There are always some of us, not a few, in every generation, who go over wholly to the green flag. It is such a passionless fealty, so reticent a love, that neither do trumpets sound for it nor quarrels arise from it. Only, you will find that those who have pledged allegiance are happy about it in quiet.

A word, a smile, and the stranger at your elbow may become an interesting friend. All through life we deny ourselves stimulating fellowship because we are too proud or too afraid to unbend.

All the great naturalists have been habitual walkers, for no laboratory, no book, car, train or plane takes the place of honest footwork for this calling, be it amateur's or professional's.

As the brain of man is the speck of dust in the universe that thinks, so the leaves—the fern and the needled pine and the latticed frond and the seaweed ribbon—perceive the light in a fundamental and constructive sense. … Their leaves see the light, as my eyes can never do. … They impound its stellar energy, and with that force they make life out of the elements.

A thing is either alive or it isn’t; there is nothing that is almost alive. There is but the remotest possibility of the origin of life by spontaneous generation, and every likelihood that Arrhenius is right when he dares to claim that life is a cosmic phenomenon, something that drifts between the spheres, like light, and like light transiently descends upon those fit to receive it.

I have often started off on a walk in the state called mad-mad in the sense of sore-headed, or mad with tedium or confusion; I have set forth dull, null and even thoroughly discouraged. But I never came back in such a frame of mind, and I never met a human being whose humor was not the better for a walk.

Time is not money; time is an opportunity to live before you die. So a man who walks, and lives and sees and thinks as he walks, has lengthened his life.