CHAPTER VII.
Note 1, p. 93. The visible is colour, &c] Aristotle[1]
says that the faculty of Sight announces to us, dis-
tinguishes, that is, the manifold and various shades of
colours, on account of all bodies partaking of colour, and
thus by Sight, especially, we are able to perceive common
properties, such as form, magnitude, motion and number;
but the Hearing, on the contrary, is perceptive only
of distinctions of sounds from sonorous bodies and the
variations of voice from such as have speech[2]. The sense
of "Hearing, however, contributes more than any other,
since speech is the channel for instruction, to the cultiva-
tion of the understanding."
Note 2, p. 93. All colour is motive of the diaphanous,
&c.] These passages seem almost to indicate a presenti-
ment of the modern or undulatory theory of light, for
they assume the existence of a diaphanous, that is, a
subtle medium which, by its motion, is creative of vision.
So too, the modern theory assumes a subtle elastic ether,
which has inertia without gravity, which fills space, per-
meates all bodies, and admits of being set in motion by
the agitation of the particles of ponderable matter, and
which particles, when set in motion, communicating a like
