of the most usual, as well as the most early symptomes, by which this odd
Pestilence disclos'd it self: And when I asked how long the Patients were
wont to be thus affected, he answered, that it was most commonly for about
a day; and when I further inquired whether or no Vomits, which in that
Pestilence were usually given, did not remove this symptome (For some used
the taking of a Vomit, when they came ashore, to cure themselves of the
obstinate and troublesome giddiness caus'd by the motion of the ship)
reply'd, that generally, upon the evacuation made by the Vomit, that
strange apparition of Colours ceased, though the other symptomes were not
so soon abated, yet he added (to take notice of that upon the by, because
the observation may perchance do good) that an excellent Physician, in
whose company he was wont to visit the sick, did give to almost all those
to whom he was called, in the beginning before Nature was much weakened, a
pretty odd Vomit consisting of eight or ten dramms of Infusion of _Crocus
Metallorum_, and about half a dramm, or much more, of White Vitriol, with
such success, that scarce one of ten to whom it was seasonably administred,
miscarried.

8 But to return to the consideration of Colours: As an apparition of them
may be produced by motions from within, without the assistance of an
outward object, so I have observed, that 'tis sometimes possible that the
Colour that would otherwise be produced by an outward object, may be
chang'd by some motion, or new texture already produced in the Sensory, as
long as that unusual motion, or new disposition lasts; for I have divers
times try'd, that after I have through a Telescope look'd upon the Sun,
though thorow a thick, red, or blew glass, to make its splendor supportable
to the eye, the impression upon the _Retina_, would be not only so vivid,
but so permanent, that if afterwards I turned my eye towards a flame, it
would appear to mee of a Colour very differing from its usual one. And if I
did divers times successively shut and open the same eye, I should see the