rue and scientific principles must be
established: what constitutes a shaded body, what constitutes a primary
shade, a derivative shade, what constitutes light: that is, darkness,
light, colour, size, shape, position, distance, propinquity, motion,
rest, which are comprehended by the mind only, and without manual
labour. And this is the science of painting which remains in the mind
of those who meditate on it, from which {146} issues the work in due
time, and is infinitely superior to the aforesaid contemplation or
science.

[Sidenote: Mechanics]

10.

Mechanics are the paradise of scientific mathematics, because with them
we arrive at the fruits of mathematics.

[Sidenote: Mechanics and Experience]

11.

Experience is indispensable for the making of any instrument.

12.

Proportion is not only to be found in figures and measurements, but
also in sound, weight, time and position, and in whatever power which
exists.

[Sidenote: Reason and Experience]

13.

The power of the projecting force increases in proportion as the object
projected is smaller; the acceleration of the motion increases to
infinity proportionately to this diminution. It would follow that an
atom would be almost as rapid as the imagination or the eye, which in a
moment attains to the height of the stars, and consequently its voyage
would be infinite, because the thing which can be infinitely diminished
would have an infinite velocity and would travel on an infinite course
(because every continuous quantity is divisible to infinity). And this
opinion is {147} condemned by reason and consequently by experience.

Thus, you who observe rely not on authors who have merely by their
imagination wished to be interpreters between nature and man, but on
those alone who have applied their minds not to the hints of nature but
to the results of their experience. And you must realize the
deceptiveness of experiments; because those which often appear to be
one and the same are often different, as is shown here.

[Sidenote: Effects correspond to the Force of their Cause]

14.

A spherical body which possesses a dense and resisting superficies will
move as much in the rebound resulting from the resistance of a smooth
and solid plane as it would if you threw it freely through the air, if
the force applied be equal in both cases.

Oh, admirable justice of thine, thou first mover! thou hast not
permitted that any tone should fail to pro