AND BLACK-BILLED AUK. 
17 
is easy to account for this, when he informs us, that the 
plumage of the Black-billed Auk in summer is just that of 
the Razor-Bill at the same season. It is farther remark- 
able, that while Fabricius gives minute details regarding 
the Razor-Bill in summer, a bird he declares he had never 
seen in Greenland during that season, he should say com- 
paratively so little of the Pica at the same season, a spe- 
cies he mentions having seen at all periods of the year. He 
^Iso states^ that the Razor-Bill lays two eggs ; and every 
other naturalist, ncluding Montagu himself, mentions 
only one ; and my observation agrees with this. And he 
asserts that the weight of the Black-billed Auk is superior 
to that of the Razor-Bill ; yet he maintains the same opi- 
nion as Montagu, of the distinction of these two species; 
These remarks shew the contradictions into which this 
author has been led; and that, though his authority is 
highly respectable in many other points of Arctic zoology, 
in this it must be received with limitation. 
If they be the same species<j Montagu conceives they 
must moult four times a-year, since four different states of 
plumage may be remarked ; but this inference is not at all 
necessary. These different states are accounted for by sup- 
posing, what is the fact, and what is acknowledged to be soj 
that they moult partially twice a-year ; and that the other 
changes of plumage are acquired, not by new feathers, but 
by the change of colour of the old ones. Of facts exem- 
plifying this change of colour in the old feathers, every 
practical naturalist has ample opportunities of satisfying 
himself ; and for farther information on this point, I have 
only to refer to a very useful and interesting work, " The 
" Philosophy of Zoology," by a most intelligent and zealous 
naturalist, Dr Fleming, whose opinion respecting these 
disputed species I am happy to find is the same as my own, 
VOL. y. B 
