THE FASCINATION OF LIGHT 327 



•whitish. While slowly creeping towards it, he saw- 

 it disappear four times at intervals of about twenty- 

 seconds, from which he inferred that the bird (for 

 such it proved to be) has the light under control, 

 and governs it by raising or depressing the feathers 

 that cover the powder down patches. When he 

 fired at the bird the light on the breast was so 

 intense that he distinctly saw the sight of his gun 

 against it. The bird — a Great Blue Heron — fell 

 where it was standing in 6 inches of water, and, 

 taking it by the wings, he threw it on the shore, 

 noticing three phosphorescent spots, one in front, 

 and one on each side of the hips between the hips 

 and the tail. The bird died slowly, the light gradu- 

 ally dying out, and disappearing entirely with death. 

 This fact is of great interest, showing, as Mr 

 Holder observes, that the phosphorescence is not 

 an accidental occurrence, depending upon a favour- 

 able condition of the greasy powder-down patches, 

 or associated entirely with their decomposition, but 

 is essentially due to some physiological action, and 

 dependent upon the life of the bird ; and the areas 

 •of the powder-down patches may be considered true 

 photogenic structures. The bird shot as above 

 stated was the Great Blue Heron [Ardea herodias), 

 popularly known to American gunners as the " Blue 

 Crane," and the other birds in which the light was 

 observed were Night Herons {Nycticorax ncevius). 

 The light was in the so-called powder-down patches, 

 which we may reasonably assume in all these birds 

 serve to attract the fish on which they prey. It 

 would be of great interest if any of our English 



