The most all penetrating spirit before which will open the possibility of tilting not tables, but planets, is the spirit of free human inquiry. Believe only in that.

Knowing how contented, free, and joyful is life in the world of science, one fervently wishes that many would enter its portals.

No law of nature, however general, has been established all at once; its recognition has always been preceded by many presentiments.

The elements, if arranged according to their atomic weights, exhibit an apparent periodicity of properties.

Why do they [Americans] quarrel, why do they hate Negroes, Indians, even Germans, why do they not have science and poetry commensurate with themselves, why are there so many frauds and so much nonsense?

I saw in a dream a table where all the elements fell into place as required. Awakening, I immediately wrote it down on a piece of paper.

We must expect the discovery of many as yet unknown elements-for example, elements analogous to aluminum and silicon- whose atomic weight would be between 65 and 75.