Nothing is so dangerous to the progress of the human mind than to assume that our views of science are ultimate, that there are no mysteries in nature, that our triumphs are complete and that there are no new worlds to conquer.

The ready apology covers a multitude of social sins.

Fortunately science, like that nature to which it belongs, is neither limited by time nor by space. It belongs to the world, and is of no country and no age. The more we know, the more we feel our ignorance; the more we feel how much remains unknown.

The wealth and prosperity of the country are only the comeliness of the body, the fullness of the flesh and fat; but the spirit is independent of them; it requires only muscle, bone and nerve for the true exercise of its functions. We cannot lose our liberty, because we cannot cease to think.

Nature is beautiful, and you are in her bosom. That voice of comfort which speaks in the breezes of morning, may visit your mind, that the delightful influences which the green leaves, the blue sky, the moonbeams and clouds of the evening diffuse over the universe, may in their powers of soul-healing, visit your day visions, is my desire and hope.

The most important of my discoveries have been suggested to me by failures.

The art galleries of Paris contain the finest collection of frames I ever saw.