How does the signalman behave toward the narrator during their first encounter?"The Signal-Man by Charles Dickens"

When the narrator calls to the signalman, instead of turning to the sound, the man turns around and looks down the "Line."  Only after doing this does the signal-man and look up to the narrator, who inquires how he might descend.  After a train suddenly rushes past, the narrator continues his descent; the man waits with his left elbow resting on his right hand and his left hand at his chin.  When the narrator comes close to the signalman, the man steps back one step and lifts his hand, daunting the narrator.

The signal-man curiously looks toward the red light near the mouth of the tunnel, searches it with his eyes, and then turns to the narrator. The narrator remarks,

The monstrous thought came into my mind, as I perused the fixed eyes and the saturnine face, that this was a spirit, not a man.  I have speculated since, whether there may have been infection in his mind.

Asking the signal-man why he looks at him in such a curious manner, the signal-man tells the narrator that he wondered whether he had seen him before.  But, after he realizes that he has not, the signal-man welcomes the narrator by talking readily to him, and by inviting him into "his box" where there is a fire, a desk, and the "little bell of which he had spoken."  Confiding in the narrator that he is a student of natural philosophy.  He is "remarkably exact and vigilant."  As he leaves the narrator leads the signalman into revealing that he is troubled.  If he will come again tomorrow night, the signalman says he will explain.