Still more obviously suffused with mystic meaning and influence are the Teutonic myths concerning the waters of the underworld. The central notion is that of Yggdrasil, the tree of the universe--the tree of time and life. Its boughs stretched up into heaven; its topmost branch overshadowed Walhalla, the hall of the heroes. Its three roots reach down into the dark regions beneath the earth; they pierce through three subterranean fountains, and hold together the universal structure in their mighty clasp. These three roots stretch in a line from north to south. The northernmost overarches the Hvergelmer fountain with its ice-cold waters. The middle one overarches Mimur's well with its stores of creative force. The southernmost overarches Urd's well with its warmer flow. They are gnawed down below by the dragon Nidhögg and innumerable worms; but water from the fountain of Urd keeps the world-ash ever green. Hvergelmer is the mother fountain of all the rivers of the world-- below, on the surface of the earth, and in the heaven above. From this vast reservoir issue all the waters, and thither they return. On their outward journey they are sucked up and lifted aloft by the northern root of the world tree, and there blend into the sap which supplies the tree with its imperishable strength and life. Rising through the trunk, they spread out into the branches and evaporate from its crown. In the upper region, thus attained, is a huge reservoir, the thunder-cloud, which receives the liquid and pours it forth again in two diverse streams. The one is the stream of fire-mist, the lightning, which with its "terror-gleam" flows as a barrier round Asgard, the home of the gods; the other falls in fructifying shower upon the earth, to return to its original source in the underworld. The famous maelstrom is the storm-centre, so to speak, of the down-tending flood. The fountain Hvergelmer may therefore be regarded as embodying impressions made on the Teuton mind by the physical forces of the universe in the grand activities of their eternal circulation. But their source was hidden. The southernmost well has the warmer water of the sunny climes--the fountain of Urd. The Norns, the three sisters who made known the decrees of fate, come out of the unknown distance, enveloped in a dark veil, to the world tree, and sprinkle it daily with water from this fountain, that its foliage may be ever green and vigorous. Urd is the eldest of the three, and gazes thoughtfully into the past; Werdandi gazes at the present; and Skuld gazes into the future. For out of the past and present is the future born. The fountain of Urd may be regarded as the embodiment of impressions of a spiritual force which upholds and renews the universe.