to
art the laws of light and shade, though the preliminary investigations
of Piero della Francesca deserve to be recorded.

He observed with strict accuracy the subtleties of chiaroscuro--light
and shade apart from colour; but, as one critic has pointed out, his
gift of chiaroscuro cost the colour-life of many a noble picture.
Leonardo was "a tonist, not a colourist," before whom the whole book
of nature lay open.

It was not instability of character but versatility of mind which
caused him to undertake many things that having commenced he
afterwards abandoned, and the probability is that as soon as he saw
exactly how he could solve any difficulty which presented itself, he
put on one side the merely perfunctory execution of such a task.

In the Forster collection in the Victoria and Albert museum three of
Leonardo's note-books with sketches are preserved, and it is stated
that it was his practice to carry about with him, attached to his
girdle, a little book for making sketches. They prove that he was
left-handed and wrote from right to left.

HIS MIND

We can readily believe the statements of Benvenuto Cellini, the
sixteenth-century Goldsmith, that Francis I. "did not believe
that any other man had come into the world who had attained so great a
knowledge as Leonardo, and that not only as sculptor, painter, and
architect, for beyond that he was a profound philosopher." It was
Cellini also who contended that "Leonardo da Vinci, Michelangelo, and
Raphael are the Book of the World."

Leonardo anticipated many eminent scientists and inventors in the
methods of investigation which they adopted to solve the many problems
with which their names are coupled. Among these may be cited
Copernicus' theory of the earth's movement, Lamarck's classification
of vertebrate and invertebrate animals, the laws of friction,
the laws of combustion and respiration, the elevation of the
continents, the laws of gravitation, the undulatory theory of light
and heat, steam as a motive power in navigation, flying machines, the
invention of the camera obscura, magnetic attraction, the use of the
stone saw, the system of canalisation, breech loading cannon, the
construction of fortifications, the circulation of the blood, the
swimming belt, the wheelbarrow, the composition of explosives, the
invention of paddle wheels, the smoke stack, the mincing machine! It
is, therefore, easy to see why he called "Mechanics the Paradise
of the Sc