This swarm follows the same orbit as the comet of 1866, which travels as far as Uranus, and comes back to the vicinity of the Sun every thirty-three years. Hence we were entitled to expect another splendid apparition in 1899, but the expectations of the astronomers were disappointed. All the preparations for the appropriate reception of these celestial visitors failed to bring about the desired result. The notes made in observatories, or in balloons, admitted of the registration of only a very small number of meteors. The maximum was thirteen. During that night, some 200 shooting stars were counted. There were more in 1900, 1901, and, above all, in 1902. This swarm has become displaced.
The night of November 27th again is visited by a number of shooting stars that are the disaggregated remains of the Comet of Biela. This comet, discovered by Biela in 1827, accomplished its revolution in six and a half years, and down to 1846 it responded punctually to the astronomers who expected its return as fixed by calculation. But on January 13, 1846, the celestial wanderer broke in half: each fragment went its own way, side by side, to return within sight from the Earth in 1852. It was their last appearance. That year the twin comets could still be seen, though pale and insignificant. Soon they vanished into the depths of night, and never appeared again. They were looked for in vain, and were despaired of, when on November 27, 1872, instead of the shattered comet, came a magnificent rain of shooting stars. They fell through the Heavens, numerous as the flakes of a shower of snow.
The same phenomenon recurred on November 27, 1885, and confirmed the hypothesis of the demolition and disaggregation of Biela's Comet into shooting stars.
There is an immense variety in the brilliancy of the shooting stars, from the weak telescopic sparks that vanish like a flash of lightning, to the incandescent bolides or fire-balls that explode in the atmosphere.
Fig. 56 shows an example of these, and it represents a fire-ball observed at the Observatory of Juvisy on the night of August 10, 1899. It arrived from Cassiopeia, and burst in Cepheus.
This phenomenon may occur by day as well as by night. It is often accompanied by one or several explosions, the report of which is sometimes perceptible to a considerable distance, and by a shower of meteorites. The globe of fire bursts, and splits up into luminous fragments, scattered in all directions. The different parts of the fire-ball fall to the surface of the Earth, under the name of aerolites, or rather of uranoliths, since they arrive from the depths of space, and not from our atmosphere.
From the most ancient times we hear of showers of uranoliths to which popular superstitions were attached; and the Greeks even gave the name of Sideros to iron, the first iron used having been sidereal.
