The fountain in its source, <br />No drought of summer fears; <br />The farther it pursues its course, <br />The nobler it appears. <br />But shallow cisterns yield <br />A scanty short suply; <br />The morning sees them amply filled, <br />At evening they are dry.<br /><br />William Cowper<br /><br />http://www.poemhunter.com/poem/living-water-3/
