World-life; or, Comparative geology . An7iular Nehxdm.—A fine example of this form isthe annular nebula in the Lyre, H. 4,457 (Figure 11). Itsspectrum consists of one bright line answering to annular nebula is sometimes presented obliquely toview, as in H. 1,909. Sometimes it appears edgewise, asin H. 2,621. At other times it is so attenuated at oppo-site sides as to be invisible in those places, and appears,accordingly, as a double nebula, as in H. 3,501 and ,552. More powerful instruments may be expected toshow the ring complete. In both these cases there is acentral mass mor
World-life; or, Comparative geology . An7iular Nehxdm.—A fine example of this form isthe annular nebula in the Lyre, H. 4,457 (Figure 11). Itsspectrum consists of one bright line answering to annular nebula is sometimes presented obliquely toview, as in H. 1,909. Sometimes it appears edgewise, asin H. 2,621. At other times it is so attenuated at oppo-site sides as to be invisible in those places, and appears,accordingly, as a double nebula, as in H. 3,501 and ,552. More powerful instruments may be expected toshow the ring complete. In both these cases there is acentral mass more or less luminous, as in H. 854, H. 604and H. 4,447. The nebula. Figure 10, seems likely to Monthly for June, 1873. Newcombs Popular Astronomy also gives views ofThe Great Nebula in Orion, the Annular Nebula in the Lyre, the Omega NebulaH. 2,008, the Nebula H. 3,722, and the Looped Nebula H. 2,941. But the mostexquisitely delicate representations of nebulae are found on two plates of Secchi:Le Soleil, vol. ii. 46 COSMICAL Fig. 11. Annular Nebula in the LtreFrom a Drawing by Prof. Holden. consist of a central masssurrounded by severalrings which may behereafter more distinct-ly discerned. 5. Planetary Nehulm,—These are nebulas withtolerably definite circu-lar outlines, and consisteither of a uniform disc,as defined by Herschel,or of a rudely annularor spiral belt surround-ing a faint luminosity,which often contains oneor more bright bright belt is often fringed by a coma or a bur oflight. H. 2,241, as shown in Figure 12, consists of a welldefined- belt of light surroundedby an irregular coma, but withouta nucleus. H. 464 shows a brightring of the spiral order. It issurrounded by a bur of light,and has two nuclei which scarce-ly sustain any relations to thegeneral structure. H. 838, Fig-ure 13, has a ring of light consist-ing of a double bami of the spiralorder. It is surrounded by a burof light, and contains two nucleisymmetrically situated, and surrounded
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