s, and borne in airy rings
Sport round the car, and wave their golden wings.
Admiring Fawns pursue on dancing hoof,
And bashful Dryads peep from shades aloof;
Emerging Nereids rise from coral cells,
Enamour'd Tritons sound their twisted shells;
From sparkling founts enchanted Naiads move,
And swell the triumph of despotic LOVE.

[Footnote: _With undulating train_, l. 373. The side fins of
fish seem to be chiefly used to poise them; as they turn upon
their backs immediately when killed, the air-bladder assists
them perhaps to rise or descend by its possessing the power
to condense the air in it by muscular contraction; and it is
possible, that at great depths in the ocean the air in this
receptacle may by the great pressure of the incumbent water
become condensed into so small a space, as to cease to be
useful to the animal, which was possibly the cause of the
death of Mr. Day in his diving ship. See note on Ulva, Botan.
Gard. V. II.

The progressive motion of fish beneath the water is produced
principally by the undulation of their tails. One oblique
plain of a part of the tail on the right side of the fish
strikes the water at the same time that another oblique plain
strikes it on the left side, hence in respect to moving to
the right or left these percussions of the water counteract
each other, but they coincide in respect to the progression
of the fish; this power seems to be better applied to push
forwards a body in water, than the oars of boats, as the
particles of water recede from the stroke of the oar, whence
the comparative power acquired is but as the difference of
velocity between the striking oar and the receding water. So
a ship moves swifter with an oblique wind, than with a wind
of the same velocity exactly behind it; and the common
windmill sail placed obliquely to the wind is more powerful
than one which directly recedes from it. Might not some
machinery resembling the tails of fish be placed behind a
boat, so as to be moved with greater effect than common oars,
by the force of wind or steam, or perhaps by hand?]

[Footnote: _On pinions broad display'd_, l. 375. The
progressive motion of birds in the a