"'November 30th--Biela touched the earth on the 27th of November. Search for him near Theta Centauri.'
"The telegram reached Madras, through Russia, in one hour and thirty-five minutes, and the sequel of this curious passage of astronomical romance may be appropriately told in the words in which Mr. Pogson replied to Herr Klinkerflues's pithy message. The answer was dated Madras, the 6th of December, and was in the following words:
"'On the 30th of November, at sixteen hours, the time of the comet rising here, I was at my post, but hopelessly; clouds and rain gave me no chance. The next morning I had the same bad luck. But on the third trial, with a line of blue break, about 17¼ hours mean time, I found Biela immediately! Only four comparisons in successive minutes could be obtained, in strong morning twilight, with an anonymous star; but direct motion of 2.5 seconds decided that I had got the comet all right. I noted it--circular, bright, with, a decided nucleus, but NO TAIL, and about forty-five seconds in diameter. Next morning I got seven good comparisons with an anonymous star, showing a motion of 17.9 seconds in twenty-eight minutes, and I also got two comparisons with a Madras star in our current catalogue, and with 7,734 Taylor. I was too anxious to secure one good place for the one in hand to look for the other comet, and the fourth morning was cloudy and rainy.'
"Herr Klinkerflues's commentary upon this communication was that he forthwith proceeded to satisfy himself that no provoking accident had led to the discovery of a comet altogether unconnected with Biela's, although in this particular place, and that he was ultimately quite confident of the identity of the comet observed by Mr. Pogson with one of the two heads of Biela. It was subsequently settled that Mr. Pogson had, most probably, seen both heads of the comet, one on the first occasion of his successful search, and the second on the following day; and the meteor-shower experienced in Europe on November 27th was unquestionably due to the passage
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near the earth of a meteoric trail traveling in the track of the comet. When the question of a possible collision was mooted in 1832, Sir John Herschel remarked that such an occurrence might not be unattended with danger, and that on account of the intersection of the orbits of the earth and the comet a rencontre would in all likelihood take place within the lapse of some millions of years. As a matter of fact the collision did take place on November 27, 1872, and the result, so far as the earth was concerned, was a magnificent display of aërial fireworks! But a more telling piece of ready-witted sagacity than this prompt employment of the telegraph for the apprehension of the nimble delinquent can scarcely be conceived. The sudden brush of the comet's tail, the instantaneous telegram to the opposite side of the world, and the glimpse thence of the vagrant luminary as it was just whisking itself off into space toward the star Theta Centauri, together constitute a passage that stands quite without a parallel in the experience of science."
But did the earth escape with a mere shower of fireworks?
I have argued that the material of a comet consists of a solid nucleus, giving out fire and gas, enveloped in a great gaseous mass, and a tail made up of stones, possibly gradually diminishing in size as they recede from the nucleus, until the after-part of it is composed of fine dust ground from the pebbles and bowlders; while beyond this there may be a still further prolongation into gaseous matter.
Now, we have seen that Biela's comets lost their tails. What became of them? There is no evidence to show whether they lost them in 1852, 1859, 1866, or 1872. The probabilities are that the demoralization took place before 1852, as otherwise the comets would have been seen, tails and all, in that and subsequent years. It is true that the earth came near enough in 1872 to attract some of the wandering gravel-stones toward itself, and that they fell,
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