Life is a struggle, but not a warfare.

Travel and society polish one, but a rolling stone gathers no moss, and a little moss is a good thing on a man.

Science is a capital or fund perpetually reinvested; it accumulates, rolls up, is carried forward by every new man. Every man of science has all the science before him to go upon, to set himself up in business with. What an enormous sum Darwin availed himself of and reinvested! Not so in literature; to every poet, to every artist, it is still the first day of creation, so far as the essentials of his task are concerned. Literature is not so much a fund to be reinvested as it is a crop to be ever new-grown.

When I look up into the starry heavens at night and reflect upon what it is I really see there, I am constrained to say, ´there is no god´.

[Theodore Roosevelt] was a naturalist on the broadest grounds, uniting much technical knowledge with knowledge of the daily lives and habits of all forms of wild life. He probably knew tenfold more natural history than all the presidents who had preceded him, and, I think one is safe in saying, more human history also.

We can outrun the wind and the storm, but we cannot outrun the demon of hurry.

If you want to see birds, you must have birds in your heart.