204 THE BIRD WATCHER 
tinguishably for som@ime. Besides this—whether 
or not this had anything to do with it—it became all 
at once of a lovely glaucous green colour, luminous, 
and with bubbles flashing about it. Gradually the 
form became lost, but the luminous green was never 
lost, and after becoming dimmer and dimmer began 
to get brighter and brighter again, till the bird re- 
appeared out of it on the surface at some distance 
off. It seems just possible that this effect may be due 
in some measure to the white patches, since when the 
shag dives nothing of the sort, or, at any rate, nothing 
so marked, is to be seen, nor do I remember noticing 
it either in the guillemot, razorbill, or puffin, which 
are all dark above and only white underneath. On 
second thoughts, however, the colouring can have 
little or nothing to do with it, since the effect is very 
marked in the eider-duck of both sexes, and the 
female is uniformly dark. But how is the effect 
produced ? by the clinging of innumerable small air- 
bubbles to the bird’s plumage? If so, they may not 
cling equally to that of all species. The seal presented 
the finest appearance of all, but his size may perhaps 
have had something to do with this. Whatever may 
be the cause, I do not remember to have remarked 
the same thing in river-birds when diving. It is 
more difficult, indeed, to follow them under water 
when they dive, on account of the absence of cliffs 
to look down from. Still, one sees them sometimes, 
and, as I say, I do not remember noticing this 
luminous effect, so that it must be, at any rate, 
