The speaker travels around Britain and keeps searching for smaller, emptier islands, the kind that look like upturned boats stuck to the shore. The longing shrinks as the islands do, until it could nearly fit in a pocket. But the islands refuse to be possessed. They are holy places, bird refuges, volcanic rock, and the poem pictures them as the skulls of ancestors, as if the land itself were made of the dead. Details like bog iron collars and turf-roofed round houses pull the past into the present.
The tone is quietly wistful, with a dry touch of humor. Traffic islands that can be circled only one way, "like the stars wheeling about Polaris," link everyday life to the cosmos. Then the speaker gets lost on the Salisbury Plain, a small, human failing. The ending jumps forward to future archaeologists who will read the speaker's wandering as hunger "for a glimpse of other worlds." The poem seems to suggest that our longing for elsewhere is what we leave behind.