The poem has two principal genres, lyric and riddle. The poem qualifies as a lyric because it represents the personal observations of the unnamed speaker. The presentation of the train is neither objective nor scientific; rather, it’s subjective, reflecting the speaker’s idiosyncratic beliefs about trains and their relationship to horses. As the speaker never actually uses the word “horse” or “train,” the poem is a riddle. The reader must figure out that the speaker is describing a train with equestrian terms. To understand the connection, the poet uses diction—specific words like “lick” (Line 2), “neigh” (Line 14), and “stable door” (Line 17) suggest the animal, while terms like “Tanks” (Line 3) and “Quarry pare” (Line 8) indicate the machine. Even without the historical context, the poem thus provides the clues to solve the imputed puzzle. 

As with nearly all of Dickinson’s poems, although the speaker is unnamed and enigmatic, they don’t completely erase themselves or try to pass their imagery off as detached and dispassionate. The speaker wants the reader to know that they’re narrating the train’s journey, so the first word is the first-person, singular pronoun “I,” foregrounding the speaker watching the train before depicting the train itself.