On Architecture

3. If the quicksilver is poured into a vessel, and a stone weighing one hundred pounds is laid upon it, the stone swims on the surface, and cannot depress the liquid, nor break through, nor separate it. If we remove the hundred pound weight, and put on a scruple of gold, it will not swim, but will sink to the bottom of its own accord. Hence, it is undeniable that the gravity of a substance depends not on the amount of its weight, but on its nature.

4. Quicksilver is a useful thing for many purposes. For instance, neither silver nor copper can be gilded properly without it. And when gold has been woven into a garment, and the garment becomes worn out with age so that it is no longer respectable to use, the pieces of cloth are put into earthen pots, and burned up over a fire. The ashes are then thrown into water and

1. I WILL now return to the preparation of vermilion. When the lumps of ore are dry, they are crushed in iron mortars, and repeatedly washed and heated until the impurities are gone, and the colours come. When the cinnabar has given up its quicksilver, and thus lost the natural virtues that it previously had, it becomes soft in quality and its powers are feeble.

2. Hence, though it keeps its colour perfectly when applied in the polished stucco finish of closed apartments, yet in open apartments, such as peristyles or exedrae or other places of the sort, where the bright rays of the sun and moon can penetrate, it is spoiled by contact with them, loses the strength of its colour, and turns black. Among many others, the secretary Faberius, who wished to have his house on the Aventine finished in elegant style, applied vermilion to all the walls of the peristyle; but after thirty days they turned to an ugly and mottled colour. He therefore made a contract to have other colours applied instead of vermilion.