Plan for the First Book on Water
An outline of topics: gravity and levity, why water moves, how it rises as vapour and falls as rain
A full page of text laying out the program for the first book of a treatise on water, written as a numbered agenda of subjects to be defined and proved. Leonardo proposes to begin with height and lowness and the arrangement of the elements, then define dense and liquid gravity, gravity and levity, and only afterwards explain why water moves, slows, speeds up and descends. Later topics include how the sun's heat lifts water into the air to fall as rain, why springs rise on mountain-tops, the comparative heights of the ocean and northern and equinoctial seas, and a boiling-water experiment producing circular waves. No diagram accompanies the text; only faint show-through from the facing leaf is visible below.
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Agenda for a treatise on water
Leonardo lists the questions the first book must answer: why water moves and why its motion ceases, why it grows slower or faster, and how it always descends when bordered by lower air. Further headings cover water drawn up by the sun's heat and returning as rain, springs breaking out on mountain summits, and whether a source higher than the ocean can pour water above the ocean's surface.
Gravity and levity to be defined first
Before treating motion the outline demands definitions of what height and lowness are and how the elements sit one within another, then what dense gravity and liquid gravity are, and first of all what gravity and levity are in themselves. A closing note describes the boiling-water experiment in which water around the centre of the boil descends in a circular wave, and how the coldest northern waters lie lowest until they turn to ice.