Of the Compound Clouds we have:
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.
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.