Oblique motion of weights, the sun raising the seas, and descent tests
Mechanics of oblique motion, a sun-and-earth water theory, and a plan to drop cardboard figures from a scaffold
Turned in several directions, this crowded blue-paper sheet is chiefly a study of the obliquity of motion: Leonardo defines 'more and less oblique' against the vertical 'direct' line and argues, through a triangle, a pulley with weights on inclined planes, and a system of cords and counterweights, that a weight is hardest to raise where its path is least oblique. Other notes and lettered diagrams set out his cosmology of water — the sun, drawn in four positions around the earth, lifts and vaporizes the seas so that rivers may rise, and the weight of the sphere of water is reckoned together with that of the earth. A sketch of a winged flying machine accompanies a memorandum to drop cardboard figures of various shapes from a scaffold and draw the motions of their fall, while a note on the right analyses the several motions a bombard's thunderclap sends through the air. Brief marginal items include a Syrian bow-horn, a press (strettoio), and, in another hand, a definition of the proportioned as against the monstrous.
On this page
Defining oblique against direct motion of a weight
Leonardo fixes his terms: 'more direct / less direct' means 'less oblique / more oblique', because a heavy body is the harder to raise the less oblique its motion, and the harder to raise the easier it is to fall back down. He concludes that the greatest difficulty and the greatest ease both lie along a single 'direct' (vertical) line, with 'mean obliquity' set midway between the greater and lesser slopes.
Pulley and weights on inclined planes
Beside a pulley with weights hung on inclined planes, of the straight lines rising from one same base to the height of a single point c b a, that line is more or less oblique which lies farther from or nearer to the direct line. The line joined at its top to the top of the direct line, with its lower end most remote, is the most oblique.
Dropping cardboard figures to study their descent
Beside a sketch of a winged flying machine labelled 'elm poles', a memorandum reads: tomorrow make figures of various shapes out of cardboard, dropped through the air from our scaffold, then draw each figure and the motions its descent makes at the different stages of the fall. It is a planned experiment on how bodies of different form behave falling through air.
The sun in four positions lifting the earth's waters
The sun is drawn in four positions around the earth. In the east a lifts water from n m and carries it to o; b lifts water from p o to n; in the west c lifts the water n m to p; and d lifts water from p o to m — a circulation of the seas driven by the sun's heat.
Where the waters vaporize and where they rise
In a companion figure of sun and earth, at the antipodes a c b the rivers pour out and raise the waters without their being vaporized, while at a b d the waters rise to the point of vaporization. It belongs to Leonardo's theory of how water is carried up over the body of the earth.
The threefold motion of a bombard's thunderclap
A note on the right analyses the gun's report as motions of different speeds through the air. The swiftest carries the impression of the sound; a slower one carries the wave generated by the flash of the flame; and a third is the flight of the ball the bombard has thrown.