Standing by the shore after midnight, the speaker hears the tide turn and the first wave sweep in with an uninterrupted rush. It’s not just noise—it feels like a voice rising from the ocean’s silence, a sound that multiplies mysteriously, like a mountain cataract or wind roaring through a forest. The mood is reverent, hushed, a little overwhelming.
Then the poem shifts inward. Longfellow says that in the same way, deep feelings or inspirations well up from the inaccessible solitudes of our being—the soul’s own sea-tides. Those sudden flashes we call our own are really something like divine foreshadowings, glimpses of things beyond our reason or control. The natural world suddenly makes inner experience feel vast and real. We’re left feeling the mystery of our own depths, stirred by a sound that’s both outside and within.