Book 3 of subterranean rivers.
Book 4 of rivers.
Book 5 of the nature of the abyss.
Book 6 of the obstacles.
Book 7 of gravels.
Book 8 of the surface of water.
Book 9 of the things placed therein.
Book 10 of the repairing of rivers.
Book 11 of conduits.
Book 12 of canals.