The sun is often reflected in vivid colors, from the under surface of clouds, at sunset. This is an indication of fair weather. It is evident the sun shines through a _clear atmosphere beyond the cloud_, or his rays would not reach and illume the lower surface of the cirro-stratus with such distinctness. He "_sets clear_," as is said; the clouds are passing off, and there are none beyond. It is this appearance, in different forms, when there happen to be patches of broken, melting cirro-stratus above the horizon, which makes the beautiful sunsets that attract attention. So the sun is reflected, in beautiful colors sometimes, from the cumulus clouds which have passed over to the east. The most beautiful and variegated I have ever seen, were reflected from that imperfect cumulus condensation which takes place occasionally during long drouths--doubtless resembling that which is seen over Peru, hereinbefore alluded to, as described by Stewart. It is not, then, the presence of cloud condensation at the west, at nightfall, which alone indicates foul weather; but such condensation, whatever its form, as evinces that it is not the _dissolving_ cloud of the day, but the eastern, approaching portion of a _still denser portion beyond, through, or under which, the sun can not shine clearly, but which wholly or partially obscures it_. _Remembering this philosophy of the matter_, the observer will soon be able to detect the various forms of condensation which originate or exhibit themselves at nightfall, and whether they indicate an approaching storm or not, without a more explicit specification of them. It is an important hour for observation; "Let not the sun go down" without attention. When the condensation is obvious, but thin, at nightfall, it may not, as I have said, be discernible in the evening. But there are methods by which the incipient storm condensation may be detected. The number of the stars visible, and the _distinctness_ with which they may be seen, indicate the absence or presence of condensation and its density. Virgil, alluding to the indications of fair weather, says: "_Brightly_ the stars shine forth; Cynthia no more _Glimmers_ obnoxious to her brother's rays; Nor fleecy clouds float lightly through the sky." The brightness of the stars and the clear appearance of the moon show the absence of condensation and the _dissolution_ of the fleecy clouds at the close of the day is, as we have seen, always a fair-weather indication. There is much true philosophy in the allusions of Virgil to the moon. Thus-- "When Luna first her scatter'd fires recalls, If with _blunt horns_ she holds the _dusky_ air, Seamen and swains predict th' abundant shower."