H. Skey. — On the Collision of a Comet with the Eartlis Atmosphere. 149 



This collision may, I think, be fairly considered to be one of the most 

 remarkable astronomical occurrences of modern times, and appears to invali- 

 date the generally received opinion as to the solidity of the matter of meteors, 

 and consequently induces us to question the correctness of what is known 

 as the " Meteoric Theory of the Sun," which assumes the sun's light and heat 

 as being sustained by its surface being bombarded by myriads of solid meteors, 

 and the zodiacal light has been conjectured as being an illuminated shower, 

 or rather tornado of stones, which are to furnish their equivalents of heat and 

 light by the sudden check to their motion when they fall into it. 



Now comets are known to be bodies of almost inconceivable tenuitv, as 

 proved by the immense perturbations they undergo by the attraction of the 

 planets, without being able to induce any appreciable effect themselves on the 

 orbits of the planets, or even of their satellites. Another proof of their tenuity 

 is the fact of their not being well seen in telescopes of high magnifyiDg power, 

 and it is highly probable that a comet, when very close to the earth, cannot be 

 seen at all by its ordinary illumination, for its light would be so much diffused, 

 and subtend so large an angle, that its illumination would fail to be detected. 



Immediately after the meteoric display alluded to it occurred to Klinker- 

 fues to suggest to the Madras astronomer a search of the heavens near theta 

 Centauri, or in direction diametrically opposite to the radiant point of the 

 meteors (gamma Anclromedce) for the missing comet, and a cometic-lookiug 

 object was actually noted by him, but not sufficiently near to that point to 

 render it demonstrable that the object he saw was the truant comet or any 

 part thereof. When, however, we consider the enormous perturbation the 

 comet must have undergone by its proximity to the earth probably that diffi- 

 culty might vanish. It has been calculated that the meteor stream of the 27th 

 November was nearly twelve weeks behind the head of the comet. Now we 

 can scarcely suppose that any detached collection of solids should be dragged 

 after a comet, such would surely be contrary to all analogy. The conclusion 

 presents itself that if a comet is so drawn out, either by the perturbations of 

 the planets, or by a resisting medium, the parts so drawn out would be of 

 greater tenuity than the comet itself. 



We may, therefore, fairly infer that matter in a non-solid or vapourous 

 form, when coming into collision with the earth's atmosphere at orbital 

 velocities is competent to produce all the phenomena known as shooting stars 

 and meteors. 



At a future meeting I shall be prepared to give another paper embodying 

 a seiies of actual observations " On the direction- — the arc subtended — and 

 times of visibility of the Zodiacal Light," made since 1872, tending to confirm 

 the theory that this medium has points of greatest elongation in a line 

 coinciding with that of the sun's motion in space. 



