NOVEL THEORY OF COMETS.

Thames Star, Volume VI, Issue 1829, 12 November 1874, Page 2

NOVEL THEORY OF COMETS.

A novel theory respecting comets it propounded by Iron :—Comets are supposed to consist of thin vapours or gases, held together by the mutual attraction of their particles. Like all' bodies so circumstanced, they necessarily assume the spherical form, and therefore the common notion that they consist of comparatively small and bright. nucleus, and an immensely long and illuminated tail, evidently derived from its appearance in the heavens, cannot" for a moment be entertained. That their spherical form, as shown by the reflected light of the sun, would scarcely be. discernable at the distance of our earth, even though the comet were as dense as the densest cloud of our atmosphere, wouldnot be surprising; but if their attenuation as described by Sir John Herschel be considered, all wonder ceases. Sir JV Herschel says 'that 'the most unsubstantial clouds which float in the higher regions of our atmosphere, and seem at sunset to be drenched in light and to glow throughout their whole depth as if in actual ignition, without any shadow or dark side, must be looked upon asdenseand massive bodies compared.with tha fiimsyand all but spiritual texture of a comet,' Owing to this extreme tenuity of matter the rays of the sun's light, as reflected by it, are absolutely invisible to the inhabitants of the earth; but the other rays, penetrating into the centre.of the comet, are refracted by this powerful lens of 20 millions of. leagues diameter into the focus which forms the nucleus of the comet, where there is, perhaps, a greater concentration of rays of light than anywhere else* not in the body of the sun. vThence this large body of concentrated light, streaming in a narrow path through the remain* ing half, of .the comet, in a direction opposite to the sun, forms that splendid appendage called the tail.. It : seems scarcely necessary to point out that this mode of viewing a comet accounts for'the circumstance of the tail being always in opposition to the sun, wjiether in iadvancing or receding; also for the wonderful celerity shown by the tail in turning round the sun when the comet is in perihelion, and for the rapidity with which the comet darts out its tail after the perihelion passage. It explains also, on the principle of the aberration of. light, the bend which the tails of someepmetshave towards tre region they have left, also the absence of a solid nucleus, and the nofe obscuration of the. stars by ; the t bbdyßf the comet. If tie conjffcture.be correct that the nucleus of a comet is near its centre, and that the comet extends in every direction round the nucleus to as great a distance, at least, as the length of the tail, then it follows that at: this present moment the sun is feasting on our comet, and that when it emerges from his embraces a few days hence it will have suffered some diminution of size."