Water as the Vital Humour of the Earth
Water circulating through the earth's veins, likened to the humours of living bodies
The left-hand leaf (235v) is blank apart from a later ownership inscription and the British Museum stamp. The facing page (234r) sets out Leonardo's analogy between the circulation of water in the body of the earth and the humours in living bodies: heat drives the moisture that nourishes the body, and water, the 'vital humour' of the dry earth, runs through branching veins from the ocean depths up to the mountain summits and back down. Several further lines of writing at the lower right of the leaf are not included in the transcription.
On this page
Water rising through the earth's branching veins to the mountain tops
Water is destined to be the vital humour of the arid earth, pouring into it and flowing with vehemence through the branching veins to succour every part in need of moisture. From the great depth of the ocean it runs into the earth's hollow caverns, then, against its natural course, climbs by continuous upsurging to the high mountain summits, whence through broken veins it returns downward.
The body of the earth, its veins and visceral caverns
The passage treats the earth as a living body: broad caverns in its 'visceral inner parts', branching veins running through the rock, and the summits of mountains where those veins are broken open. Water moves through this stony body as a fluid moves through flesh.
Heat moving the humours that nourish the body
The heat infused in living bodies moves the humours that nourish them, and the motion made by the humour preserves itself and gives life to the body that encloses it. Leonardo states that the very cause moving water through the earth's veins is the same that moves the humours in every species of living body.