How Raindrops Form and the Motion of Water Veins
Droplets condensing in air, and the flow, reflux and waves within water channels
A dense page of hydraulics in which Leonardo explains how raindrops form: mists and clouds moving at different speeds collide and condense, a faster mass overtaking a slower one so that many small droplets merge into a single large drop heavy enough to fall, while drops too small to combine are consumed by friction with the air. The accompanying diagrams treat 'veins' of water, showing how equal opposing forces make the flow descend perpendicular and how the obtuseness of the entry angles governs the balance of flow and reflux. A closing note observes that an incoming wave can raise water to a set level, and that a drop cannot fall until its weight overcomes the surface tension that holds it. Faint additional sketches accompany the water-vein diagrams across the sheet.
On this page
How droplets form in the air
Droplets form when mists and clouds moving at different speeds collide and condense within one cloud; the faster part, being behind the slower, overtakes and compresses it, so that many small drops merge into one large drop that gains weight and falls. Drops too small to combine are consumed by the friction they make with the air as they pass through it.
Vein of water with equal opposing forces (b, d, c, a)
Because the water at a c is as powerful as the water at b d, the angles c and d are equal to one another, and the water descends perpendicular between the two forces.
Narrowing of the vein by flow and reflux (a, d, c, b)
The vein is constricted more from a b than from c d, because the course of the water runs from d c — that is, by the flow and reflux (ebb and flow).
Obtuse angles governing flow, reflux and the lifting wave
When angle a is more obtuse than angle b, the reflux c a is more powerful than the flow d b, and the reverse follows when b is the more obtuse. The water n d c cannot fall along the line d f until it gains weight enough to overcome the tenacity of the drop; failing that, the incoming wave d c has the power to raise the water to the level r, along the line c r.