River currents, water level, and an apparatus of cylinders
Red-chalk notes on eddies sorting sand from stones and the level of still water, with a cylinder device
Written upside down in red chalk, this page mixes a machine sketch with river studies. A framed apparatus with rotating cylinders is drawn but left unlabelled in the notes. A lettered watercourse (a-d, b-e, c) accompanies the rule that water is at rest only when its surface is equidistant from the centre of the world, while a river study observes that sand and light matter follow the twisting eddies as the heavy stones (a, b) run straight along the bed.
On this page
Framed apparatus with rotating cylinders
At the lower part of the sheet Leonardo draws a framed apparatus fitted with rotating cylinders, a large wheel-like disc set within a trestle frame. The device is captioned but carries no explanatory note of its own.
Water is at rest only when its surface lies level to the earth's centre
A note states that water will not be at rest whose surface is not equidistant from the centre of the world. It expresses the condition of hydrostatic equilibrium: still water takes a level surface everywhere the same distance from the earth's centre.
Eddies carry sand while heavy stones run straight
In a lettered stretch of river (a stones - sand - b stones), the sand and other light matter obey the twists and circulations of the water's eddies, while the large stones run in a straight line as at a b. It distinguishes how a current sorts light and heavy debris.