Air Enclosed Under Water: Why Bubbles Rise Serpentining
From 'Book 43'; a bellows blowing air beneath water, and observations of furious whirlwinds
Headed 'Book 43: on the motion of air enclosed under water,' this page treats how a mass of air trapped beneath water behaves. Leonardo reasons that because heavy water cannot rest on light air, the surrounding water drives the air out through the corners of the vessel (n, m), so it escapes winding upward. A second passage, with a bellows blowing air under water, equates moving a body through still air with moving air against a still body, and recalls furious whirlwinds that tore up forest trees and palace roofs and lifted gravel, sand and water more than half a mile into the sky.
On this page
Book 43: the motion of air enclosed under water
Leonardo opens a numbered section, 'Book 43,' on how air trapped beneath water moves — the buoyant behaviour of a light body held down by a heavy one.
Why trapped air escapes through the corners
Because heavy water cannot be sustained by light air, the surrounding water (d e and n m above; a b e f and a b c d at the sides) presses on the enclosed air until it escapes through the corners n, m on one side or the other and winds upward as it rises.
A bellows under water, and furious whirlwinds
Air blown under water by a bellows rises serpentining. Leonardo equates moving a body through still air with moving air against a still body, and recalls whirlwinds that carried off forest trees and whole palace roofs and lifted gravel, sand and water more than half a mile aloft.