Adam Clarke on Psalms 104:10

He sendeth the springs into the valleys - Evaporation is guided and regulated by Divine Providence. The sun has a certain power to raise a certain portion of vapours from a given space. God has apportioned the aqueous to the terrene surface, and the solar attraction to both. There is just as much aqueous surface as affords a sufficiency of vapours to be raised by the solar attraction to water the earthy surface. Experiments have been instituted which prove that it requires a given space of aqueous surface to provide vapours for a given space of terrene surface; and the proportion appears ordinarily to be seventeen of water to three of earth; and this is the proportion that the aqueous bears to the terrene surface of the globe. See Ray's three Physico-theological Discourses.