and show a bank when the sun shines horizontally
through a mass of it. I am now speaking of _storm_ condensation, or that
which indicates the approach of a storm. Thunder clouds at nightfall,
dark, dense, and isolated, are, of course, to be distinguished. Those,
every one understands to indicate a shower, and immediate succeeding fair
weather.

The halos do not, in cases of incipient storm condensation, always appear.
The moon may not be present: though, in her absence, I have seen them in
the light of the primary planets; or she may be in the eastern portion of
the heavens. When this is so, and the condensation forms slowly, there may
be less appearance of it, after the sun disappears, than before, although
a storm is approaching, and sure to be on by the middle of next day, and
perhaps with great violence. When the failure of the light no longer
reveals the denser condensation in the west, the stars may shine, as did
the sun, dimly but visibly, through the partial and invisible
condensation; and one who did not notice the bank in the west, at
nightfall and before dark, may be deceived by the seeming clearness of the
evening. Thus Virgil--

"Mark, with attentive eye, the rapid sun--
The varying moon that rolls its monthly round;
So shalt thou count, not vainly, on the morn;
_So the bland aspect of the tranquil night
Will ne'er beguile thee with insidious calm_."

All early condensation and indications derived from it, must be looked for
in the west. From that quarter all storms come. These indications at
nightfall are of a varied character. They may consist of primary
condensation in the trade, or of secondary condensation, scud running
north toward a storm, the condensation of which has not yet visibly
reached us, but which will extend south and pass over us. It may be a
heavy bank, or consist of narrow cirrus bands. Cirro-stratus cloud banks,
in the S. W., in the fall and winter, of a foggy and uniform character,
are indicative of snow. The body of the storm will pass south of us, and a
portion over us, the wind be north of east, and the snow will not be
likely to turn to rain before it reaches the earth, by reason of a
southern middle current.

Banks in the N. W. indicate rain at all seasons. The storm is north of us,
working southerly, and such storms rain on the southern border--in winter
even--because they have the wind on that border from south of east. It
may, indeed, snow, but if so, probably i