ARKANSAS: The Marked Tree Siphons installation, dating to 1939, is said to be the only engineering structure of its kind in the United States. Built at a cost of $215,000, the three steel tubes integral to the design were among the largest in the world, with diameters of nine feet and lengths of 228 feet. As described by the Arkansas encyclopedia, "Their operation was deceptively simple. First, a vacuum pump primed each siphon. Once the siphon was primed, the vacuum pump was turned off, and the flow was self-sustaining. An air valve regulated the rate of flow."
Once activated, the siphons can run indefinitely, powered only by gravity. Eight decades later, the pumping process still functions properly after an overhaul in the 1990s.
Grandma's new gravy container she picked up at the garage sale.
