IV
Let us inquire therefore, in the first place, how the earth can contain sufficient water to maintain the unbroken flow of the rivers, and where such a vast quantity of water comes from. We are surprised that the ocean is not sensible of the additional water derived from rivers. It is no less surprising that the earth is not sensible of the loss of all the water that issues from it. What is it that has so filled it up that it can from its hidden recesses furnish such quantities and continually make good the loss as it does? Whatever explanation we give regarding a river must apply also to streams and springs.