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        Concepts covered in this lecture include gases and incompressible liquids, Pascal's Principle, hydrostatic and barometric pressure. Professor Lewins concludes with a discussion of overpressure in our lungs. The lung capacity, our ability to overcome hydrostatic pressure, is measured with a manometer. This is related to how deep snorkeling works, and why scuba-divers use pressurized air tanks. Professor Lewin demonstrates that by blowing on a manometer, or by sucking on it, we can raise or lower a column of water by about 1 meter (0.1 atmosphere). So why then was he able to suck fluid up a straw of several meters long?