I am convinced, by repeated observation, that marbles, lime-stones, chalks, marls, clays, sand, and almost all terrestrial substances, wherever situated, are full of shells and other spoils of the ocean.

Genius is only a greater aptitude for patience.

The human mind cannot create anything. It produces nothing until having been fertilized by experience and meditation; its acquisitions are the germs of its production.

He [man] abuses equally other animals and his own species, the rest of whom live in famine, languish in misery, and work only to satisfy the immoderate appetite and the still more insatiable vanity of this human being who, destroying others by want, destroys himself by excess.

To be and to think are one and the same for us.

The cat is the only animal which accepts the comforts but rejects the bondage of domesticity.

The discoveries that one can make with the microscope amount to very little, for one sees with the mind's eye and without the microscope the real existence of all these little beings.