The circulation of water through the earth's veins
Water's continual revolution up and down, likened to the humours of living bodies
This opening continues the body-of-the-earth argument, with all the writing gathered on the left-hand folio (233v) while the facing folio (236r) is left almost blank. Water moved from the deep sea up to the mountain summits falls back through broken veins to the low sea and mounts again, obeying now its own desire, now that of the body enclosing it. Leonardo repeats that the cause driving water through the earth's veins, against the natural course of heavy things, is the same that moves the humours in every animate body and comes to the aid of every injury, and he again invokes the rising sap of the vine. He ends with the vision of the whole element endlessly transmuting, one vein having already passed many times through many veins.
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Up and down in continual revolution
Water moved from the deep sea to the mountain summits falls back through the broken veins to the low sea and mounts again to the high break, running here and there, up and down; when one part descends the other rises, so that the whole element is transmuted and one vein has already passed many times through many veins.
Broken veins in the mountain summits
The force drives the waters upward and pours them through the broken veins cut into the summits of the mountains, moving the low waters up to the earth's high channels. The mountains are treated as a body threaded with veins through which water is forced against gravity.
The cause that succours every injury
The cause that moves the humours in all species of animate bodies, and with that succour comes to every injury, is the same that raises water from the lowest depth of the sea to the highest height of the mountains. The circulation of the body's humours is the model for the circulation of the earth's water.
Water rising in the vine
Leonardo again likens the process to the way water rises from the lower part of the vine to the high cuts of its branches, using the plant's ascent of sap as a parallel for water climbing within the earth.
