Charles Dickens makes effective use of literary devices to generate a mood of uncertainty and a disturbing sense of dislocation, loneliness, and even powerlessness.
Using visual imagery and personification, Dickens describes the narrator's first sight of the signal-man. The narrator remarks from his vantage point that, as he looks below, the signal-man seems "foreshortened and shadowed." He is high above this man, standing in the "glow of an angry sunset." This attribution of human qualities to the sunset initiates the sense of preternatural powers in this setting.
As the narrator descends to meet the signal-man, he reflects upon the man's "air of reluctance or compulsion with which he had pointed out the path. . . . His attitude was one of such expectation and watchfulness. (This is a particularly poignant example of mood.)
When he arrives at the level of the signal-man, the narrator encounters the "dark sallow man" (visual imagery), and he notices what a dismal place the man's post is.
On either side, a dripping-wet wall (visual and aural imagery) of jagged stone, excluding all view but a strip of sky; the perspective one way only a crooked prolongation of this great dungeon(visual imagery). . . . This was a lonesome post.
Further, the tunnel is described as having a "dismal mouth" (personification).
This imagery, as well as Dickens's diction ("crooked prolongation," "dungeon," and "lonesome"), creates an atmosphere/mood of gloom.
In addition, the mood of powerlessness is developed bt the signal-man's description of the ghost that he sees:
"For God's sake, clear the way. . . . Below there! Look out!" It stands waving to me. It rings my little bell."
This vision also acts as foreshadowing of future events in the narrative. The signal-man's presentiment, coupled with his helplessness against preventing anything, points to the powerlessness of man against technological progress, as symbolized by the train.