Hello. I'm reading a physics book on my own and am learning about pressure measurements. I have a question with how pressure is measured using a manometer. Here is a link talking about it: http://www.upscale.utoronto.ca/PVB/Harrison/Manometer/Manometer.html My question is, why do points at the same height necessarily have the same pressure (as in Cases 2 and 3)? If the liquid is in equilibrium, why can't we say that the pressure at any point in the liquid is equal to the pressure at any other point? Thanks!