For it deemeth not of the thing that is seen. And easy moving is
needful, for if the thing that is seen moveth too swiftly, the sight
is cumbered and disparcled with too swift and continual moving: as it
is in an oar that seemeth broken in the water, through the swift
moving of the water. In three manners the sight is made. One manner by
straight lines, upon the which the likeness of the thing that is seen,
cometh to the sight. Another manner, upon lines rebounded again: when
the likeness of a thing cometh therefrom to a shewer, and is bent, and
re-boundeth from the shewer to the sight. The third manner is by
lines, the which though they be not bent and rebounded, but stretched
between the thing that is seen and the sight: yet they pass not always
forthright, but other whiles they blench some whether, aside from the
straight way. And that is when divers manners spaces of divers
clearness and thickness be put between the sight and the thing that is
seen.

Aristotle rehearseth these five mean colours [between white and black]
by name, and calleth the first yellow, and the second citrine, and the
third red, the fourth purple, and the fifth green.

In the book Meteorics, a little before the end, Aristotle saith that
gold, as other metals, hath other matter of subtle brimstone and red,
and of quicksilver subtle and white. In the composition thereof is
more sadness of brimstone than of air and moisture of quicksilver, and
therefore gold is more sad and heavy than silver. In composition of
silver is more commonly quicksilver than white brimstone. Then among
metals nothing is more sad in substance, or more better compact than
gold. And therefore though it be put in fire, it wasteth not by
smoking and vapours, nor lesseth not the weight, and so it is not
wasted in fire, but if it be melted with strong heat, then if any