NOVEL THEORY OF COMETS.

New Zealand Herald, Volume XI, Issue 4048, 3 November 1874, Page 3

NOVEL THEORY OF COMETS.

A novel theory inspecting comets is propounded by Iron :—" Comets are .supposed to consist- of thin vapours of gases, held together by the mutual attraction of their particles. Eikc all bodies so circumstanced, tlicy necessarily assume the spherical form, and therefore the common notion that they consist of a comparatively small and bright nucleus, ami an immensely loug and illuminated tail, evidently derived from its appearance in the heavens, cannot for a moment be entertained. That their spherical form, as shewn by the reflected light of the sun, would scarcely be discernible at the distance of our earth, even though the comet were as dense as the densest cloud of our atmosphere, would not bo surprising; but if their attenuation as described by Sir John Herseliel be considered, all wonder ce;;ses. Sir J. Herschel says that ' the most unsubstantial clouds which float in the highest regions of our atmosphere, and seem at sunset to be drenched in liglic and to glow throughout their whole depth as if in actual ignition, without any shadow or dark side, must be looked upon as dense and massive bodies, compared with the flimsy and all but spiritual texture of a comet.' Owing to this extreme tenuity of matter the rays of t;ie sun's light, as reflected by it, are absolutely invisible to the inhabitants of the earth j but the other rays, penetrating into the centre of the comet, aro refracted by thig 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. Thcuce tliis large body of concentrated light, streaming in a narrow path, through the remaining 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, whether ill advancing , or receding ; also for the wonderful celerity I shewn l>y the tail in turning round the sun when the comet is in perihelion, and for the rapidity witli which the comet darts out its tail after the perihelion passage. It explains, also, 011 the principle of the aberration of light, the bend which the tails of some comets have towards the region they have left, also the absence of a solid nucleus, and the non-obscuration of the stars by the body of the comet. If the conjecture 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, theu it follows that at this present moment the sun is feasting on our comet, and that when it emerges from liis embraces a few days hence it will have suffered some diminution of size."