The diagram shows a "cross tube" filled with water. The cross tube is made form two identical cylindrical glass tubes of radius r = 2.2 cm, joined together in the shape of an X, such that each tube "leg" makes an angle ? = 45.9 degrees with respect to the horizontal bench top on which the cross tube rests. The vertical distance from the bench top to the mid point of the join (red dot) is d₁ = 8.3 cm, as shown in the diagram, and then a further vertical distance d₂ = 2.7 cm from the mid point to the surface of the water filling the tube, as shown. Both top ends of the tube are open to the atmosphere.