QQ INSTRUCTIONS TO MARINE METEOROLOGICAL OBSERVERS 



Real cirrocumuliis is luicoiiiinon. It must not be confused with 

 small altocumulus patches on tlie edges of altocumulus sheets. 



Cirrostratus. — A thin, whitish veil, which does not blur the out- 

 lines of the sun or moon, but oives rise to halos. Sometimes it is 

 quite diffuse and merely gives the sky a milky look; sometimes it 

 more or less distinctly shows a fibrous structure with disordered 

 filaments (fig. 17). 



riGURE IG. — Cirrocumuliis, undulated form. 



Barnard.) 



A milky veil of fog is distinguished from a veil of cirrostratus of 

 a similar appearance by the halo phenomena, which the sun or the 

 moon nearly always produce in a layer of cirrostratus. 



Altocumulus. — A layer, or patches, composed of lamina or rather 

 flattened globular masses (fig. 18), the smallest elements of the 

 regularly arranged layer being fairly small and thin, w^ith or without 

 shading. These elements are arranged in groups, in lines, or waves 

 (fig. 19), following one or two directions, and are sometimes so 

 close together that their edges join. 



The thin and semitransparent edges of the elements often show 

 irisations, which are rather characteristic of tliis class of cloud. 



