Page:Popular Science Monthly Volume 3.djvu/142

132 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 constellation of Orion (Figs. 1, 2). It is situated rather below the three stars of second magnitude composing the central part of that magnificent 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 nebula. Four bright stars, forming a trapezium, are situated in it, one of which only is visible to the naked eye. The nebula surrounding 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 [sic] the heavens, and for reckoning the hour of the night.