his Claws upon the fame Twig, comes to his Affiftance, juft as if the Twig were held faft by two stiff compreffed Knippers; for that fuch Contraction is perform'd with much Strength, only by the Bird's fitting down, and by bending with its Weight the Bones BC, DE, upon each other, iş already demonftrated by Borelli, and by the aforefaid Experiments. And to any one that has but Eyes to obferve the Care and Providence of GoD over all his Creatures, and even for the Birds themfelves, this feems to be a particular and palpable Demonftration of his great Goodness and Wifdom, who has beftow'd upon thefe Animals fuch a Structure with refpect to their Bones, Mufcles and Tendons, as that without any Pains on their Part, or once waking from their Sleep, their own Weight and Figure preferves them from falling, in fuch Circumftances, that no body could imagine that they could remain one Minute upon the Twig at the leaft Motion thereof.

SECT. XIX. The Feet of Water-Fowl.

LET no Body think, that forafmuch as this Pinching or Contraction of the Claws, is likewife found in fome Birds that live both upon Land and Water, as Swans, the fame happens by Chance or by other neceffary Laws, because these Birds are feldom obferv'd to fit upon Trees, and therefore have little or no occafion for fuch a Structure of their Feet; for if it be confidered that Ducks, Geefe, and Swans, make ufe of their Feet in Swimming, as Men do of Oars; and that their Feet are of fuch a Figure, that being thruft out backwards, they are expanded likewife by the Refiftance of the Water, and fo exert a greater Force in the Progreffion of the Bird; we may likewife fee at the fame time, that if thefe Feet, in their

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their whole Breadth were to have been drawn forwards, it would have driven the Bird as much backwards; for which reason then, the Contraction of their Feet (as may be observed in Womens Fans, but after another Manner) is neceffary to them, to the End, that they might strike out their Feet, without giving the Water too great a hold of them: Now this happens in them likewise by thofe Tendons which, when they bend their Legs upwards (and fo caufe the Bones thereof to approach more to the others) draw their Claws together, and only by this Structure, without being obliged to make any particular Motion thereto. This Experiment may, like the former, be tried upon a dead Duck or a Teal.

SECT. XX. The Tails of Birds.

Bur after having faid thus much concerning the Structure and Ufe of the Wings, let us add a Word or two more about the Action of Flying, of which we have already faid fomething, fo far as may relate to the horizontal Motion thereof. The Structure of a Bird, if there had been nothing more in it than what they have already confidered, would have been a wonderful and irrefragable Proof of the Wisdom of GoD; but how much more. furprising is it ftill, when we contemplate another Part that he has bestowed upon these Creatures, to enable them to fly perpendicularly, that is to fay, directly upwards or downwards, I mean the Tail, which is to them as the Rudder to a Ship; this the Bird raises at BH, when it moves upwards from the Line B F to the Line KL; and when downwards, in the Line N O, it lowers it to BI; for that it does not ferve, or at leaft not commonly, in a lateral Motion to the Right or Left, is plain, from the Structure thereof. The farther Reasons

Reasons may be seen in Borelli, Prop. CXCVIII, and CXCIX; who teaches us (as does alfo Obfervation and Experience) that when Birds which fly horizontally, without rifing or falling, have a mind to turn themselves nimbly to the Right or Left, they move the Wing of the oppofite Side more strongly, and after an uncommon Manner, as a Man uses his Arm and Hand, when he would turn himself in Swimming; tho' fuch Birds as thrust out backwards long and flender Legs in Flying, do feem likewife to ufe the fame as a Rudder, when they turn to the one fide or the other.

There ftill remains fomething which does as it were appear wonderful to thofe that confider it ; namely, how it is poffible that swift flying Birds, that defcend perpendicularly from any great heighth, do not fall flat upon the Ground at once, the rather, fince the Swiftnefs of their Fall feems to be then increased by the Weight of their Bodies: Now they that have ever feen how artfully they ufe their Wings, to moderate and ftop their progreffive Motion, and how they fpread their Tails, muft at least acknowledge that they are admirably provided with every thing neceflary for Flying, and for the various Ufes of their Wings and Tails.

SECT. XXI. The Center of Gravity and Force of the Mufcles of the VVings.

Now, after all that has been faid, I fhall not dwell upon that wonderful Structure which Mathematicians obferve in Birds with Astonishment; whereby their Center of Gravity always remains in their Breaft, below the Rife of their Wings, and which alone enables them, whilft floating in the Air, without any manner of trouble, to difpose their Wings, Legs, and other Joints for the moft convenient Ufes. Thus we fee that the ftrong,

ftrong Mufcles with which they move their Wings, are inferted in their Breaft; infomuch, that even that Muscle which raises the Wings, and which one fhould otherwife have expected to have found in the Back, is likewife feated in the Breast, and is carried through a Hole exprefly made for it after a wonderful manner, to the Legs, in order to perform its Function: Concerning which, fee the foremention'd Borelli, Prop. CLXXXIV. where, befides what has been already faid, thofe that please to confult that learned Work, will find a great deal more, to convince them of the odorable Wifdom of him that has created all kinds of Animals.

To inftance in one Thing that feems almoft incredible; Could any one imagine that the Force of the Muscles whereby the Wings are moved, is ten thousand times greater than the Weight of the Bird that flies with thofe Wings; and if one defires to be more fully fatisfy'd thereof, with an intent to admire the Greatnefs of the Creator, he need but confult the aforefaid Author, Prop. CLXXXIII, and CLXXXIV. We have already given a brief Demonftration of the amazing Strength of the Muscles of Men, fo that this will not feem incredible to fuch as understand what has been there reprefented.

SECT. XXII. Convictions from the foregoing ObServations.

I Now ask again, whether any one (that reflects upon all that has been here faid about Birds, and comprehends how many things concur to the fame End, and to the most proper Purposes within fo fmall a compafs, as that of a contemptible Bird) can imagine, that this Creature is formed without Wifdom, and difpofed as he