Beginning with δ, the upper of the three stars which form the belt, the two components will be visible in almost any instrument which may be used for seeing them, being of the second and seventh magnitudes, and well separated. The companion to β, though of the same magnitude as that to δ, is much more difficult to observe, in consequence of its proximity to its bright primary, a first-magnitude star. Quaint old Kitchener, in his work on telescopes, mentions that the companion to Rigel has been seen with an object-glass of 2¾-inch aperture; it should be seen, at all events, with a 3-inch. ζ, the bottom star in the belt, is a capital test both of the dividing and space-penetrating power, as the two bright stars of the second and sixth magnitudes, of which the close double is composed, are exactly 2½˝ apart, while there is a companion to one of these components of the twelfth magnitude about ¾˝ distant. The small star below, which the late Admiral Smyth, in his charming book, “The Celestial Cycle,” mentions as a test for his object-glass of 5·9 inches in diameter, is now plainly to be seen in a 3¾. The colours of this pair have been variously stated; Struve dubbing the sixth magnitude—which, by the way, was missed altogether by Sir John Herschel—“olivaceasubrubicunda.” That either our modern opticians contrive to admit more light by means of a superior polish imparted to the surfaces of the object-glass, or that the stars themselves are becoming brighter, is again evidenced by the point of light preceding one of the brightest stars in the system composing σ. This little twinkler is now always to be seen in a 3¾-inch, while the same authority we have before quoted—Admiral Smyth—speaks of it as being of very difficult vision in his instrument of much larger dimensions. In this very beautiful compound system there are no less than seven principal stars; and there are several other faint ones in the field. The upper very faint companion of λ is a delicate test for a 3¾-inch, which aperture, however, will readily divide the closer double of the principal stars which are about 5˝ apart. These objects, with the exception of ζ, have been given more to test the space-penetrating than the dividing power; the telescope’s action on 52 Orionis will at once decide this latter quality. This star, just visible to the naked eye on a fine night, to the right of a line joining α and δ, is a very close double. The components, of the sixth magnitude, are separated by less than two seconds of arc, and the glass which shows a _good wide black division_ between them, free from all stray light, the spurious disk being perfectly round, _and not too large_, is by no means to be despised. Then, again, we have a capital test object in the great nebula to which reference has already been made.