The numberless kinds of clouds makes it quite difficult to describe and
arrange them or illustrate them in any manner that makes it easy to
recognize them. Although some may be recognized from description and
with a fair amount of observation, you will be able to classify them in
their proper place. For instance, the thunder clouds most anyone
recognizes without any experience whatever.
[Illustration:
Fig. 28
]
There are really four simple cloud formations and three compound
formations:
=1. The Cirrus Cloud.= (Fig. 24.)
The Cirrus cloud is always seen high in the sky and at a great
elevation. Its formation is fibrous and it is particularly characterized
for its many varieties of shapes. It also has a marked delicacy of
substance and it is pure white.
=2. The Cumulus Cloud.= (Fig. 25.)
The Cumulus cloud is of moderately low elevation. It is a typical cloud
of a summer day. It may be recognized by little heaps or bushes rising
from a horizontal base. In summer-time we are all familiar with the
cumulus clouds rising with the currents of air in huge masses. They form
one of the most accurate indications of fair weather when you see them
gradually dissolving. Sometimes these clouds become very large, and,
while the texture is generally of a woolly white, naturally, when they
assume such large sizes, they gradually change in color to a darkish
tint.
=3. The Stratus Cloud.= (Fig. 26.)
This is the opposite of the Cirrus cloud, because it hangs the lowest of
all, in gray masses or sheets, with a poorly-defined outline.
=4. The Nimbus Cloud.= (Fig. 27.)
Any cloud can be classed as a nimbus cloud from which rain or snow is
falling.
Of the Compound Clouds we have:
[Illustration:
Fig. 29
]
1. The Cirro-Cumulus Cloud (Fig. 28), which has all the characteristics
of both the Cirrus and the Cumulus. The most characteristic form of this
cloud, and the one most commonly known, is when these clouds form small
round masses, which appear to be cirrus bands broken up and curled up.
This is what people call the “mackerel” sky.
2. The Cirro-Stratus Cloud (Fig. 29), which is known when the clouds
arrange themselves in thin horizontal layers at a great elevation.
[Illustration:
Fig. 30
]
3. The Cumulo-Stratus (Fig. 30) is the cumulus and the stratus blended
together. Their most remarkable form is in connection with approaching
thunder storms, and are often called thunder heads. They rapidly change
their outline and present a beautiful spectacle in the sky at times.
The Cirrus, Cirro-Cumulus and Cirro-Stratus are known as the upper
clouds and the others are known as the lower.