. In 

 this figure [our Fig. 4], the nebulous diffusion at the [western] angle and along 

 the [western] base-line of the Omega is represented as very conspicuous ; indeed, 

 much more so than I can persuade myself it was his intention it should appear." 



When Lassell mounted liis great four-foot reflector at Malta, lie 

 devoted much of his time to a systematic review of those nebula; 

 which had previously been figured either by himself or by Rosse and 



Fig. 5. Lassell, 1862. 



others, and, as was expected from the excellence of the climate, the 

 superiority of the great telescope and the skill of the observer, this 

 series of drawings at once took its place among the acknowledged 

 classics on this subject. Too much praise can hardly be given to 

 Lassell for confining his attention principally to objects previously 

 figured, and for resisting the temptation to roam in those fields which 



