And that means the larger the difference from here to here, the lower this section will be. Now, the same way that you could measure the temperature of the atmosphere using a thermometer, you can also measure atmospheric pressure using a barometer. A barometer can be semblasing three things a long cylindrical tube open at one end and then select usually mercury and a cup. Now, you take the cup, you fill it up with mercury. You take the tube, you fill that up to the rib of mercury. You take the tube, flip it upside down, and place it into the cup.