Although human ingenuity may devise various inventions which, by the help of various instruments, answer to one and the same purpose, yet will it never discover any inventions more beautiful, more simple or more practical than those of nature, because in her inventions there is nothing lacking and nothing superfluous; and she makes use of no counterpoise when she constructs the limbs of animals in such a way as to correspond to the motion of their bodies, but she puts into them the soul of the body.

Just as iron rusts from disuse, and stagnant water putrefies, or when cold turns to ice, so our intellect wastes unless it is kept in use.

It is an acknowledged fact that we perceive errors in the work of others more readily than in our own.

If you throw a stone in a pond... the waves which strike against the shores are thrown back towards the spot where the stone struck; and on meeting other waves they never intercept each other's course... In a small pond one and the same stroke gives birth to many motions of advance and recoil.

Some promises and time disappoint us

Shadow is the diminution alike of light and of darkness, and stands between darkness and light.

The motive power is the cause of all life.