On the wavering motion of the arms of the balance between themselves.

h – c – e n d – g a b f; c b – e a d
The wavering motion, alternating between the arms of the balance, is shown here to arise from the impetus generated by the inequality produced in their weights, which is seen to be generated alternately in the said arms of the balance.
What impetus is.
Impetus is a power transferred from the mover to the moving body and maintained by the wave that such a mover generates in the air within the air. And this arises from the vacuum that, contrary to natural law, would be produced if the air ahead did not fill the void from which the air, driven out of its place by the said mover, flees; and that air ahead would not fill the place from which it parted unless another quantity of air filled the place from which that air divided; and so it must follow successively; and this motion would continue to infinity, if air were not infinitely condensable.

The sides of the droplet that descends through the air move in a motion contrary to that of the droplet itself and make a circular and continuous wave from the edges to the middle of its upper part; and this wave does not rebound from the middle to the circumference, but submerges in the middle of its circle and sinks deep and emerges from the underside and returns upward to the topmost part, from which it first divided, and there the circular wave is regenerated anew, and again submerges into the middle of it.

water
The water of a vessel that revolves upon itself is higher at the sides than in the middle.

h g f c — m n; c d b a - p o
The surfaces of all motionless liquids that are joined together between themselves will always be of equal height.
Of waters joined together, all those that exceed the height of the great ocean will have gravity and will be in natural motion.
Of the wavering wave.
The wavering wave is that which strikes upon the opposite banks and, rebounding from them so many times while diminishing, consumes itself together with the impetus that moves it.

Water placed in a broad vessel shows that it has a more tenacious contact with the air than with the bottom of the vessel, both in the circular motion of that vessel and in the straight motion. And the proof of this is seen in the sudden motion of the vessel, for then a sudden wave is generated in the water it contains. And the reason for this is that the water does not have weight upon its bottom as it does at its contact with the air, where it finds more resistance than at its contact with the bottom of the vessel; and for this reason it makes a wave in the sudden motion of the vessel, because it is held back more by the air than by the vessel.
That is, at the contact with that air it is manifest that, through the motion of the air which is in contact with the surface of the water, the air moves the skin of the water, and the motion of the water would do the like to the air. We shall say therefore of the contact of the two liquids placed one upon the other: the one moves the other.

p o m – n o S; d c b a
Glass, so that the motes may be seen in the water that moves.
Water within water has as much weight as it has motion, and every natural action is done by the shortest way. Therefore the water of the horn n m p will be of as great a thickness in the quantity of its motion as is the width of the smaller mouth n, and the motion will be along the line n o m, and the remainder of the water rests upon the remainder of the horn that lies beneath it and at its sides; and this will be seen in the motes that will move, drawn by the motion of the water in the glass horn n m p.

Hero, on water.
Of liquids of various gravities that do not mix, and of those that do mix.

c a - b; n - p o m
n m water - m o p quicksilver.
Let a b be quicksilver, b c be common water, and b be a valve that separates the quicksilver from the said water. I say that if this valve is turned so that the conduit is joined, the quicksilver will pass beneath the water and no part of the water will pass beneath the quicksilver, and it will make the weights of water and quicksilver equal.