precise
character. Many ingenious hypotheses have been thrown out, which may
perhaps be accepted as steps towards a true explanation; and while
waiting the result of further inquiry, we shall endeavour to make our
readers acquainted with the interesting phenomenon.

The zodiacal light is a peculiar brightness, pyramidal or wedge-like
in form, seen at certain periods of the year in the eastern or western
sky, before sunrise and after sunset. Its direction is in the line of
the zodiac, whence its name--not perpendicular to the horizon, but at
a varying angle, being in the spring from 60 to 70 degrees. The base
of the wedge, which has a breadth generally of from 10 to 12 degrees,
is below, and the sides rise in a line, curving outwards, to the apex,
but so vague and diffuse as to be frequently indefinable. In our
latitudes, it is best seen at or just after the equinoxes; before
sunrise in autumn, and after sunset in spring; and becomes invisible
as twilight increases, or if the moon shines; the light even of Venus
and Jupiter is sufficient to render its discovery difficult. It is
brightest at the base, and grows fainter the further it stretches from
the horizon, vanishing entirely at the point. Unpractised observers
would be apt to overlook it altogether, and those accustomed to watch
the heavens are at times obliged to fix one eye on a dark space of
sky, while they search for the light with the other, and discover it
only by the contrast. A stratum of black cloud resting on the horizon
often affords a means of detection, as the light can then be seen
shooting from it with comparative distinctness. The soft, clear
atmosphere which usually precedes or follows rain, is very favourable
to a view of the light.

The luminous wedge varies in length with the progress of the seasons:
sometimes but little more than its point is visible; at others, it is
seen extending over a space of 120 degrees. Astronomically speaking,
the axis of the zodiacal light is said to lie in the plane of the
solar equator, with an angle of more than 7 degrees to the ecliptic,
which it consequently intersects, the points of intersection becoming
its nodes, and these nodes are the parts through which the earth
passes in March and September. The light travels forward along the
zodiacal signs from Gemini to Cancer and Leo from August to November,
keeping pace with the sun. It grows dim towards the end of November,
and fades more and more until January; but