Quicksilver at Giza

How can anyone involved in construction not speculate on how they built and carved the monuments of ancient Egypt? The pyramids of Giza were built very early in Egypt’s history—around 2570 BC—and the great pyramid remained the tallest structure on earth for 3800 years. They were built during the lifetime of the pharaoh Khufu—about 27 years. The marvels of this structure never seem to stop.

In an earlier post I wrote about how early occupants might have moved large (800 ton!) stones in Baalbek, Lebanon. I have no idea how they actually moved them, and never visited the site, and I wear my title of amateur speculative archaeologist with pride—it means I can live fine after being proven wrong, plus I don’t have to demonstrate mastery of all historical details before opening my mouth. I just have to make sure that any proposals of mine are consistent with what I do know. My ideas are sitting ducks for experts out there.

I proposed that they might have floated the stones, on mercury. They had canals, they had gold. Gold can be processed to purity only by making first a mercury-gold amalgam then evaporating the mercury. A few dozen tons of mercury might be all you need to lift the stones from their supports in the quarry and get them on their way. Gliding the stones into place certainly seems preferable to manhandling them over dry landscapes.

The civilized world at the time was rich in the mineral cinnabar. It was the source of their widely-used dye vermilion. Heating cinnabar (HgS) releases mercury as a gas. The gas has to be captured and cooled in order to distill (condense) the gas into liquid mercury. An alembic—a container of stoneware with a long down-ward pointing snout—was used for distillation in the Middle Ages, and I presume may have been used at this time. I figure that distillation must also include releasing the gas into a container of water to complete the cooling. In any case, extracting elemental mercury from cinnabar must have been tedious. The alembic could probably only be used once, leaving it with molten sulfur inside.

The site at Giza contained canals, coming from upstream. If stones floated on water, then the whole construction process would be greatly facilitated. How can mercury be integrated with water canals to achieve flotation? The specific gravity of mercury is 13.6 (g per cm3, kg per liter, or tons per cubic meter); specific gravity of limestone is in the 2-3 range. So limestone would float in a bed of mercury with about 1/5 of the vertical dimension immersed and 4/5 exposed above the mercury.

First we may note that mercury has a very high surface tension, a few times higher than the surface activity of the masonry materials of canals. This means that mercury can, at atmospheric pressure, bridge across cracks in the micrometer range. Of course, canal surfaces can be treated with wax or bitumen to help make them tight to mercury or water. Mercury and water are immiscible, so the canal could contain beds of mercury. Stone could float on the mercury and be propelled along the canal by moving water. The canal bottom would have to contain weirs that contain the mercury in beds, and stone would have to be lifted over these weirs. The bottom could also contain deepened sections, with a greater depth of mercury, where the stones could be flipped, leaving a different face exposed to the bottom.

A benefit of transport in a mercury-water canal is that the stone could be dressed and sized effortlessly as it moves along. The canal bottom may contain an abrasive such as flint or chert or diamond embedded in the bitumen so it doesn’t float away. A stone sized to dimension on a given axis would float smoothly above the abrasive, while an oversize stone would naturally be abraded down to size, perhaps with a little persuasion from the quality control guy on the assembly line. Individual stones could be gathered in a mercury-bottomed yard at the base of the pyramid, awaiting lift.

I’ve always been bothered by the roughness of rolling or scraping stones up the sides of ramp. If the stones are of a finished dimension, could they not be lifted to the appropriate height of the pyramid without the rough-and-tumble of straining beasts—human or otherwise—up to place leaving the finish surface, and finish dimension, intact? Can they be floated up the pyramid?

Well, yes. Imagine a stepped ramp, with each step slightly larger than the standard stone dimension. And imagine a lock, say of wood, at the downstream edge of each step, a lock that can be opened and closed, and would be somewhat tight to contain mercury when closed. Say the short dimension of the stone is 1m. It would float in 20 cm of mercury. If the steps are 20 cm difference in depth, then the lock would have to be 40 cm high, certainly attainable with a wood lock.

To move one stone up one step, the lock downstream from the target stone must be closed. Then the ramp segment with the stone needs to be filled with mercury, enough to lift the stone so that it can slide onto the next step up. Once that’s done, the lock behind the stone can be closed. This process can be done with a stone on each step of the ramp. With one load of mercury delivered to the top of the ramp, each stone on each step of the ramp can be lifted up one step. See the figures attached, and this video. The mercury load that was used for this achievement winds up in the yard at the base of the ramp. With a system like this, stones are all handled delicately as they are dressed, arrive in the yard at the base and are lifted to their final height.

Stepped ramp showing a lateral shift at an upper step. Here the lock planks are slid laterally into place, and kept from floating upward by metal straps at each end.
In this diagram sluice locks are lifted rather than slid, as above. Mercury fills the upper step to 20 cm and the lower step to 40 cm. The stone on the lower step can float to the upper step. A lower sluice is opened, draining the mercury from the stone just moved. this allows the stone below to belifted up one step. In fact, several stones on the ramp may be moved at the same time.

I can’t speak to how they were put in place in the pyramid. I don’t have a clue. But someone or something must carry tons of mercury up to the top of the ramp. I suspect they had no water-powered pumps or lifts, though that would have helped immensely. They may have used ox-drawn sledges. They may have used roller logs on the ramp. They need to deliver a mercury load that was greater than the weight of the stones, perhaps twice a great, and only one stone gets delivered to the top with each mercury load.

How they quarried the stone, transported it down the Nile, transferred it to a canal system, and did final placement, all these are outside this amateur’s purview. To say nothing of the granite elements at the interior and the finish stones at the outside. I welcome any comments.

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