418 



On the Spectra of some of the Southern Nehulce. [May 28, 



April 5. Seen in telescope as a slightly oval nebulous ball, easily seen but 

 not very bright (perhaps owing to moon, nearly full) ; found with some diffi- 

 culty in spectroscope ; a faint continuous spectrum of considerable width ; 

 no trace or suspicion of lines. 



(No. 4173. Seen easily in telescope; but looked for in spectroscope 



for two hours in vain.) 

 No. 4390. [_M 18^^ 6"^: N.P.D. 83° 10': planetary nebula; very 

 bright, very small, little hazy.] 

 April 6. Scarcely recognized as a nebula in the telescope. Seen in spec- 

 troscope : a short bright line with a fainter one on the more refrangible 

 side, and a third strongly suspected. (Knowing so well the relative posi- 

 tions of the usual" lines, it is impossible that an unprejudiced corrobo- 

 rative opinion can be offered on such slight foundation as I have.) A 

 very slight extension laterally was given in this instance with the cylin- 

 drical lens. 



No. 2102. [JR,10M8^: N.P.D. 107^59': !!; planetary nebula, very 

 bright, little extended.] 

 April 9. Seen at once in telescope with low power ; and seen distinctly 

 in the spectroscope as a bright and a faint line (the third line not seen) ; 



principal line measured with wires and found =D+ | 2-16~^''^^ } ' 

 5 + 48, F=6+l-06. 



No. 1 1 79. Nebula in Orion. Examined for comparison. The spectrum 

 of this nebula shows the three lines distinctly, and three only ; they were 

 measured (with wires), and the results were : — 



2-17 



D+ \ 2-20=2-19 \ =5 + 0-52, 

 2-21 



or 



^+ {2-40 = ^*^^}=^ + ^'^^' 



D+ 2-78 =5 + 1-11. 



The places and descriptions of the objects enclosed within brackets are 

 ken from Sir John ' 

 Phil. Trans, for 18G4. 



taken from Sir John Herschel's "General Catalogue of Nebulae" in the 



P.S. — The other day a storm passed over us. As there was a good deal 

 of lightning, I took the opportunity to examine its spectrum. I saw, as I 

 expected, numerous bright lines; the blue nitrogen one, I suppose, much 

 the brightest. A suspicion also of the red hydrogen-line C. I was much 

 surprised at the brightness of the continuous spectrum, in which all the 

 principal prismatic colours were brilliant. 



