lished in 1754 one of the most original and interesting
of his works, _Recherches sur l'usage des feuilles dans les plantes_; in
which among other things he advances many considerations tending to show
(as has quite recently been done by Francis Darwin) that plants are
endowed with powers of sensation and discernment. But Bonnet's eyesight,
which threatened to fail altogether, caused him to turn to philosophy.
In 1754 his _Essai de psychologie_ was published anonymously in London.
This was followed by the _Essai analytique sur les facultes de l'ame_
(Copenhagen, 1760), in which he develops his views regarding the
physiological conditions of mental activity. He returned to physical
science, but to the speculative side of it, in his _Considerations sur
les corps organises_ (Amsterdam, 1762), designed to refute the theory of
epigenesis, and to explain and defend the doctrine of pre-existent
germs. In his _Contemplation de la nature_ (Amsterdam, 1764-1765;
translated into Italian, German, English and Dutch), one of his most
popular and delightful works, he sets forth, in eloquent language, the
theory that all the beings in nature form a gradual scale rising from
lowest to highest, without any break in its continuity. His last
important work was the _Palingenesie philosophique_ (Geneva, 1769-1770);
in it he treats of the past and future of living beings, and supports
the idea of the survival of all animals, and the perfecting of their
faculties in a future state.

Bonnet's life was uneventful. He seems never to have left Switzerland,
nor does he appear to have taken any part in public affairs except for
the period between 1752 and 1768, during which he was a member of the
council of the republic. The last twenty five years of his life he spent
quietly in the country, at Genthod, near Geneva, where he died after a
long and painful illness on the 20th of May 1793. His wife was a lady of
the family of De la Rive.

They had no children, but Madame Bonnet's nephew, the celebrated H.B. de
Saussure, was brought up as their son.

Bonnet's philosophical system may be outlined as follows. Man is a
compound of two distinct substances, mind and body, the one immaterial
and the other material. All knowledge originates in sensations;
sensations follow (whether as physical effects or merely as sequents
Bonnet will not say) vibrations in the nerves appropriate to each; and
lastly, the nerves are made to vibrate by external physical stimul