Everything great in science and art is simple. What can be less complicated than the greatest discoveries of humanity - gravitation, the compass, the printing press, the steam engine, the electric telegraph?

Liberty is worth paying for.

It is for others one must learn to do everything; for there lies the secret of happiness.

With happiness as with health: to enjoy it, one should be deprived of it occasionally.

Science, my lad, is made up of mistakes, but they are mistakes which it is useful to make, because they lead little by little to the truth.

Imagine a society in which there were neither rich nor poor. What evils, afflictions, sorrows, disorders, catastrophes, disasters, tribulations, misfortunes, agonies, calamities, despair, desolation and ruin would be unknown to man!

Nothing is more dreadful than private duels in America. The two adversaries attack each other like wild beasts. Then it is that they might well covet those wonderful properties of the Indians of the prairies - their quick intelligence, their ingenious cunning, their scent of the enemy.

Put two ships in the open sea, without wind or tide, and, at last, they will come together. Throw two planets into space, and they will fall one on the other. Place two enemies in the midst of a crowd, and they will inevitably meet; it is a fatality, a question of time; that is all.

In spite of the opinions of certain narrow-minded people, who would shut up the human race upon this globe, as within some magic circle it must never outstep, we shall one day travel to the moon, the planets, and the stars, with the same facility, rapidity, and certainty as we now make the voyage from Liverpool to New York!

Ah! Young people, travel if you can, and if you cannot - travel all the same!

We may brave human laws, but we cannot resist natural ones.

The sea is everything. It covers seven tenths of the terrestrial globe. Its breath is pure and healthy. It is an immense desert, where man is never lonely, for he feels life stirring on all sides.

The sea does not belong to despots. Upon its surface men can still exercise unjust laws, fight, tear one another to pieces, and be carried away with terrestrial horrors. But at thirty feet below its level, their reign ceases, their influence is quenched, and their power disappears.

I believe cats to be spirits come to earth. A cat, I am sure, could walk on a cloud without coming through.

The Chinaman has only a passive courage, but this courage he possesses in the highest degree. His indifference to death is truly extraordinary. When he is ill, he sees it approach, and does not falter. When condemned, and already in the hands of an officer, he manifests no fear.

I seriously believed that my last hour was approaching, and yet, so strange is imagination, all I thought of was some childish hypothesis or other. In such circumstances, you do not choose your own thoughts. They overcome you.

The industrial stomach cannot live without coal; industry is a carbonivorous animal and must have its proper food.