To be worthy of the name, an experimenter must be at once theorist and practitioner. While he must completely master the art of establishing experimental facts, which are the materials of science, he must also clearly understand the scientific principles which guide his reasoning through the varied experimental study of natural phenomena. We cannot separate these two things: head and hand. An able hand, without a head to direct it, is a blind tool; the head is powerless without its executive hand.

Feeling alone guides the mind.

The true worth of an experimenter consists in his pursuing not only what he seeks in his experiment, but also what he did not seek.

True science teaches us to doubt and, in ignorance, to refrain.

A contemporary poet has characterized this sense of the personality of art and of the impersonality of science in these words,-'Art is myself; science is ourselves. '

The investigator should have a robust faith - and yet not believe.

The experimenter who does not know what he is looking for will not understand what he finds.