Leonardo challenges the traditional explanations of the presence of water sources in mountain tops. He rejects the siphon effect, which was based on the belief that the oceans’ surface was higher than mountain tops. He considers the theory that the Sun’s heat turns the water into vapor, which rises to an altitude where it is condensed by the cold and turns into water again. He takes into account the hypothesis of the distillation of waters by the Earth’s internal heat and their later condensation at altitude, as well as the hypothesis of water rising by capillarity.
Perhaps you will say ... that the surface of the sea is higher than the summits of the highest mountains. The answer to this is that the exact opposite is the case, for the lowest part visible to the sky is the surface of the sea.