Weights, siphons and the winding of rivers
Mechanics of siphons and pulleys, river erosion, and colour seen at a distance
A working sheet mixing mechanics with the movement of water. Leonardo lays down the principle that every heavy body weighs along the line of its motion and applies it to a siphon (cicognola) hung from a balance, asking whether the water weighs inside the tube; he studies pulleys on a balance, where a weight of eight raises a weight of one, and a pump in which the column of water presses on its little valve. He also explains why a tortuous river deepens its own bends by breaking the outer bank and shedding gravel on the inner curve, and closes with notes on wind born from clouds and on how an object's visibility at a distance depends on its colour against its background. Diagrams of a meandering river, a siphon, pulleys and a pump accompany the text.
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Heavy bodies weigh along the line of motion
Every heavy body weighs along the line of its motion; therefore water does not weigh except on the sides of its siphon that are rubbed by it. The principle also frames a note on measuring the descent of a mountain.
Why a tortuous river increases its bends
The running water a b strikes and breaks the bank b and unloads its gravel into the convexity b c f; the more it strikes at b, the more it erodes and deposits, and this is the cause of the river's winding. The lateral bank-waves formed by the bends always travel toward the mouth of the river.
Does water weigh inside a siphon on a balance?
A siphon (cicognola) is hung from a balance, and it is asked whether the water n a m weighs at a. Since the water n a moves upward it seems to press on the upper wall of its tube, and a m to press on the air, so the water does not weigh within the conduit; Leonardo calls this a fine doubt because two quantities move, one continuous and one discontinuous and infinite.
Pulley on a balance: load on the pivot
With a b equal to 8 and c d equal to 1, it is asked what weight the pole of the wheel feels as the eight falls and raises the one. When the descent of the greater weight raises the opposite lesser weight, the pole feels twice the lesser weight.
Pump: water pressing on the valve
The water b n weighs on the little valve n with all the force pressing it and with its own weight, increased by the weight of the rod, which displaces as much water as the rod's entry occupies in the tube.
Visibility of objects at a distance by colour
Many large bodies lose their visibility at a long distance because of their colour, while small things may keep it. A body the colour of the air is seen at a middling distance, one whiter than air at a long distance, and one darker than air is lost at a short distance; of these three, the one seen from farthest is that whose ground most differs from its own colour.