Why water rises to mountain summits: heat and the earth's veins
Cruet, wet-cloth and vessel experiments argue heat draws moisture up, feeding the veins of mountains
Leonardo argues that heat draws moisture upward while cold fixes it, illustrating the principle with a heated cruet whose mouth stands in water, a wet cloth held before a fire, and a semicircular vessel r f that expels water through an opening a when heated from above. He extends the analogy to the body of the earth: just as natural heat keeps blood in the veins at the top of a living man, the earth's inner heat holds water in veins at the summits of mountains. A cross-section of a mountain shows these water-bearing veins, and a distant view of the globe shows peaks rising beyond its curve. A closing passage rejects the opinion that sea water stands higher than the mountains, reasoning that water cannot rise of itself and invoking the endless flow of the Tigris and Euphrates.
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The heated cruet fills with water by itself
Heat a cruet, invert its mouth into a shallow vessel of water, and set a burning coal on its base; the enclosed moisture rises to follow the heat, the air escapes through the mouth, and the cruet fills with water on its own. This is offered as proof that heat draws moisture, complementing the earlier demonstration that the cold region halts the clouds.
Why water stands at the summits of mountains
As natural heat keeps blood in the veins at the top of a living man, so the earth's dispersed inner heat holds water in the elevated veins at the high tops of the mountains; when the man dies the cold blood sinks, and water walled in a mountain conduit will not rise unless the vital heat of the first vein warms it. The heat of fire and of the daytime sun can awaken the moisture of the low places and draw it upward.
Vessel r f expels water through opening a when heated
If instrument r f is heated from above, the water leaves r f and rises to issue through a. The semicircular vessel over a flat basin makes the heat-driven rise of water visible.
Against the claim that the sea stands higher than the peaks
Water will not move from place to place unless a lowness draws it, and cannot return by a natural course to the height it first left the mountains. Had the sea truly poured over the high summits, it would long ago have been consumed by draining through their openings, as the long flow of the Tigris and Euphrates shows.