 While analog barometers aren't used much anymore, a similar concept is still occasionally used. Even if they're not all that practical, they are a useful way of practicing this skill. Those devices are called monometers. The monometer is a way of indicating pressure difference as the height of a column of fluid. So in this particular case, we are looking at a gas cube here, and that gas has a higher pressure than its surroundings. We know that because this fluid is pushed up higher on the right side than it is on the left. Because we know P1 and P2 are going to be equal because they're at the same height, that means that the pressure of the gas is going to be the same as what you would get if you use the height difference between this point and this point to figure out the pressure increase and added that to atmospheric pressure. Let's try an example now. ... ... ... ... ... ...