EXTERNAL ANATOMY. WING FEATHERS. 01 
but by their peculiar shape, anti by the great develop- 
ment of the secondaries ; these latter being often so long, 
as nearly to equal the primary quills. This structure, in 
fact, is the very opposite to that which we see in the 
wings of the humming-birds, where the secondary 
quills are so small that they become almost obsolete. 
Indications, showing a tendency to this structure, may 
be traced in many perching birds possessed of rounded 
wings ; but those which we term mmrial differ 
from these last sufficiently to authorise a distinct name 
being applied to them. 1'his will be evident on ex- 
amining the wing of a partridge ( Tetrao Perdix L.), 
and comparing it with any of the common birds we 
have already named. The primary quills, in their 
substance, have an unusual strength and rigidity : 
their shape is almost falcate, and their form very nar- 
row ; their curved shape gives to the wing a great 
degree of convexity, and also indicates much strength ; 
although, when the wing is closed, the primary quills 
are hardly half an inch longer than the tertials, while 
the secondaries are near three-fourths as long as the 
primaries. It is well known that the noiseless flight of 
the owl originates in the looseness, or rather the discon- 
nection of the points, of the laminse of the quills, which 
breaks the sudden resistance which the act of flight 
makes to the air : it may therefore be supposed that a 
W'ing, constructed on an entirely opposite principle, 
would have as opposite an effect ; and this we accord- 
ingly find. The wing of the partridge, from the pecu- 
liar rigidity and compactness of its quiU feathers, may 
be said with truth to cut the air ; and as the owls are 
the most silent flyers of all birds, the partridges are the 
most noisy: the sudden whirring produced by their 
wings on first arising, is entirely caused by the sharp- 
ness and equality with which the air is beat, and is 
probably intended to startle the intruder from that 
fixed attention he would otherwise pay to his game. 
In the Brazilian Tinamou partridges (^Crypturus'), the 
lesser quills and the tertials are more developed than in 
