The Rivers: Simple and Compound Motion of Water
How rivers gain or lose their waters as they move
This page opens a heading 'Of rivers,' sorting flowing water into 'simple' and 'compound' motion. Leonardo lists four cases: rivers that increase their waters at every degree of motion without loss, those that lose without ever gaining, those that gain more than they lose, and those that lose more than they gain. He treats a river's changing volume as a problem of motion, with the labels 'moto semplice' and 'moto composto' repeated as marginal notes.
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Simple and compound motion of rivers
Under the heading 'Of rivers,' Leonardo distinguishes simple motion (water that increases at every stage without loss, or that only loses) from compound motion (water that gains more than it loses, or loses more than it gains). The four short clauses form a classification of how a river's volume behaves along its course.