t – a – water – g – air · water · water – air, c – water, S – b · water · water, d – water · water · water · air – f, e – K – water · water · water – n, m.

The counterweight e, standing in g, has descended to the low point you see, and has driven up the water that was in reservoir e·m through the tube t·n, and has filled reservoir a. Now it must be considered that the tube t·n is always full of water together with one of its reservoirs, and both counterweights — that is, e and f — must together weigh as much as the water of one reservoir and somewhat more, so that they overcome the weight of the water. And when the counterweight e drives the water upward, the other counterweight forcibly opens its reservoir, to which it is attached, so that, like a leech, it rouses and sucks the water with no less vigour than the counterweight e does when it drives it up. Now note that every quantity of lead requires 10 of water to stand at equal weight, and just so much must the water of a single reservoir weigh here, as is said above. But remember to experiment with different thicknesses and heights of tubes and of reservoirs with their counterweights. And so that the time of the clock does not go by jerks, you shall make this instrument long, in the manner of a drum; and where this one has 4 arms, make it 16, and it will run more evenly. Know that if ...

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Reservoir S and reservoir K are empty, and the other two opposite them are full of water or wine, so that the bellows does not rot. And if the counterweights c d weigh 13 ounces, the water of reservoir b weighs one pound, and the centre of its gravity is nearly twice as far from the pole of the wheel as is the centre of gravity of the two counterweights, so that it almost doubly overcomes those counterweights; and almost similarly the two lower counterweights, that is e f, will be overcome by the upper reservoir a, full of water. Doubts. ... that the counterweight e, when it is at its first height — that is, in g — the reservoir K is full up to the height of e and counterbalances as much water as is found in the tube filled likewise up to the height of e, so that the water in the tube from e upward alone weighs upon the counterweight that presses it. But when the reservoir is half empty, the water of the tube — which always stands at the same level as that of the reservoir — comes to sink together with the reservoir; and therefore that part of the tube's water standing above the level, the more that level lowers, so much the more it grows in weight, in such a way that the counterweight, being no longer able to overcome it, will stop at a certain height of your reservoir and will not descend to the appointed descent.

Every measure of lead stands equal in the balance to 12 like measures of water. That is, a pound of water occupies 12 times as much space as the lead. ** Every quantity of water stands equal in the balance to ... * Water pressed by a weight of lead, if it is in a tube of the thickness of that lead, will rise 12 times the height of the very body of the counterweight that presses it, the reservoir being of the same thickness; that is, it will rise above the level of the reservoir's water 12 times the height of the lead that presses it. If the lead is reduced to a columnar shape and then used as counterweight to a reservoir of similar shape, and the tube from which the water rises is of the same thickness as the reservoir, the water of the tube will rise above the level of that of the reservoir 12 times the height of the lead that presses it. But if the tube is half as narrow as the reservoir, it will rise half as low, that is 6 times the height of the lead. And likewise, whatever proportion the thickness of the tube has to that of the reservoir, such will the rise of the water have to the first one. But if the tube is twice as wide as the reservoir, its water will rise 6 times above the level of the reservoir.