Visibility of stars through the atmospheres and tails of cornets; ancient and modern observations upon this point– Are the nuclei of cornets opaque, or transparent like the atmospheres and tails?–Reported eclipses of the sun and moon produced by comets.

The visibility of stars, even of very small ones, through the comæ and tails of comets is a fact which had been observed by the ancients. Aristotle in his meteorology mentions the stars seen by Democritus notwithstanding the interposition of a comet. Seneca says likewise, in his Quæstiones Naturales, ‘that we may see stars through a comet as through a cloud;’ and further on, ‘the stars are not transparent, and we can see them through comets– not through the body of the comet where the flame is dense and solid, but through the thin and scattered rays which form the hair; it is through the intervals of the fire, not through the fire itself, that you see.’ Humboldt, in quoting this last passage, ‘per intervalla ignium, non per ipsos vides,’ adds:‘This last remark was unnecessary, for it is possible to see through a flame the thickness of which is not too great.’ This is true ; but Seneca has merely recorded the fact that up to his time stars had been seen behind the tail or coma, not behind the nucleus itself. The want of the telescope did not, in fact, permit the ancients to distinguish the body or nucleus of a comet, even when the comet had a nucleus.