White Plumage of Sea-Birds

Abstract

In a recent communication¹ on this subject, Craik makes some suggestions which we have attempted to examine further. A simple experiment in which conditions natural to fish were imitated was made on the flat roof of the Zoology Building here. The observer looked vertically upwards through a glass trough filled with water at a piece of opaque cardboard 3 in. × 5 in. in size held 6 ft. above his head. The agitation of the water by the wind made visibility of details very poor. With any overcast sky, when the observer was presented successively with a black and a white piece of cardboard, he was unable to tell which was which. But when the sun was shining on them, the white cardboard was at once distinguished from the black.