THE NEBULA ABOUT 6 ORIONIS. 91 



separates become less numerous, in a manner quite different 

 from that which would result from viewing it under a greater 

 angle merely. The clusters increase in magnitude, while they 

 diminish in number. Sir John Herschel, when describing this 

 portion, as seen at Slough with his twenty-foot reflector, compares 

 its appearance to that of " a curdling liquid, or the mottling of 

 the sun's disk, only the grain is much coarser and the intervals 

 darker." To me it appears composed of several clusters of stars, 

 the components being separately seen for a moment under fa- 

 vorable circumstances. This resolution I hav« noticed more par- 

 ticularly north of star No. 26, and likewise in the vicinity of No. 

 12 and No. 43 ; but where the nebula assumes a cirrous charac- 

 ter, as in the Messierian branch, I can see nothing of the kind. 



There is quite a remarkable feature of the subn<ebulous region, 

 which I do not find has been noticed heretofore. It is that of 

 radiation, spreading and shooting southward from the stars Nos. 

 45, 50, and 61, near its base. I have noticed this appearance 

 only on clear nights, when the moon has been absent, but then, 

 on several occasions, it was very decided, and forcibly reminded 

 me of an active aurora borealis. 



There is something of the same character belonging to the 

 light on the preceding side of the Huygenian region, but not so 

 delicate ; it is there more abrupt. 



The Messierian branch, although extremely well defined, and 

 presenting a bold outline on the preceding side from star No. 80 

 to No. 61, yet thence to its junction with the brightest portion 

 of the nebula it presents no certain outline on either side, but 

 fades insensibly into the Proboscis Minor on the one side and 

 into the subnebulous region on the other. I mention this more 

 particularly, because Sir John Herschel's last drawing exhibits a 



