in force. the stone throwing has stopped, and they're advancing forward, mingling now with the anti-mubarak demonstrators here in tahrir square. that momentary cease-fire suddenly collapsed after this charge on horseback in the heart of a modern city. the horse riders came from the side of the regime supporters, and triggered another vicious street battle. mob violence at its worst. the battle lines drawn in front of cairo's landmark egyptian museum. a constant stream of wounded combatants. men, women and children in the opposition beat a makeshift war drum. once peaceful demonstrators started digging up stones for ammunition. nightfall brought sporadic