against the ramparts far to the right , giant wheels turned slowly , spread-eagle slaves going round and round , their enflamed thighs and bu**ocks targets for apple cores , peach stones , and even raw eggs from the crowd , while several other slaves hobbled along at a squat behind their masters , necks tethered by two short leather chains to their widespread knees , their arms stretched out to support long poles with baskets of apples for sale dangling from the ends of them .