A balance of special design demonstrates the principle of the siphon, and incidentally, if desired, that of Archimedes at the same time. A vertical rod, ending at the top in a hook that hangs from a knife-edge, supports a horizontal platform at its center. Placed symmetrically on the platform near its ends, are two equal beakers containing water in equal amounts. If the beakers are connected by a siphon tube, when water is added to or taken from either of them, the system will rebalance itself automatically. After rebalance, the volumes of water in the beakers are again equal. Putting a floating object into either beaker causes the same deflection that the same weight of water would (Archimedes' principle), and again the pointer returns automatically to zero. If the floating object is now removed, the balance behaves as if the same weight of water had been removed. But laying a weight on the platform outside a beaker causes the siphon to increase the deflection to a new equilibrium value.