HYDROSTATIC Law, the rate of increase of pressure in a vertical direction is EQUAL to weight density of the fluid at that point when the fluid is stationary.The pressure at any point in a fluid at rest is obtained by the Hydrostatic Law which states that the rate of increase of pressure in a vertically downward direction must be equal to the specific weight of the fluid at that point.\(\frac{{dP}}{{dh}} = w\) for downward direction\(\frac{{dP}}{{dh}} = - w\) in upward directionThus, pressure in a stationary water COLUMN increases with depth and varies linearly and does not depend UPON viscosity.It INDICATES that a negative pressure gradient exists upward along any vertical.