The stratification is produced using salt water. The density changes continuously from the heavy salt water at the bottom to the lighter fresh water on the top.
First, two tanks are prepared; one filled with salt water and another with fresh water. Saturated salt water was used for this preparation. Because of the density difference between fresh and salt water, the masses of the fresh and salt water were adjusted to be equal at pipe (1). We used 55 liters of fresh water and salt water with 15 kg of salt dissolved into 40 liters of fresh water in this experiment.
When water is drawn out quietly through pipe (2), water passes through (1) to maintain balance. If the water in the left tank is stirred thoroughly, the density of water obtained through pipe (2) will change gradually.
The salt water is injected into the bottom of the experiment tank. By injecting the heavier salt water after the lighter water, the heavier salt water flows beneath the previously injected water. If the water is injected quietly enough to prevent mixing in the tank, stable stratification is produced.

Appendix Figure 1 Apparatus for preparing stratified water