of some of the Nebula, 525 



lines. I suspect this is not uniform, but is crossed with dark 

 spaces. Subsequent observations on other nebulae induce me to 

 regard this faint spectrum as due to the solid or liquid matter of 

 the nucleus, and as quite distinct from the bright lines into 

 which nearly the whole of the light from the nebula is concen- 

 trated. 



In the diagram (fig. 5, Plate V.) the three principal lines only 

 are inserted, for it would be scarcely possible to represent the 

 faint spectrum without greatly exaggerating its intensity. 



The colour of this nebula is greenish blue. 



[No. 4390. 2000 h. 2 6. R.A. 18 h 5 m 17 s '8. N.P.D. 83° 

 10' 53"*5. A planetary nebula ; very bright ; very small ; round ; 

 little hazy.] In Taurus Poniatowskii. 



The spectrum is'essentially the same as that of No. 4373. 



The three bright lines occupy the same positions in the spec- 

 trum, which was determined by direct comparison with the spec- 

 trum of the induction-spark. These lines have also the same 

 relative intensity. They are exceedingly sharp and well defined. 

 The presence of an extremely faint spectrum was suspected. In 

 connexion with this it is important to remark that this nebula 

 does not possess a distinct nucleus. 



The colour of this nebula is greenish blue. 



[No. 4514. 2050 h. 73 H. IV. R.A. 19M1* 7 S 5. N.P.D. 39° 

 49' 41"' 7. A planetary nebula with a central star. Bright; 

 pretty large ; round ; star of the 11th magnitude in the middle.] 

 In Cygnus. 



The same three bright lines were seen. Their positions in the 

 spectrum were verified by direct comparison with the induction- 

 spark. In addition to these a spectrum could be traced from about 

 I) to about G of the solar spectrum. This spectrum is much 

 stronger than the corresponding spectrum of 4373. This agrees 

 with the greater brightness of the central star, or nucleus. The 

 opinion that the faint continuous spectrum is formed alone by the 

 light from the bright central point was confirmed by the following 

 observation. When the cylindrical lens was removed, the three 

 bright lines remained of considerable length, corresponding to 

 the diameter of the telescopic image of the nebula ; but the faint 

 spectrum became as narrow as a line, showing that this spectrum 

 is formed by light which comes from an object of which the 

 image in the telescope is a point. 



Lord Rosse remarks of this nebula, " A very remarkable object, 

 perhaps analogous to H. 450 "*. 



The colour of this nebula is greenish blue. 



[No. 4510. 2047 h. 51 H. IV. R.A. 19 h 36 m 3 S '0. N.P.D. 



* Philosophical Transactions, Part III. 1861, p. 733. For a figure of 

 H. 450 see Philosophical Transactions, 1850, plate 38. fig. 15.! 



