After Gibbs, one the most distinguished [American scientists] was Langley, of the Smithsonian. ... He had the physicist's heinous fault of professing to know nothing between flashes of intense perception. ... Rigidly denying himself the amusement of philosophy, which consists chiefly in suggesting unintelligible answers to insoluble problems, and liked to wander past them in a courteous temper, even bowing to them distantly as though recognizing their existence, while doubting their respectibility.

He too serves a certain purpose who only stands and cheers.

Every one must bear his own universe, and most persons are moderately interested in learning how their neighbors have managed to carry theirs.

They know enough who know how to learn.

Every man should have a fair-sized cemetary in which to bury the faults of his friends.

It is impossible to underrate human intelligence - beginning with one's own.

One friend in a life-time is much; two are many; three are hardly possible. Friendship needs a certain parallelism of life, a community of thought, a rivalry of aim.