The poem is about a "meeting at night," so it's only natural that we should have several descriptions of nighttime (like the moon and the "black land"). We tend to associate darkness and night with secrecy, and the meeting that takes place in the poem is clearly an illicit or clandestine (a fancy word for "hidden" or "secret") encounter.
- Line 1: The speaker describes the land as "black." While this sounds weird at first, after a moment's reflection we realize it's black because it's dark outside. The speaker tells us it's nighttime without telling us. Very clever, Mr. Browning!
- Line 2: The speaker refers to the color and location of the moon, another hint that it's nighttime. The moon's position – "low" – could mean that it is either early in the evening, or close to morning (because the moon rises and sets just like the sun).
- Line 4: The speaker describes the waves as leaping from their "sleep"; naturally, we assume things sleep at night. Waves don't literally "leap" or "sleep," so this is an example of personification, the attribution of human qualities to non-human things. Also, the speaker compares the waves to something that is fiery and sleeps, which means these are also metaphors.
- Line 10: The speaker describes a "lighted match," which implies that it is dark, or nighttime.