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.

Obervation is a passive science, experimentation is an active science.

Science does not permit exceptions.

Proof that a given condition always precedes or accompanies a phenomenon does not warrant concluding with certainty that a given condition is the immediate cause of that phenomenon. It must still be established that when this condition is removed, the phenomen will no longer appear.

The joy of discovery is certainly the liveliest that the mind of man can ever feel.

The first requirement in using statistics is that the facts treated shall be reduced to comparable units.

The better educated we are and the more acquired information we have, the better prepared shall we find our minds for making great and fruitful discoveries.