lar continuance or repetition of
ideas belonging to the sense of touch, instead of to the sense of vision;
and should therefore be called a tangible, not a visual, vertigo. In common
language this belief of continuing to revolve for some time, after he
stands still, when a person has turned round for a minute in the dark,
would be called a deception of imagination.

Now at this time if he opens his eyes upon a gilt book, placed with other
books on a shelf about the height of his eye, the gilt book seems to recede
in the contrary direction; though his eyes are at this time kept quite
still, as well as the gilt book. For if his eyes were not kept still, other
books would fall on them in succession; which, when I repeatedly made the
experiment, did not occur; and which thus evinces, that no motion of the
eyes is the cause of the apparent retrocession of the gilt book. Why then
does it happen?--Certainly from an hallucination of ideas, or in common
language the deception of imagination.

The vertiginous person still imagines, that he continues to revolve
forwards, after he has opened his eyes; and in consequence that the
objects, which his eyes happen to fall upon, are revolving backward; as
they would appear to do, if he was actually turning round with his eyes
open. For he has been accustomed to observe the motions of bodies, whether
apparent or real, so much more frequently by the eye than by the touch;
that the present belief of his gyration, occasioned by the hallucinations
of the sense of touch, is attended with ideas of such imagined motions of
visible objects, as have always accompanied his former gyrations, and have
thus been associated with the muscular actions and perceptions of touch,
which occurred at the same time.

When the remains of colours are seen in the eye, they are termed ocular
spectra; when remaining sounds are heard in the ear, they may be called
auricular murmurs; but when the remaining motions, or ideas, of the sense
of touch continue, as in this vertigo of a blindfolded person, they have
acquired no name, but may be termed evanescent titillations, or tangible
hallucinations.

Whence I conclude, that vertigo may have for its cause either the ocular
spectra of the sense of vision, when a person revolves with his eyes open;
or the auricular murmurs of the sense of hearing, if he is revolved near a
cascade; or the evanescent titillations of the sense of touch, if he
revolves blindfold. All these I