132 THE POPULAR SCIENCE MONTHLY. 



Rosse; and they may all be projected on to a screen by means of the 

 electric or lime-light lantern, and made visible to a large audience. 



The largest and most irregular of all the nebulae is that in the con- 

 stellation of Orion (Figs. 1, 2). It is situated rather below the three 

 stars of second magnitude composing the central part of that magnifi- 

 cent constellation, and is visible to the naked eye. It is extremely 

 difficult to execute even a tolerably correct drawing of this nebula ; 

 but it appears, from the various drawings made at different times, that 

 a change is taking place in the form and position of the brightest 

 portions. Fig. 2 represents the central and brightest part of the 



Fig. 4. 



Nebula of the Form of a Sickle. 



nebula. Four bright stars, forming a trapezium, are situated in it, 

 one of which only is visible to the naked eye. The nebula surround- 

 ing these stars has a flaky appearance, and is of a greenish- white 

 color; single portions form long curved streaks stretching out in a 

 radiating manner from the middle and bright parts. 



Much less irregularity is apparent in the great Magellanic or Cape 

 clouds (Fig. 3), which are two nebulae in the Southern Hemisphere, one 

 of them exceeding by five times the apparent size of the moon. They 

 are distinctly visible to the naked eye, and are so bright that they 

 serve as marks for reconnoitring the heavens, and for reckoning the 

 hour of the night. 



