According to the mechanical properties of fluids pdf,  Pascal observed that the pressure in a fluid at rest is the same at all places if the heights are equal. He also deduced that the pressure differential between the two sites is proportional to the vertical distance between them. As a result, the pressure differential provided to the enclosed fluid can be communicated to every point of the fluid, as well as the container vessel's walls, without loss. As a result, when an incompressible fluid passes through a pipe with a non-uniform cross-section every second, the volume is equal to the steady flow.