. Earth, sky, and sea. Trieste (Bathyscaphe); Balloons. and whose density is equal to that of water. This rod consists of an aluminium tube filled with petrol. Its length is equal to the height of the vessel containing stabilizing petrol, 11-55 feet. Thus its apparent weight will always exactly compensate the variable thrust of the petrol upon the valve. This design, at first sight, seems perfect. It has, however, a defect ; when the valve opens, the petrol flows out and necessarily the pressure of the liquid decreases at this moment. (The kinetic energy is acquired at the expense of the
. Earth, sky, and sea. Trieste (Bathyscaphe); Balloons. and whose density is equal to that of water. This rod consists of an aluminium tube filled with petrol. Its length is equal to the height of the vessel containing stabilizing petrol, 11-55 feet. Thus its apparent weight will always exactly compensate the variable thrust of the petrol upon the valve. This design, at first sight, seems perfect. It has, however, a defect ; when the valve opens, the petrol flows out and necessarily the pressure of the liquid decreases at this moment. (The kinetic energy is acquired at the expense of the potential energy, which is represented by the pressure, according to a funda- mental law of hydrodynamics.) It follows that the force that must be exerted to lift the valve must be increased pro- gressively as this rises. The compensation is thus no longer perfect. Technical problems often appear thus: you search up to the moment when you find one solution, then you go on to other problems; and it is only later that you see you have indeed fouAd a solution, but not the solution, the only one, generally, which was perfect. That is what happened with my valve. I was satisfied to see it functioning, although the valve flap could not be raised as much as we should have liked. It was only a little while before our leaving for Ponza that I found the solution : its simplicity is such that I should have found it at the first attempt. It is derived directly from the compensated valve of a steam engine that Professor Stodola explained to us when I was a student at Zurich. I am sure that I should have thought of it earlier, if I had not been fascinated by the invention of my compensating rod. The principle of this compensated control valve will be understood at once by a glance at Figs. 26 and 27. The first is diagrammatic. Coming from the reservoir tz, the petrol enters the distributing chamber. This has two openings, one at the top, the other at the bottom. Each of these openings is clo
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