In lines 2-3, the narrator describes the evening “spread out against the sky / Like a patient etherized upon a table.” What effect does this image have on the poem’s meaning?

A.J. is inviting someone (a woman he loves) on a trip. The trip will take place in the evening (stated), and we will assume that the couple is actually taking a walk. As for the evening resembling an anesthetized patient....... this is an interesting way imagery can allude to a sleepy, lifeless evening. In other words..... nothing's happening.