National Geographic : 1925 Aug
Photograph by Ebro Observatory CIRRUS: A BUNCHED FORM This type is somewhat denser than those shown in the two preceding plates (page 18). Cirrus clouds are described in the International Cloud Atlas as "detached clouds of delicate and fibrous appearance, often showing a featherlike structure, generally of a whitish color." Photograph by A. J. Henry CIRRO-STRATUS The form shown in the lower part of this illustration is cirro-stratus. The upper portion shows bits of cirrus. The cirro-stratus sheet often produces halos-well-defined narrow circles of light surrounding the sun or moon and at a distance from it. They are to be distinguished from coronas, which appear to touch the source of light (see page 177).