Note Book VII. Chap. 1. Note (d) (e) — BOOK VII.

[d] The wise Author of Nature hath afforded an Example of the great Nicety in the Formation of Birds, by the Nicely observ’d in a Part no more considerable than the Vanes of the Flag-feathers of the Wing. Among others, these two Things are observable: 1. The Edges of the exterior or narrow Vanes bend downwards, but of the interior or wider Vanes upwards; by which Means they catch, hold, and lie close to one another, when the Wing is spread; so that not one Feather may miss its full Force and Impulse upon the Air. 2. A yet lesser Nicety is observ’d, and that is, in the very sloping the Tips of the Flag-feathers: The interiour Vanes being neatly slop’d away to a Point, towards the outward Part of the Wing; and the exteriour Vanes slop’d towards the Body, at least in many Birds; and in the Middle of the Wing, the Vanes being equal, are but little slop’d. So that the Wing, whether extended or shut, is as neatly slop’d and form’d, as if constantly trimm’d with a Pair of Scissors.