Eddies wide below, narrow above, with an experiment
Falling water drives to the bottom and turns in circles; a bladed-paddle test for eddies
Folio 60v studies how forcefully falling water penetrates a stream and spends its energy in eddies. A drawing at the top shows water cascading onto a surface and producing great circles of eddies that shrink toward the surface, while the text argues that the stronger the driving force, the straighter the path, so heavy water drives to the bottom before turning in circular revolution. The lower half proposes an experiment, illustrated by a bladed paddle hung by a wire from a staff and plunged underwater, to prove that all eddies are wide at the bottom and narrow above. A brief Italian label marks the 'experimental eddy.'
On this page
The greater the force, the straighter the fall to the bottom
Water driven by a great weight strikes the lower water and penetrates to the bottom; if it finds no resistance at first it passes through with the same fury, then, meeting resistance, turns in great circles that diminish as they near the surface, because its fury ends where the other water is still nearly at rest.
Forced motion is proportional to the mover and the thing moved
Every movement made by force produces a course in proportion between the thing moved and the mover; and if it meets resisting opposition it finishes its proper voyage in circular motion or in various leaps, so that, reckoning by time and distance, it is as if the course had met no opposition at all.
Experiment: are eddies wide at the bottom and narrow above?
Take a wand fitted with little wings of metal blades, weighted at the base so the lower part sinks. Tie it by a wire suspended from a stick, plunge part of it underwater, and note whether the upper part bends in its turning, and how much — a test of whether all eddies are wide below and narrow above.