The continuous exchanges between air and water are a recurrent theme in the Codex Leicester. Leonardo is fascinated by their reciprocal transmutations caused by heat, cold, or violent shocks. He states that wind is generated by the evaporation of water. As winds clash, they create vortexes, eddies, and ridges. Leonardo depicts a tornado with the same drilling power as a vortex of water. He points out that when rain falls, it is consumed through attrition with air. He interprets the formation of clouds as the result of the evaporation of sea water, which, when reaching high altitudes, is condensed by cold.
Write on swimming under water and you will understand the flight of birds.