is related to the level difference 
by the formula 
where 
is the density of mercury and 
the magnitude of the acceleration due to gravity. [P7.2]
is: a device for measuring one pressure relative to another (commonly atmospheric pressure relative to a vacuum). [P7.2]
consists: of mercury contained in a U-tube. [P7.2]
works: when the two pressures are applied to the two sides. The difference is registered as a level difference. The pressure difference is related to the level difference by the formula where is the density of mercury and the magnitude of the acceleration due to gravity. [P7.2]
Copyright 1997, The Open University