What is macro absorption?

I’m not sure if you mean siphoning; if so, it is the difference in liquid level heights that is used to draw the liquid out of towers and other containers.

The principle of siphoning: it is the same principle as that of a communicating vessel, whereby the pressure exerted on the liquid inside a sealed container is equal everywhere. The siphon tube is filled with water, without any air; the water level at the inlet side is high, and the outlet is covered with the palm of the hand or some other object. At this point, the pressure inside the tube is equal everywhere. Once everything is in place, the outlet is opened. Although the atmospheric pressure on both sides is equal, the water level at the inlet side is higher and the pressure is greater, which drives the water to flow continuously out of the outlet. The discovery and application of the siphon principle: The Chinese understood how to apply this principle very early on. Siphons made using the principle of siphoning were called “zhuzi”, “piantai”, “kewu” or “guoshanlong” in ancient China. At the end of the Eastern Han Dynasty, the Kewu was invented for irrigation. The ethnic minorities in the southwest region use a long, bent bamboo tube without joints to drink alcohol, which also makes use of the physical phenomenon of siphon action. In Song Dynasty scholar Zeng Gongliang’s “Wujing Zongyao,” there are records of using bamboo tubes as siphons to draw spring water that was blocked by steep mountains down from the mountain. In ancient China, the siphon principle was also used to create water pumps. A pump is an essential fire extinguisher for defending a city during war. In Volume 4 of Su Shi’s “Dongpo Zhilin” from the Song Dynasty, it is recorded that in the salt wells of Sichuan, pumps were used to draw salty water to the surface. The book states: Use a bamboo tube, without a bottom but with an opening at the top; hang a piece of dried leather several inches above it, and submerge it in water. The air flow enables the tube to open and close on its own, allowing several doubs of water to be lifted using one such tube. “The Ming Dynasty’s “Book on Tree Planting” also discusses the method of using a water pump to irrigate seedlings, and ancient China had writings as well on the principle of siphoning. The ‘Guanyinzi·Jiuyao Pian’, written during the Northern and Southern Dynasties, states: “The bottle has two openings; fill it with water and then pour it out.” ； If it is closed, water will not flow downward; for if the energy does not rise, then the water will not descend. Though the well is a thousand cubits deep, water can be drawn to the surface ； If the qi does not descend, then the water will not rise. ”A bottle with two small holes can pour out water; if one of the holes is blocked, the air pressure outside the other hole becomes greater than the pressure of the water inside the bottle, and as a result, the water cannot flow out. In Wang Bing’s annotations to the Suwen from the Tang Dynasty, the physical phenomena related to atmospheric pressure are described quite clearly. Wang Bing said, “When a hollow tube is filled with water and then hung upside down, the water does not flow downward, as there is no upward-moving air force to push it down.” ； The small opening of the empty bottle prevents fluid from flowing in; it is because air cannot exit that no fluid can enter. ”It is pointed out that a small-mouthed empty bottle cannot be filled with water because the gas inside the bottle cannot escape. In his work *Shang Fu Tan* from the Song Dynasty, Yu Yan built upon the findings of his predecessors, stating that ； “When I was young, a Taoist priest showed me how to do this: he would burn a piece of paper and put it into an empty bottle, then quickly place the bottle in water in a silver basin; the water would flow into the bottle, causing the silver bottle to make a clanging sound, due to the heat generated ； It was also placed on the chest of a strong man in accordance with the law, so that it wouldn’t fall. ”When burning paper in an empty bottle, some of the air inside the bottle is forced out, and after the fire goes out, a negative pressure is created inside the bottle, resulting in a vacuum. The air pressure outside the bottle then presses the bottle tightly against a person’s abdomen. If the bottle is placed in water, water immediately flows into the bottle. Zhuang Yuanchen of the Ming dynasty also pointed out in his work \"Shuju Zi·Nei Pian\" that when a gourd spoon is pressed underwater, water does not enter the gourd, because there is air inside it.