We have now to give some brief account of one of the most remarkable cometary apparitions on record, and—with the single exception of that identified with the name of Halley—the most instructive to astronomers. The lessons learned from it were as varied and significant as its aspect was splendid; although from the circumstance of its being visible in general only before sunrise, the spectators of its splendour were comparatively few.
The discovery of a great comet at Rio Janeiro, September 11, 1882, became known in Europe through a telegram from M. Cruls, director of the observatory at that place. It had, however (as appeared subsequently), been already seen on the 8th by Mr. Finlay of the Cape Observatory, and at Auckland as early as September 3. A later, but very singularly conditioned detection, quite unconnected with any of the preceding, was effected by Dr. Common at Ealing. Since the eclipse of May 17, when a comet—named "Tewfik" in honour of the Khedive of Egypt—was caught on Dr. Schuster's photographs, entangled, one might almost say, in the outer rays of the corona, he had scrutinized the neighbourhood of the sun on the infinitesimal chance of intercepting another such body on its rapid journey thence or thither. We record with wonder that, after an interval of exactly four months, that infinitesimal chance turned up in his favour.
On the forenoon of Sunday, September 17, he saw a great comet close to, and rapidly approaching the sun. It was, in fact, then within a few hours of perihelion. Some measures of position were promptly taken; but a cloud-veil covered the interesting spectacle before mid-day was long past. Mr. Finlay at the Cape was more completely fortunate. Divided from his fellow-observer by half the world, he unconsciously finished, under a clearer sky, his interrupted observation. The comet, of which the silvery radiance contrasted strikingly with the reddish-yellow glare of the sun's margin it drew near to, was followed "continuously right into the boiling of the limb"—a circumstance without precedent in cometary history.[1314] Dr. Elkin, who watched the progress of the event with another instrument, thought the intrinsic brilliancy of the nucleus scarcely surpassed by that of the sun's surface. Nevertheless it had no sooner touched it than it vanished as if annihilated. So sudden was the disappearance (at 4h. 50m. 58s., Cape mean time), that the comet was at first believed to have passed behind the sun. But this proved not to have been the case. The observers at the Cape had witnessed a genuine transit. Nor could non-visibility be explained
The Great Comet of September, 1882.
Photographed at the Royal Observatory, Cape of Good Hope
by equality of lustre. For the gradations of light on the sun's disc are amply sufficient to bring out against the dusky background of the limb any object matching the brilliancy of the centre; while an object just equally luminous with the limb must inevitably show dark at the centre. The only admissible view, then, is that the bulk of the comet was of too filmy a texture, and its presumably solid nucleus too small, to intercept any noticeable part of the solar rays—a piece of information worth remembering.
On the following morning, the object of this unique observation showed (in Sir David Gill's words) "an astonishing brilliancy as it rose behind the mountains on the east of Table Bay, and seemed in no way diminished in brightness when the sun rose a few minutes afterward. It was only necessary to shade the eye from direct sunlight with the hand at arm's length, to see the comet, with its brilliant white nucleus and dense white, sharply bordered tail of quite half a degree in length."[1315] All over the world, wherever the sky was clear during that day, September 18, it was obvious to ordinary vision. Since 1843 nothing had been seen like it. From Spain, Italy, Algeria, Southern France, despatches came in announcing the extraordinary appearance. At Cordoba, in South America, the "blazing star near the sun" was the one topic of discourse.[1316] Moreover—and this is altogether extraordinary—the records of its daylight visibility to the naked eye extend over three days. At Reus, near Tarragona, it showed bright enough to be seen through a passing cloud when only three of the sun's diameters from his limb, just before its final rush past perihelion on September 17; while at Carthagena in Spain, on September 19, it was kept in view during two hours before and two hours after noon, and was similarly visible in Algeria on the same day.[1317]