World-life; or, Comparative geology . Fig 7. Sickle-shaped Nebula, IIekschel 3,239. impossible to gaze upon these figures without feelingthe conviction that a spiral movement is in progress. Thespectra of these nebulae have not been certainly ascer-tained ; but we may venture the conjecture that they willbe found to consist of bright lines. Such a spectrum, atleast, is given by the spiral nebula H. 4,0G4, in which lines *See view in Schellen, op. cit., 538. 44 COSMICAL DUST. answering to nitrogen and hydrogen appear, besides twoother bright lines not Fig. 8. Spiral Nebula ix Canes
World-life; or, Comparative geology . Fig 7. Sickle-shaped Nebula, IIekschel 3,239. impossible to gaze upon these figures without feelingthe conviction that a spiral movement is in progress. Thespectra of these nebulae have not been certainly ascer-tained ; but we may venture the conjecture that they willbe found to consist of bright lines. Such a spectrum, atleast, is given by the spiral nebula H. 4,0G4, in which lines *See view in Schellen, op. cit., 538. 44 COSMICAL DUST. answering to nitrogen and hydrogen appear, besides twoother bright lines not Fig. 8. Spiral Nebula ix Canes Vexatici, Herschel 3. Spiro-annular N^ebulce.—These seem to be undergo-ing a transition from the spiral to the annular form. H. 604 (Figure 9) is one ofthese. Another equal-ly transitional is (Figure 10), inwhich we see severalsegments of spiral orannular forms sur-rounding a bright nu-cleus, as in H. spectra of thesenebulae are also un- Spiro-axsular Nebula, Herschel 604. known.* * This, like most of the other nebular types mentioned may be found wellfigured in Schellens Spectral Analysis, and better in The Popular Science
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