The Common Center of Earth and Water; a Bell Motion
A cosmological diagram of the centers of weight, with an address to the reader and two small mechanisms
The large central diagram treats the earth and its enveloping sphere of water as one body, marking a as the center of the earth's weight, m as the center of the water sphere, and n as the universal center of the world; the inner globe carries the labels Nile, Africa and Asia. An opening address invites the reader to delight in the work and to come and see the miracles that such studies uncover in nature. Below are two small pen mechanisms, one described as a bell motion with long and short arms (a n and m o) and another whose two handles come to rest whenever they stand perpendicular. Further Italian notes surround the figures and continue this reasoning.
On this page
Earth and water share one center, common to the center of the world
The point a is taken as the center of the weight of the earth, m as the center of the weight of the sphere of water, and n as the universal center of the world. Treating the water and the earth as a single body, Leonardo concludes they may be said to have one single center, common to the center of the universal world. The inner globe is labeled with Nile, Africa and Asia.
A bell motion with long and short arms
The lower-right sketch is annotated so that arm a n is long and arm m o is short. Leonardo tells the reader to reckon this as the motion of a bell, letting a n be 3 and m o be one at most.
Two handles that stop when perpendicular
The lower-left mechanism, marked f, is described so that its two handles will come to rest every time they stand in a perpendicular line, provided there is no ratchet (wheel of increase) at f.