Let us not underrate the value of a fact; it will one day flower into a truth.

Man is an animal who more than any other can adapt himself to all climates and circumstances.

How important is a constant intercourse with nature and the contemplation of natural phenomena to the preservation of moral and intellectual health!

We can never have enough of Nature.

When I hear a grown man or woman say, "Once I had faith in men, now I have not," I am inclined to ask, "Who are you whom the world has disappointed? Have not you rather disappointed the world?"

As for the dispute about solitude and society, any comparison is impertinent. It is an idling down on the plane at the base of a mountain, instead of climbing steadily to its top.

The cost of a thing is the amount of what I will call life which is required to be exchanged for it, immediately or in the long run.