We took a glass tube 1 m long, sealed at one end. The tube is filled with mercury. The free end of the tube is closed and the tube is inverted. The tube is placed in a jar of mercury and the opening is opened. Part of the mercury from the tube is poured into the vessel. The column of mercury in the tube is set at a certain height. It is approximately equal to 760mm.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.