Fig. 353.
It will be seen that the perihelion point of this orbit is at about the distance of the earth from the sun; so that the earth encounters the meteors once a year, and this takes place in the month of August. The orbit is a very eccentric ellipse, reaching far beyond Neptune. As the meteoric display is about equally brilliant every year, it seems probable that the meteoroids form a stream quite uniformly distributed throughout the whole orbit. It probably takes one of the meteoroids about a hundred and twenty-four years to pass around this orbit.
Fig. 354.
313. The November Meteors.—A somewhat brilliant meteoric shower also occurs annually, about the 13th of November. The radiant point of these meteors is in the constellation Leo, and hence they are often called the Leonids. Their orbit has been determined with great accuracy, and is shown in Fig. 354. While the November meteors are not usually very numerous or bright, a remarkably brilliant display of them has been seen once in about thirty-three or thirty-four years: hence we infer, that, while there are some meteoroids scattered throughout the whole extent of the orbit, the great majority are massed in a group which traverses the orbit in a little over thirty-three years. A conjectural form of this condensed group is shown in Fig. 355. The group is so large that it takes it two or three years to pass the perihelion point: hence there may be a brilliant meteoric display two or three years in succession.
Fig. 355.
The last brilliant display of these meteors was in the years 1866 and 1867. The display was visible in this country only a short time before sunrise, and therefore did not attract general attention. The display of 1833 was remarkably brilliant in this country, and caused great consternation among the ignorant and superstitious.
Fig. 356.