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the scene is a description of a night on an ocean beach when the ocean waves seem to be preparing to destroy the land and its people. the shore, cliff and continent are allied together against the threat of the coming storm, but the narrator doubts that they will be successful at quelling the destructive force of the ocean,. moreover this destruction will not last a single night rather for an age, perhaps even at the order of a higher power.
the speaker means that the aoccurences happens at night and it will not last soon but forever.
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