ON THE MOVEMENT AND MEASUREMENT OF WATER

The weight of the water is the cause of its movement.

When the water is in its natural state, it does not move unless it is provoked by a lack of balance Leonardo uses the concept of "equilibrium" to describe why water remains still or begins to flow. If the surface of the water is perfectly level, it remains at rest; but if one part is lower than another, the water will seek to fill that void, creating a current.

OF THE EDDIES AND VORTICES

The water that falls perpendicularly into other water creates a circular motion. This motion is not merely on the surface, but penetrates deep into the body of the pool.

Observation:
Observe the movement of the surface of the water, which resembles that of hair, which has two motions, of which one responds to the weight of the strands, the other to the direction of the curls; thus the water has its eddying motions, one part of which responds to the principal current, the other to the random and reverse motion. Leonardo frequently compared the patterns of nature, such as flowing water and human hair, to find universal laws of physics.

The air also moves in this way, though it is invisible to the eye.

Water is the driver of nature. original: "vetturale di natura"