Many an object is not seen, though it falls within the range of our visual ray, because it does not come within the range of our intellectual ray.

I love you not as something private and personal, which is my own, but as something universal and worthy of love which I have found.

In love and friendship the imagination is as much exercised as the heart; and if either is outraged the other will be estranged. It is commonly the imagination which is wounded first, rather than the heart,--it is so much the more sensitive.

Write while the heat is in you.

Fishermen, hunters, woodchoppers, and others, spending their lives in the fields and woods, in a peculiar sense a part of Nature themselves, are often in a more favorable mood for observing her, in the intervals of their pursuits, than philosophers or poets even, who approach her with expectation. She is not afraid to exhibit herself to them.

Books of natural history aim commonly to be hasty schedules, or inventories of God's property, by some clerk. They do not in the least teach the divine view of nature, but the popular view, or rather the popular method of studying nature, and make haste to conduct the persevering pupil only into that dilemma where the professors always dwell.

The study of geometry is a petty and idle exercise of the mind, if it is applied to no larger system than the starry one. Mathematics should be mixed not only with physics but with ethics; that is mixed mathematics.