William of Conches held that the great ocean in the equatorial zone is the source of all dampness in the earth (_fons humoris_) and that the land is seamed with canals full of water derived from that source.[836] Peter Alphonsi describes the circulation of the waters from the sea into the atmosphere by evaporation, thence in the form of rain to the rivers, and so back to the sea.[837] Peter Comestor, however, held that the river which springs from Paradise and divides in four is the source of all the water of the earth;[838] and Gervase of Tilbury, who follows Comestor in this respect, mentions in another connection that springs have their sources in the sea.[839] Perhaps if he had analyzed the question he would have said that the waters of the sea must find their way at some time through the rivers of Paradise and thence to the springs. THE EARTH ESTABLISHED ON THE WATERS The phrase in the Psalms, that God established the earth above or on (_super_) the waters,[840] also proved puzzling to the thinkers of our period. The easy explanation that such a phenomenon might be due to the arbitrary working of God’s will was not always readily accepted. Some commentators on the Psalms observed dubiously that it surpassed their understanding.[841] Alexander Neckam stated that it might possibly refer to waters beneath the earth, since “Alfraganus [Al-Farghānī] says that the sphere of the waters and of the earth are one.” Saints who had expounded the phrase, he added, tried to explain away the difficulty by referring to the colloquial manner of saying that Paris is founded “on the Seine.” “The truth of the matter, however, is that the terrestrial paradise is above the waters, since it is above the sphere of the moon.”[842] An allegorical interpretation was also resorted to, and the reader was told to conceive of “earth” as being the Church and “the waters” as the many peoples upon which the Church is founded.