THE CUMULUS, OR STACKEN-CLOUD.
“And now the mists from earth are clouds in heaven:
Clouds, slowly castellating in a calm
Sublimer than a storm; while brighter breathes
O’er the whole firmament the breadth of blue,
Because of that excessive purity
Of all those hanging snow-white palaces,
A gentle contrast, but with power divine.”
The Cumulus is a day cloud; it usually has a dense, compact appearance, and moves with the wind. In the latter part of a clear morning a small irregular spot appears suddenly at a moderate elevation. This is the nucleus or commencement of the cloud, the upper part of which soon becomes rounded and well defined, while the lower forms an irregular straight line. The cloud evidently increases in size on the convex surface,
one heap succeeding another, until a pile of cloud is raised or stacked into one large and elevated mass, or stacken-cloud, of stupendous magnitude and beauty, disclosing mountain summits tipped with the brightest silver; the whole floating along with its point to the sky, while the lower surface continues parallel with the horizon.
When several cumuli are present, they are separated by distances proportioned to their size: the smaller cumuli crowding the sky, while the larger ones are further apart. But the bases always range in the same line; and the increase of each cloud keeps pace with that of its neighbour, the intervening spaces remaining clear.
The cumulus often attains its greatest size early in the afternoon, when the heat of the day is most felt. As the sun declines, this cloud gradually decreases, retaining, however, its characteristic form till towards sunset, when it is, more or less, hastily broken up and disappears, leaving the sky clear as in the early part of the morning. Its tints are often vivid, and pass one into the other in a most pleasing manner, during this last hour of its existence.
This cloud accompanies and foretells fine weather. In changeable weather it sometimes evaporates almost as soon as it is formed; or it appears suddenly, and then soon passes off to some other modification.
In fair weather this cloud has a moderate elevation and extent, and a well-defined rounded surface. Before rain it increases more rapidly than
at other times, and appears lower in the atmosphere, with its surface full of loose fleeces.
The formation of large cumuli to leeward, in a strong wind, indicates the approach of a calm with rain. When they do not disappear or subside about sun-set, but continue to rise, thunder is to be expected in the night.
Independently of the beauty and magnificence which this description of cloud adds to the face of nature, it serves to screen the earth from the direct rays of the sun; by its multiplied reflections to diffuse and, as it were, economise the light; and also to convey immense stores of vapour from the place of its origin to a region in which moisture may be wanted.