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ago 0                 Tbe Anatomical Defeription
Motion like to that of the Oars which Watermen do make to turn a little?
when they do raife them upwards: For each of the great feathers has this
Motion apartby which it is a little obliquely turned, when tile wing is raifed,
and this feather is reduced into its former Situation when the wing is loxrer-
cd.  This Aftion is very difhinfaly obfcrved when Birds do for home time
hold their wings ereEted, by an extension like to that which is done in reach-
ing; this State affording more leifure to fee that winding of the feathers,
than when they do ftrike their wings in flight: for than the wings being
thus raifed, it is obferved that the great feathers, which are the Principal
Organs of flight, are all feparated from each other, by reafon of their obliqui-
tie, which feems to open, for the paffage of the Air, as many Doors as there
are feathers ; which are clofed when the wing coming to lower it felfe, all
thefe feathers do retake their former Situation, and do beat one upon the
o-
ther to make of the whole wing one continued Ifurface, capable of overfpread-
ing a great quantity of Air.
  In the fourth place, it mufl be obferved that this oblique Motion of every
feather belongs not to thofe of the Taill, which has diffirent uf's from
thole
of the wings. There are two Principal ones ; the firft is to Rerve as a Rud-
der, and to keep in the whole Bird a ftrait Motion, when it is kept ftrait
and ofturning the body downwards, when it is kept lowered, or upward
when it is raifed. The other ufe is to ferve to help it forward, when it
is fud-
dainly moved by thefe two fuccelEve Motions, which do produce the fame
effie& as the Tail of Fidlles.:
  N ow this whole Mechanifme is wanting in the feathers and Wings of the
Ot1rich: For the threads of the Dedards which are at the two fides of the
ftrem of the Quill of the greatfeathers are never faffned one to the other,
but
floating and flexible, not being crooked, but ftrait and even without having
any of the Difpofitions neceffary for the facilitating the interlacing which
they have with each other in the feathers of other Birds. Therefore Arij/otle
fay s that the feathers of Ofjriches are like the IHaire of Terreffial Animalsthat
is to fay that they are more proper to cover their Body's than to fly with.
  Thefe Feathers' have not likewife that particular motion which renders
them fomne times firait, fome times oblique, becaufe that this would be ufe-
lefs to them, the Beards not being joyned together to make the Texture and
Continuity which the other feathers have, to ffrikeq all the Air that is
met-
w ith under the Wing; fo that it may be faid that the feathers of the Wings
of the OJIrich are more like to the Pendants of Ships than to their Sails
; altho'
£hliah eports that thefe Animals do make ufe thereof as of Sails, when
to
rendertheir courfe fwifter and lighter, they do extend thefe feathers to
the
wind, to the end that it may drive them: For fiils are not only fervicable
in Ships meerly as an Obficle, which refifing the wind by its bignefs only,
receives a fimple ilnpullf fo as the hull of the Veffell does; but they mudf
be
considered as an obftacle of a commodious figure and <iape,- hvich being
mnanaged and governed after a certain manner, may drawl a greater advan
tage from the agitation of the Airfor the motion of the Veffel, than it would
4o without this figure and Government. Tllus the Plunes ofthe OJ richcap
not be ufefull to it; -by their figure or Motion , for if they alLift thern
to ad-
v .ncc forw-ard by forcing their winlgs backwards, they would. hinder them
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