imes it may seem as if they must
coalesce and form showers, yet they frequently do not, but gradually melt
away, as before stated.

The cumulus is the principal cloud of the tropics, and is not often seen
with us except in summer, or when our weather is tropical in character.

The engraving on the preceding page, shows a phase of these fair-weather
summer cumuli.

The last in order occupying (with their compounds) the higher portions of
the atmosphere, are the cirrus and stratus. The cirrus is often the
skeleton of the other, and precedes it in formation.

These are the proper clouds of the storm, in our sense of the term. While,
however, the cirrus remains a cirrus, it furnishes no rain. When it
extends and expands, and its threads widen and coalesce into cirro-stratus
and stratus, or it induces a layer of stratus below it, the rain forms.

The following is Dr. Howard's description of cirrus: "Parallel, flexuous
or diverging fibers, extensible by increase in any or in all directions.
Clouds in this modification appear to have the least density, the greatest
elevation, and the greatest variety of extent and direction. They are the
earliest appearance after serene weather. They are first indicated by a
few threads penciled, as it were, on the sky. These increase in length,
and new ones are in the mean time added to them. Often the first-formed
threads serve as stems to support numerous branches, which in their turn,
give rise to others."

The illustrations in the general cut are imperfect, and do not represent
the delicate fibers of the cloud, for it is a difficult cloud to
daguerreotype or engrave, but the representation is sufficiently accurate
to give the reader a general idea of the different varieties, and enable
him to discover them readily by observation. They are the most elevated
forms, always of a light color, and often illuminated about sunset by the
rays of the sun shining upon their inferior surface; the sun, however,
often illuminates, in like manner, the dense forms of cirro-stratus, and
the latter, from their greater density, are susceptible of a brighter and
more vivid illumination.

The stratus is a smooth, uniform cloud--the true rain cloud of the storm;
often forming without much cirrus above, or connected with it. It may be
seen in its partially formed state in the bank in the west, at nightfall,
or in the circle around the moon in the night. When it becomes
sufficiently condensed, rain always