to the meridian south of the zenith, where its apex at last vanishes
in the starlight. It continues visible during the evenings of March
and part of April, after which, ordinarily, it is seen no more, or if
seen is relatively faint and unimpressive. But when autumn comes it
appears again, this time not like a wraith hovering above the westward
tomb of the day-god, but rather like a spirit of the morning
announcing his reincarnation in the east.

The reason why the Zodiacal Light is best seen in our latitudes at the
periods just mentioned is because at those times the Zodiac is more
nearly perpendicular to the horizon, first in the west and then in the
east; and, since the phenomenon is confined within the borders of the
Zodiac, it cannot be favorably placed for observation when the
zodiacal plane is but slightly inclined to the horizon. Its faint
light requires the contrast of a background of dark sky in order to be
readily perceptible. But within the tropics, where the Zodiac is
always at a favorable angle, the mysterious light is more constantly
visible. Nearly all observant travelers in the equatorial regions have
taken particular note of this phenomenon, for being so much more
conspicuous there than in the temperate zones it at once catches the
eye and holds the attention as a novelty. Humboldt mentions it many
times in his works, for his genius was always attracted by things out
of the ordinary and difficult of explanation, and he made many careful
observations on its shape, its brilliancy, and its variations; for
there can be no doubt that it does vary, and sometimes to an
astonishing degree. It is said that it once remained practically
invisible in Europe for several years in succession. During a trip to
South Africa in 1909 an English astronomer, Mr E. W. Maunder, found a
remarkable difference between the appearance of the Zodiacal Light on
his going and coming voyages. In fact, when crossing the equator going