[…] their Local Motion […] is neither by Fins nor Wings, as in Fishes or Birds, who are fain to sustain themselves by these instruments from sinking to the bottome of either Element: but it is meerly by the direction of the agitation of the particles of their Vehicle toward the place they aime at; and in such a swiftness or leasureliness as best pleases themselves, and is competible to their natures.