A 879, a freestanding extrageneric fragment or pensée, is also a rough- copy variant version of another fragment (A 851) composed in the last decade of Dickinson's life. In this case the closing passage of the fragment inscribed on A 879—"A something | over takes the | mind - we do | not hear it | coming"—appears, truncated, as the closing passage of the text inscribed on A 851—"A something | overtakes the | Mind -." The precise nature of the relationship between the two fragments, one a meditation on the disorienting experience of reading (the book of) nature, the other on the similarly disorienting experience of reading poetry, remains unknown. The text on A 879 may be an oblique allusion to a passage in R. W. Emerson's "The Poet": "As the traveller who has lost his way throws his reins on the horse's neck and trusts to the instinct of the animal to find his road, so must we do with the divine animal who carries us through this world." Neither A 879 nor A 851 was incorporated into another extant composition. Here Dickinson's handwriting is unusually large and ill- formed, suggesting that she was ill at the time of the fragment's composition or that she was writing under unfavorable circumstances, in darkness, for instance, or under great stress. For other examples of distorted handwriting, see A 809 and A 848.

Four editorial notations, in Millicent Todd Bingham's hand, are penciled on the manuscript; the notes clarify faintly written or difficult to decipher words: "something," "do," "not," and "coming."