As the Cumulus belongs to the day, so does the Stratus to the night. It is the lowest of all the clouds, and actually rests upon the earth, or the surface of water. It is of variable extent and thickness, and is called Stratus, a bed or covering. It is generally formed by the sinking of vapour in the atmosphere, and on this account has been
called Fall-cloud. It comprehends all those level, creeping mists, which, in calm evenings, spread like an inundation from the valleys, lakes, and rivers, to the higher ground. [85] But on the return of the sun the beautiful level surface of this
cloud begins to put on the appearance of cumulus, the whole, at the same time, rising from the ground like a magnificent curtain. As the cloud ascends, it is broken up and evaporates or passes off with the morning breeze. The stratus has long been regarded as the harbinger of fine weather; and, indeed, there are few days in the year more serene than those whose morning breaks out through a stratus.
THE CIRRO-CUMULUS, OR SONDER-CLOUD.
The cirrus having continued for some time increasing or stationary, usually passes either to the cirro-cumulus or to the cirro-stratus, at the same time descending to a lower station in the atmosphere.
The Cirro-cumulus is formed from a cirrus, or a number of small separate cirri, passing into roundish masses, in which the extent of the cirrus is no longer to be seen. This change takes place either throughout the whole mass at once, or progressively from one extremity to the other. In either case the same effect is produced on a number of neighbouring cirri at the same time, and in
the same order. It appears, in some instances, to be hastened by the approach of other clouds.
The cirro-cumulus forms a very beautiful sky, exhibiting sometimes numerous distinct beds of small connected clouds floating at different heights. It is frequent in summer, and accompanies warm,