Machine Power

"Zonca shows a large copperplate engraving of a huge pipe for raising water. It had a large, sealed inverted U-tube with larger diameter on one side. The figure shows the larger tube (A) on the left emptying water at a higher level than the water intake on the right. This water then powered a horizontal turbine at the bottom, which drives a millwheel for grinding grain. The sealed port at the top was to facilitate the initial filling of the tube with water.

For want of a better name, I call this a "perverted siphon", though it doesn't work as a siphon*. (It's so hard to name devices that don't work.) Didn't folks in the 17th century know that siphons can only lift water over an elevation if the output tube's opening is lower than the input water level? Perhaps not. Roman engineers had successfully used water tubes or pipes to transport water over hills, but the output was always lower than the input water level. These tubes were a last resort for engineers, for the apex of the tube could not be higher than 10 meters above the water level at the input end. It was difficult to seal the tubes so that air would not seep into the top of the tube and eventually form an air pocket that destroyed the continuity of the water and halted water flow. Perhaps some felt that it was only such practical "engineering difficulties" that prevented the use of siphons to actually deliver water to a higher level.

Remember that the role of atmospheric pressure in these devices wasn't understood. So why did the water stay in the inverted U-tube? This was explained by Aristotle's principle that "nature abhors a vacuum", that is, nature will not allow a vacuum in the top of the tube and will do whatever necessary to prevent it. This explained why a suction pump could lift a column of water (but didn't explain why it could only lift water about 33 feet)." [cont]. {see also}