Qg INSTRUCTIONS TO MARINE METEOROLOGICAL OBSERVERS 



(his is a colored ring, Avith red outside and blue inside; the colors 

 may }:>e repeated more than once. Tliis phenomenon is infrecpient 

 in the case of ciiTOCumulus, and only tlie higher forms of strato- 

 cumulus can show it. 



Irisation, mentioned above, is a phenomenon of the same type 

 as the corona ; it is a sure mark of altocumulus as distinguished from 

 cirrocumulus or stratocnmulus. 



Altostratus. — Striated or fibrous veil, more or less grey or bluish 

 in color. This cloud is like thick cirrostratus but without halo pheno- 

 mena; the sun or moon shows vaguely, with a faint gleam, as though 



