Nature is always applying her reagents to character, if you will take the pains to watch her.
 Oliver Wendell Holmes Sr., The Professor at the Breakfast-Table (1860). copy citation

Context

“Chance has thrown together at the table with me a number of persons who are worth studying, and I mean not only to look on them, but, if I can, through them. You can get any man's or woman's secret, whose sphere is circumscribed by your own, if you will only look patiently on them long enough. Nature is always applying her reagents to character, if you will take the pains to watch her. Our studies of character, to change the image, are very much like the surveyor's triangulation of a geographical province. We get a base-line in organization, always; then we get an angle by sighting some distant object to which the passions or aspirations of the subject of our observation are tending;” source