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The great train of the November meteors, known as the Leonids, which at regular periods of thirty-three years had in the past encountered the earth's atmosphere, was due, and over-due. The cause of this, and of their finally eluding observation, need only be very briefly touched on here.
For convenience, the most familiar image should come first; and this is probably that of the comet, or meteoric streams, like the Leonids and Perseids; a complex of minute mechanical agencies, reacting within and without, and guided by the sum of forces attracting or deflecting it.
The inference was, then, an easy one, that the meteors were pursuing the same path with the comet; and it was separately arrived at, early in 1867, by Weiss, D'Arrest, and Galle. But Biela travels in the opposite direction to Tempel's comet and its attendant "Leonids"; its motion is direct, or from west to east, while theirs is retrograde.
This was the last link in the chain of evidence proving that the November meteors or "Leonids," as they had by that time come to be called revolve round the sun in a period of 33·27 years, in an ellipse spanning the vast gulf between the orbits of the earth and Uranus, the group being so extended as to occupy nearly three years in defiling past the scene of terrestrial encounters.
The last time we passed through the swarm was in 1899, and then the show was very disappointing. Here in England thick clouds prevented our seeing much, and there will not be another chance for us to see it at its best until 1932. These November meteors are called Leonids, because they seem to come from a group of stars named Leo, and though the most noticeable they are not the only ones.
Starting up, I found myself clutching Chapman, who had called to the pilot to stop the boat. A few of the attendants were grouped near us, and the loudly suppressed exclamations made me realize that these visitations were perhaps infrequent upon Mars. "It was a meteoric shower, like our leonids in November.
And other figures, hosts of them, were everywhere stooping, picking, loading one another's backs and shoulders. To and fro they shot and glided, like Leonids in autumn round the Earth. All were collecting, though the supply seemed never to grow less. An inexhaustible stream poured in through the narrow opening, and scattered itself at once in all directions as though driven by a wind.
Train after train, each with its full complement of passengers, flashed forth across that summer sky, till the people in the Observatories must have thought they had miscalculated strangely and the Earth was passing amid the showering Leonids before her appointed time. 'Where would you like to go first? Mother heard her friend ask softly.
This is easily understood when we remember that the Andromedes overtake the earth, while the Leonids rush to meet it; the velocity of encounter for the first class of bodies being under twelve, for the second above forty-four miles a second. The spectacle was, nevertheless, magnificent.
The majority, too, were true Leonids, issuing from the radiant point in the "Sickle," but these were not more numerous than may be counted on that night in any year, and served to emphasise the fact that no real display was in progress.
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