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A FLIGHT THROUGH SPACE.
sky from horizon to horizon. What inconceivable numbers should we arrive at, were we to go down to the twentieth magnitude! or attempt to count the myriads of star-clusters composing those "clouds of suns" that are comprehended under the general name of nebulæ [1] and of which Sir William and Sir John
- ↑ Sir William Herschel was enabled, by the powers of his large reflecting telescope, to divide and arrange the nebulous masses of light discovered by him in his general sweep of the northern heavens into the following six classes: —1st. Distinct clusters of separate stars; 2nd. Resolvable nebulæ, or such as, though not distinctly resolved, yet clearly indicated that their resolution might be accomplished by more powerful optical instruments. Most of these have indeed now yielded to the powers of Lord Rosse's gigantic six-feet reflector; 3rd. Nebulæ showing no trace of resolution in his (Sir William Herschel's) telescope. In some of these, also, separate stars have been detected by Lord Rosse's telescope, and by the great refractor of the observatory at Cambridge, near Boston, United States; and with every new increase in the dimensions and power of our optical instruments, we may expect to see these "clouds of light" more and more resolved into myriads upon myriads of separate stars; 4th. Planetary nebulæ, or such as have the appearance of planets; 5th. Stellar nebulæ; and, 6th. Nebulous stars, which, according to Sir John Herschel's definition, consist of "a sharp and brilliant star, concentrically surrounded by a perfectly circular disk or atmosphere of faint light, in some cases dying away insensibly on all sides, in others almost suddenly terminated." This may also be the proper place to make a passing allusion to two most remarkable phenomena visible with the naked eye in southern latitudes, called the Magellanic Clouds. They are "two cloudy masses of light of a somewhat oval shape. When examined through powerful telescopes, they are found to
