The poem's speaker, the stream itself, recounts that it began in a body of water where coot and heron frequently congregate. The creek suddenly surges forth. As the brook flows through the foliage that grows beside the stream bank, the sunshine gleams on the water. Summer is approaching, so the brook is filled with cool waters. Brook starts are important because they tell us about the source of the stream. A brook usually begins in a pond or another body of still water. If there is no evidence of previous movement in the soil near the stream, then it probably comes from a spring. A stream that runs through a valley floor must come from somewhere above the earth's surface. If you look at a topographic map, you will see that most stream valleys are shaped like this: their floors are made of solid rock, while the walls of the valley are formed by steep-sided hills called prominences. Where these rocks meet the ground, you will often find small springs. These are the sources of the streams that flow into the valley bottoms. Prominences can be caused by anything that rises above the surrounding land. If a hill or mountain was once part of a continent but has been separated off by oceanic plates, it becomes a prominence.