Emily Dickinson has a characteristic ability to compress information and, in so few words, encourages the reader to imagine her perspective revealing far more than meets the eye. In What Mystery Pervades a Well, she reveals how something so simple and so taken for granted - a well - holds secrets in its "floorless" depths. She wonders and considers the well which is man-made but, to her, has all the natural elements, as if it belongs there and "is awe to me." She expresses her desire for something clearly beyond her reach to a place "none has ever seen." She suggests that no one will ever be able to understand how phenomenal nature is and, even for those who consider themselves experts on the subject, nature will remain a "stranger."
There is a respect that Dickinson has for anyone who does try to explore and her own yearning is disclosed as she considers how insignificant mankind is in the whole scope of things. She is not as "bold" as the "grass" for example and her own knowledge is limited. Even so, the well itself suggests that nature is so diverse that it can alter to the point that even "those who know her, know her less / The nearer her they get." The "regret" that is therefore felt that no one can ever really understand makes it easier to manage but is no less disappointing, when trying to look into the "abyss," and only a reflection stares back.
The element of desire and yearning is presented in Dickinson's recognition that, although she may feel at home in natural surroundings, she will never quite belong.