Page:Popular Science Monthly Volume 1.djvu/410

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system in January, a. d. 126, and passed so near the planet Uranus as to be brought by its attraction into an elliptic orbit round the sun. This orbit is the same as that of the comet discovered by Tempel, and calculated by Oppolzer, and is identical with that in which the November group of meteors make their revolution.

Since that time, this cosmical cloud, in the form of a comet, has completed fifty-two revolutions round the sun, without its existence being otherwise made known than by the loss of an immense number of its components, in the form of shooting-stars, as it crossed the earth's path in each revolution, or in the month of November in every 33 years. It was only in its last revolution, in the year 1866, that this meteoric cloud, now forming part of our solar system, was first Been as a comet.

The orbit of this comet is much smaller than that of the August meteors, extending at the aphelion as far as the orbit of Uranus, while the perihelion is nearly as far from the sun as our earth. The comet completes its revolution in about 33 years and three months, and encounters the earth's orbit as it is approaching the sun toward the end of September. It is followed by a large group of small meteoric bodies, which form a very broad and long tail, through which the earth passes on the 13th of November. Those particles which come in contact with the earth, or approach so near as to be attracted into its atmosphere, become ignited, and appear as falling stars. As the earth encounters the comet's tail, or meteoric shower, for three successive years at the same place, we must conclude the comet's track to have the enormous length of 1,772,000,000 of miles. In Fig. 4, C D represents a portion of the orbit of this comet which is identical with the orbit (Fig. 3) of the November meteors.—Spectrum Analysis.


By Dr. J. B. MOZLEY,


THERE is no one who, coming for the first time to a knowledge of our English system of education, would not be very much surprised by the fact that, while we take the greatest trouble to instruct young men in the language, history, and institutions of nations that lived two thousand years ago, and whose whole being belongs to a past stage in the world's existence, we take no trouble at all to instruct them concerning the nations who now live, with whom we have an every-day intercourse, on whom we depend for so many benefits, as well material as spiritual, whose temper, character, and friendly or inimical