446 HUM MING-BIRD 
The extraordinarily brilliant plumage which most of the 7'rochi- 
lide exhibit has been already mentioned, and in describing it 
ornithologists have been compelled to adopt the vocabulary of the 
jeweller in order to give an idea of the indescribable radiance that 
so often breaks forth from some part or other of the investments 
of these feathered gems. In all save a few of other birds, the most 
imaginative writer sees gleams which he may adequately designate 
metallic, from their resemblance to burnished gold, bronze, copper, 
or steel, but such similitudes wholly fail when he has to do with 
the Trochilidy, and there is hardly a precious stone—ruby, ame- 
thyst, sapphire, emerald, or topaz—the name of which may not 
fitly, and without exaggeration, be employed in regard to Hum- 
ming-birds. In some cases this radiance beams from the brow, in 
some it glows from the throat, in others it shines from the fae 
coverts, in others it sparkles from the tip only of elongated feathers 
that crest the head or surround the neck as with a frill, while 
again in others it may appear as a luminous streak across the cheek 
or auriculars. The feathers that cover the upper parts of the 
body very frequently have a metallic lustre of golden-green, which 
in other birds would be thought sufficiently beautiful, but in the 
Trochilide its sheen is overpowered by the almost dazzling splen- 
dour that radiates from the spots where Nature’s lapidary has set 
her jewels. ‘The flight-feathers are almost invariably dusky—the 
rapidity of their movement would, perhaps, render any display of 
colour ineffective ; while, on the contrary, the feathers of the tail, 
which, as the bird hovers over its food-bearing flowers, is almost 
always expanded, and is therefore comparatively motionless, often 
exhibit a rich translucency, as of stained glass, but iridescent i ina 
manner that no stained glass ever is—cinnamon merging into 
crimson, crimson changing to purple, purple to violet, and so to 
indigo and hottle-ereen. But this part of the Humming-bird is 
subject to quite as much modification in form as in colour, though 
always consisting of ten rectrices. It may be nearly square, or at 
least but slightly rounded, or wedge- shaped with the middle quills 
prolonged beyond the rest; or, again, it may be deeply forked, 
sometimes by the overgrowth of one or more of the intermediate 
pairs, but most generally by the development of the outer pair. 
In the last case the lateral feathers may be either broadly webbed 
to their tip, or acuminate, or again, in some forms, may lessen to 
the filiform shaft, and suddenly enlarge into a terminal spatulation 
as in the forms known as “ Racquet-tails.”” The wings do not offer 
so much variation; still there are a few groups in which occur 
diversities that require notice. The primaries are invariably ten 
in number, the outermost being the longest, except in the single 
instance of Aithurus, where it is shorter than the next. The group 
known as “Sabre-wings,” comprising the genera Campylopterus, 
