Smells are not divided into kinds; all of them are transitional, and arise
out of the decomposition of one element into another, for the simple air or
water is without smell. They are vapours or mists, thinner than water and
thicker than air: and hence in drawing in the breath, when there is an
obstruction, the air passes, but there is no smell. They have no names,
but are distinguished as pleasant and unpleasant, and their influence
extends over the whole region from the head to the navel.

Hearing is the effect of a stroke which is transmitted through the ears by
means of the air, brain, and blood to the soul, beginning at the head and
extending to the liver. The sound which moves swiftly is acute; that which
moves slowly is grave; that which is uniform is smooth, and the opposite is
harsh. Loudness depends on the quantity of the sound. Of the harmony of
sounds I will hereafter speak.

Colours are flames which emanate from all bodies, having particles
corresponding to the sense of sight. Some of the particles are less and
some larger, and some are equal to the parts of the sight. The equal
particles appear transparent; the larger contract, and the lesser dilate
the sight. White is produced by the dilation, black by the contraction, of
the particles of sight. There is also a swifter motion of another sort of
fire which forces a way through the passages of the eyes, and elicits from
them a union of fire and water which we call tears. The inner fire flashes
forth, and the outer finds a way in and is extinguished in the moisture,
and all sorts of colours are generated by the mixture. This affection is
termed by us dazzling, and the object which produces it is called bright.
There is yet another sort of fire which mingles with the moisture of the
eye without flashing, and produces a colour like blood--to this we give the
name of red. A bright element mingling with red and white produces a